Search Results (6,972)

The presence of heavy metals plays a significant role in indoor air quality, which poses a serious public health problem since most of the population spends over 90% of their time in indoor environments. This work investigates heavy metals in indoor dust across different occupational settings in Macao. Field sampling was conducted in five representative locations, which included restaurants, student dormitories, auto repair shops, offices, and parking security rooms, with a total of 11 samples collected in this study. Dust in the form of particulate matter was collected from air conditioning filters to quantify 14 heavy metal contents. The PMF model was applied for source apportionments of the heavy metals, while a health exposure model was used to assess health risks and evaluate the non-carcinogenic and carcinogenic risks in the five representative workplaces. The PMF model identified six major pollution sources: traffic emissions (23.800%), building materials (21.600%), cooking activities (18.500%), chemicals (15.200%), electronic devices (12.300%), and outdoor seaport activities (8.600%). The health risk assessment showed that the overall non-carcinogenic risk (HI = 6.160 × 10⁻⁶ for inhalation, 1.720 × 10⁻³ for oral ingestion, and 2.270 × 10⁻⁵ for dermal contact) and total HI (1.749 × 10⁻³) and carcinogenic risk (6.570 × 10⁻⁹) were below the safety threshold, showing minimal health risk problems. Nevertheless, nickel and chromium were identified as the main contributors to potential long-term risks. Full article

The detrimental effects of anthropogenic pollution are often magnified across ecosystems due to the interconnected nature of land, rivers, and oceans. Phytoremediation is an accessible technique that leverages the ability of plants to absorb and sequester pollutants and can potentially mitigate contaminants entering the ocean. It is a cost-effective and minimally invasive alternative to traditional water treatment methods. This study investigates the potential of the grapevine species Cissus verticillata (L.), a native plant from Puerto Rico, to be used in the phytoremediation of a creek in a highly urbanized site impacted by contaminated runoff due to heavy rainfall and sanitary waters. A mesocosm experiment was conducted using distilled water mixed with nutrients and known concentrations of cadmium (Cd) and lead (Pb) salts to assess whether C. verticillata could accumulate heavy metals in its tissues. Results showed that C. verticillata successfully absorbed heavy metals, with removal efficiencies of 80.13% (±0.16 SE) for Pb and 44% (±1 SE) for Cd. Results indicated a translocation factor <1 for both cadmium and lead, meaning C. verticillata is not a hyperaccumulator, but a metal stabilizer, as evident by the below detection limit (BDL) of the metals in Juan Mendez Creek. Despite evidence of new vegetative growth among individuals, no significant changes in total biomass or chlorophyll concentration were detected, indicating that C. verticillata maintained physiological stability under heavy metal exposure. Therefore, C. verticillata’s wide availability, adaptability to various environments, and climbing nature—which makes it less vulnerable to runoff and strong currents during rainy seasons—position it as a promising candidate for conservation initiatives and pollution management strategies. Full article

In this work, two novel nanoscale zero-valent iron (nZVI) composites (nanoscale zero-valent iron and copper-intercalated montmorillonite (MMT-nFe⁰/Cu⁰) and carbon microsphere-supported sulfurized nanoscale zero-valent iron (CMS@S-nFe⁰)) were used to treat soil contaminated with both Cr(VI) and p-nitrophenol (PNP), and added persulfate (PMS). Experiments found that the pollutant removal effect has a great relationship with the ratio of water to soil, the amount of catalyst, the amount of PMS, and the pH value. When the conditions are adjusted to the best (water–soil = 2:1, catalyst 30 g/kg, PMS 15 g/kg, pH 7–9), both materials fix Cr(VI) well and decompose PNP. The removal rates of Cr(VI) and PNP by the MMT-nFe⁰/Cu⁰ system are 90.4% and 72.6%, respectively, while the CMS@ S-nFe⁰ system is even more severe, reaching 94.8% and 81.3%. Soil column leaching experiments also proved that the fixation effect of Cr can last for a long time and PNP can be effectively decomposed. Through detection methods such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS), we found that Cr(VI) was effectively reduced to Cr(III) by Fe⁰ and Fe²⁺ ions and subsequently transformed into stable FeCr₂O₄ spinel oxides, and the groups produced after the decomposition of PNP could also help fix the metal. This work provides a way to simultaneously treat Cr(VI) and PNP pollution, and also allows the use of multifunctional nZVI composites in complex soil environments. Full article

