Mapping Scientific Research on Microplastics in Wetland Ecosystems in South Asia and Southeast Asia: Bibliometric Insights on Remediation Technologies, Including Nanoremediation

Abstract

Microplastic (MP) contamination has become a widespread environmental concern in coastal and freshwater wetlands, ecosystems that play a crucial role in hydrological regulation, nutrient cycling, and biodiversity conservation. Despite their ecological importance, research on MPs in wetlands remains fragmented and comparatively underexplored. This study presents a comprehensive bibliometric and visualization analysis of global research on MPs in coastal wetlands. A total of 17,523 publications were retrieved from the Web of Science Core Collection (2002–2025) using predefined search strings and screening criteria. Analytical tools, including VOSviewer version 1.6.20, were employed to examine co-authorship networks, country contributions, and keyword co-occurrence patterns. The results indicate a significant increase in MP-related publications after 2016, with China, the United States, and India emerging as leading contributors. However, wetland-specific studies constitute only a small fraction compared to marine-focused MP research, highlighting a substantial research gap. Key research themes identified include MP sources, transport pathways, sediment–water interactions, and ecotoxicological impacts. Additionally, there is growing attention to remediation approaches, particularly those involving TiO₂, ZnO, Fe₃O₄, and graphene derivatives, employing photocatalytic, magnetic, and adsorptive mechanisms. Overall, the findings underscore the limited focus on wetland ecosystems in MP research and emphasize the urgent need for integrated research efforts and management strategies to address MP contamination in these vulnerable ecosystems.

1. Introduction

Plastic waste generation and disposal have been increasing exponentially worldwide [1]. China is identified as the largest contributor, producing nearly 60 million tons of plastic waste [2,3]. In Southeast Asia, Indonesia leads with about 5.046 million tons, followed by Thailand at 3.533 million tons and Vietnam at 3.268 million tons. Malaysia ranks fifth in the region, generating a significant amount of plastic waste [4]. Concerning primary microplastics emissions, India and South Asia account for the largest share at 18.3%, followed by North America at 17.2%, Europe and Central Asia at 15.9%, China at 15.8%, and East Asia and Oceania at 15.0% [5]. South America (9.1%) and Africa and the Middle East (8.7%) show relatively lower emissions. Globally, the main sources of microplastic contamination—excluding urban particulate matter—include textiles in India and Southeast Asia (15.9%), tyres in North America (11.5%), textiles in China (10.3%), and tyres in Europe and Central Asia (10.3%) [5]. Notably, microplastic particles smaller than 5 mm pose risks to ecosystems and human health due to their potential impacts [6]. Recent studies reveal various ecotoxicological effects on aquatic life, including decreased feeding activity, oxidative stress, neurotoxicity, increased energy expenditure, delayed growth, and even death [7]. According to the Organisation for Economic Co-operation and Development, 2024 Global plastic production has exceeded 400 million tons annually in recent years, with plastic waste generation reaching over 350 million tons worldwide [1].

Wetlands, regarded as the Earth’s third most significant ecosystem, are crucial for maintaining about 40% of global ecosystem functions and services, including groundwater replenishment, nutrient cycling, and serving as habitats for numerous species [2]. Among the various ecosystems affected by microplastic contamination, coastal wetlands are among the most sensitive environments and are being increasingly contaminated. Wetlands provide important ecosystem services, such as flood regulation, provision of fresh water through stormwater treatment, and maintenance of habitats for a diverse ecosystem of plants and animals, many of which are a source of livelihood for people. Wetlands also add to the aesthetic value and recreational amenities [3]. Furthermore, wetlands function as reservoirs, serving as both sources and sinks for contaminants, including microplastics. Coastal wetlands, known for their rich biodiversity and vital ecological services, are increasingly threatened by microplastic (MP) contamination, yet research on the distribution, fate, and ecological impacts of MPs in these systems remains limited. Very few studies have investigated the prevalence and accumulation trends of microplastics (approximately 4%) in the wetland ecosystems compared to marine environments [4]. The distribution of microplastics in wetlands depends on several key factors, such as geographical location, analytical method, wetland characteristics, and anthropogenic activities [5]. The distribution and abundance of microplastics in wetlands vary because of differences in soil texture and vegetation cover [6]. Composites of materials, of which the main types are PET (polyethene terephthalate), PS (polystyrene), PVC (polyvinyl chloride), PP (polypropylene), PE (polyethene), PA (polyamide), PMMA and the least dense PE (LDPE) [7] are widely used synthetic polymers that contribute significantly to wetland microplastic pollution due to their extensive production, durability, and resistance to degradation. The main aim of the paper is to highlight the role of coastal wetlands as potential sinks for MPs, emphasizing the need to investigate their contamination sources, fate, pathways, and impacts and the need for nano remediation of microplastics from these ecosystems. This review summarizes the literature and current knowledge on the source, transport, and impacts of microplastics in coastal wetland ecosystems, especially in Southeast Asian countries. A bibliographic analysis of research trends on microplastics in wetland ecosystems has been carried out using VOS viewer. Furthermore, the various remediation technologies for microplastics in wetland ecosystems have also been reviewed.

