Sequestration and export of microplastics in urban river sediments

Distribution and characteristics of microplastics in fluvial sediments from the Koshi River Basin, Nepal

Microplastics (MPs) are emerging contaminants found in various ecosystems including oceans, lakes, rivers, sediment, air, and soil. Mapping of MPs in different deposition zones in fresh water sediment is important to identify their potential sources, sink, and transport mechanism. In this study, MPs were analyzed in sediment samples from Arun, Tamor, and Koshi Rivers in eastern Nepal. A total of 78 samples from 26 sites were collected from three independent deposition regions i.e., recent deposition (R0), recent past deposition (R1), and past deposition (R2) during monsoon season in 2023. All samples were analyzed following standard methods involving drying, peroxidation, density separation, microscopic examination and chemical identification by FTIR. In all the river basins differences in MPs count, color, and morphology were observed in three deposition regions. In Koshi basin the MPs count ranged from 7016-8876 MPKg-1, 8396-10596 MPKg-1, and 9416-9816 MPKg-1 in R2, R1 and R0 regions, respectively. The mean abundance was found to be higher in downstream especially in Koshi River. The predominant shapes, sizes, and colors found in all three river basins were fragment (52.5 %), 20-100 μm (58.86 %), and black (33.76 %). The particles were identified as polyamide, polypropylene, polyvinyl chloride, polysulfone, nylon, and polyether ether ketone. The pollution risk assessment indicated minimal MPs contamination upstream and moderate contamination downstream. Finally, principal component analysis (PCA) and land use and land cover change (LULC) data were utilized to identify the potential sources of MPs. Agricultural and anthropogenic sources were identified as major contributors to the MPs load. This study provides baseline data for MP concentrations and their potential sources in Arun, Tamor, and Koshi river sediments. These insights could be important for future MPs mitigation strategies.

Comprehensive analysis of microplastics at typical outlets around Hainan Island: From spatial distribution to flux estimation and correlation analysis

Previous studies on microplastics (MPs) distribution have predominantly focused on water bodies within specific regions, with limited emphasis on the contributions of MPs directly discharged from functional zones surrounding isolated island. This study addressed this gap by investigating the occurrence and distribution of MPs in water and sediment directly discharged into the adjacent coast of Hainan Island, a geographically isolated and ecologically sensitive region in the South China Sea. Based on the sampling from 40 typical sewage outlets (affiliated to five functional zones, i.e., wastewater treatment plants (WWTP), industrial area (ID), residential area (RA), aquaculture area (QA), estuary (EST)) around the Hainan Island, we analyzed the MPs abundance and composition in water and sediment. Our findings revealed significant contributions of land-derived MPs, with an average abundance of 15,900 items/m3 in water and 3171 items/kg in sediment. Annually, approximately 61.6 trillion MPs were discharged into the South China Sea via rivers from Hainan Island, highlighting its role as a major land-derived source of MPs pollution in this critical marine ecosystem. Risk assessments indicated the H and PLI level of Hainan Island as II and I, respectively, with H-water level highest in WWTP and EST as III and H-sediment level highest in WWTP, RD and QA as II, and this indicated the critical function of WWTP to control the release of land-derived MPs and reduce the environmental risks. Correlation analysis underscored the influence of natural factors (currents, tides, waves, and drifts), socio-economic factors (population density, regional area, and agricultural output), and anthropogenic activity (tourism development) on coastal MPs pollution. On the basis of existing timely MPs prevention and control measures in Hainan province, such as intercepting the MPs via WWTP and prohibiting the direct discharge of aquaculture wastewater to the surrounding sea, this study re-underscored the urgency of MPs management on the protection of the South China Sea's eco-environmental quality in view of the pivotal role of Hainan Island on the isolated geographic position and the South China Sea's ecological health. Overall, this study offered scientific insights to support source-oriented strategies for coastal MPs pollution control by providing fundamental data for predicting land-derived MPs contributions on an island-scale.

