Phytoremediation of Co-Contaminated Environments: A Review of Microplastic and Heavy Metal/Organic Pollutant Interactions and Plant-Based Removal Approaches

Abstract

The increasing presence of microplastics (MPs) in terrestrial ecosystems, particularly when combined with organic pollutants and heavy metals, presents a considerable environmental challenge. This review examines the intricate interactions between MPs, co-contaminants (both organic and inorganic), and plants involved in phytoremediation processes. A literature search was performed across the databases Scopus, ScienceDirect, and Google Scholar, covering the timeframe from 2015 to 2025. The studies selected specifically addressed the synergistic and antagonistic effects of microplastics in conjunction with heavy metals or organic pollutants (such as PAHs and pesticides) within plant–soil systems. The findings reveal that MPs influence pollutant mobility, bioavailability, and toxicity through adsorption and desorption mechanisms, leading to varied implications for plant growth, microbial communities, and contaminant uptake. Depending on the physicochemical characteristics of MPs and co-pollutants, the effects can range from increased phytotoxicity to diminished contaminant accumulation in plants. Additionally, physiological and molecular disruptions, including oxidative stress, hormonal imbalances, and impaired enzymatic activity, were frequently noted in co-contamination scenarios. Recent developments, such as the creation of genetically modified hyperaccumulator plants and the use of nanotechnology and microbial consortia, demonstrate potential to enhance phytoremediation efficiency in complex polluted soils. This review underscores the pressing need for integrated, multidisciplinary strategies to overcome the limitations of existing phytoremediation methods in co-contaminated environments. Future research should focus on standardized methodologies, a mechanistic understanding, and the safe implementation of emerging biotechnologies for sustainable soil remediation.

1. Introduction

Soil pollution (e.g., by plastic litter) is a global environmental phenomenon, and numerous initiatives have been undertaken to identify effective remediation techniques [1,2]. Soil pollution leads to various environmental issues, including the degradation of water bodies, desertification, as well as the pollution of food crops. These factors can result in health problems for humans, either directly or indirectly [3].

Agriculture is commonly acknowledged as a major contributor to human-induced pollution such as microplastics (MPs) [4], yet its effects are frequently underestimated in comparison to other sectors [5,6]. Contemporary agriculture methods, which typically depend heavily on fertilizers, pesticides, and irrigation, contribute greatly to this type of pollution. These practices result in downstream contamination through various processes, including water runoff, nutrient drainage, topsoil loss, airborne transport, and settling of sediments [5]. Therefore, it is crucial to implement strategies for the remediation of polluted soils [3]. The role of MPs as vectors for both inorganic and organic pollutants in the environment should also be taken into consideration [7].

The remediation of soils mainly affected by MP–pollutant co-contamination [8] can address these issues, and a range of approaches may be applied, including methods based on chemical processes, physical interventions, and biological treatments. Phytoremediation, as described by Barbosa et al. [9], is a promising technique that utilizes plants to mitigate soil pollution. In order to enhance the effectiveness of phytoremediation, the use of microbial agents, engineered organisms, and chemical enhancers has been proposed, along with integrated biological and nanotechnological restoration techniques [10].

Historically, plant-assisted bioremediation has been classified as a form of phytoremediation [11]. Chaney [12] first proposed the idea of phytoremediation in 1983. The word originated from the Greek root “phyto”, referring to plants, and the Latin term “remediation,” which comes from “remedium”, indicating restoration or purification [13]. Human-induced pollution has existed since the start of human civilization, coinciding with the development of traits that distinguish humans from other animals [13]. The fascination with examining how plants interact with pollutants dates back to the 16th century, when researchers began to identify species that exhibit tolerance to heavy metals [14]. Phytoremediation refers to the use of plants to extract and degradation toxic metals and organic pollutants from water, soil, and air [15].

In recent decades, different kinds of plastic materials have been detected across a variety of soil environments, showing both confirmed and possible negative effects on ecosystems, as well as on the flora, fauna, and ultimately human health within these areas [6]. Although plastics are extensively applied in agricultural activities, they have recently been identified as an emerging threat to soil health [16,17]. MPs are regarded as possible vectors for a range of pollutants, owing to their significant ability to adsorb substances, thereby facilitating the long-distance transport of contaminants into the environment [7]. Some of them also include different substances such as glue on their surface (or additives), like insect glue trap plastic (IGTP) [18].

Research has demonstrated that certain plant species can take up and transport MPs and nanoplastics (NPs) within their tissues [19]. Consequently, plants may effectively eliminate MPs/NPs from polluted environments. Beyond absorption and movement within the plant, additional factors like root secretions and symbiotic relationships with mycorrhizal fungi might contribute to the immobilization or breakdown of MPs and NPs [19].

The objective of the current study is to explore the effects of the simultaneous presence of microplastics (MPs), organic pollutants, and heavy metals on the efficacy of phytoremediation techniques. In particular, this research aims to comprehend the dynamic interactions—both synergistic and antagonistic—that take place between plants and various co-existing pollutants in contaminated soils. The investigation is based in a systematic review of scientific literature published over the last decade (2015–2025), with the goal of identifying the mechanisms and impacts that emerge during the remediation of soils that are concurrently contaminated with microplastics and organic pollutants (such as PAHs or pesticides) and/or heavy metals. By analyzing pertinent experimental studies, the aim is to underscore how intricate pollution scenarios affect the effectiveness of phytoremediation and to enhance the understanding of the interactions between plants, plastics, and co-contaminants within the soil ecosystem.

2. Literature Search Strategy

A structured search was conducted using the databases Scopus, Science Direct and Google Scholar to ensure a comprehensive and transparent literature review. The search covered a 10-year period publications from 2015 to 2025, focusing on studies related to co-contamination, phytoremediation, microplastics, heavy metals, and organic pollutants. The criterion was to select data from research articles that examined the parallel effects of plastic–plant–pollutant (organic or inorganic) combinations. The primary keywords used included: “soil”, “plastic”, “plants” and “heavy metals” for inorganic pollutants and “soil”, “plastic”, “plants”, “organic pollutants”, “PAHs” and “pesticides” for organic pollutants, combined using Boolean operators (AND/OR) as appropriate. Only peer-reviewed journal articles were included. Studies were screened based on relevance to the scope of this review, with emphasis on experimental evidence, recent technological advances, and mechanistic insights. Reviews, editorials, and studies lacking full text were excluded. A total of 30 articles were selected after screening 50 initial results, in order to collect data for the sections “phytoremediation of soils contaminated with microplastics encapsulating other organic contaminants” and “phytoremediation of soils contaminated with MPs encapsulating heavy metals”. Before this, a general literature review on phytoremediation was carried out.

3. Phytoremediation

Overall, an evaluation of different soil remediation strategies indicates that they can be grouped into three primary categories [20]: physical, chemical, and biological. Physical remediation includes methods such as (1) soil replacement, (2) soil containment, (3) vitrification, and (4) electrokinetic treatment. Biological approaches generally involve (5) phytostabilization, (6) phytoevaporation, and (7) phytoextraction, whereas chemical techniques cover (8) immobilization and (9) soil washing. It is important to note that biological and chemical methods can be utilized in conjunction, depending on the specific metal, soil characteristics, plant species, and chemical agents involved. Furthermore, the efficacy of various phytoremediation strategies can be improved through the use of microbial, chelate, and genetic enhancements [20].

Phytoremediation refers to an ecological restoration technology that primarily utilizes plants [21]. The process involves utilizing various plants such as shrubs, trees, aquatic vegetation, and grasses, alongside their symbiotic microbes, to remove, degrade, or immobilize pollutants in affected areas [21]. Phytoremediation is an environmentally friendly approach [22] that is also practical, cost-effective, and efficient for the treatment of groundwater, industrial effluents, and contaminated land [23].

Based on a research [24], plants that exhibit resilience to contaminants in polluted soils tend to be more robust and enduring, resulting in the development of healthier root systems and increased above-ground biomass. On the other hand, environmentalists argue that certain plant species employed in phytoremediation may become invasive in nearby natural habitats, potentially disrupting ecosystem functions, reducing native biodiversity, and causing negative socioeconomic and public health impacts [25]. They might also alter the characteristics of ecosystem functionality [26]. Consequently, in the latest understanding of phytoremediation, researchers are exploring the potential of both wild and cultivated plants to function as hyperaccumulators [27].

Phytoremediation employs hyperaccumulator plants along with their associated rhizospheric microorganisms [22] and it depends on soil condition and type of pollutants [28]. Hyperaccumulators describe a distinctive trait of certain plants that allows them to concentrate high levels of pollutants in their roots and above-ground tissues without experiencing any physiological damage or showing signs of stress [29]. Two separate types of hyperaccumulation have been identified: active and passive hyperaccumulation. Active hyperaccumulation occurs when plants take up metals at relatively low or moderate soil metal concentrations, reflecting a physiological capacity to concentrate metals, whereas passive hyperaccumulation is observed at very high soil metal concentrations, where metal uptake may occur as a consequence of exposure rather than specific physiological regulation [30].

The processes involved in phytoremediation are (1) phytoextraction, (2) phytostabilization/phytoimmobilization, (3) rhizofiltration, (4) phytovolatilization, (5) phytodegradation and rhizodegradation and (6) phytodesalination [31]. Specifically, (1) phytoextraction, also known as phytoaccumulation, refers to the process in which toxic metals are taken up by plant roots. The metals are subsequently transported to the shoots, where they are sequestered in vacuoles, cell walls, membranes, and other metabolically inactive compartments within plant tissues [31]. (2) Remediation can be achieved by either inactivating or immobilizing toxic substances or pollutants within the plant root system or the surrounding soil environment. The stabilizing function of plant roots reduces the mobility and bioavailability of contaminants, thereby diminishing their toxic effects [31]. (3) Rhizofiltration is a process that utilizes the roots of plants in a saturated environment to eliminate toxic substances, thereby addressing aqueous pollutants found in wastewater, groundwater, or surface water. This technique functions through processes such as binding, accumulation, and chemical deposition of pollutants on the root systems or other underwater structures of metal-resistant aquatic plants [32]. In this method, the plants’ subterranean tissues either retain contaminants externally or internalize them, thereby contributing to the purification of groundwater and surface water bodies like lakes and rivers [31]. (4) Phytovolatilization involves several steps. First, plants take up pollutants from the soil, transform substances that are less volatile into more volatile forms, and then release these compounds into the atmosphere through the process of volatilization. This method is especially effective when the volatilized pollutants become less toxic as they move from the soil into the air [33]. (5) Plants possess the ability to metabolize and eliminate contaminants within their tissues through a mechanism referred to as phytodegradation. This process permits the elimination of organic pollutants, including pesticides, through degradation or transformation carried out by various parts of the plant. In phytodegradation, the various components of vegetation can play a crucial role, either through direct or indirect mechanisms. In the direct approach, the organism absorbs the pollutants, metabolically processes them, and decomposes them to smaller, less toxic substances, which are then distributed throughout the plant tissue. Since plants do not possess active transport mechanisms, these organic pollutants are taken up passively. When the degradation of contaminants happens in the rhizosphere, this process is specifically referred to as rhizodegradation [31]. (6) Certain salt-tolerant plants possess the ability to absorb considerable quantities of salts from the soil, thereby rehabilitating saline soils to enhance productivity through a process known as phytodesalination. Saline soil diminishes the reduction potential, which can result in dehydration and disrupt plant physiological processes [34].