Microplastics enter the wetland environment as either primary or secondary microplastics [8,9]. Primary MP are intentionally manufactured pieces of plastic smaller than 5 mm, and secondary MP are created through the degradation of larger plastic materials [10]. They may be deliberately added to various products, such as exfoliating agents in cosmetics and personal care items (e.g., shower gels). Secondary microplastics are formed from the fragmentation of larger plastic materials, which deteriorate into smaller particles under marine or environmental conditions. This degradation primarily occurs through processes like photodegradation, weathering, and mechanical stress, often involving mismanaged plastic waste such as discarded bags, packaging materials, or lost fishing nets. Because these particles result from the breakdown of macroplastics, tracing their exact origins is difficult, making it challenging to estimate the amount of plastic transformed into microplastics. Consequently, studies often focus on quantifying primary microplastics, as they are easier to measure with existing data [11]. Nonetheless, secondary microplastics are far more prevalent in the environment and are generated through mechanical, chemical, and biological fragmentation processes, leading to a wide range of diverse and abundant sources [11,12]. Reported concentrations of microplastics in freshwater wetlands range from 17 to 1533 particles/kg in sediments and up to 2328 particles/m³ in water, indicating significant environmental contamination and underscoring the need for comprehensive research synthesis in this field. An overview of the various sources of microplastics is depicted in Figure 1.

This study is novel in integrating bibliometric mapping with quantitative evidence on microplastic occurrence and an evaluation of conventional and nanoremediation-based removal strategies in coastal and freshwater wetlands of South Asia and Southeast Asian countries, thereby bridging the gap between research trends and practical environmental applications.

2. Materials and Methods

2.1. Analysis of Literature on Microplastic Studies in Wetlands

A comprehensive bibliometric analysis, as shown in Figure 2, was conducted using the Web of Science Core Collection database. The search was performed on 6 March 2026. The literature was retrieved from the Web of Science Core Collection database using a comprehensive search strategy. The keywords included combinations of: “microplastics” AND “wetland” OR “coastal wetland” OR “freshwater wetland” “microplastics in wetland” AND “sources of microplastics” AND “degradation of microplastics in wetland”. The search was limited to English-language publications up to 2025. The search was limited to keyword fields.

2.2. Inclusion and Exclusion Criteria

The Inclusion Criteria

• Articles (16,652) and review articles (871);
• Publications in English;
• Time span from 2002 to 2025.

The exclusion criteria included conference proceedings, book chapters, duplicate records, and unrelated subject areas.

2.3. Data Cleaning and Processing

A total of 18,792 journal articles were initially retrieved, and after refinement, 17,523 records were retained for analysis. The dataset was exported and cleaned by removing duplicates, standardizing author names, and merging similar keywords.

2.4. Data Analysis

Visualization of networks was performed using VOSviewer to identify research hotspots and collaboration patterns. VOS (Visualization of similarities) viewer is a tool meant for the analysis and visualization of bibliometric data [13].

Bibliometric indicators such as publication trends, keyword co-occurrence, citation of countries, citation of institutions, and citation of source networks were analyzed [14].

3. Results

3.1. Research on the Trend of “Microplastics” in Transition Literature

The trend line diagram shows an increasing trend in research on microplastics in wetlands over the last two decades (Figure 3). The publication trend can be divided into three phases: an initial phase (2002–2010), a growth phase (2011–2016), and a rapid expansion phase (2017–2025). The sharp increase after 2016 indicates heightened global research interest in microplastic pollution. Growth between 2000 and 2015 was relatively slow and stable, suggesting perhaps this was an area of less interest or awareness during that time. However, the number of studies began to increase significantly from about 2016 onward, with truly exponential growth post-2020. The rising pattern agrees with intensified global concern towards plastic pollution, especially the presence of microplastics and their ecological and health effects on humans. This pattern indicates the increasing recognition of microplastics as a serious issue in the environment that is driving enhanced research to investigate the sources and impacts on wetland ecosystems and potential mitigative measures.

3.2. Research on the Co-Occurring Keywords of “Microplastics in Wetland

The VOS viewer visualization, as shown in Figure 4, points out the major themes and co-occurring keywords in research on “microplastics in wetlands.” The central node, “microplastics,” is highly connected to terms such as “pollution,” “sediments,” “accumulation,” and “contamination,” which point to the sources, pathways, and impacts in aquatic ecosystems (Figure 4). Related concepts such as “wetland,” “river,” “lake,” and “marine environment” suggest that research spans different water bodies and their interconnections. These are keywords like “particles” and “ingestion,” which reflect research into the behavior, degradation, and possible biological impacts of microplastics. Related references include “plastic debris” and “degradation,” and the time gradient suggests increased interest in topics like “pollution” and “accumulation” in recent years, as concern about the ecological impacts of microplastics in wetland ecosystems. Cluster 1 comprises keywords such as accumulation, freshwater, ingestion, microplastics, particles, plastic debris, and sediments, highlighting the fate and biological interactions of microplastics in freshwater systems. Cluster 2 includes degradation, marine environment, plastic pollution, removal, and stormwater, reflecting studies focused on sources, transformation processes, and mitigation strategies. Cluster 3 consists of coastal, contamination, surface water, and wetland, emphasizing pollution distribution and environmental characteristics of coastal wetland ecosystems.

3.3. Research on the Country Distribution of “Microplastics in Wetlands” Literature

The VOSviewer visualization depicts the global distribution of research contributions on “microplastics in wetlands,” highlighting the prominent roles of countries such as China, the USA, and India (Figure 5). China appears as the most prominent node, indicating its dominant contribution to the literature, which may be attributed to rapid industrialization, vast wetlands, and growing awareness of environmental issues. The USA also demonstrates its presence, as its connections with other countries, like Germany and India, are strong, indicating robust international collaborations. India, though smaller in node size, is connected to key contributors like Australia and Argentina, suggesting that there is growing interest in microplastic pollution in the context of developing economies and tropical wetlands.

Smaller nodes such as Malaysia and Argentina represent the contribution of European and other regions on a much smaller scale. Such countries are probably dealing with niche areas or specific case studies. The time gradient in the visualization depicts the increased output of research over recent years, especially from the USA(United States of America) and China. Overall, the network highlights significant geographic variation in research focus, with developing countries like India emerging as important contributors. This trend is likely driven by growing environmental challenges in their wetland ecosystems.