Most risk assessment and source apportionment studies of the heavy metals in the surface soils in China have focused primarily on East China, whereas studies focused on Northwest China, particularly regarding heavy metals in surface soils in the central and western areas, remain limited. In this study, surface soils in the central–western Ali region were investigated, and the concentrations of nine heavy metals were determined. Moreover, the distribution patterns and ecological risks of these heavy metals were elucidated via a combination of the geoaccumulation index, pollution load index ($PLI$), comprehensive potential ecological risk index ($RI$), and integrated X-ray diffraction (XRD)–multivariate statistical techniques. Additionally, the pollution characteristics and sources were analyzed. The results indicated the following: (1) The spatial distribution of heavy metal pollution is closely linked to the geological background, and high–pollution zones (e.g., Cr, Ni, Co, Cu, As, and Cd) conform well with the distributions of ultramafic rocks and iron/chromite ore beds. The geoaccumulation index revealed that Cd caused slight and moderate contamination at 29.1% and 5.5% of the sites, respectively, whereas As affected 14.6% of the sites. The pollution load index indicated moderate pollution in 20% of the sites, and the potential ecological risk index indicated that 41.8% of the sites posed moderate risks, which was largely driven by Cd (mean $E_r^i$ = 43.1). The comprehensive ecological risk index ($RI$ = 115) confirmed a moderate risk level overall. Principal component analysis revealed three primary sources: natural weathering (Cr–Ni–Co–Cu, 39.1%); a mixed source influenced by nonagricultural anthropogenic activities such as transport and regional deposition, combined with natural processes such as arid climate and alkaline soil conditions that influence Cd mobility (Cd–Mo–Pb, 20.8%); and industrial/mining activities (As–Sb, 14.2%). Mineralogical analyses further indicated that heavy metals are present via lattice substitution, adsorption, and precipitation. This study systematically clarifies the composite pollution pattern and sources of heavy metals in the alpine Ali region, supporting targeted contamination control. Full article

Chlorobenzoic acids (CBAs) are a group of chlorinated persistent environmental pollutants with hard biodegradability, high water solubility, and well-documented carcinogenic and endocrine-disrupting properties. Electrocatalytic hydrodechlorination (ECH) is a highly efficient method under mild conditions without harmful by-products, but the ECH process commonly requires adding precious metal catalysts such as palladium (Pd). To address the economic constraints and more effective utilization of Pd, a palladium/manganese dioxide (Pd/MnO₂) composite catalyst was developed in this study by chemical deposition. This method utilized the excellent electrochemical activity of MnO₂ as a carrier as well as the hydrogen storage and activation capacity of Pd. The test showed the optimal Pd loading was 7.5%, and the removal percent of 2,4-dichlorobenzoic acid (2,4-DCBA), a typical CBA, reached 97.3% using 0.5 g/L of Pd/MnO₂ after 120 min of electrochemical reaction. Under these conditions, the dechlorination percent can also be as high as 89.6%. A higher current density enhanced the dechlorination efficiency but showed the lower current utilization efficiency. In practical applications, current density should be minimized on the premise of compliance with the water treatment requirement. Mechanistic studies showed that MnO₂ synergistically promoted hydrolysis dissociation and hydrogen spillover and facilitated Pd-mediated adsorption of atomic hydrogen (H*) for dehydrogenation of 2,4-DCBA. The presence of MnO₂ can effectively disperse the loaded Pd and reduce the amount of Pd via the above process. The catalyst exhibited excellent stability over multiple cycles, and the 2,4-DCBA removal could still reach more than 80% after the five cycles. This work establishes electrocatalytic strategies for effectively reducing Pd usage and maintaining high removal of typical CBAs to support CBA-related water treatment. Full article