3.1. Secondary Metabolites in Phytoremediation

Phytoremediation, enhanced by plant growth-promoting bacteria (PGPB), is an eco-friendly approach used to clean up metal-polluted soils. Generally, plants produce secondary metabolites to defend themselves against metal toxicity [35]. Secondary metabolites (SMs) were characterized by Kossel in 1891 [36] as molecules primarily produced by microbes and plants, typically possessing a low molecular weight, often around 3 kDa. Moreover, plants and fungi serve as producers of these molecules, whose physiological roles, in numerous cases, remain unknown [37]. Secondary metabolites are crucial in the responses of plants to stress, thus offering a significant biochemical basis for comprehending how plants manage co-contaminant stressors like MPs, heavy metals, and organic pollutants. It is essential to take into account contemporary review examples, as they affect the defense, detoxification, and tolerance mechanisms associated with the effectiveness of phytoremediation.

Plants efficient in phytoremediation can tolerate and accumulate large amounts of metals in their above-ground tissues by producing secondary metabolites. Metal-induced stress causes alterations in the plant’s metabolic profile, promoting the production of new biochemically related metabolites that aid in metal tolerance [38]. Plant secondary metabolites are divided into three groups based on their biosynthetic origins: (1) flavonoids and phenolic compounds, (2) nitrogen-containing alkaloids, and (3) terpenoids [37].

As noted by Mukherjee et al. [39], recent geogenic and human activities have caused significant contamination of soil with heavy metal(loid)s (HMs), adversely impacting environmental quality, plant health, and human well-being. Phytoremediation is an innovative, cost-efficient, and environmentally friendly in situ technology that utilizes both native and non-native plant species as natural agents to extract toxic HM(s) from degraded soil. Notably, the rhizomicrobiome of plants plays a crucial role in enhancing overall plant nutrition, health, and the process of phytoremediation. Specific secondary metabolites synthesized by plant growth-promoting rhizobacteria (PGPR) play a direct role in the bioremediation of heavy metal(loid)s (HM) via processes like chelation, mobilization, sequestration, bioadsorption, and bioaccumulation, thus altering the bioavailability of metals for plant uptake, accumulation, and transport [39]. Zulfiqar et al. [35] highlighted the beneficial role of PGPB in enhancing the phytoremediation of heavy metals, alongside the diverse metabolite responses to different types of metal stress, which correlate with the metal tolerance ability of Vigna radiata.

Multiple studies have shown that secondary metabolites—including phenolic compounds, flavonoids, and alkaloids—play a crucial role in phytoremediation by assisting in heavy metal detoxification and protecting plants from environmental stress [35,37,40]. For example, Catharanthus roseus (Madagascar periwinkle) produces terpenoid indole alkaloids, which are present in small amounts, making their extraction difficult and costly. The plant’s low alkaloid content combined with their high market value has made Catharanthus roseus an important model for research in plant biotechnology and secondary metabolism. A study focused on the responses of Catharanthus roseus to metal stress under controlled pot culture conditions. Metals such as Zn and Cu were found to positively influence the accumulation of specific secondary metabolites in Catharanthus roseus [41].

Silybum marianum (L.) Gaertn., widely recognized as milk thistle, is an encouraging plant species due to its capacity to generate silymarin, a significant secondary metabolite with considerable medicinal properties, even when cultivated in poor and polluted soils [42]. Vasilou et al. [43] investigated the potential of industrial hemp (Cannabis sativa L.) to remediate Cu-contaminated Mediterranean soils. Particular attention was also given to Cu accumulation in various plant parts and to the influence of soil contamination on cannabidiol (CBD) production. Hemp has demonstrated potential as a plant for phytostabilization in soils contaminated with Cu, since its above-ground biomass is nearly devoid of metals and can be utilized for fiber production. The existence of Cu in soils seemed not to hinder the production of the significant secondary metabolite CBD, but instead rose with higher soil Cu levels [43]. In addition, in a two-year research trial by Papadimou et al. [42], conducted using soils collected from both rural and urban zones within Central Greece, silymarin yield showed a proportional increase relative to Cu concentrations, with an 8.2–15% rise observed in polluted, unfertilized urban soils compared to rural soils [42]. Crucially, silymarin is produced without metal contamination, despite the plant’s propensity to accumulate heavy metals, predominantly in its root system. These results underscore the potential of S. marianum for the safe production of silymarin in challenging environmental conditions [42].

Milk thistle (Silybum marianum (L.) Gaertn.) has also been studied for its notable medicinal properties, largely attributed to the presence of silymarin. In a separate two-year field study, Liava et al. [44] investigated the impact of conventional and stabilized nitrogen fertilizers—applied at two different rates—on plant development, fruit yield, and fruit quality [44]. While nitrogen fertilization did not significantly change the silymarin concentration in the fruits, the yield of silymarin was indirectly increased due to the enhanced fruit production resulting from fertilization [44]. Importantly, both types of fertilizers exhibited similar effects when applied at the same nitrogen rates, suggesting that the rate of fertilization, rather than the type of fertilizer, was the key factor affecting plant performance [44]. Moreover, it was demonstrated for the first time that stabilized nitrogen fertilizer, applied at a rate of 125 kg N/ha, was equally effective as conventional fertilizer in enhancing yield, highlighting its potential as a sustainable alternative for milk thistle cultivation. These results underscore the importance of optimized nitrogen management in enhancing biomass and silymarin production without compromising the fruit’s overall quality [44].

According to Rodrigues et al. [40] eliminating secondary metabolites from plant biomass did not meaningfully change cadmium removal efficiency, disputing the widely accepted notion that these metabolites are crucial for heavy metal sequestering. Moreover, the findings have shown that Cd absorption is more strongly linked to the structural elements of plant tissues than to the existence of certain secondary metabolites [40].

The intricate interactions among soil, plants, and pollutants can influence the communities of bacteria associated with plants in reaction to environmental stress induced by the presence of xenobiotics [45,46]. Specific pollutants can impact both the structural and functional diversity of soil microorganisms [47], and influence how plants respond to stress. These responses may include the exudation of plant secondary metabolites (PSMs) into the rhizosphere and changes in the soil’s physical and chemical characteristics caused by leftover contaminants [48,49].

Phenoxy pesticide residues, such as 2-chloro-4-methylphenoxy acid (MCPA), are among the developing contaminants that are commonly found in non-targeted areas. Phytoremediation supported by endophytes represents a biological approach that can be employed to eliminate MCPA from various environmental media. Bacteria associated with plants, including endophytes, along with certain plants that release plant secondary metabolites (PSMs) into the rhizosphere, can interact in ways that enhance the plants’ tolerance to pollutants such as MCPA and accelerate the degradation of organic compounds [50].

Although root exudates and plant-derived extracts offer promising and eco-friendly strategies to enhance phytoremediation, their effectiveness varies across environmental conditions, posing a considerable challenge. This inconsistency underlines the need for further investigation into the composition and functional significance of exudates in plant responses to stress under diverse contamination scenarios. Moreover, extensive reliance on plant extracts could prove unsustainable if the extraction process requires significant resources or takes place in environmentally sensitive regions. In addition, the long-term effects of adding concentrated bioactive substances to soils remain unclear, potentially leading to shifts in microbial community composition or the accumulation of soil-derived secondary metabolites [51]. Regarding omics-centered approaches such as transcriptomics, proteomics, and metabolomics, these are facilitating advancements in the systems biology perspective of plant reactions to pollutants alongside genetic engineering. These approaches have revealed a wide range of genes and enzyme pathways involved in stress responses, as well as various secondary metabolites. These genes, pathways, and metabolites play a role in the detoxification of metals and the repair of cells [51,52,53].

For thousands of years, secondary plant metabolites have influenced interactions with microorganisms, insects, and even humans, resulting in a complex network of relationships that can be either beneficial, such as mutualistic associations, or harmful, such as pathogenic interactions. These metabolites have played a crucial role in the evolution of a wide array of enzymes capable of degrading organic pollutants in nature. Nevertheless, the link between secondary metabolites and enzymatic diversity remains underexplored, offering promising opportunities in fields such as pest control, environmental remediation, and the production of high-value chemical compounds [54].

3.2. Molecular and Genetic Basis of Phytoremediation: Advances and Applications in Genoremediation

Understanding the molecular and genetic underpinnings of phytoremediation is essential for comprehending plant reactions to intricate pollution situations. These processes dictate how plants manage stress signaling, pollutant movement, and detoxification routes, all of which are pertinent when tackling interactions between MPs and pollutants in environments with multiple contaminants.

The molecular and genetic foundations of phytoremediation have garnered increasing scientific interest due to their pivotal role in environmental detoxification. Phytotechnology, particularly when employing hyperaccumulator species, offers promising solutions for remediating polluted environments. The enhancement of these systems through genetic engineering—a strategy known as genoremediation—marks a major advancement in tackling the inherent limitations of natural phytoremediation, such as its slow uptake rates and lack of specificity [55]. Investigating the molecular pathways that govern transgenic plant responses is vital for optimizing the efficiency of these phytotechnology applications [55,56,57].

Hyperaccumulators targeting inorganic pollutants display notable variability in their phytoremediation efficiency. This variability is largely attributed to differences in their capacity to perceive and transmit environmental stress cues that in turn initiate a series of molecular, biochemical, and physiological reactions [58,59]. Central to these responses are photosynthetic and associated metabolic processes, which facilitate the compartmentalization and sequestration of pollutants within different plant tissues—including roots, stems, and leaves [60,61].

Gene manipulation technologies have proven instrumental in accelerating the phytoremediation of hazardous substances, particularly within agricultural systems where rapid and sustainable detoxification is critical [62]. Through targeted genetic modifications, hyperaccumulator species can be tailored to exhibit enhanced pollutant uptake, improved tolerance, and faster growth under toxic conditions.

When dealing with inorganic pollutants, the plant’s ability to tolerate and sequester metallic elements is often facilitated by the activity of natural membrane transporters [63]. These pollutants interact with plant roots initially through the apoplastic and symplastic pathways, including communication via plasmodesmata. However, the uptake efficiency is highly dependent on environmental and biological variables including the makeup of root exudates, soil pH, organic matter levels, and the arrangement of microbes in the rhizosphere [55,64].

In summary, the integration of molecular biology, genetics, and plant physiology is revolutionizing phytoremediation. These molecular insights, although not exclusive to MPs, offer crucial context that aids in understanding plant tolerance and remediation potential in the presence of mixed pollution. Finally, the continued development of genoremediation strategies holds significant promise for enhancing the resilience and efficiency of phytotechnologies in diverse environmental contexts.

4. Phytoremediation of Soils Contaminated with Microplastics

Numerous approaches have been suggested for the elimination of MPs from the environment. Phytoremediation is less commonly utilized for the removal of MPs compared to bioremediation, raising questions about its effectiveness and whether its application is restricted primarily to photosynthetic organisms such as algae, including green algae, which are considered mainly aquatic organisms but differ in structure from higher terrestrial plants [65]. However, the complex biogeochemical nature of soils, combined with the limitations of current methods for detecting MPs in terrestrial environments, has kept research in this area at an early stage [66].

Research on the uptake of MPs by plants has primarily relied on fluorescence-based tracking methods [67,68]. More advanced quantitative approaches have been developed by incorporating trace metals [e.g., palladium (Pd)] or lanthanide chelates into polymers [69,70]. Nevertheless, due to the structural complexity of plant tissues and current technological limitations, accurately detecting MPs within plant systems remains a significant challenge.

Certain submerged aquatic plants are capable of absorbing and accumulating MPs, primarily through electrostatic interactions and by interactions with biofilms formed by microorganisms on the plant surfaces [71]. MPs can also become entrapped within the plant cell walls [72]. The uptake of MPs through the leaves of terrestrial plants has become an increasing concern, especially since atmospheric deposition introduces over 280 MP particles per square meter into the environment each day [73]. Upon exposure to sunlight, stomata on terrestrial plant leaves open to dimensions of roughly 25 μm in length and 3 to 10 μm in width, enabling small MPs to penetrate the leaves [74].