3.4. Analysis of Research Institutions and Their Literature Citation

Analysis of research institutions contributing to the literature on microplastics in wetlands indicates that the Chinese Academy of Sciences (CAS) remains the most influential organization, with the highest citation count (1018) and a strong research presence despite a limited number of publications (5), reflecting high-impact outputs (Figure 6). RMIT University demonstrates notable collaborative strength with the highest total link strength (7) and substantial citations (324), highlighting its central role in international research networks. Institutions such as Nalanda University and Anhui University of Technology show moderate citation counts (177 and 83, respectively) along with relatively strong link strengths, suggesting growing contributions and collaboration in the field. Meanwhile, organizations including Guangxi Academy of Sciences, South China Agricultural University, and Universiti Malaysia Terengganu exhibit comparatively low citations and weaker link strengths, indicating limited research influence or emerging involvement. Overall, the findings emphasize the dominance of Chinese institutions in this domain, while contributions from international universities such as RMIT reflect expanding global collaboration in microplastics research.

The analysis of citation sources reveals that Science of the Total Environment, Water Research, and Marine Pollution Bulletin are the most influential journals, each with three documents and high citation counts (400, 345, and 314, respectively), along with strong total link strengths, underscoring their central role in disseminating impactful research. Integrated Environmental Assessment and Management and Journal of Water Process Engineering show moderate citation performance (193 and 109 citations), indicating their contribution to specialized and applied aspects of the field. Although Wetlands has a comparable number of documents (3), its low citation count (55) and zero link strength suggest limited influence within this research network. Similarly, Frontiers in Environmental Science and Microplastics exhibit relatively lower citation counts but contribute to emerging and niche research areas. The density visualization further supports these findings, where high-density (yellow) regions correspond to leading institutions such as the Chinese Academy of Sciences and RMIT University, indicating strong research activity and collaboration, while low-density (green/blue) regions represent institutions with comparatively lower contributions. Overall, the visualization highlights a concentrated yet evolving research landscape characterized by strong institutional dominance and increasing interdisciplinary collaboration.

Analysis of research institutions contributing to the literature on “microplastics in wetlands” shows that the Chinese Academy of Sciences (CAS) leads both in the volume of documents (7) and total citations (827), reflecting its prominent role in advancing research and producing highly cited studies (Figure 5).

Parameters such as the number of publications, total citations, and total link strength (TLS) were used to evaluate research productivity and collaboration patterns. Institutional and country affiliations were standardized based on the database records to ensure consistency. The density visualization map generated using VOSviewer represents the research intensity of institutions based on publication output and collaboration strength. Higher density regions (yellow areas) indicate institutions with greater research activity and stronger collaboration networks, whereas lower density regions (green/blue areas) represent comparatively lower contributions. The higher research output observed for institutions such as the Chinese Academy of Sciences and Zhejiang University reflects their significant contribution to the field based on publication volume and collaboration networks. However, the underlying factors driving these patterns were not explicitly analyzed in this study and require further investigation.

3.5. Microplastic Pollution in Freshwater Wetlands and Coastal Wetlands

Microplastic pollution in freshwater wetlands primarily stems from urban runoff, agricultural practices, wastewater treatment plants, and littering. These wetlands function as sinks for microplastics carried by rivers, streams, and atmospheric deposition. Microplastics accumulate within sediment layers, modifying the soil’s physical structure, and are ingested by aquatic organisms, resulting in bioaccumulation and disturbances in the food web. This pollution also deteriorates water quality by releasing toxic additives and adsorbing pollutants. The resulting impacts include biodiversity loss, diminished ecosystem services, and significant challenges for communities dependent on wetlands for water and other resources. Studies on the distribution of microplastics in freshwater wetlands are limited, accounting for only about 4% of studies compared to the coastal environment [4,15]. According to [16], a significant level of microplastic contamination was observed in freshwater fish from the East Kolkata Wetlands and surrounding areas, with 77% of the examined fish specimens indicating microplastic presence. On average, each microplastic-affected fish contained approximately 4.3 microplastic particles, indicating a concerning level of pollution in these aquatic environments [16]. In coastal wetlands, microplastic sources include marine debris, tidal inflows, industrial effluents, and waste generated by tourism. Coastal processes such as tidal movements and ocean currents facilitate the transport and deposition of microplastics, leading to their accumulation in mangroves, seagrass beds, and sediments. These pollutants adversely affect marine life, including fish, birds, and mangroves, through ingestion and physical harm. Furthermore, coastal ecosystems suffer from habitat degradation, which diminishes their functions in storm protection and carbon sequestration.

The observed differences between coastal and freshwater wetlands in terms of microplastic distribution and impacts can be attributed to a combination of environmental, climatic, and trophic factors. Environmentally, coastal wetlands are influenced by tidal dynamics, salinity gradients, and marine inputs, which enhance the fragmentation, transport, and redistribution of microplastics. In contrast, freshwater wetlands are primarily affected by riverine inputs, catchment land use, and lower hydrodynamic energy, resulting in greater retention and sediment accumulation of microplastics. Climatic factors such as precipitation intensity and seasonal flooding further regulate microplastic fluxes in freshwater systems, while coastal regions are more susceptible to storm surges and sea-level rise, which can resuspend and redistribute accumulated particles. From a food web perspective, coastal wetlands typically support more complex and diverse trophic interactions, increasing the likelihood of microplastic bioaccumulation and biomagnification across multiple trophic levels. Conversely, freshwater wetlands often exhibit localized food chains where microplastics may accumulate within benthic organisms and detritus-based pathways. These combined factors explain the distinct patterns of microplastic occurrence and ecological risks observed between the two wetland types.

Table 1. (a) Microplastics in freshwater wetlands. (b) Microplastics in coastal wetlands.