Heavy metal pollution remains one of the major environmental challenges due to the persistence and toxicity of metals such as Pb(II). This study investigates the potential of natural diatomite from Mugaldzhar, Kazakhstan, as a low-cost and sustainable sorbent for lead removal from aqueous solutions. The effects of key parameters, including sorbent dosage, particle size, contact time, temperature, and initial Pb(II) concentration, were systematically examined. Adsorption experiments revealed a maximum adsorption capacity of 74.9 mg/g at 45 °C and an initial Pb(II) concentration of 800 mg/L. The adsorption behavior followed the pseudo-second-order kinetic model, indicating a chemisorption mechanism, while isotherm analysis showed a transition from Langmuir to Freundlich type with increasing temperature. Thermodynamic data confirmed the spontaneous and endothermic nature of the process. These results demonstrate that unmodified natural diatomite exhibits high efficiency for Pb(II) removal, emphasizing its suitability as an eco-friendly and cost-effective material for water purification and environmental remediation. Full article

The Água Forte (AF) stream located in the Southern Alentejo region (Portugal), is a tributary of the Roxo river. The AF stream has acid mining drainage (AMD) traits, which contributes to the degradation of the river’s water quality and the adjacent soils. The use of ecological floating beds (EFBs) is an eco-rehabilitation strategy for polluted waters. This work aimed to evaluate the application of EFBs at real-scale as a water treatment system for the AF stream. Thus, three EFB, planted with Vetiveria zizanioides (3.3 m²·unit⁻¹; density 40.5 plants·m⁻²), were placed on the stream. The water quality was monitored monthly, upstream (Inlet) and downstream (Outlet) of EFBs, from May 2020 to November 2021. With the use of the EFBs, the pH remained acidic, and the other main parameters showed average removal rates of around: 8% organic matter; 7% sulphates; 4% chlorides; 18% nitrogen, 30% copper, 29% zinc, 53% iron, and 10% manganese. Inlet and Outlet mass loads correlations showed high removal diversity. For the parameters under analysis, during the treatment period, the removal efficiency showed high variability due to the hydraulic conditions. The higher removal efficiencies were obtained for low-hydraulic retention times, except for heavy metals. Overall, EFBs showed some potential, but their efficiency was variable, highlighting the need for optimization under variable hydraulic conditions. Full article

Developing efficient photocatalysts is essential for sustainable wastewater treatment and tackling global water pollution. Graphitic carbon nitride (g-C₃N₄) is a promising material because it is active under visible light and chemically stable. However, its practical application is limited by fast recombination of charge carriers and a low surface area. In this study, we report a simple hydrothermal method to synthesize exfoliated porous g-C₃N₄ (E-PGCN) combined with Ti₃C₂ MXene to form a heterojunction composite that addresses these issues. Various characterization techniques (FTIR, XRD, XPS, SEM, BET) confirmed that adding MXene improves light absorption, increases surface area (53.7 m²/g for the composite versus 21.4 m²/g for bulk g-C₃N₄ (BGCN)), and enhances charge separation at the interface. Under UV-visible light irradiation with Rhodamine B (RhB) as the model pollutant, the E-PGCN/Ti₃C₂ MXene composite containing 3 wt% MXene demonstrated an impressive degradation efficiency of 93.2%. This performance is superior to BGCN (66.6%), E-PGCN (82.5%), and E-PGCN/Ti₃C₂ MXene-5 wt% composites (81%). This is due to the excess Mxene which caused agglomeration and reduced activity. Scavenger studies identified electron radicals as the dominant reactive species, with optimal activity at pH ~4.5. This enhanced performance, 1.4 times greater than BGCN and 1.13 times higher than E-PGCN, is ascribed to the synergistic interplay between the excellent electrical conductivity of MXene and the porous structural features of E-PGCN. This work highlights the importance of morphological engineering and heterojunction design for advancing metal-free photocatalysts, offering a scalable strategy for sustainable water purification. Full article