MPs, especially NPs [75], exhibit significant bioaccessibility and bioavailability [76] and are known to induce phytotoxic effects. The absorption of MPs by plant roots causes both physical damage and chemical stress, including oxidative stress at the root tips. This leads to abnormal root structure, reduced root functionality, and inhibited root growth [77]. The phytotoxic impacts of MPs are complex and depend on multiple factors such as their type, shape, size, surface charge, concentration, and bioavailability in the environment. Moreover, the way plants are exposed to MPs, their functional classification (e.g., tree, shrub, vine, or herbaceous), as well as the species and developmental stage of the plant, significantly influence these effects [78]. The presence of additional pollutants in the rhizosphere further affects these outcomes [66,79].

A variety of approaches have been suggested to address MP pollution, including the physical elimination of improperly managed plastic materials and the use of microorganisms and biocatalysts for the biodegradation of MPs [65]. Nevertheless, there was insufficient evidence indicating the degradation of MPs following their adsorption, uptake, and accumulation [65]. MPs that become trapped and build up within plants may be transferred to higher levels in the food chain through consumption, raising important concerns about their potential ecotoxicological impacts (Figure 1) [65,80,81].

Phytoremediation offers an environmentally friendly strategy for mitigating MP pollution. Established remediation methods designed for conventional pollutants like heavy metals can provide a valuable framework for developing phytoremediation technologies targeting emerging MP pollutants [82]. Utilizing a range of OMICS approaches—including genomics, metabolomics, proteomics, and transcriptomics—allows for a deeper and more accurate understanding of the mechanisms driving phytotoxicity and phytoremediation of MPs. This knowledge can facilitate genetic engineering efforts to improve the ability of plants and microorganisms to tolerate, accumulate, and metabolize MP contaminants [83]. Additionally, soil amendments such as chemical treatments and biochar can be applied to boost MP rhizoremediation via biostimulation or co-immobilization processes [84].

Selecting suitable plant species and promoting the activity of MP degraders is a significant area of research [25]. Phytoremediation can be incorporated into landscape and functional area planning at contaminated sites, enabling productive use while simultaneously aiding environmental restoration [85]. Within this framework, it is essential to conduct comprehensive assessments of ecological risks, including the identification of potential sources, exposure routes, susceptible organisms to MPs, and their impact on global climate change [86,87]. Consequently, the development of effective phytoremediation approaches for MP pollution requires not only environmental experts but also collaboration among agronomists, engineers, policymakers, and regulatory bodies [88].

Selecting appropriate plant species and evaluating the economic viability of using harvested plants containing MPs pose major challenges in phytoremediation of MP pollution [66]. Employing plants to remediate micro- and NPs from the environment is becoming a promising and environmentally sustainable strategy. According to Yuan et al. [89], three key phytoremediation mechanisms have been identified in this context: phytoaccumulation, where plants absorb and store micro/nanoplastics within their tissues; phytostabilization, which involves the stabilization of plastic particles within the soil via root-mediated processes; and phytofiltration, where plant roots or aerial parts act as filters, trapping plastic particles from aqueous environments. These mechanisms emphasize the significant contribution of plants to the biotechnological control of plastic pollution.

Figure 1. Conceptual framework illustrating the interactions between MPs, organic pollutants, and heavy metals in soil environments and their potential ecological effects [80,81,89,90,91,92,93,94,95,96]. The diagram summarizes reported mechanisms, including adsorption processes, altered contaminant mobility, changes in soil properties and microbiome, phytotoxicity, and bioaccumulation in the food chain. Supporting literature for each process is provided in

Table A1. Literature Supporting Figure 1 Mechanisms. This table summarizes key literature supporting each process presented in Figure 1, which describes the interactions between microplastics (MPs), organic pollutants, and heavy metals in soil environments.

Stage/Process in Figure 1	Description	Supporting Literature
Adsorption of Organic Pollutants on MPs surface	MPs adsorb organic pollutants including PAHs, PCBs and pesticides, due to hydrophobic and surface properties.	[91]
Adsorption of Heavy Metals on MPs surface	Heavy metals such as Pb, Cd, and Cu associate with MPs via electrostatic interactions and functional groups.	[91]
Prolonged exposure, reduced biodegradability	Extended exposure of soils to MPs causes surface aging and inhibits microbial activity, which leads to decreased biodegradability and a reduction in the effectiveness of biotic degradation and phytoremediation processes.	[89,92]
Transport to deeper layers and groundwater	Combination of MPs and organic pollutants increases persistence and facilitates transport to groundwater.	[93,94]
Changes in mobility and bioavailability	MPs modify the bioavailability of heavy metals and other pollutants in soil systems.	[94]
Changes in pH, water retention and structure	MPs affect soil physicochemical properties (e.g., pH, porosity, and water-holding capacity).	[95]
Changes in microbiome	Changes in soil properties result in variations in the composition and function of microbial communities.	[96]
Phytotoxicity	The combination of MPs and pollutants leads to oxidative stress and inhibit plant growth.	[80]
Accumulation of toxic compounds into the food chain	Toxic compounds and MPs are passed on to higher trophic levels via the food web.	[81]

(Appendix A).

Figure 1. Conceptual framework illustrating the interactions between MPs, organic pollutants, and heavy metals in soil environments and their potential ecological effects [80,81,89,90,91,92,93,94,95,96]. The diagram summarizes reported mechanisms, including adsorption processes, altered contaminant mobility, changes in soil properties and microbiome, phytotoxicity, and bioaccumulation in the food chain. Supporting literature for each process is provided in Table A1 (Appendix A).

5. Phytoremediation of Soils Contaminated with Microplastics Encapsulated Other Organic Contaminants

Organic pollutants can be classified into different categories based on their chemical composition and associated risk. One way to distinguish them is by their halogen content, dividing them into halogenated compounds (such as chloroform) and non-halogenated organic compounds (like the methane greenhouse gas methane, but it is not considered a conventional pollutant), which constitute the two main groups of organic pollutants. Furthermore, pollutants can be additionally classified based on the structure of their carbon chains. Specifically, this classification depends on whether the carbon chain is saturated (characterized by single bonds between carbon atoms, such as butane which is not considered a conventional pollutant) or unsaturated (characterized by multiple bonds between carbon atoms). Moreover, aromatic compounds are those that include one or multiple aromatic rings in their molecular structure, such as polycyclic aromatic hydrocarbons (PAHs) [6,97].

Phytoremediation efforts targeting organic pollutants have mainly focused on three groups of substances: chlorinated solvents, explosives, and petroleum hydrocarbons [98]. An old study [99] also explored the potential of phytoremediation to remove pollutants such as PAHs and polychlorinated biphenyls (PCBs). Furthermore, research by Meagher [100] identified several major organic pollutants as promising targets for phytoremediation, including PCBs like dioxin, PAHs such as benzo[a]pyrene, nitroaromatic compounds like trinitrotoluene (TNT), and linear halogenated hydrocarbons such as trichloroethylene (TCE). Many of these substances are known not only for their toxicity and teratogenic effects but also for their carcinogenic potential [100].

Agriculture is commonly acknowledged as a major contributor to human-induced pollution, yet its effects are frequently underestimated in comparison to other sectors. Contemporary agricultural methods, which typically rely on significant use of fertilizers, pesticides, and irrigation water, play a crucial role in this type of pollution. These practices result in downstream contamination through processes such as surface runoff, leaching, soil erosion, wind dispersal, and sedimentation [5]. Contemporary agricultural methods, which often involve heavy application of fertilizers, pesticides, and irrigation, significantly contribute to this kind of pollution. These activities lead to contamination in surrounding areas via mechanisms like surface runoff, leaching, soil erosion, wind transport, and sediment deposition [5].

For instance, pesticides are classified according to the pests they target, such as algicides, bactericides, fungicides, herbicides, insecticides, nematicides, and rodenticides [101]. Chemically, organic pesticides can be grouped into categories like organochlorines, organophosphates, acetamides, carbamates, triazoles, triazines, neonicotinoids, and pyrethroids [101]. A significant category of pesticides consists of those recognized as persistent organic pollutants (POPs) [101]. The POP list includes 14 organochlorine compounds, such as dichlorodiphenyltrichloroethane (DDT), chlordane, heptachlor, and toxaphene [101].

Annual plants have proven to be more effective than perennial plants in the remediation of pesticide-contaminated environments, primarily due to their rapid growth rates and elevated metabolic activity, which facilitate contaminant uptake in shorter periods. Among the numerous factors that affect phytoremediation efficiency, the choice of plant varieties is crucial, as various plants exhibit different capacities for pesticide absorption, degradation, and translocation. Furthermore, the physicochemical characteristics of pesticides—such as solubility, molecular weight, and lipophilicity—are essential in influencing how these compounds are absorbed and transported within plants, ultimately determining the overall effectiveness of phytoremediation strategies [102]. Furthermore, the physicochemical properties of pesticides—such as solubility, molecular weight, and lipophilicity—are crucial in influencing how these compounds are absorbed and transported within plants, ultimately shaping the success of phytoremediation approaches [102].

On the other hand, pharmaceuticals are frequently detected in both aquatic and agricultural environments due to human activities and the subsequent discharge of wastewater effluents into the ecosystem. Moreover, the irrigation of crops with treated wastewater, along with the application of manure and biosolids to soil, contributes to the introduction of these substances into farmland and crops [103].

Plants are capable of actively taking up pharmaceuticals through both solutions and soils, with the bioavailability of these compounds being influenced by the surrounding environmental matrix [103]. Noteworthy findings have emerged regarding the biochemical processes involving pharmaceuticals in plants, suggesting that plants have developed mechanisms to manage the toxicity of pharmaceutical compounds and are able to efficiently remove these compounds [103]. In the context of agriculture, the uptake of pharmaceuticals through plant absorption presents a potential risk to human health; however, this risk is generally considered low. Nonetheless, several knowledge gaps remain that require further investigation [103].

Table 1. Summary table of MPs encapsulated organic pollutants, in different soil environments.