(a)
Continent	Country	Wetland	MP Range	Major Polymers	Reference
Asia	India	Lower Ganga River	Water: 380−684 particles/1000 m3	PE, PP, PVC, PE, polytetrafluoroethene:propene, polystyrene, polytrimellitic amide imide, polyacrylonitrile vinyl chloride	[17]
			Sediments: 17−36 particles/kg of dry weight (dw)	PVC, PP, PS, PE, poly(butadiene:acrylonitrile), polyvinyl chloride: ethylene, polyvinyltoluene: butadiene, polyethylene propylene, poly(trimellitic amide imide)	[17]
		Ganga river	Water: Average 0.038 particles/L	Rayon, acrylic, PET, PVC, PS, Nylon	[18]
		Alaknanda River, Uttarakhand	Water: 566 particles/L	PT, HDPE, PVC, LDPE, PP, PS	[19]
			Sediments: 389 particles/kg	PT, HDPE, PVC, LDPE, PP, PS	[19]
		Netravathi River, Southern India	water: 56 to 2328 particles/m3,	PP, PE, PET, PVC	[20]
			Sediments: 9.44−253.27 particles/kg dw	PP, PE, PET	[20]
		Brahmaputra River	Sediments: 20−24 MP/kg dw	PTFE, PE, PP, PS, PVC	[21]
		Kaveri River	sediments: 1 to 699 ± 66.00 particles/kg	PE, PA, PET, PP, PS, PEG	[22]
		Anchar Lake, NW Himalaya	Sediments: 233 to 1533 particles/kg	PS, PP, PA, PVC	[23]
		Red Hills Lake	Water: Mean 5.9 particles/L	LDPE, PP, HDPE, PE	[24]
			Sediments: Mean 27 particles/kg	PE, PP, HDPE, LDPE	[24]
		Kodaikkanal Lake	Sediments: Mean 28.31 ± 5.29 particles/kg	particles/L PE, PP, PS, PET, PVA	[25]
			water: Mean 24.42 ± 3.22	PE, PP, PS, PET	[25]
		Veeranam Lake	Sediments: 309 particles/kg	PE, PP, PS, PVC, NY	[26]
			Water: 28 particles/L	PS, PP, PE, PVC, NY	[26]
		Renuka Lake	Sediments: 180 ± 143 particles/kg dw	PE, PS, PP	[27]
			Water: 21 ± 13 particles/L	PP, PS, PE	[27]
		Pangong Lake	Sediments: 160−1000 MP/kg dw	PP, PS, PE, PA, PET, POM, PMMA	[21]
		Manipal Lake	Water: 0.423 particles/L	PET, CL	[28]
		Adyar River	Water: Mean 330 particles/m3	PE, PP, PS	[28]
		Tiruchendur groundwater	Water: Mean 4.2 particles/L	PA, PE, PE	[29]
	Indonesia	Wonorejo River in Surabaya	Sediments: 264 g/m2	LDPE, PP, PV, PETP, HDPE, PS	[30]
		Citarum River	Water: 0.00004–0.00009 particles/L Sediments: 12,452–20,316 particles/kg	N/A	[31]
		Ciwalengke River	Water: 2.57–9.13 particles/L Sediments: 14.446.2 particles/kg	N/A	[31]
	Vietnam	Red River Delta	Sediments: 0 to 4941 particles/kg	PP, PE, PET, PA, PS, PLE	[32]
		Saigon River	Water: 0.01–519 particles/L	N/A	[33]
	Thailand	Chao Phraya River	Water: 0–0.052 particles/L	N/A	[34]
	Malaysia	Cherating River	Water: 0.000004–0.00001 particles/L	N/A	[35]
		Dungun River	Water: 0.04–0.30 particles/L	N/A	[36]
		Skudai River	Sediments: 120–280 particles/kg	N/A	[37]
		Tebrau River	Sediments: 540–820 particles/kg	N/A	[37]
	China	Manas River Basin	Water: 21 ± 3–49 ± 3 particles/L	PE, PP	[38]
		Pearl River	Water: 0.36 ± 0.01 to 1.96 ± 0.90 particles/L	PE and PP	[39]
			Sediments: 685 ± 342 particles/kg	PP and PE
		Poyang Lake	Water: 5 to 34 particles/L Sediments: 54–506 particles/kg	PP, PE	[40]
		Lake Ulansuhai	Water: 1760 ± 710 to 10,120 ± 4090 particles/L	PE	[41]
			Sediments: 14 ± 3 to 24 ± 7 particles/kg	PE
		Wei River	Water: 3.67 to 10.7 particles/L Sediments: 360 to 1320 particles/kg	NA	[41]
		Urban Lakes in Changsha	Water: 2425 ± 247.5 to 7050 ± 1060.66 particles/L	PP	[42]
			Sediments: 270.17 ± 48.23 to 866.59 ± 37.96 particles/kg	PS
		Dongting Lake	Water: 900–2800 particles/m3	PE and PP	[43]
			Sediments: 200 to 1150 particles/kg	PE and PET
		Huixian Wetland (Guilin, Guangxi)	Water: 1.65 × 104 –8.9 × 104 particles/ m3, (4.18 × 104 particles/m3)	PE (37.6%), PP (24.7%), PVC (15.3%)	[44]
		Taihu Lake	Water: Items: 3.4 to 25.8 particles/L	Cellophane	[45]
			Sediments: 11.0 to 234.6 particles/kg	Cellophane
(b)
Continent	Country	Wetland	MP Range	Major Polymers	Reference
Asia	India	Vellar estuary	Water: 5.14 to 15 particles/L	PE, PP	[46]
			Sediments: 24.8 to 43.4 particles/kg	PP, LDPE, PVC, PVA
		Chennai coast	Water: 274 to 1191 particles/L	PE, PP	[47]
		Kayamkulam estuary	Water: N/A Sediments: 438.8 particles/kg	PP, PE	[48]
		Goa esturine system Mandovi-Zuari	Water: 0.107 particles/L	N/A	[49]
	Indonesia	Benoa bay	Water: 0.36 particles/L	PS, PP, PE	[50]
		Muara Angke Wildlife Reserve	Sediments: 28.09 particles/kg	PS, PP, PE	[51]
		Jagir estuary and Wonorejo coast	Sediments: 590 particles/kg	polyester, PE, PP	[52]
	Malaysia	Carey Island (Pulau Carey)	Sediments: 936 to 1227 particles/kg	N/A	[53]
		Port Dickson	Water: 2.10 to 6.80 particles/L	Cellophane, PES, PE	[54]
		Baram River estuary	Water: 15 particles/L	PS, PE, PP	[55]
	Thailand	Bang Yai canal mouth	Sediments: 300 to 900 particles/kg	rayon, PE	[56]
		Chao Phraya River Estuary	Sediments: 39 particles/kg	PE, PES, PE	[57]
			Water: 48 particles/L	Polyurethane and polybutylene	[58]
		Pattani Province coastal	Sediments: 106 to 413 particles/kg	Rayon, PE, rubber, styrene, poly vinyl acetate, paint	[59]
	Bangladesh	Cox’s Bazar	Sediments: 0.5 particles/kg	Nylon, PE, rayon, PP, PS, PU, Epoxy alkyd	[60]
	Singapore	Persian Gulf coastal	Sediments: 36.8 particles/kg	Nylon, PVC, PP	[58]