The spatio-temporal variability of soil microplastic distribution and erosion-induced microplastic export under extreme rainfall event using sediment fingerprinting and 7Be in intensive agricultural catchment

Intensive agricultural production and land management often lead to soil microplastics (MPs) accumulation and aggravated erosion consequently polluting water bodies. However, little is known about the occurrence and migration of soil MPs induced by soil erosion at the catchment scale. This study firstly reported the spatio-temporal variability in soil MPs distribution, and erosion-induced microplastic export loads under extreme rainfall events in an intensive agricultural catchment. The results indicated that microplastic abundance peaked in November 2022 and varied by land use types, among which cropland converted from forest (C(F)) and crop farmland (C) had the highest abundance, vegetable farmland (V) had the lowest abundance on average. Most MPs were < 500 μm and the primary polymers were polyamide (PA), polypropylene (PP) and polyethylene (PE). Sediment contribution and microplastic export loads were identified using compound specific stable isotope and Berillium-7 under an extreme rainfall event. F and C(F) were merged because their δ13C values were non-distinguishable and were identified as the primary sediment source (50.14 ± 0.27 %), contributing most to microplastic export loads due to land management policy shifting. Changed land uses should be the main focus for catchment erosion control and microplastic pollution prevention in intensive agriculture in China and elsewhere.

Microplastic contamination in sediments: Analytical techniques and case-based evaluations

Microplastics (MPs) pollution in sediments has gained critical attention due to its pervasive presence and potential ecological risks. This review synthesizes the latest advancements in analytical techniques, providing a comprehensive overview of separation and identification methods tailored to complex sedimentary matrices. Density-based approaches, such as ZnCl2 or NaI solutions, and enzymatic digestions are increasingly refined to isolate MPs of varying sizes, yet discrepancies in mesh sizes, reagent concentrations, and digestion protocols continue to complicate cross-study comparisons. Meanwhile, cutting-edge spectroscopic tools-μFTIR, Raman imaging, thermal analyses-have greatly enhanced polymer identification down to the tens-of-micrometers scale. Case studies spanning urban estuaries to remote deep-sea basins underscore the pervasive nature of MPs worldwide, with fibers and fragments frequently dominating sediment samples. Factors such as polymer density, hydrodynamics, and biofouling contribute to the diverse distribution patterns, revealing that even ostensibly pristine environments are not exempt from contamination. Although the precise ecological and toxicological consequences of long-term sediment-bound MPs remain partly unclear, growing evidence points to intricate interactions with co-occurring contaminants and potential trophic transfer. To address these knowledge gaps, this review emphasizes the urgent need for methodological standardization and collaborative initiatives, particularly for emerging challenges like nanoplastic detection. By integrating robust sampling approaches, advanced analytical tools, and interdisciplinary research, scientists and policymakers can more accurately map and mitigate the impacts of sediment-associated MPs on aquatic ecosystems.

Review of Techniques for the Detection, Removal, and Transformation of Environmental Microplastics and Nanoplastics

Plastic residues have emerged as a significant challenge in the environmental sector. Microplastics, which are plastic fragments smaller than 5 mm, have the ability to disperse through the atmosphere, oceans, and land, posing a serious threat to human health by accumulating in the food chain. However, their minuscule size makes it difficult to effectively remove them from the environment using the current technologies. This work provides a comprehensive overview of recent advancements in microplastic detection and removal technologies. For detection methods, we discuss commonly used techniques such as microscopic analysis, thermal analysis, mass spectrometry, spectroscopic analysis, and energy spectrometry. We also emphasize the importance of integrating various analytical and data-processing techniques to achieve efficient and nondestructive detection of microplastics. In terms of removal strategies, we explored innovative methods and technologies for extracting microplastics from the environment. These include physical techniques like filtration, adsorption, and magnetic separation; chemical techniques such as coagulation-flocculation-sedimentation and photocatalytic conversion; and bioseparation methods such as activated sludge and biodegradation. We also highlight the promising potential for converting microplastic contaminants into high-value chemicals. Additionally, we identify current technical challenges and suggest future research directions for the detection and removal of microplastics. We advocate for the development of unified and standardized analytical methods to guide further research on the removal and transformation of microplastics.