Type of Plastic	Concentration of Plastics	Dimensions of the Plastics	Soil pH	Other Characteristics of Soil	Plant	Organic Pollutants	Concentration of the Pollutants	Reference
LDPE	2 · 103 particles kg−1 and area of 60 cm2 kg−1	>100 μm	Alkaline (7.8–9.1)	0–10 cm depth, haplic calcisol (loamic, hyper calcic), soil organic carbon between 0.7% to 2.1% and the soil nitrogen between 0.7% to 1.9% Soil Texture (ST): Loamy Field experiment	Vegetables	4–10 different pesticide residues in all soil samples: azoxystrobin, imidacloprid, chlorantraniliprole, boscalid, difenoconazole, chlorantraniliprole, cypermethrin, imidacloprid, oxyfluorfen, pendimethalin	0.14 mg kg−1	[104]
Plastic wastes				Farmland soil, 0–15 cm. Field experiment.	Wheat: Triticum aestivum L.	Organophosphate esters (OPEs)	Total concentrations of 0.038–1.25 mg kg−1	[105]
Fluorescent PS	10 mg kg−1	0.1 μm, 1 μm, 10 μm and 100 μm	7.2	SOM: 27.8 g kg−1, CEC: 21.6 cmol kg−1, TN: 1.79 g kg−1, TP: 0.82 g kg−1 Pot experiment	Glycine max L. Merrill	Phenanthrene		[106]
PE and PLA	Four groups (3,5-DCA, MPs, MPs + 3,5-DCA, and control with no MPs or 3,5-DCA): 0.1%, 0.2%, and 2%, respectively	50–100 μm	7.41	0–20 cm, Organic matter: 29 g kg−1, Cation exchange capability 8.9 cmol+ kg−1 ST: Yellow loam soil Pot experiment	Chive: Allium ascalonicum	3,5-dichloroaniline (3,5-DCA): a toxic metabolite of dicarboximide fungicides	10 mg kg−1	[107]
PE	2% of the soil fresh weight	150 μm		Field soil and sand together at 2:1 Pot experiment	10 terrestrial plants (5 alien species: Ageratina adenophora (Spreng.) R. M. King & H. Rob., Bidens pilosa L., Chromolaena odorata (L.) R. M. King & H. Rob., Phytolacca americana L. and Tithonia diversifolia (Hemsl.) A. Gray; and 5 native species: Coix lacryma-jobi L., Cyanthillium cinereum (L.) H. Rob., Laggera crispata (Vahl) Hepper & J. R. I. Wood, Puhuaea sequax (Wall.) H. Ohashi & K. Ohashi and Senecio scandens Buch.-Ham. ex D. Don)	Indoxacarb		[108]
PS		Small PS (SPS): 100–1000 nm 0.1–1 μm and large PS (LPS) > 10 μm			Lettuce: Lactuca sativa L. var. ramosa Hort.	Di-butyl phthalate (DBP)		[109]
Polyester	0.03% and 7%	Microplastic fibers: Average length: 3300 μm Width: 100 μm	6.88	Ablend of peat moss, bark mulch, perlite, and an NPK fertilizer of 0.21%–0.11%–0.16%. Electrical Conductivity: 322.8 ± 24.5 μS cm−1 Pot experiment	Lactuca sativa	Naproxen		[110,111]
Butylene adipate co-terephthalate (PBAT), LDPE and PLA	20% w/w (85% of PBAT, LDPE & 10% of PLA)	Pellets: 200 to 500 μm	6.95	83% sand, 11% silt and <1% clay with an organic matter content of 4%. ST: Sandy soil Ceramic pot experiment	Radish: Raphanus sativus	Pesticides (chlorpyrifos (CPF), difenoconazole (DIF) and their mixture)	15 mg kg−1	[111]
Three types of MPs-PS: carboxyl PS (PS-COO−), neutral PS (PS) and amino PS (PS-NH3+)		0.2 μm	7.0	0–20 cm depth, 12.0% clay, 20.6% silt, 67.4% sand, 29.3 g kg−1 organic matter ST: Silty loam	Cherry tomato: Lycopersicon esculentum	Antiviral pesticide Dufulin (DFL)		[112]
LDPE, PET, uPVC		LDPE (average particle diameter of 509 ± 221 μm), PET (161 ± 79 μm) and uPVC (159 ± 4 3 μm)			Lepidium sativum and Sinapis alba.	Pesticides (alachlor, clofibric acid, diuron, pentachlorophenol)		[113]
PET	1 g of MPs in 20 mL of both naphthalene and phenanthrene	2000 μm		Rhizosphere soil	Wheat	Naphthalene and phenanthrene	Naphthalene 0.018 mg kg−1 & phenanthrene 0.00011 mg kg−1	[114]
PE	0.5%, 1%, 2%, 5%, 8% w/w	200–250 μm	6.43	Yellow brown, organic matter content: 2.04% Pot experiment (contained 500 g soils)	Wheat	Phenanthrene	100 mg kg−1	[115]
PE	2% w/w	550 μm		Farmland soils Field experiment (greenhouse)	Zea mays L.	Phenanthrene	150 mg kg−1	[116]
PE	20 mg L−1	50–100 μm		Rhizosphere soil in hydroponic conditions. Field experiment	Oryza sativa L.	14C-pyrene		[117]
PE, PLA	2%	50–100 µm	7.41	0–20 cm depth, Organic matter: 29.0 g kg−1, Cation exchange capability: 8.96 cmol+ kg−1 Pot experiment	Allium ascalonicum	3,5-dichloroaniline (3,5-DCA)	10 mg kg−1	[107]
PE, PVC	1%, 5%, 10%, and 20% by soil dry weight	<125 μm	5.7	0–20 cm depth, organic C content: 3.5%, total N: 0.26% ST: Silty clay loam Pot experiment	Wheat: Triticum aestivum L.	Herbicide (simazine)	1%, 5%, 10% and 20% of soil w/w	[118]

below presents a concise summary of different soil types that contain plastics of diverse forms and dimensions, along with a range of other organic substances that together contribute to pollution. The percentage distribution of published articles is presented in Figure 2. While not statistical, Figure 2 offers a visual synthesis of the conceptual relationships recognized among the primary themes.

The literature that has been reviewed reveals significant trends concerning the types of polymers that are most often studied in relation to organic contaminants. As illustrated in Figure 2 (left), PE is the most frequently examined MP, constituting 38.2% of the articles reviewed. Following this, polyester, LDPE, PS, PET, and PLA are noted with lower percentages, which range from 6.2% to 14.1%. These findings indicate that research has predominantly focused on the most prevalent and enduring polymers, while other categories of MPs have been relatively less investigated.

Simultaneously, the examination of organic compounds linked to MPs (Figure 2, right) indicates that pesticides represent the most thoroughly researched group, making up 58.3% of the total studies. PAHs and phthalates are also present with significant frequency (17.9% and 16.8%, respectively), while other categories of organic contaminants are less frequently represented. This distribution highlights a research emphasis on compounds known for their environmental persistence and toxicity, underscoring their interactions with MP particles in terrestrial environments.

6. Phytoremediation of Soils Contaminated Microplastics Encapsulated Heavy Metals

Inorganic pollutants mainly comprise heavy metals, which exist largely in ionic form both on soil particle surfaces and dissolved in the soil solution [119]. Heavy metals are defined as metallic elements with an atomic density greater than 5 g/cm³ [120]. They are divided into two categories: trace elements, essential in small amounts for the normal biological functions of plants and animals (e.g., Cu and Zn), and toxic elements, such as Cd, Pb, and Hg [119,120]. Although trace elements are crucial for growth at low concentrations, they can become harmful if their levels exceed specific thresholds, which differ depending on the metal and organism. As a result, the term Potentially Toxic Elements (PTEs) has gained prominence in recent decades [6,119,120].

Heavy metals constitute one of the most significant categories of pollutants due to their toxicity, potential for bioaccumulation, and challenges associated with their removal from the environment [121,122]. The primary representatives of this group are Pb, Cd, Hg, As, and Cr, which predominantly arise from human activities such as industrial processes, mining operations, and the combustion of fossil fuels [123,124]. A multitude of studies has underscored the detrimental impacts of these metals on human health, which include neurotoxic effects, damage to the kidneys, and the potential for cancer development, in addition to their harmful effects on ecosystems [125].

The management and remediation of heavy metals in the environment presents significant challenges due to their stability and capacity to convert into various chemical forms that exhibit differing levels of toxicity and mobility [126]. Methods for physical and chemical removal, including sedimentation, precipitation, and chemical immobilization, tend to be energy-intensive and expensive [127]. Consequently, biological remediation, especially phytoremediation, has surfaced as a more sustainable and economically viable alternative [128].

Heavy metal phytoremediation utilizes the capability of specific plants to either accumulate or stabilize metals within their root or shoot tissues [129]. Certain species, including Brassica juncea, Helianthus annuus, and Pteris vittata, have been thoroughly researched for their ability to absorb Pb, Cd, and As, respectively [130,131,132]. The success of phytoremediation is influenced by various factors, including the type of metal, the bioavailability of metals in the soil, physicochemical conditions, and the selection of plant species [133].

Despite advancements, the widespread implementation of phytoremediation encounters obstacles, including long remediation times and limited efficiency due to metal toxicity to plants themselves [134]. Consequently, strategies for enhancement that involve microbial collaboration (phytomicrobiome), the application of biostimulants, and genetic enhancements are currently prominent areas of research focused on improving the efficiency of phytoremediation [135,136]. In

Table 2. Summary table of MPs encapsulated inorganic pollutants, in different soil environments.

Type of Plastic	Concentration of Plastics	Dimensions of the Plastics	Soil pH	Other Characteristics of Soil	Sampling Area	Plant	Inorganic Pollutants	Concentration of the Pollutants	Reference
PE	2.5% and 5% w/w	<5000 μm	Alkaline soil	Soil Texture (ST): Clay Loam	Rural and urban	Lettuce	Cd and Zn		[17]
PE	0.001%, 0.01%, or 0.1% PE-MPs	Average size: 293 μm	7.38	Organic matter content of 2.39%, total nitrogen (N) content of 1.03 g kg−1, total phosphorus (P) content of 0.56 g kg−1	Northeast Forestry University (Harbin, China)	Brassica napus L.	Cu2+ and Pb2+	Cu2+: 50 and 100 mg/kg, Pb2+: 25 and 50 mg kg−1	[137]
Polystyrene (PS)	100 and 1000 mg kg−1	MPs (PS-MPs) and NPs (PS-NPs)	6.3	SOM: 35.3 g kg−1, TN: 4.1 g kg−1, TP: 2.9 g kg−1	A vegetable field in Liaoyuan, China, characterized by the long-term use of organic fertilizer	Lettuce: Lactuca sativa L.	Cu, Zn and Pb, Cd	The concentrations of Cu, Zn, Pb, and Cd in the soil are measured at 82.00, 174.84, 42.08, and 0.20 mg kg−1, respectively	[138]
Polyethylene terephthalate (PET), polylactic acid (PLA), and polyester (PES)	3 doses (0, 0.2%, and 2%, w/w) of PET and PLA, and 2 doses (0% and 0.2%) of PES	PET, PLA: average particle size ~51 µm; Fibrous PES: average length of 6000–10,000 μm and an average diameter of 10–25 µm	5.63	0–30 cm depth, NH4+-N 1.71 mg kg−1, NO3−-N 40.2 mg kg−1, available P 9.82 mg kg−1, available K 53.6 mg kg−1, organic matter 11.8 g kg−1, Cd 0.03 mg kg−1	Nanquan Town, Jimo District, Qingdao, Shandong Province, China	Rice	Cd	0 and 5 mg Cd kg−1 soil	[139]
Polypropylene (PP), polyamide (PA), polyethylene (PE), Polyethylene terephthalate (PET) and polyethylene vinyl acetate (PEVA)	D1 = 1 mg kg−1 of soil and D2 = 100 mg kg−1 of soil.	Per 1 mg of plastic powder, MPs size distribution was 15.23% > 3 μm, 35.56% 3 μm–1.2 μm and 49.21% 1.2 μm–0.45 μm.		0–15 cm depth	Jebel Ressass mine, north Tunisia	Medicago sativa	Cu, Zn, Pb, Cd and Ni.		[140]
PE	1.2 kg of soil in each pot: 2 g of 0.5 μm PE, 4 g of 0.5 μm PE, 2 g of 1 μm PE, and 4 g of 1 μm PE	0.5 μm and 1.0 μm			Restoration area of the Siding Pb-Zn mine in Liuzhou, China	Bidens pilosa L.	Cd and Pb		[141]
LDPE, PET and PP		1 × 1 cm squares (mesoplastics)		0–20 cm depth	Przychody, Jelnica and Dąbrowa Górnicza in Polland	Lepidium sativum	Cd, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, and Zn		[142]
PLA and PP	1% MPs (PP2/PLA2, mass/mass) and 5% MPs (PP3/PLA3, mass/mass) across three different levels of Cd	The material was filtered using a 500 μm mesh	7.23, 7.22 and 7.18	0–20 cm depth. Cation exchange capacity (CEC): 20.7, 21.0, and 22.3 c mol kg−1 Dissolved organic carbon (DOC): 1.69, 1.57, and 1.45 g kg−1	Qingdao, northern China	Pak choi	Cd	The total Cd in the sampled soils were 0.49, 2.52, and 10.1 mg kg−1	[143]
PP	100 mg L−1	6.5 and 13 µm		Petri plates experiment		Oryza sativa L. seeds	Cd	Cd-5 mg kg−1, 13 µm PP100 mg kg−1, 6.5 µm PP- 100 mg kg−1, 13 µm PP + Cd- 100 mg kg−1 + 5 mg kg−1, 6.5 µm PP + Cd100 mg kg−1 + 5 mg kg−1 in Petri plates	[144]
PS	1.4 g kg−1 soil	T1 = 106 µm, T2 = 50 µm, and T3 = 13 µm	Highest value (T3): 7.79; Lowest value (for day 0): 7.37	Day 0: EC (µS cm−1): 763.6, OM (%): 1.01, TP (mg kg−1): 104.42, TN (mg/kg): 449.33, NH3 (mg kg−1): 2.5. Pot experiment	Tongling, central part of Anhui Province, Southeast China	Lettuce (Lactuca sativa)	HMs: Cd, As, Cu, Zn, Pb		[145]
HDPE (Carbon black + uv additive)	0.2 g kg−1	2000–5000 μm and 20 µm thick	5.61	Volcanic ash-derived soil (Andisol); Soil–sand; 1:1 = Vol:Vol. 82.2 mg kg−1 of available nitrogen, 47.6 mg kg−1 of available Olsen P, 220.6 mg kg−1 of available potassium, 17 cmolc kg of exchangeable Ca, 3 cmolc kg−1 of exchangeable Mg, 3.41% organic matter. Experiment: Clay pots	The plants came from Llahuen Nursery, Llahuen Farm in Huelquen Paine, Metropolitan Region, Chile	Strawberry plants (Fragaria x ananassa Duch)	Cd	0.5 mg kg−1	[146]
PP		50 and 100 µm		Agricultural soil		Wheat	Cd	40 mg kg−1	[147]