Water resource management and agricultural practices in the Mediterranean region, characterised by the excessive use of pesticides, pose significant environmental and human health challenges. As they can be easily and inexpensively produced from various biomass sources, biochars are frequently recommended as a low-cost secondary decontamination strategy to address soil contamination problems. This study investigates the properties and sorption behaviours of biochars produced in a low-cost metallic kiln using local rosemary, giant reed, St. John’s wort, olive, cypress, and palm tree biomass residues to evaluate their potential for environmental remediation, with a special focus on the mobility and retention of contaminants. Analytical and experimental techniques were employed to characterise the biochars’ physicochemical attributes and sorptive capacities. The core analyses included measurement of basic physicochemical properties, including pH, electrical conductivity, functional group identification via Fourier transform infrared (FTIR) spectroscopy, and the molarity of ethanol droplet (MED) test to assess the surface hydrophobicity. Batch sorption experiments were conducted using methylene blue (MB) and two fluorescent tracers—uranine (UR) and sulforhodamine-B (SRB)—as proxies for organic contaminants to assess the adsorption efficiency and molecule–biochar interactions. Furthermore, the adsorption isotherms at 20 °C were fitted to different models to assess the biochars’ specific surface areas. Thermodynamic parameters were also evaluated to understand the nature and strength of the adsorption processes. The results highlight the influence of feedstock type on the resulting biochar’s properties, thus significantly affecting the mechanism of adsorption. Rosemary biochar was found to have the highest specific surface area (SSA) and cation exchange capacity (CEC), allowing it to adsorb a wide range of organic molecules. Giant reed and palm tree biochars showed similar properties. In contrast, wood-derived biochars generally showed very low SSA, moderate CEC, and low hydrophobicity. The contrasting properties of the three dyes—MB (cationic), UR (anionic), and SRB (zwitterionic)—enabled us to highlight the distinct interaction mechanisms between each dye and the surface functional groups of the different biochars. The reactivity and sorption efficiency of a biochar depend strongly on both the nature of the target molecule and the intrinsic properties of the biochar, particularly its pH. The findings of this study demonstrate the importance of matching biochar characteristics to specific contaminant types for optimised environmental applications, providing implications for the use of tailored biochars in pollutant mitigation strategies. Full article

Long-term mining activities have introduced heavy metals (HMs) into the soil, ultimately threatening environmental sustainability. Precisely forecasting the spatial patterns of HMs and performing risk evaluations in mining regions are essential for efficient pollution control. In this study, 213 topsoil samples were collected from the Fengfeng Mining Area, which has a 150-year mining history. To determine the spatial distribution of soil HM speciation, correlation analysis was conducted by integrating landform types, and visualization was carried out through Kriging interpolation. Results indicate that the mean levels of Cd, Cu, Pb, and Zn exceed their respective background values by 6.48, 1.61, 4.79, and 4.35 times. The bioavailability sequence is Cd > Pb > Zn > Cu, with elevated levels of bioavailable Cd and Pb observed in the western hilly region. Based on the secondary phase to primary phase ratio (RSP) and the risk assessment code (RAC), Pb and Cd were identified as posing high ecological risks, whereas Cu and Zn do not cause severe contamination. This study provides a scientific foundation for industrial transformation and sustainable development in resource-exhausted cities. Full article

The ubiquitous environmental pollution with micro- and nano-sized plastic particles (MNPs) is a current and significant problem today. At the same time, lung cancer is responsible for the largest number of cancer-related deaths worldwide. Many research groups have investigated the relationship between lung cancer development and exposure to MNPs in recent years. Studies have demonstrated that these particles could enter the respiratory system in a variety of ways—both directly through inhaled air and through the bloodstream, and through internalization in the intestines and other digestive organs. Data regarding the possibility of their aggregation in the respiratory system, thyroid gland, and brain are also concerning, as the harmful effects of MNPs have been proven to depend on their concentration and exposure time. The primary response of cells to plastic particles is an increase in oxidative stress. This is generated both by the cell itself (especially macrophages) and induced by damage caused by mechanical damage to cellular organelles by MNPs. The consequences of MNP exposure can include metabolic disturbances, DNA damage, and mutations, ultimately inducing neoplastic transformation in healthy cells. This can lead to changes in tissue architecture and increase their susceptibility to other pathogens, such as pathogenic microorganisms or heavy metals. These, in turn, can be internalized along with MNPs, forming a corona surrounding them. Full article