Risk assessment of potentially toxic elements, microplastics, and microorganisms in groundwater around municipal solid waste landfill

Risk assessment of potential toxic elements (PTEs), microplastics (MPs) and microorganisms in groundwater around landfills is critical. Waste from landfills seeps into groundwater contaminating water quality, threatening groundwater safety, and negatively affecting the ecosystem. This study explored spatial and temporal changes in PTEs, MPs, and microorganisms in the groundwater around a closed landfill. The results showed that Mn and Cr were the most predominant PTEs in the groundwater, average Mn and Cr concentrations in June being 1.16 and 4.51 times higher than in November, respectively. The Risk assessment of PTEs in groundwater Mn was heavily contaminated, Cr was moderately contaminated. The abundance of MPs the average value of MPs in June was 1.55 times higher than that in November; the MPs indicated that groundwater is more heavily contaminated, especially in the downstream areas. The Proteobacteria is the main phylum, and PLS-PM, PTEs were positively correlated with the phylum of microorganisms, negatively correlated with the genus of microorganisms and the abundance of MPs. This study emphasizes the importance of environmental management of landfills, provide new insights into the monitoring and identification of groundwater contamination as well as scientific guidance on appropriate remediation strategies for leachate-contaminated groundwater.

Holistic assessment of chemical and biological pollutants in a Mediterranean wastewater effluent-dominated stream: Interactions and ecological impacts

The discharge of treated wastewater from wastewater treatment plants (WWTPs) into river systems is a significant source of pollution, introducing a range of chemical and biological pollutants that impact the chemical and ecological quality status of rivers. This study evaluates the effect of a secondary treated wastewater effluent on the Onyar River, in the northeast of Spain. Water and biofilm samples were collected at one upstream and four downstream sampling points (up to 2.8 km from the discharge point) across four seasons. A wide array of pollutants, including metals, pharmaceuticals, microplastics (MPs), per- and polyfluoroalkyl substances (PFAS), antibiotic resistance genes (ARGs), among other emerging pollutants, were detected downstream, with significant differences between upstream and downstream concentrations. Our results show that WWTP discharge also altered biofilm microbiome composition and ARGs presence, being these changes distinguishable from seasonal variations. Nevertheless, a partial recovery further downstream (525 m) was observed for biofilm microbiome and ARGs composition. These findings highlight the value of microbiome analysis in assessing wastewater impacts on river ecosystems and emphasize the need for further research to improve pollutant attenuation and biofilm recovery strategies in river streams.

Assessment of microplastics and associated ecological risk in the longest river (Godavari) of peninsular India: A comprehensive source-to-sink analysis in water, sediment and fish

Persistent microplastics (MPs) accumulation in the aqueous environments is considered a threat to the ecosystem, potentially harming aquatic species and human health. In view of the escalating problem of MPs pollution in India, a comprehensive investigation of MPs accumulation in major riverine systems is necessary. The current study aims to estimate MPs abundance in surface water, sediment, and fish samples along the entire stretch of Godavari, the largest river in peninsular India. Average MPs concentrations in water lie in the range of 311-939 MPs/m3 and 2-144 MPs/kg d.w. for sediment. Urban regions and dam reservoirs showed elevated MPs abundance, emphasizing the impact of anthropogenic activities. The μ-Raman analysis revealed PE and PP were the abundantly occurring polymers in all matrices. Polymer and ecological risk index identify most sampling sites as extremely high-risk zones, posing a potential threat to aquatic ecosystems and human health. Plotted t-SNE (t-distributed Stochastic Neighbour Embedding) revealed similarities in MPs morphology and compositions among water, sediment and fish samples. Examined MPs in edible (flesh+skin) and inedible parts (GIT and gills) of seven different fish species showed a higher average MPs abundance in edible parts (10.7 ± 14.9 MPs/fish) than gills (7 ± 8.1 MPs/fish) and GIT (6.6 ± 5.5 MPs/fish). This suggests that removing gills and GIT from fish doesn't eliminate the consumer's risk of MPs intake. Overall, our work highlights the significant MPs pollution in the Godavari River, further providing essential data on the ecological risk of MPs to guide municipal action plans, improve waste management, target high-risk areas, and raise awareness to mitigate impacts.