below, published data from journals are presented, referring to soils containing plastics of various chemical types and dimensions, as well as heavy metals, all acting cooperatively as pollutants. The percentage distribution of published articles is presented in Figure 3. While not statistical, Figure 3 offers a visual synthesis of the conceptual relationships recognized among the primary themes.

A review of the pertinent literature reveals that most studies have concentrated on a narrow spectrum of polymer types. As depicted in Figure 1 (left), PP and PET are the most commonly studied MPs, comprising 24.3% and 22% of the articles reviewed, respectively. Other polymers, including LDPE, HDPE, and PS, have attracted relatively less focus; nevertheless, 18.1% were broadly categorized as PE rather than being specifically recognized as LDPE, among others [6]. This observation reflects that these polymers are of particular interest within the context of microplastic research.

The distribution of heavy metals documented in the examined studies (Figure 1, right) indicates a significant focus on Cd, which constitutes 55.9% of the total investigations. Pb, Zn and Cu are also frequently mentioned, whereas Ni, Mn, and As are notably underrepresented. These findings indicate that some elements have attracted more focus than others.

7. Effects on Soils and Plants

According to the scientific articles (Table 1 and Table 2), various findings have been reported regarding the impacts on soils and, consequently, on plants.

7.1. Organic Pollutants

Based on Wan et al. [105], the management of plastic waste leads to organophosphate ester (OPE) pollution in soils, affecting not only the treatment locations but also the surrounding agricultural lands. Specifically, a total of eight OPEs were identified in soils from the treatment sites, with concentrations ranging from 38 to 1250 ng/g on a dry weight basis [105]. Among these, tributoxyethyl phosphate and tri(2-chloroethyl) phosphate were found to be the most prevalent. Meanwhile, wheat plants absorbed organic pollutants from the soil and accumulated various compounds at different levels depending on their hydrophobic properties [105].

In a recent study by Chen et al. [110], examining the effects of polyester MPs in combination with naproxen, MPs significantly increased soil moisture depletion rates. However, no effects of MPs or naproxen were observed on soil pH or electrical conductivity [110]. The presence of 7% polyester MPs in contaminated soil led to a marked reduction in total aboveground biomass and coarse root biomass [110]. Additionally, both 0.03% and 7% polyester MP-contaminated soils significantly reduced leaf count and average leaf size. Naproxen, whether applied alone or in combination with MPs, did not affect plant growth or development [110].

Using a specific type of plastic, Abbasi et al. [114] reported that when PET particles come into contact with naphthalene and phenanthrene in soil, they adsorb these substances. The typical level of adsorbed naphthalene on PET exceeds that of phenanthrene [114]. The effects on plants (wheat) showed that PET particles exhibited an adsorption capacity of 96.89% for naphthalene and 27.27% for phenanthrene, while subsequently desorbing 21.65% of the adsorbed naphthalene and 29.17% of the phenanthrene in a simulated wheat root exudate. The transfer of PAHs into the rhizosphere via PET particles was also observed [114].

PET, along with LDPE and uPVC, in combination with two plants (Lepidium sativum and Sinapis alba), was examined by Miranda et al. [113]. Exposure to ozone or the effects of urban weathering enhanced the sorption capacity of MPs in soil, while most of the substances examined showed a higher affinity for LDPE and uPVC compared to PET [113]. The organic micropollutants adsorbed onto MPs exhibited either negligible or minimal phytotoxic effects [113].

Under field conditions, LDPE in combination with vegetables was studied by another scientific team [104]. All soil samples were found to contain plastic residues, approximately 2 × 10³ particles per kg and around 60 cm² per kg. Soils subjected to conventional farming contained more than four pesticide residues. Bacteria showed heightened susceptibility to contamination from plastics and pesticides [104]. Plastic debris and pesticide residues played a significant role in altering variations within the soil microbiome. Moreover, fungal communities exhibited greater sensitivity to soil physicochemical properties than to the influence of pesticides or plastics [96]. In contrast, bacterial communities responded only to the presence of the fungicide boscalid [104].

Testing PE, Zea mays L., and phenanthrene in combination with laccase and maize [116] resulted in the elimination of 83.47% of phenanthrene from the soil. Laccase enhanced the biosafety of the bioremediation process. Moreover, PE MPs notably impeded the elimination of soil phenanthrene by 10.88% and reduced the translocation factor of phenanthrene in maize by 87.72%, compared to the phenanthrene + laccase treatment. Laccase decreased the accumulation of phenanthrene in maize. Additionally, MPs reduced laccase activity and decreased the relative abundance of certain PAH-degrading bacteria in the soil [116].

Using PE, Oryza sativa L., and ¹⁴C-pyrene, Tian et al. [117] found that the concentration of pyrene associated with PE MPs in rice was lower than that of freely dissolved pyrene. The movement of pyrene was restricted due to its adsorption onto PE MPs [117]. The biological effects showed that: (1) the adsorption of MPs limited the transfer of pyrene from the cell wall to the organelles; (2) pyrene associated with PE MPs exhibited reduced toxicity to rice seedlings compared to its freely dissolved form, as indicated by measurements of biomass, chlorophyll content, and oxidative stress levels; and (3) the bioaccumulation and toxicity of pyrene in plants were reduced when associated with MPs, due to limited mobility caused by adsorption [117].

Based on recent research [107], the presence of PE and PLA MPs enhanced the soil’s adsorption capacity for 3,5-DCA and extended its degradation half-life by 6.24 days and 16.07 days, respectively [107]. The levels of 3,5-DCA residues in PLA-microplastic-treated soil were consistently higher than those in PE-MP-treated soil. Both MPs mitigated the adverse effects of 3,5-DCA on the root length and fresh weight of chives, whereas PE MPs exhibited a beneficial, dose-dependent effect on the levels of photosynthetic pigments in chive leaves [107].

Recently, Shi et al. [108] reported that PE MPs enhanced the biomass production of native plant species under conditions of elevated nutrient availability, while exerting minimal impact on the growth of non-native species. The non-native plants exhibited a decrease in root mass fraction (RMF) with increased nutrient levels, as well as an increase in specific leaf area (SLA) in response to the addition of nutrients and MPs [108]. Pesticide residues in the soil significantly reduced the RMF across all three studied species; however, no significant differences were observed between the responses of native and non-native species. Although alien species adjusted their functional traits more rapidly, native species experienced greater growth gains when exposed to both fertilization and MPs [108].

A few years ago, Liu et al. [115] demonstrated that PE MPs at concentrations above 1% promote the elongation of wheat roots. The simultaneous presence of PE MPs and phenanthrene leads to reduced phenanthrene accumulation in wheat roots and leaves, compared to treatments with phenanthrene alone [115]. The activity of antioxidant enzymes in wheat roots increases with rising concentrations of PE MPs within the 0–5% range. However, both phenanthrene and high concentrations (8%) of PE MPs cause damage to the antioxidant system in wheat roots [115]. The presence of PE MPs alone damages the photosynthetic system of wheat leaves, while their combination with phenanthrene exacerbates this damaging effect. Consequently, the combined presence of PE MPs and phenanthrene results in greater overall harm to wheat growth [115].

The presence of both PE and PVC led to a reduction in the mineralization of ¹⁴C-labeled simazine in soil, as evidenced by the decreased cumulative release of ¹⁴CO₂ [118]. The half-life of simazine was found to be prolonged in the presence of MPs, with only minor differences observed among different types of MPs. The accumulation of MPs in soil inhibited the degradation of herbicides, which in turn caused the persistence of herbicide residues [118]. On the other hand, the fungi-to-bacteria ratio in the soil rose by 9% to 18% following the addition of 1% MPs, whereas enzyme activities related to carbon cycling diminished by 20% to 46% in soil treated with PVC compared to the control group. Enzyme activities exhibited a negative correlation with the half-life of simazine when combined with PVC [118]. Consequently, the authors attributed the suppressed degradation of simazine to alterations in the microbial community structure, specifically an increased ratio of fungi to bacteria, along with diminished enzyme activities [118].

Ju et al. [111] investigated the effects of PBAT, LDPE, and PLA MPs, along with the pesticides chlorpyrifos (CPF), difenoconazole (DIF), and their mixture, on Raphanus sativus. They found that the presence of aged LDPE MPs resulted in a 44% decrease in radish root biomass, while aged biodegradable MPs led to a 59% decrease [111]. Additionally, older MPs increased CPF accumulation in radish roots compared to newer MPs when a single pesticide was applied. Furthermore, the presence of LDPE MPs caused higher CPF accumulation in roots when mixed pesticides were applied, compared to the application of a single pesticide [111].

A different combination of PS MPs (carboxyl PS (PS-COO⁻), neutral PS (PS), and amino PS (PS-NH₃⁺) was used by Nie et al. [112]. In the experiment, Lycopersicon esculentum and the antiviral pesticide dufulin (DFL) were included. The impact of differently charged PS MPs on the fate of DFL in hydroponics varied. In contrast to DFL alone, the combination of PS MPs with DFL resulted in a decrease in both the biomass and yield of tomatoes. The BCFs of DFL in tomato exhibited a decreasing trend as follows: control > PS-NH₃⁺ > PS > PS-COO⁻ [112]. PS MPs significantly impeded the movement of DFL from the roots to the above-ground portions of the tomato plant [112]. PS-COO⁻ markedly reduced the dietary risk associated with DFL in the hydroponic tomato system [112].

Using fluorescent PS MPs, Glycine max L. Merrill (soybean), and phenanthrene, Xu et al. [106] found that MPs reduced the absorption of phenanthrene in soybean roots and leaves by causing damage to the roots. MPs inhibited root activity and decreased the relative abundance of microorganisms in the rhizosphere soil, resulting in reduced uptake of phenanthrene compounds by soybean roots [106]. Simultaneous exposure to MPs and phenanthrene exhibited greater genotoxic effects compared to exposure to either MPs or phenanthrene alone [106]. Moreover, MPs amplified the detrimental effects of phenanthrene at both cellular and molecular levels, while also influencing the kinetics and toxicity of phenanthrene in soybean plants [106].