Freshwater quality criteria (FWQC) are essential scientific thresholds established to protect human health and aquatic ecosystems, serving as the foundation for water quality standards, environmental risk management, and pollution control. The latest research advancements were summarized, including the screening of priority pollutants for FWQC and the theory and methodology for environmental criteria in China in the last decade. The potential work has been meticulously analyzed and discussed concerning FWQC to be conducted in the short-term future. The possible prioritized list of pollutants for FWQC should be concerned with including nine categories of heavy metal ions, three categories of non-metal ions, and five categories of organic compounds in the short-term future research. The guidelines for deriving FWQC for the protection of human health for organoleptic effects and for sediment need to be modified and emphasized to ensure the safety of drinking water sources, address issues related to black and odorous surface water, and protect the biodiversity of benthic organisms. Toxicity data, water quality parameters, exposure data, and the geographical distribution of freshwater species should be systematically collected to support the development of FWQC in China. The potential applications of FWQC were also explored in the evaluation and formulation of WQS, ecological risk assessments, and the management of environmental emergencies and damage assessments to support environmental protection and management in China. Full article

Recent advances in microbial bioremediation have significantly enhanced the effectiveness of wastewater management, offering innovative and sustainable alternatives to conventional treatment methods. Microorganisms, including bacteria, fungi, and algae, are increasingly recognized for their remarkable ability to degrade, transform, and remove a broad spectrum of pollutants such as organic compounds, heavy metals, and emerging contaminants from wastewater. Cutting-edge research has led to the development of novel approaches such as bioaugmentation, bio-stimulation, and the use of genetically engineered microbes, which have improved the efficiency, specificity, and resilience of bioremediation processes. The application of microbial consortia and advanced bioreactor designs further optimizes pollutant removal under diverse environmental conditions. Additionally, omics technologies and systems biology are providing deeper insights into microbial community dynamics and metabolic pathways, enabling the fine-tuning of bioremediation strategies for targeted outcomes. Despite ongoing challenges related to scalability, environmental variability, and regulatory considerations, these advances are paving the way for more robust, cost-effective, and eco-friendly wastewater management solutions. Overall, the integration of innovative microbial technologies holds great promise for addressing global water quality challenges and promoting environmental sustainability. Full article

Spatial distribution of trace elements (TEs) in soils of the city of Dschang (Cameroon) was studied to identify their origin (geogenic vs. anthropogenic). The topsoil (at different depths) of 71 sites was analyzed using the rapid portable X-ray fluorescence analysis method. Soils from locations associated with metal-related activities exhibited the highest levels of contamination (average concentrations in mg kg⁻¹: As, 8.2; Cr, 213.7; Cu, 201.8; Pb, 97.4; Zn, 838.0), followed by household waste dumps and agricultural plots (levels close to those of cultivated low-lying areas). The observed decrease in TE concentrations with depth (notably for Zn) supports the hypothesis of a human origin (compared with soil-geochemical background of control sites). Geostatistical approach indicated an underestimation of health risks associated with the consumption of crops from several sites. Specifically, 87.32%, 49.30%, and 47.89% of the sites exceeded the Food Crops Reference Value (FCRV) for Cr, Zn, and Cu, respectively. Additionally, the number of contaminated sites for each TE varies depending on the method: Cu > Zn > Pb > Cr > As = Ni > Cd and Cr > Zn > Cu > Ni > Pb > As > Cd with the geostatistical and FCRV approach respectively. From the first step of the soil chemical quality investigation, our study highlights the need to use methods based on health risks, especially for sensitive uses of soils such as food production. Full article

Surfactants are chemical compounds present in a large number of products that people use on a daily basis, starting with detergents for washing clothes, dishes, personal hygiene products, etc. Some products also contain certain heavy metals. Their uses cause heavy contamination of wastewater that must be purified before discharge into receivers. Given that some types of surfactants are very persistent and heavy metals are non-biodegradable and toxic even in small concentrations, the purification process requires a complex approach and a combination of different methods. Bioremediation, as an environmentally acceptable and economically clean technology, has great potential. It is based on the use of indigenous microorganisms that have developed different mechanisms for breaking down and removing or detoxifying a large number of pollutants and are excellent candidates for bioremediation of wastewater. Bacteria can degrade surfactants as sole carbon sources and exhibit tolerance to various heavy metals. This paper summarizes the most significant results, highlighting the potential of bacteria for the biodegradation of surfactants and heavy metals, with the aim of drawing attention to their insufficient practical application in wastewater treatment. Bioreactors and microbial fuel cells are described as currently relevant strategies for bioremediation. Full article