Legacy and emerging organophosphate flame retardants (OPFRs) in water and sediment from the Pearl River Delta to the adjacent coastal waters of the South China Sea: Spatioseasonal variations, flux estimation and ecological risk

The industrialization and urbanization along the Pearl River Delta (PRD) have exacerbated the issue of pollution in aquatic environments by organophosphate flame retardants (OPFRs). Historical cumulative pollution from legacy OPFRs, combined with newly emerging OPFRs, has increased the severity and complexity of OPFR pollution in this region. We explored the contamination profile, input flux and risk of legacy and emerging OPFRs in surface waters and in sediment samples of the PRD. The results indicated that all OPFRs we targeted were detectable in the water samples; The sum concentration of OPFRs in the water ranged from 17.35 ng/L to 673.30 ng/L, with an average level of 215.11 ng/L; In sediments it ranged from 5.68 ng/g to 802.46 ng/g dry weight (dw). Tris(2-chloroisopropyl) phosphate (TCPP, 99.58 ng/L) and Bisphenol A diphenyl phosphate (BDP, 51.09 ng/g dw) were the most abundant OPFRs in the surface water and sediment, respectively. Notably, although Tetrekis (2-chlorethyl) dichloroisopentyl-diphosphate (V6) has only been used in recent years, its relatively high concentrations and proportions, both in water and sediment samples, demonstrate its now widespread occurrence in the PRD. The estimated annual flux of ΣOPFRs from the eight estuaries to the South China Sea was 45.04 t/y. The four estuaries (Humen, Modaomen, Hengmen and Honqimen) contribute 80% of the mass loading. Triphenyl phosphate (TPHP) and Tris (2-chloroethyl) phosphate (TCEP) in water posed relatively higher ecological risks to algae, daphnia, and fish than other OPFRs. Our results provide scientific support for continuing monitoring and control of OPFR pollution in the PRD.

Study on Rapid Quantitative Detection of Soil MPs Based on Terahertz Time-Domain Spectroscopy

The presence of microplastics (MPs) in agricultural soils substantially affects the growth, reproduction, feeding, survival, and immunity levels of soil biota. Therefore, it is crucial to investigate fast, effective, and accurate techniques for the detection of soil MPs. This work explores the integration of terahertz time-domain spectroscopy (THz-TDS) techniques with machine learning algorithms to develop a method for the classification and detection of MPs. First, THz spectral image data were preprocessed using moving average (MA). Subsequently, three classification models were developed, including random forest (RF), linear discriminant analysis, and support vector machine (SVM). Notably, the SVM model had an F1 score of 0.9817, demonstrating its ability to rapidly classify MPs in soil samples. Three regression models, namely, principal component regression (PCR), RF, and least squares support vector machine (LSSVM), were developed for the detection of three MPs polymers in agricultural soils. Six feature extraction methods were used to extract the relevant parts of the data containing key information. The results of the study showed that the regression accuracies of PCR, RF, and LSSVM were greater than 83%. Among them, the RF had the highest overall regression accuracy. Notably, PE-UVE-RF had the best performance with Rc2, Rp2, root mean square error of calibration, and root mean square error of prediction values of 0.9974, 0.9916, 0.1595, and 0.2680, respectively. Furthermore, this model gets a better performance by hypothesis testing and predicting real samples.

Exploring action-law of microplastic abundance variation in river waters at coastal regions of China based on machine learning prediction