Gao et al. [109] investigated the effects of PS and dibutyl phthalate (DBP) on lettuce. Treatments with PS and DBP individually resulted in reduced lettuce biomass, increased production of superoxide (O₂⁻) and hydrogen peroxide (H₂O₂), and caused oxidative damage along with defensive responses in both leaves and roots [109]. Compared to treatments with DBP alone, the presence of two different PS sizes significantly decreased the accumulation of DBP and monobutyl phthalate (MBP) in both lettuce leaves and roots. However, this combination notably increased the accumulation of O₂⁻ and H₂O₂, leading to biochemical and subcellular damage within the plants [109]. Molecular docking analysis revealed that DBP and MBP can interact with superoxide dismutase (SOD) through secondary interactions such as hydrogen bonding, π-π stacking, alkyl conjugation, and van der Waals forces, potentially altering the structure and function of SOD [109]. Furthermore, small-sized PS (SPS) exhibited slightly greater negative effects on the biochemical and subcellular properties of lettuce compared to large-sized PS (LPS) [109].

7.2. Heavy Metals

On the other hand, PS (MPs and NPs) in combination with heavy metals (Cu, Zn and Pb, Cd) and a plant (Lactuca sativa L.) were tested by Xu et al. [138]. The presence of micro- and nanoplastics (MNPs) enhanced the absorption of Cu, Zn, Pb and Cd in lettuce. Biomarkers and gene expression analyses indicated that a dosage of 1000 mg/kg of nanoparticles resulted in more significant damage to the lettuce plants by the conclusion of the study [138]. Metabolomic analysis revealed that nanoparticles disrupted the metabolism of ATP-binding cassette transporters (ABC transporters) and the signaling pathways of plant hormones in lettuce roots, leading to an enhanced absorption of heavy metals by the lettuce. The interference of MNPs-induced stress disrupted the normal metabolic functions of the roots. Additionally, the key metabolites in the roots of lettuce subjected to treatment with MNPs were identified [138].

Lactuca sativa L. and PS MPs were tested by another recent research [145] using Cd, As, Cu, Zn, and Pb in their experiments. Their study revealed both synergistic and competitive interactions among soil physicochemical properties. The heavy metals did not solely affect metabolic functions, likely due to the significant presence of arbuscular mycorrhizal fungi (AMF) species in the control and larger microplastic treatments [145]. The application of small MPs at the end of the treatment notably increased the diversity of both bacterial and fungal populations. PS MPs, varying in size and shape, as well as exposure time, significantly influenced microbial diversity [145]. A reduction in microplastic size contributed to a decline in AMF abundance and an increase in bacterial and fungal pathogens, particularly within the rhizosphere community associated with smaller MPs. AMF appeared to support metabolic functions and demonstrated a degree of tolerance to certain heavy metals, suggesting some resistance to metal toxicity [145].

PE MPs, Cd and Zn with lettuce were examined by a different scientific team [17]. Both metals and MPs are resistant to rapid and efficient degradation. The incorporation of PE MPs led to a reduction in soil pH [17]. Moreover, MPs increased the concentrations of both metals that were bioavailable. The metal with lower toxicity was more accessible to plants. The occurrence of PE MPs in soil samples from both rural and urban areas led to an increased accumulation of metals in the roots of lettuce compared to the edible portions of the plants above ground [17].

PE with different heavy metals (Cu²⁺ and Pb²⁺) and the plant (Brassica napus L.) were used by Jia et al. [137]. The pollutants resulted in adverse impacts on self-regulation mechanisms, including an increase in MDA levels and a decline in plant quality. An increased concentration of PE MPs in the soil further intensified the harmful impacts of heavy metals by enhancing their accumulation within living organisms [137]. The presence of 0.1% PE MPs in soil resulted in an elevated concentration of heavy metals in rape plants. Specifically, the levels of Cu²⁺ and Pb²⁺ in the plants subjected to combined pollutant treatments were found to be 1.1 and 1.08 times higher, respectively, compared to those in treatments involving single heavy metals (Cu100 or Pb50) [137].

PE with a different combination with a plant (Bidens pilosa L.) and heavy metals (Cd and Pb) were studied by He et al. [141]. MPs increased the levels of reactive oxygen species (ROS), enhanced lipid peroxidation, and elevated the activities of antioxidant enzymes. Changes in microbial composition were linked to the ability of plants to tolerate stress and their capacity for nutrient absorption [141]. PE MPs impeded the growth of Bidens pilosa L. in soil that is contaminated with Cd and Pb. Additionally, improved tolerance to oxidative stress, augmented biosynthesis of secondary metabolites, and a greater occurrence of stress-resistant phenotypes were observed under conditions of increased concentrations of PE and reduced particle sizes [141].

Working with HDPE (carbon black + UV additive), strawberry plants and Cd Pinto-Poblete et al. [146] found that there was a positive relationship between Cd and microbial biomass. The presence of HDPE and HDPE combined with Cd influenced various growth parameters in plants, including height, stem diameter, biomass production, root volume, and surface area [146]. The combination of Cd and HDPE resulted in a reduction in both the total number of fruits and biomass produced per plant [146]. The underlying mechanisms involved include the inhibition of chlorophyll synthesis and its stable association with proteins [146].

A different type of MPs (PP) in combination with Cd and wheat were used by Han et al. [147]. The growth of both wheat roots and shoots was adversely affected by Cd, whether applied alone or in conjunction with PP microplastic treatments [147]. The antioxidant enzyme system in wheat seeds and seedlings exhibited an increase when exposed to Cd alone; however, the activities of superoxide dismutase, catalase, and peroxidase diminished under conditions of combined pollution [147].

Similarly, PP, Cd and Oryza sativa L. seeds were studied by Kaur et al. [144]. The interaction between PP and Cd demonstrated that a concentration of 13 µm PP combined with Cd exhibited an antagonistic effect on the growth of rice seedlings, whereas a concentration of 6.5 µm PP combined with Cd resulted in a synergistic effect [144]. The application of PP and Cd individually on rice seedlings significantly suppressed various germination indicators [144]. However, the simultaneous presence of PP and Cd resulted in a partial alleviation of the overall toxicity [144]. The application of both contaminants simultaneously markedly reduced root length, stem length, fresh weight, and the activities of the enzymes catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) in rice seedlings; however, there was no notable impact on dry weight [144].

PP as well as PLA plastics were correlated by Liu et al. [143] in combination with Pak choi and Cd. The findings indicate that both categories of MPs had a substantial effect on plant biomass and biomarker levels at all three concentrations of Cd [143]. The extent of the impact was influenced by the type and dosage of MPs, which led to a decrease in soil pH and CEC, while simultaneously enhancing the levels of DOC, microbial biomass carbon, and nitrogen in the soil [143]. PP demonstrated a more significant inhibition of root growth and increased phytotoxicity at elevated concentrations of 1% and 5% in comparison to PLA. PLA exhibited a lesser impact on plant phytotoxicity, Cd availability, and soil characteristics in comparison to PP. MPs enhanced the uptake of shoot Cd by modifying the physical and chemical properties of the soil, as well as the microbial characteristics [143].

Different plastic samples (LDPE, PET, and PP), Lepidium sativum, and Cd, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, and Zn were used by a scientific team [142]. Only LDPE among the plastics demonstrated adsorptive properties for metals [142]. The leaching of metals was observed to increase in solutions characterized by low pH, high dissolved organic carbon (DOC), and elevated electrical conductivity (EC). The extracts of LDPE demonstrated a higher level of toxicity for the plant compared to those of PET or PP [142].

The five plastics [PP, polyamide (PA), PE, PET, and polyethylene vinyl acetate (PEVA)] with Medicago sativa and Cu, Zn, Pb, Cd, and Ni were examined recently [140]. The impact of MPs is influenced by their concentration and the extent of heavy metal pollution [140]. MPs contribute to the accumulation of heavy metals in plants [140]. MPs elevate oxidative stress levels in plants cultivated in polluted soils. MPs disrupted agronomic parameters and the photosynthetic processes of the plants [140].

Using rice, Cd, and the plastics PET, PLA, and PES, Liu et al. [139] found that MPs can affect Cd accumulation by altering soil properties. MPs enhanced the bioavailability of cadmium while simultaneously reducing its accumulation in rice seedlings. The application of 2% PLA resulted in the most significant changes in soil characteristics, plant development, Cd accumulation, and arbuscular mycorrhizal fungi communities; however, it did not exhibit any synergistic interaction with Cd. MPs can influence rice productivity and Cd accumulation by modifying soil properties, enhancing nutrient absorption, and altering root mycorrhizal communities [139]. MPs affected the diversity and community structure of arbuscular mycorrhizal fungi, influenced by the type and concentration of the MPs, as well as the presence of co-existing Cd. Biodegradable PLA MPs, which are considered environmentally friendly, may exhibit greater phytotoxicity compared to traditional MPs. Biodegradable PLA has the potential to produce intermediate metabolites and rapidly release additives, which can ultimately affect the sporulation of arbuscular mycorrhizal fungi (AMF) and their community structure [139].

7.3. Thematic Overview and Synthesis of Literature

In general, the existing literature indicates that MPs considerably influence soil–plant interactions by regulating the mobility, persistence, and bioavailability of different pollutants. However, the mechanistic understanding is still incomplete, as the majority of research concentrates on isolated plant–pollutant systems in controlled laboratory settings. This synthesis is crucial to determine whether MPs predominantly function as mitigators or amplifiers of chemical stress within terrestrial ecosystems.

7.3.1. General Patterns and Mechanisms of Interaction

Recent studies indicate that the interaction between MPs and co-contaminants, such as organic pollutants, pesticides, and heavy metals, consistently modifies soil physicochemical properties, pollutant bioavailability, and plant physiological responses. While the majority of research agrees that MPs function as both sorbents and carriers for contaminants (e.g., [105,113,114]) their impact on plant uptake and toxicity is context-dependent, influenced by factors such as MP type, size, concentration, and the characteristics of co-pollutants. In general, PE and PET dominate the research landscape due to their widespread occurrence, whereas biodegradable MPs (PLA, PBAT) produce distinct degradation products that may exacerbate phytotoxicity [111,139]. Figure 4 provides a summary of the interactions among MPs, heavy metals, and organic pollutants concerning adsorption, competition, and plant uptake.

7.3.2. Effects of MPs Combined with Organic Pollutants

Research on MPs containing organic pollutants has identified two primary trends: (1) MPs frequently adsorb and reduce the mobility or bioavailability of hydrophobic organic compounds (for instance, PAHs like phenanthrene, pyrene, and naphthalene), which consequently reduces direct uptake by plants and their associated toxicity [114,117] and (2) under specific circumstances, MPs hinder microbial degradation processes, leading to the persistence of pollutants in soil environments [110,115]. While these pollutants may accumulate to a lesser extent in plants, the combined impact of MPs and chemicals often induces oxidative stress responses and modifies antioxidant enzyme activity, as evidenced in wheat and maize [106,115]. Therefore, the overall findings suggest that MPs play a dual role—acting as sinks for pollutants that decrease bioavailability while simultaneously serving as stressors that disrupt the physiological equilibrium of plants.

7.3.3. MPs and Heavy Metals: Synergistic and Antagonistic Effects

When co-exposed to heavy metals such as Cd, Pb, Cu, and Zn, MPs frequently alter the mobility and uptake of these metals by modifying soil pH, cation exchange capacity (CEC), and the composition of microbial communities [137,141,143]. The majority of studies indicate an increased accumulation of metals in plant roots and heightened oxidative stress, implying a synergistic toxic effect [148]. Nevertheless, certain combinations, such as small PP particles with Cd in rice, exhibit antagonistic interactions that diminish overall toxicity [144]. Notably, the size and composition of MPs are critical factors: smaller particles tend to increase microbial stress and reduce the abundance of arbuscular mycorrhizal fungi [149], whereas biodegradable MPs significantly influence soil nutrient dynamics compared to conventional types [139]. In summary, the existing literature suggests that MPs function as modulators of heavy metal bioavailability and plant stress responses, at times exacerbating and at other times alleviating toxic effects. Figure 5 summarizes conceptual diagrams illustrating synergistic and antagonistic interactions that consider not only heavy metals but also their combined effects with organic pollutants.