(a) Note: PE—Polyethylene; PP—Polypropylene; PVC—Polyvinyl chloride; PVA—polyvinyl Acetate; LDPE—low-density polyethylene; PS—polystyrene; PU—polyurethane; PES/PEST—Polyester; PET/PETE—Polyethylene Terephthalate; HDPE—high-density polyethylene; PMMA—Polymethylmethacrylate; PA—Polyamide (Nylon); PUR/PU—Polyurethane; PTFE—Polytetrafluoroethylene; PEG—Polyethylene glycol; PLE—Poly(L-glutamic acid); POM—Polyoxymethylene; NY—Nylon; CL—Chlorinated polymers; N/A—Not available. (b) Note: PE—Polyethylene; PP—Polypropylene; PVC—Polyvinyl chloride; PVA—polyvinyl Acetate; LDPE—low-density polyethylene; PS—polystyrene; PU—polyurethane; PES/PEST—Polyester; PET/PETE—Polyethylene Terephthalate; HDPE—high-density polyethylene; PMMA—Polymethylmethacrylate; PA—Polyamide (Nylon); PUR/PU—Polyurethane; PTFE—Polytetrafluoroethylene; PEG—Polyethylene glycol; PLE—Poly(L-glutamic acid); NY—Nylon; CL—Chlorinated polymer; N/A—Not available.

summarizes the microplastic contamination in freshwater and coastal wetlands.

3.6. Fate and Pathways of Microplastics in Wetlands

Environmental microplastics primarily originate from poorly managed plastic waste and are formed through weathering processes [36], suggest that these particles are then redistributed via atmospheric and oceanic currents. Over time, atmospheric deposition and gravitational forces lead to their accumulation in different environmental compartments. These particles are then redistributed via atmospheric and oceanic currents. Over time, atmospheric deposition and gravitational forces lead to their deposition in different environmental segments.

The major pathways of microplastics in wetlands are surface water flow, tidal and ocean currents, sediment transport, groundwater pathways, and biological transport. One major pathway involves surface water flow, where microplastics are transported from wetlands into downstream rivers, streams, and estuaries, eventually reaching coastal and marine ecosystems (Figure 7). In coastal wetlands, tidal actions further drive the transfer of microplastics into estuarine waters, where they can enter global ocean currents and spread across vast marine areas. Sediment transport also plays a key role, with microplastics becoming embedded in wetland sediments and later resuspended during high-flow events such as floods or storms, facilitating their movement to riverbeds, deltas, and coastal sediments. Groundwater pathways contribute as well, with smaller microplastic particles infiltrating porous wetland soils, potentially reaching aquifers or reemerging in downstream springs and surface water systems. Biological transport is another crucial mechanism, as wetland organisms ingest microplastics, which are then redistributed through migration or trophic interactions, introducing these pollutants into a new environment.

3.7. Impacts of Microplastics in Wetland Ecosystem

According to the 2012 report by the Secretariat of the Convention on Biological Diversity titled Impacts of Marine Debris on Biodiversity, marine debris has negatively impacted all recognized species of sea turtles, nearly 50% of marine mammal species, and around 20% of seabird species through entanglement or ingestion [61]. Plastics are composed of a variety of potentially hazardous chemicals added during manufacturing, including monomers, oligomers, bisphenol-A (BPA), phthalate plasticizers, flame retardants, and antimicrobial agents [62]. These substances can enter the human body through multiple pathways, such as food and beverage containers, medical devices, and plastic toys. In addition to leaching these additives, plastic debris can adsorb persistent, bio-accumulative, and toxic substances, such as persistent organic pollutants (POPs), from the surrounding marine environment [61]. Over time, plastics undergo further fragmentation and degradation due to physical, chemical, and biological processes, leading to the formation of microplastics [63]. For instance, microplastics and debris fragments found on beaches have been shown to affect the sediment’s porosity and its ability to transfer heat [64]. Furthermore, climate change worsens microplastic pollution by disrupting ocean currents and modifying weather patterns, thereby influencing the distribution and impact of these pollutants [39].