Surface waters, particularly the river systems, constitute a vital freshwater resource for human beings and aquatic life on Earth. In economically developed and densely populated coastal regions, river water is facing severe microplastic pollution, posing a threat to public health and ecological safety. Reliable prediction of microplastic abundance (MPA) can significantly reduce the costs associated with microplastic field sampling and analysis. This study employed spatial correlation, geographical detector, principal component analysis and five mainstream machine learning models to analyze 79 datasets of MPAs in seven coastal areas of China and performed correlation, regression and attribution analyses based on 19 terrestrial influencing factors that potentially affect the MPA life cycle processes (generation, aging, and migration). The results showed that the Neural Network (NN) and the Gaussian Process Regression (GPR) models achieved the best prediction performance, with the predicted R2 close to 1. Principal component analysis and Shapley additive explanations concluded that meteorological factors, in particular the annual geotemperature, surface solar radiation, and annual relative humidity, had a key influence on the aging of microplastics. The second key factor in improving the MPA prediction ability was the dynamic description of microplastic migration, which was primarily governed by hydrological factors such as annual precipitation and average terrain slope. Unexpectedly, the effects of land use and level of urbanization were relatively small in describing the generation of microplastics. Only the percentage of built areas was strongly correlated with the MPA levels. Note that the MPA prediction and its contribution factors may vary across different basins. Nevertheless, the findings of this study are applicable to predicting and analyzing the distribution of microplastics in other coastal rivers, and for indicating the main contributing factors, ultimately serving as a basis for guiding microplastic pollution control strategies in different river basins.

Hotspots lurking underwater: Insights into the contamination characteristics, environmental fates and impacts on biogeochemical cycling of microplastics in freshwater sediments

The widespread presence of microplastics (MPs) in aquatic environments has become a significant concern, with freshwater sediments acting as terminal sinks, rapidly picking up these emerging anthropogenic particles. However, the accumulation, transport, degradation and biochemical impacts of MPs in freshwater sediments remain unresolved issues compared to other environmental compartments. Therefore, this paper systematically revealed the spatial distribution and characterization information of MPs in freshwater (rivers, lakes, and estuaries) sediments, in which small-size (<1 mm), fibers, transparent, polyethylene (PE), and polypropylene (PP) predominate, and the average abundance of MPs in river sediments displayed significant heterogeneity compared to other matrices. Next, the transport kinetics and drivers of MPs in sediments are summarized, MPs transport is controlled by the particle diversity and surrounding environmental variability, leading to different migration behaviors and transport efficiencies. Also emphasized the spatio-temporal evolution of MPs degradation processes and biodegradation mechanisms in sediments, different microorganisms can depolymerize high molecular weight polymers into low molecular weight biodegradation by-products via secreting hydrolytic enzymes or redox enzymes. Finally, discussed the ecological impacts of MPs on microbial-nutrient coupling in sediments, MPs can interfere with the ecological balance of microbially mediated nutrient cycling by altering community networks and structures, enzyme activities, and nutrient-related functional gene expressions. This work aims to elucidate the plasticity characteristics, fate processes, and potential ecological impact mechanisms of MPs in freshwater sediments, facilitating a better understanding of environmental risks of MPs in freshwater sediments.

Potential mechanisms of aortic medial degeneration promoted by co-exposure to microplastics and lead

Microplastics (MPs) have attracted widespread attention because they can lead to combined toxicity by adsorbing heavy metals from the environment. Exposure to lead (Pb), a frequently adsorbed heavy metal by MPs, is common. In the current study, the coexistence of MPs and Pb was assessed in human samples. Then, mice were used as models to examine how co-exposure to MPs and Pb promotes aortic medial degeneration. The results showed that MPs and Pb co-exposure were detected in patients with aortic disease. In mice, MPs and Pb co-exposure promoted the damage of elastic fibers, loss of vascular smooth muscle cells (VSMCs), and release of inflammatory factors. In vitro cell models revealed that co-exposure to MPs and Pb induced excessive reactive oxygen species generation, impaired mitochondrial function, and triggered PANoptosome assembly in VSMCs. These events led to PANoptosis and inflammation through the cAMP/PKA-ROS signaling pathway. However, the use of the PKA activator 8-Br-cAMP or mitochondrial ROS scavenger Mito-TEMPO improved, mitochondrial function in VSMCs, reduced cell death, and inhibited inflammatory factor release. Taken together, the present study provided novel insights into the combined toxicity of MPs and Pb co-exposure on the aorta.