7.3.4. Influence of Microplastics–Pollutant Complexes on Plant Metabolic Functions

The simultaneous presence of MPs and co-contaminants, including pesticides and heavy metals, can modify their environmental behavior and bioavailability, thus affecting plant metabolic and physiological processes [149]. MPs serve not only as passive sorbents but also as active agents that influence pollutant dynamics and plant metabolic functions [150,151]. Their presence in soil modifies the bioavailability of both organic pollutants and metals, consequently impacting plant physiology and biochemical responses. For example, LDPE and PVC MPs have been found to extend the persistence of pesticides by inhibiting microbial enzyme activity [118], whereas PE and PP MPs can decrease soil pH and increase metal solubility, resulting in enhanced root uptake and oxidative stress in Brassica napus and Bidens pilosa [137,141,143]. In lettuce, the simultaneous exposure to PS MPs and heavy metals (Cu, Zn, Pb, Cd) altered the activity of ATP-binding cassette transporters and hormonal pathways, indicating a direct metabolic effect on roots [138,145]. Furthermore, the combined exposure to MPs and organic pollutants (such as phenanthrene and naproxen) modified antioxidant defense mechanisms and photosynthetic efficiency in wheat, rice, and maize [106,116,117].

While these species do not qualify as conventional hyperaccumulators, their responsiveness to interactions with MPs—pollutants—underscores possible consequences for edible crops [152]. These interactions may influence oxidative metabolism, the production of secondary metabolites, and nutrient absorption, which in turn can impact plant productivity and the quality of food. Additional research is required to clarify the mechanistic connections between MP-mediated sorption processes and the metabolic regulation of crop plants in co-contaminated environments.

8. Key Challenges and Emerging Strategies for Phytoremediation Under Co-Contamination Conditions

To discuss and better understand the complex interactions found in co-contaminated soils, this review utilizes a hierarchical framework that outlines the effects arising from MP characteristics to plant responses. Initially, the type of MP, such as PE or PS, affects the physicochemical properties of the soil, including pH, porosity, and water retention [95]. These changes subsequently impact the bioavailability of co-contaminants, including heavy metals and organic pollutants, by altering sorption and desorption dynamics as well as microbial activity. Ultimately, variations in pollutant availability lead to diverse physiological and molecular responses in plants, which include mechanisms for stress tolerance, pathways for uptake, and changes in gene expression. This structured approach enhances the understanding of how MPs influence pollutant behavior within soil–plant systems and highlights critical knowledge gaps that require further exploration.

8.1. Key Bottlenecks in Co-Contaminant Phytoremediation

The presence of MPs in terrestrial ecosystems poses a significant environmental challenge, particularly when they are found alongside organic pollutants and heavy metals. A key obstacle in the phytoremediation of soils contaminated with multiple substances is the unpredictable interactions between MPs and these co-existing pollutants. MPs can function as both facilitators and hindrances: they can enhance the longevity of organic pollutants and heavy metals by adsorbing them, while simultaneously influencing their bioavailability to plants in varying ways, depending on factors such as polymer type, size, weathering, and aging [153,154]. This complexity makes it difficult to forecast plant uptake and the success of remediation efforts. For instance, research has revealed conflicting outcomes, where MPs decreased phenanthrene uptake in soybean due to root damage [106], whereas in other instances, they increased heavy metal absorption in lettuce through root metabolic disruption [138].

A second challenge lies in the physiological stress MPs impose on plants, which can compromise their remediation potential [80]. The oxidative stress induced by MPs, along with impaired photosynthesis and decreased biomass—observed in crops such as lettuce, wheat, rice, and radish—directly obstructs the capacity for phytoremediation [103]. Concurrently, MPs alter the structures of microbial communities (for instance, by increasing the ratios of fungi to bacteria) and affect the enzymatic activities that are crucial for the degradation of organic pollutants, thus disrupting the remediation axis involving soil, plants, and microbes [136,141,155]. This complicates the task of isolating the role of plants in the removal of pollutants, particularly in scenarios where MP loading conditions are uncontrolled [156].

Ultimately, the absence of standardized methodologies across various studies—such as differing pot sizes, soil types, MP concentrations, plant species, and combinations of pollutants—restricts the ability to compare and scale findings effectively [80]. In the absence of unified metrics for assessing co-contaminant dynamics, it becomes difficult to formulate transferable recommendations or create decision-support tools [157]. Additionally, validation at the field scale is still limited, as most data is obtained from controlled pot experiments that fail to account for real-world variability (for instance, hydrological fluxes, MP aging, or microbial succession). These elements together hinder the advancement of robust, evidence-based phytoremediation protocols for complex polluted environments. In specific, methodological variations, especially between regulated pot experiments and more diverse field studies, have a considerable impact on the results of phytoremediation research. Pot experiments enable meticulous control over environmental factors and contaminant concentrations, yet they may oversimplify the intricate interactions between soil and plants. On the other hand, field studies offer realistic conditions but introduce variability that can obscure mechanistic understanding. To progress in this field, it is essential to establish standardized protocols that strike a balance between control and ecological relevance, which should include consistent pollutant dosing, criteria for plant selection, and timelines for monitoring. Such standardization will improve reproducibility and aid in making comparisons across different studies.

8.2. Aged MPs vs. Pristine MPs

The effects of aging on MPs significantly modify their physicochemical characteristics, which in turn affects their ability to absorb and release pollutants in the environment [158]. Aged MPs generally show increased surface roughness, oxidation, and the development of functional groups such as hydroxyl, carbonyl, and carboxyl groups [159]. These alterations enhance their adsorption capacity for both organic and inorganic contaminants when compared to pristine MPs [111]. Such modifications can result in a stronger attachment of pollutants, which may reduce their bioavailability to soil organisms and plants, while also potentially promoting longer-term retention and secondary release under varying environmental conditions [160,161]. Consequently, it is essential to comprehend the differing behaviors of aged versus pristine MPs to accurately evaluate pollutant dynamics in co-contaminated soils and to formulate effective phytoremediation strategies.

Recent research indicates that aged MPs may serve as more efficient carriers for pollutant transport due to their altered sorption characteristics and interactions with soil matrices [162]. For example, aged MPs have demonstrated a greater capacity to sorb elevated levels of PAHs and heavy metals in comparison to their pristine counterparts, thereby modifying the distribution and mobility of these pollutants [158]. Additionally, the desorption kinetics of pollutants from aged MPs can vary, with certain pollutants showing slower release rates, which influences their availability for plant uptake or microbial degradation [163]. Integrating these insights into phytoremediation studies is crucial for enhancing the prediction of contaminant behavior and customizing remediation strategies that consider the dynamic nature of MPs in the environment.

8.3. Comparative Assessment: Phytoextraction vs. Phytostabilization in Co-Contaminated Soils

Phytoextraction and phytostabilization represent the two most extensively researched techniques in the field of phytoremediation; however, their effectiveness in soils contaminated with MPs has not been sufficiently explored [20,31]. Phytoextraction refers to the process of absorbing and relocating contaminants into plant tissues that can be harvested [31]. Nevertheless, the presence of MPs can lead to the adsorption of pollutants onto plastic surfaces, which may hinder their mobility and restrict root absorption, particularly for hydrophobic organic compounds (e.g., PAHs) [114]. For instance, research has indicated that the presence of MPs can result in lower translocation factors and reduced pollutant absorption, attributed to damage inflicted on roots or disruption of the transport system between cell walls and organelles [156]. In these scenarios, phytoextraction may not perform optimally or may necessitate extended periods to achieve significant levels of decontamination.

Conversely, phytostabilization may yield more dependable outcomes in the presence of high levels of MP, especially when the objective is to immobilize pollutants and minimize their leachability or dispersal due to erosion [43]. Plants with extensive root systems, such as Bidens pilosa or Brassica napus, can effectively stabilize contaminated soils by modifying the rhizosphere and enhancing soil aggregation, even in the face of oxidative stress induced by microplastics [132,137,141]. Moreover, phytostabilization is enhanced by synergistic interactions with microbial communities, particularly arbuscular mycorrhizal fungi (AMF), which have demonstrated resilience to specific metal contaminants and exposure to microplastics [43,145]. However, shifts in soil microbial dynamics caused by plastics could potentially compromise long-term stability [8].

Ultimately, the decision between phytoextraction and phytostabilization in soils with multiple contaminants should take into account the type of pollutants, the characteristics of MPs (size, shape, polymer type), the species of plants involved, and the intended remediation goal (whether it is removal or risk reduction). In soils rich in MPs where the bioavailability of pollutants is diminished and plant stress levels are elevated, phytostabilization may be the more suitable option. Conversely, in situations where MPs enhance the mobility of heavy metals (as seen with PE and Cd in lettuce), phytoextraction could be effectively optimized, particularly when combined with amendments that promote desorption. It is crucial to conduct comparative field trials to substantiate these theories in real-world scenarios.

8.4. Coherent Frameworks and Emerging Trends in Phytoremediation Under Co-Contamination Conditions

The literature that has been reviewed indicates an increasing interest in the intricate interactions among MPs, heavy metals, and organic pollutants in soil environments, emphasizing notable challenges and opportunities in phytoremediation strategies. Studies consistently demonstrate that MPs can serve as carriers for co-contaminants, influencing bioavailability and toxicity profiles in soils [164]. However, the behavior of sorption and desorption varies significantly between pristine and aged MPs, with aged particles frequently showing a higher sorption capacity for pollutants due to surface oxidation and biofilm development [165]. These dynamics imply that remediation approaches must consider the physico-chemical changes in MPs over time to accurately forecast pollutant behavior and plant absorption.

The effectiveness of phytoremediation is also affected by the choice of hyperaccumulator species; however, the criteria for selecting plants are still not sufficiently standardized in the literature [166,167]. While species like Brassica juncea and Pteris vittata show significant potential for metal absorption, recent advancements in biotechnology—including genetically modified hyperaccumulators—present promising opportunities to customize plants for specific co-contaminant profiles [52]. Incorporating decision-making frameworks that take into account the type of pollutant, soil properties, and the physiological characteristics of plants could greatly improve remediation results, although such frameworks are still inadequately developed in existing research.

Furthermore, the majority of current research is based on controlled laboratory settings, mainly in developed areas, which restricts their relevance to agriculture-dependent nations that encounter distinct socio-economic and environmental challenges [168]. To effectively scale phytoremediation technologies, it is essential to address issues related to cost-effectiveness, local policy support, and community involvement to achieve practical application [169]. The existing literature points out a deficiency in socio-economic feasibility assessments, highlighting the necessity for interdisciplinary strategies that integrate technical advancements with regulatory frameworks and collaboration among stakeholders to promote sustainable remediation practices on a global scale [170].

8.5. Decision Framework for Plant Choice Under Combined Pollution

The process of selecting hyperaccumulator plant species for phytoremediation in environments with multiple contaminants necessitates a systematic decision-making framework that considers the intricate interactions among various pollutants, soil characteristics, and plant physiology [171]. Conventional criteria for selecting hyperaccumulators typically emphasize their ability to absorb and withstand elevated levels of a single contaminant, predominantly heavy metals. However, when addressing combined pollution that includes MPs, organic pollutants, and heavy metals, it is essential to take additional factors into account. These factors encompass the plant’s tolerance to organic contaminants, its root structure and exudate profile that influence pollutant bioavailability, as well as its capacity to flourish in modified soil conditions affected by the presence of MPs. Establishing a well-defined selection framework based on these considerations can enhance the effectiveness and applicability of phytoremediation techniques in complex contaminated environments [31].