Empirical studies have demonstrated the ingestion of microplastics by aquatic organisms. For instance, zooplankton have been reported to ingest microplastic particles, particularly microfibres, within measurable concentration ranges ingested between 0.03 and 2.04 microplastic particles per cubic meter [65]. These fibres are believed to mainly originate from fishing activities and other offshore recreational sources. Additionally, ref. [66] evidence indicates microplastics in myctophid fish and in the scats of Hooker’s sea lions and fur seals, pointing to the movement of microplastics through the pelagic food web -starting from zooplankton, then to myctophid fish, and eventually to marine mammals like sea lions and fur seals as such, lower trophic level organisms play a key role in transporting microplastics and the contaminants they carry through marine ecosystems [66]. These findings suggest that lower trophic organisms may facilitate the movement of microplastics through aquatic ecosystems, although the extent of biomagnification requires further investigation (Figure 8).

Laboratory-based studies provide evidence of physiological effects associated with microplastic exposure. For example, short-term exposure to microplastics (MP) has been shown to weaken the immune system, as seen in the scleractinian coral Pocillopora damicornis, where researchers observed a significant drop in alkaline phosphatase enzyme levels [67]. In Southeast Asia, only a limited number of studies have specifically looked at freshwater ecosystems. One such study by [68] investigated the presence of microplastics in fish species like Mystus bocourti, Puntioplites proctozysron, Hemibagrus spilopterus, and Cyclocheilichthys repasson from Thailand’s Chi River. However, similar to most marine-focused research, this study did not examine the biological impacts of microplastics. Research on microplastics present in commercially important marine fish has also been conducted in Malaysia; for instance, [35], reported microplastic particles in 9 out of the 11 fish species they analyzed. According to [38], nearly 70% of freshwater fish examined in earlier studies were found to have ingested fibres. Compared to other forms of plastic particles, fibres are more flexible, making them easier for smaller invertebrates within the food web to consume [69]. As a result, fibres are more likely to be accidentally ingested either through trophic transfer or when mixed with sediment. They are also commonly detected within freshwater sediments [70]. This ingestion can negatively impact aquatic organisms by reducing their growth rates, lowering hatchability, and affecting their ability to feed [71].

In wetland vegetation, experimental evidence suggests that microplastics may influence plant growth and physiological processes. For example, reduced germination rates negatively impact the growth of Bacopa species, a wetland plant, leading to reduced fresh weight and shorter plant height [72]. The accumulation of ingested polystyrene microplastics in the foraging structures responsible for capturing and digesting prey has been found to significantly retard the growth of aquatic plants [73]. Aquatic plants, whether emergent, floating-leaved, free-floating, or submerged, serve as vital primary producers in wetland ecosystems [74,75]. However, exposure to microgram-level concentrations of microplastics can impair both plant growth and the efficiency of nitrogen removal in these environments [76]. The accumulation of MPs in wetland sediments can severely destabilize plant root functions, disrupting water, nutrient, and oxygen transport, thereby reducing plant biomass development [77]. The findings of this study enhance our understanding of coastal vegetation as a sink for microplastics and indicate that variations in microplastic characteristics influence their accumulation patterns within biogenic canopies [78].

Regarding human health, exposure to microplastics is primarily associated with ingestion through contaminated food and water. Current literature indicates possible health effects such as oxidative stress and inflammatory responses, but direct causal relationships and long-term impacts are still under investigation [79]. Among these, ingestion through the gastrointestinal tract appears to be the most common exposure pathway (Figure 8). Ubiquitous plastics and their derivatives were found in all surveyed field samples, indicating widespread degraded microplastic residues that readily enter and bio-magnify within the food web [80].

3.8. Removal Technologies of Microplastics in Wetland Systems

The removal techniques presented include both conventional adsorption-based methods and emerging nanoremediation approaches. While conventional materials such as biochar and sponges are effective, nanomaterial-based systems offer enhanced surface area, reactivity, and potential for targeted removal, although they remain limited by cost, scalability, and environmental concerns.

These technologies primarily include adsorption-based removal, magnetic separation, and photocatalytic degradation processes. Adsorption techniques utilize natural, bio-based, and engineered materials with high surface area and affinity for plastic particles, offering cost-effective and environmentally friendly solutions. Magnetic adsorption enhances removal efficiency by enabling the rapid separation of MPs using externally applied magnetic fields. In contrast, photocatalytic degradation focuses on breaking down MPs into smaller or mineralized products under light irradiation, thereby reducing their environmental persistence. Each approach presents distinct advantages and limitations in terms of efficiency, cost, scalability, and environmental compatibility. Therefore, selecting an appropriate remediation strategy depends on factors such as the type of microplastics, environmental conditions, and the desired level of removal or degradation. Nanoremediation refers to the process of removing contaminants using nanomaterials or nanoparticles. Depending on the properties of these nanoparticles, the remediation can occur through mechanisms such as reduction, oxidation, sorption, or a combination of these processes [81]. Various forms of nanoparticles, like carbon-based nanomaterials, zero-valent iron nanoparticles, zinc oxide (ZnO), and titanium dioxide (TiO₂) have been well explored for remediation methods during the last couple of years. They may be employed in a variety of forms to increase their removal capacity, like catalysts, coatings, modifiers, and composites [82]. The benefits of nano-remediation include a high rate of removal with different contaminants and environmental conditions, fast degradation rate, quick clean-up time for contaminated sites, low toxicity, and the possible ability to be used over a wider scope [83]. Nanomaterials have the ability to be applied as absorbents, catalysts, and flocculants in the treatment process. Activated carbon, which has historically been employed as a solid adsorbent, proves to be successful because of its high surface area and porosity. The disadvantages of nano-remediation include the expense, agglomeration of nanomaterials within living organisms, and possible harm to human health and the environment by nanomaterials [83].