A decision-making framework of this nature could encompass various parameters, such as the type and concentration of contaminants, the tolerance thresholds of plants, the bioavailability of pollutants, and the prevailing environmental conditions [171]. For example, species that exhibit a combined tolerance to both heavy metals and organic pollutants, or genetically modified hyperaccumulators with improved metabolic pathways for organic degradation, could be given priority. Furthermore, factors such as the growth rate of the plant, its biomass production, and its adaptability to local climates should be taken into account to guarantee successful remediation results [31]. The integration of recent advancements in molecular biology and omics technologies may also facilitate the identification of candidate species possessing desirable characteristics for environments with multiple pollutants, thereby allowing for a more focused and effective phytoremediation strategy [172].

8.6. Emerging Biotechnologies: Genetically Edited Hyperaccumulators and Advances in Addressing Co-Contamination

The presence of MPs in terrestrial ecosystems poses a multifaceted environmental challenge, particularly when they are found alongside organic pollutants and heavy metals [7]. The application of genetically modified hyperaccumulators is among the most promising strategies for the phytoremediation of soils tainted with various pollutants. Naturally occurring hyperaccumulator plants have an innate ability to absorb and retain heavy metals and other contaminants; however, they frequently encounter limitations such as low biomass and slow growth rates. By employing genetic editing methods, including CRISPR/Cas9, alterations to metal transporter genes, and the enhancement of antioxidant mechanisms, the efficiency of uptake and internal movement of pollutants can be markedly improved [128]. These genetic modifications also bolster plant resilience against the harmful effects of complex co-contamination scenarios that involve MPs, heavy metals, and organic pollutants. Therefore, genetically enhanced plants with high biomass can effectively merge productivity with substantial remediation capabilities [173].

Recent advancements in biotechnology have significantly broadened the resources available for tackling co-contamination issues. The creation of transgenic plants that overexpress metal transporter gene families, including ZIP, HMA, and MTP, along with genes that play a role in phytochelatin production and antioxidant enzymes, facilitates the swift transformation of standard plants into effective hyperaccumulators [31,174]. Moreover, synergistic methods that incorporate genetically modified root microbiomes and nano-material enhancements have been suggested to enhance the bioavailability of contaminants or alleviate the detrimental effects of MPs within soil environments (e.g., genetically engineered bacteria in combination with magnetic nanoparticles) [148]. These comprehensive strategies present considerable potential for the remediation of locations affected by intricate combinations of MPs alongside both organic and inorganic pollutant.

Despite these encouraging advancements, the real-world implementation of genetically modified hyperaccumulators in co-contaminated environments encounters significant obstacles [175]. Regulatory and biosafety issues restrict the use of genetically modified organisms in open environments, particularly in agricultural or semi-natural areas with diverse contaminant loads [176]. Furthermore, the challenge of applying laboratory-scale findings to field conditions persists due to environmental variability, interactions within microbial communities, and the requirement for adequate biomass production [177]. The intricacies of co-contamination involving MPs, organic compounds, and metals demand the creation of standardized methodologies and integrated remediation strategies that combine genetic, microbial, and chemical techniques [178]. Future achievements in this field will depend on interdisciplinary collaboration and comprehensive risk assessment frameworks to formulate sustainable and effective biotechnological solutions.

8.7. New Ideas and Approaches

Innovative strategies in phytoremediation (e.g., using nanophytoremediation) need to progress beyond conventional techniques to effectively tackle the intricate challenges posed by co-contamination with MPs, heavy metals, and organic pollutants [179,180]. A promising direction involves the utilization of engineered plant-microbe symbioses, wherein arbuscular mycorrhizal fungi (AMF) or pollutant-degrading rhizobacteria are selectively introduced to improve the efficacy of phytoremediation under stress induced by MPs [181]. Given that MPs significantly modify the composition of microbial communities and enzyme activities, a strategic approach to microbial restoration—potentially aided by biochar or compost carriers—could mitigate the detrimental impacts of MPs on biodegradation and the uptake of nutrients by plants [182].

Another developing concept pertains to the incorporation of genetically modified hyperaccumulators designed for the uptake of co-contaminants in the presence of microplastics. Utilizing CRISPR-Cas gene editing technology, it is feasible to improve root exudate profiles, enhance antioxidant responses, and increase the expression of transporters that specifically address complex interactions with pollutants [128]. This approach would assist in mitigating the decreased bioavailability or mobility of pollutants that occur when they are adsorbed onto plastic particles. Concurrently, precision agriculture technologies—such as in situ sensors for pollutant speciation and mapping of plastic particles—could facilitate site-specific phytoremediation strategies, ensuring real-time adaptability in large-scale field applications [183].

Furthermore, hybrid systems that integrate phytoremediation with physicochemical methods (such as nano-enabled amendments or biochar-enhanced soils) have the potential to enhance the desorption of contaminants from MPs and promote plant absorption [51,184]. These hybrid systems (i.e., a hybrid remediation system that integrates living plant organisms with physicochemical modifications of the soil (or water) to enhance pollutant uptake and detoxification [185]) would enable plants to take advantage of increased pollutant bioavailability while providing a buffer against toxicity induced by MPs. Investigating these innovative combinations through mesocosm trials could lead to the development of practical guidelines for sites affected by multiple contaminants, particularly those influenced by agricultural plastic residues.

8.8. Research Gaps and Future Directions

Overall, understanding the joint behavior of organic pollutants, heavy metals, and MPs in soil remains an important challenge. Future research should focus on clarifying their synergistic and antagonistic interactions to enhance understanding of their collective impact on soil fertility, plant metabolism, and the sustainability of ecosystems over the long term. Despite the increasing amount of research focused on the phytoremediation of soils tainted with MPs, heavy metals, and organic pollutants, several significant limitations persist. These limitations encompass the dominance of laboratory-scale studies that may not adequately reflect the complexities found in field conditions, a lack of standardization in the criteria for selecting hyperaccumulator plants, and a limited comprehension of how aged MPs interact within contaminant dynamics [178,186]. Additionally, socio-economic factors and challenges related to scalability remain insufficiently examined.

This section aims to guide future research by synthesizing critical gaps and suggesting directions: (1) performing additional field-based studies across various agroecological contexts to validate laboratory results; (2) creating decision-making frameworks that incorporate plant traits and pollutant characteristics for improved remediation; (3) exploring the long-term interactions between aged MPs and co-contaminants; and (4) evaluating the socio-economic viability and policy frameworks necessary for practical implementation [187]. Addressing these gaps would allow the scientific foundation to be strengthened and the effective implementation of phytoremediation technologies in complex soil pollution contexts to be promoted.

8.9. Socio-Economic Feasibility and Policy Considerations for Phytoremediation

The socio-economic viability of phytoremediation is a significant element affecting its practical implementation and widespread use. In comparison to traditional remediation methods, phytoremediation typically provides a more cost-effective and environmentally sustainable option, characterized by reduced operational costs and minimal disruption to the site [186]. Nonetheless, its scalability may be constrained by various factors, including the duration needed for effective contaminant extraction, the presence of appropriate hyperaccumulator species, and site-specific variables such as climate, soil composition, and the severity of pollution. Economic evaluations suggest that although initial expenses might be lower, extended treatment periods could influence the overall cost–benefit ratio, especially for locations that necessitate swift decontamination.

Moreover, the effective execution of phytoremediation on a large scale is significantly reliant on supportive policy frameworks and the engagement of stakeholders. Regulatory incentives, subsidies, and well-defined guidelines can facilitate adoption by mitigating financial risks and encouraging research into more effective plant varieties and remediation methods [188]. Public awareness and community participation are also crucial to ensure social acceptance and the integration of phytoremediation initiatives within local development strategies. Therefore, the combination of scientific progress with economic assessments and policy support is vital to realize the full potential of phytoremediation as a sustainable approach for managing co-contaminated soils [189].

8.10. Challenges and Case Studies from Agriculture-Dominant and Developing Regions

The majority of current research regarding the phytoremediation of soils contaminated with MPs and other pollutants primarily stems from controlled laboratory studies carried out in developed countries [190]. Although these investigations offer significant mechanistic insights and validation of concepts, their relevance to real-world agricultural settings, particularly in developing nations, is still quite restricted [191]. Countries that are predominantly agricultural often encounter distinct challenges, including limited access to advanced technologies, fluctuating climatic conditions, and socio-economic limitations that affect the success of remediation efforts [191,192]. Additionally, the heterogeneity of soils, various cropping systems, and differing sources of pollution necessitate tailored adaptations of phytoremediation approaches [193].

To address this gap, the inclusion of case studies from regions with intensive agriculture would improve the relevance and applicability of phytoremediation research. Examples from countries in Asia, Africa, and Latin America illustrate how local crop species, traditional farming methods, and socio-economic factors influence remediation results [193]. Challenges such as limited resources, farmer awareness, and policy support need to be tackled to guarantee effective implementation [194]. Emphasizing these real-world scenarios can assist in the creation of customized frameworks that incorporate phytoremediation into sustainable agricultural management and pollution control in areas most impacted by soil co-contamination [193].

9. Conclusions

The existence of MPs within terrestrial ecosystems presents a complex environmental challenge, especially when they coexist with organic pollutants and heavy metals. MPs affect not only the physical and chemical characteristics of the soil but also the biological reactions of plants and soil microorganisms. Their capacity to adsorb and transport pollutants modifies the environmental behavior, bioavailability, and toxicity of co-pollutants, frequently leading to either increased or decreased uptake by plants.

In accordance with the review’s focus, it is crucial to emphasize that plants have considerable potential for remediating environments that are co-contaminated through mechanisms such as uptake, translocation, sequestration, and degradation of both MPs and their associated pollutants. Essential phytoremediation mechanisms—including phytoextraction, phytostabilization, rhizofiltration, and rhizo-/phytodegradation—play a significant role in the removal or immobilization of heavy metals and organic contaminants that interact with MPs within the rhizosphere. Recent findings indicate that interactions between plants and microbes may further facilitate the transformation and degradation of pollutants, although the impact of MPs on these processes is still not fully understood.

At the physiological level, MPs are linked to diminished plant growth, reduced photosynthetic efficiency, and impaired nutrient uptake, while also inducing oxidative stress and disrupting antioxidant enzyme systems. Concurrently, MPs modify the structure of soil microbial communities and their enzymatic activities, hindering the breakdown of hazardous substances and altering the equilibrium between beneficial and pathogenic organisms.

On a molecular scale, MPs and their associated contaminants disrupt gene expression, interfere with hormone signaling pathways, and modify enzyme structure and function, thereby undermining plant defense mechanisms. Furthermore, MPs may trigger the production of secondary metabolites as an adaptive response to environmental stress, although such alterations could have subsequent effects on crop quality and food safety. Secondary metabolites and molecular/genetic responses influence plant performance in environments with multiple pollutants. Although these processes are not exclusively related to MPs, they offer essential insights for remediation efforts that utilize plants.

In summary, MP pollution constitutes a multifaceted and dynamic challenge that transcends mere surface-level toxicity. It intersects with critical biological processes at cellular, biochemical, and ecological levels, necessitating comprehensive strategies for soil health management, agricultural sustainability, and environmental conservation. Combined soil pollution, i.e., the coexistence of different types of pollutants in the soil, is a major challenge for researchers. MPs, combined with either inorganic contaminants such as heavy metals or with other organic pollutants, may pose risks to both soil health and human health if products cultivated in contaminated soils are consumed. In any case, a thorough study of the mechanisms governing the physicochemical changes undergone in soils is necessary, as adverse effects on the soil ecosystem and human health can be anticipated.