Various technologies for the removal or degradation of microplastics (MPs) in aquatic environments can be categorized into adsorption, magnetic adsorption, and photocatalytic degradation, as presented in

Table 2. Microplastic Removal Technologies and Efficiencies.

Mechanism	Technique	Removal Efficiency	Remarks (Advantages/Limitations)	Reference
Adsorption	Oat protein sponges	81.2%	Biodegradable and eco-friendly; moderate efficiency and limited data on MP specificity	[84]
	Sponge	92.2%	Simple and cost-effective; lacks information on polymer type and reuse	[85]
	Chitin-based sponge	89.6–92.1%	Sustainable material; efficiency depends on environmental conditions	[86]
	Biochar and modified	94.81%	Low-cost and widely available; potential secondary pollution and regeneration issues	[87]
	Biochar	98.75%	High adsorption capacity; saturation and disposal challenges	[88]
	Three-dimensional graphene	53.85%	High surface area; expensive and not scalable	[88]
	Photocatalytic TiO2-based Micromotor	71% removal in 0.2% H2O2 solution	Active removal mechanism; requires chemical additives (H2O2)	[89]
	Fe2O3-MnO2 MNMs	>10% of suspended MPs separated from polluted water within 2 h	Rapid separation; low removal efficiency limits application	[90]
	Zirconium metal -organic framework-based foam	95.5%	High efficiency and selectivity; high cost and stability concerns	[90]
	Zn-Al LDH	100% removal at pH 4	Excellent removal efficiency; strongly pH-dependent	[91]
	GAC	98%	Established technology; adsorption saturation over time	[92]
	Coffee grounds	74%	Sustainable and low-cost; moderate efficiency and variability	[93]
Magnetic adsorption	Hydrophobic Fe nanoparticles	Large MPs: 74–105%; Medium MPs: 59–100%; RO water: 49–90%; Small MPs in sediment: ~90%	Easy magnetic recovery; aggregation and stability issues	[94]
	M-Carbon nanotubes	100%	High efficiency; high production cost and scalability issues	[95]
	Magnetic-CNTs	PA, PE, PET: 100%	Polymer-specific high efficiency; environmental concerns of nanomaterials	[96]
	Fe-HDTMS	92%	Strong hydrophobic interaction; chemical stability concerns	[95]
	Fe3O4	80%	Simple magnetic separation; moderate efficiency	[94]
	Fe3O4	Sea water: 80.56% Domestic sewage: 82.28%	Applicable in real samples; efficiency varies with water matrix	[95]
Photocatalytic degradation	Hydroxy-rich ultrathin BiOCl	PE-S mass loss 5.38%; PE-mass loss 0.22%	Environmentally friendly; very low degradation efficiency	[96]
	TiO2 nanoparticle film (with Triton X-100)	98.40% mineralization of 400 nm PS in 12 h	High degradation efficiency; requires UV light and controlled conditions	[97]
	Poly (styrene-block-acrylic acid)/TiO2 gel (PS-b-PAA/TiO2)	The molecular weight decreases: 10% to 11%	Partial degradation; slow reaction kinetics	[98]
	Protein-based porous N-TiO2 semiconductor	A total mass loss of 1.85% during the first 16 h of irradiation	Low degradation efficiency; limited practical application	[99]
	Mesoporous N-TiO2 coating	HDPE_A: 0.22 ± 0.02%; HDPE_B: 4.65 ± 0.35%; LDPE: 0.97 ± 0.32%; small LDPE: 1.38 ± 0.13%	Polymer-specific degradation; overall low efficiency	[100]

Note: MPs—microplastics; PA—polyamide; PE—polyethylene; PET—polyethylene terephthalate; PS—polystyrene; HDPE—high-density polyethylene; LDPE—low-density polyethylene; CNTs—carbon nanotubes; GAC—granular activated carbon; MNMs—magnetic nanomaterials; LDH—layered double hydroxide, N-TiO₂—Nitrogen-doped titanium dioxide; BiOCl—Bismuth oxychloride photocatalyst; Fe-HDTMS—Iron particles functionalized with hexadecyltrimethoxysilane; N/A—Not available.

.

With materials such as biochar, chitin-based sponges, and granular activated carbon, adsorption-based techniques exhibit above 90% removal rates, while modified biochar reaches up to 98.75%. Oat protein sponges and coffee grounds, which are bio-based materials, also prove to be sustainable and low-cost adsorbents.

Magnetic nanoparticles and carbon nanotube composites are used to separate microplastics in magnetic adsorption processes through magnetic fields. High removal efficiencies are achieved using hydrophobic materials such as iron nanoparticles, magnetic CNTs, and Fe₃O₄ nanoparticles for certain polymers.

Semiconductor catalysts such as TiO₂, ZnO, and BiOCl are used in photocatalytic degradation processes to degrade plastic polymers under light exposure. Studies show that further optimization is required to achieve mineralization efficiencies up to 98.4% for polystyrene particles using TiO₂ nanoparticle films.

3.9. Advantages and Limitations of Nanoremediation

Although nanoremediation strategies have demonstrated promising efficiency in the removal and degradation of microplastics, it is important to note that most of the current findings are based on controlled laboratory-scale experiments. The performance of nanomaterials such as TiO₂, ZnO, Fe₃O₄, and graphene-based composites under real environmental conditions remains insufficiently explored. Factors such as complex wetland matrices, variable hydrodynamics, natural organic matter, and competing pollutants may significantly influence their effectiveness in field conditions. The removal techniques summarized in Table 2 demonstrate considerable variability in efficiency depending on the material properties, microplastic type, and experimental conditions. Adsorption-based methods, particularly those using biochar, graphene, and metal–organic frameworks, exhibit high removal efficiencies; however, their performance is often limited by issues such as saturation, regeneration challenges, and lack of specificity toward different polymer types. Magnetic adsorption techniques offer the advantage of easy recovery and high efficiency, especially for polymers such as polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET), but concerns remain regarding aggregation, cost, and large-scale applicability. In contrast, photocatalytic degradation methods show potential for the breakdown of microplastics; however, their efficiency is generally lower and dependent on factors such as irradiation time, catalyst properties, and polymer composition. Furthermore, several studies do not specify the type of microplastics targeted, limiting comparability and practical application. Overall, while these methods demonstrate promising removal capabilities, challenges related to scalability, environmental safety, and real-world implementation remain significant, highlighting the need for further research, particularly in the development of efficient and sustainable nanoremediation approaches.

4. Discussion

The removal techniques summarized in Table 2 demonstrate considerable variability in efficiency depending on the material properties, microplastic type, and experimental conditions. Adsorption-based methods, particularly those using biochar, graphene, and metal–organic frameworks, exhibit high removal efficiencies; however, their performance is often limited by issues such as saturation, regeneration challenges, and lack of specificity toward different polymer types. Magnetic adsorption techniques offer the advantage of easy recovery and high efficiency, especially for polymers such as polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET), but concerns remain regarding aggregation, cost, and large-scale applicability. In contrast, photocatalytic degradation methods show potential for the breakdown of microplastics; however, their efficiency is generally lower and dependent on factors such as irradiation time, catalyst properties, and polymer composition. Furthermore, several studies do not specify the type of microplastics targeted, limiting comparability and practical application. Overall, while these methods demonstrate promising removal capabilities, challenges related to scalability, environmental safety, and real-world implementation remain significant, highlighting the need for further research, particularly in the development of efficient and sustainable nanoremediation approaches.

Limitation of the study: This study is limited by the use of a single database (Web of Science), which may exclude relevant studies indexed elsewhere. The bibliometric approach focuses on publication trends and does not evaluate experimental quality. Furthermore, variability in sampling methods and analytical techniques across studies limits direct comparison of microplastic concentration data. It should be noted that bibliometric analyses are dependent on database indexing and may not fully capture all global research outputs, particularly from non-indexed or regional publications.

This study is subject to potential sources of bias. The use of a single database (Web of Science Core Collection) may exclude relevant studies indexed elsewhere. Additionally, the restriction to English-language publications introduces language bias.

5. Conclusions

This study highlights the increasing prevalence of microplastic pollution in wetland ecosystems, driven by sources such as urban runoff, industrial discharge, fisheries and agricultural practices. The review demonstrates that the particles originating from diverse sources accumulate in sediments and water columns, facilitating their entry into the food web through aquatic micro-organisms. Despite the growing body of research, significant gaps remain in understanding the unique interactions between microplastics and wetland dynamics, including sediment–water–plant systems, advanced remediation technologies such as nanomaterial-based adsorption, photocatalytic degradation and magnetic separation, which are promising methods for microplastic removal. The findings emphasize the critical role of wetlands as both sinks and sources of microplastics, with implications for biodiversity, water quality, and ecosystem services. The bibliometric trends reveal a rapid increase in research post-2016, reflecting the growing global recognition of microplastic pollution, with China, the USA, and India emerging as key contributors. Methodological advancements, such as VOSviewer analysis, have facilitated a deeper exploration of research hotspots, but developing regions remain underrepresented in the literature. Overall, the study stresses the need for future research that prioritizes stronger international collaboration and improved policy frameworks to mitigate microplastic pollution. Such efforts are essential to alleviate the ecological impacts of microplastic accumulation in wetlands and explore integrated conservation strategies that align with global sustainability goals, particularly SDG 6 (Clean Water and Sanitation), SDG 13 (Climate Action), SDG 14 (Life Below Water) and SDG 15 (Life on Land). These bibliometric findings have direct and measurable implications for sustainability goals. The underrepresentation of wetland-focused studies identified in this analysis constrains scientific progress toward SDG 6 (Clean Water and Sanitation) by limiting understanding of microplastic behavior in critical freshwater systems. Similarly, the fragmented and laboratory-dominated nature of remediation research hinders effective contributions to SDG 14 (Life Below Water), where ecosystem-scale solutions are essential.

6. Recommendations and Future Directions

This study aligns with SDG 15 (Life on Land), focusing on conserving wetland ecosystems by addressing microplastic pollution. It further contributes to SDG 6 (Clean Water and Sanitation) by improving water quality in these habitats and to SDG 14 (Life Below Water) by mitigating land-based pollution that impacts marine environments. “Future research should integrate the goals of Ramsar Convention on Wetlands, Global Plastics Treaty under UNEP (United Nations Environment Programme), SDG 6 (Clean Water and Sanitation), SDG 12 (Responsible Consumption and Production), SDG 13 (Climate Action), SDG 14 (Life Below Water) and SDG 15 (Life on Land) by developing innovative approaches for wetland restoration and sustainable management. Additionally, the study of microplastic transport from wetlands to oceans can guide strategies under SDG 14 to prevent marine pollution. According to [62], proactive policies and programs effectively manage waste and recycling to reduce land-based sources of marine debris. Examples include packaging and plastics reduction, eco-labelling, green procurement, extended producer responsibility (EPR), deposit-return programs, user fees for single-use plastics, waste resource utilisation, corporate engagement in sustainability, green chemistry, improved product and packaging design, and marine debris awareness initiatives. The study also concludes that emerging remediation approaches should be further evaluated for environmental safety and scalability before integration into environmental management strategies. Finally, wetland management policies should explicitly represent the growing global environmental concern related to ecological, economic, and public health implications, incorporating microplastic pollution as a key environmental threat. To address this, it requires coordinated international policy action, including technological innovations, scientific research, pollution prevention and strengthened governance frameworks.