Environmental fate of microplastics in high-altitude basins: the insights into the Yarlung Tsangpo River Basin

Microplastics (MPs) have been found in remote high-altitude areas, but the main source and migration process remained unclear. This work explored the characteristics and potential sources of MPs in the Yarlung Tsangpo River Basin. The average abundances of MPs in water, sediment, and soil samples were 728.26 ± 100.53 items/m3, 43.16 ± 5.82 items/kg, and 61.92 ± 4.29 items/kg, respectively, with polypropylene and polyethylene as the main polymers. The conditional fragmentation model revealed that the major source of MPs lower than 4000 m was human activities, while that of higher than 4500 m was atmospheric deposition. Community analysis was further conducted to explore the migration process and key points of MPs among different compartments in the basin. It was found that Lhasa (3600 m) and Shigatse (4100 m) were vital sources of MPs inputs in the midstream and downstream, respectively. This work would provide new insights into the fate of MPs in high-altitude areas.

Pollution of Beach Sands of the Ob River (Western Siberia) with Microplastics and Persistent Organic Pollutants

Microplastics (MPs) in aquatic environments can be associated with various substances, including persistent organic pollutants, which add to the problem of plastic ecotoxicity. The abundance of 1-5 mm microplastics and concentrations of particle-adsorbed organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in sandy sediments from three beaches in recreational areas along the upper Ob River in Western Siberia were assessed. MP pollution levels in the Ob River beach sands ranged from 24 ± 20.7 to 104 ± 46.2 items m-2 or, in terms of mass concentration, from 0.26 ± 0.21 to 1.22 ± 0.39 mg m-2. The average abundance of MP particles reached 0.67 ± 0.58 items kg-1 or 8.22 ± 6.13 μg kg-1 in the studied sediments. MP concentrations were significantly higher in number (p < 0.05) and mass (p < 0.01) at the riverbank site downstream of the Novosibirsk wastewater treatment plant (WWTP) outfall compared to these at the upstream and more distant beaches. Most MPs (70-100%) were represented by irregularly shaped fragments. The polymer composition of MPs varied between sites, with a general predominance of polyethylene (PE). The study revealed associations of MPs with PCBs and OCPs not previously detected in the riverbed and beach sediments, suggesting that these substances are circulating in the Ob River basin. Although MP concentrations were higher downstream of the WWTP, the maximum levels of particle-associated OCPs were observed in the beach sands of the site farthest from the urban agglomeration. The pesticides γ-HCH, 4,4-DDT, and 4,4-DDE were detected on MPs at relatively low concentrations. PCBs were more abundant in the studied samples, including 118 dioxin-like congener. The results obtained indicate that the Ob River is susceptible to plastic and persistent organic pollutant (POP) contamination and serve as a starting point for further studies and practical solutions to the problem.

Significant regional disparities in riverine microplastics

Research on riverine microplastics has gradually increased, highlighting an area for further exploration: the lack of extensive, large-scale regional variations analysis due to methodological and spatiotemporal limitations. Herein, we constructed and applied a comprehensive framework for synthesizing and analyzing literature data on riverine microplastics to enable comparative research on the regional variations on a large scale. Research results showed that in 76 rivers primarily located in Asia, Europe, and North America, the microplastic abundance of surface water in Asian rivers was three times higher than that in Euro-America rivers, while sediment in Euro-American rivers was five times more microplastics than Asia rivers, indicating significant regional variations (p < 0.001). Additionally, based on the income levels of countries, rivers in lower-middle and upper-middle income countries had significantly (p < 0.001) higher abundance of microplastics in surface water compared to high-income countries, while the opposite was true for sediment. This phenomenon was preliminarily attributed to varying levels of urbanization across countries. Our proposed framework for synthesizing and analyzing microplastic literature data provides a holistic understanding of microplastic disparities in the environment, and can facilitate broader discussions on management and mitigation strategies.

Assessment and accumulation of microplastics in the Indian riverine systems: Risk assessment and implications of translocation across the water-to-fish continuum

Microplastic (MP) pollution has engulfed global aquatic systems, and the concerns about microplastic translocation and bioaccumulation in fish and other aquatic organisms are now an unpleasant truth. In the past few years, MP pollution in freshwater systems, particularly rivers and subsequently in freshwater organisms, especially in fish, has caught the attention of researchers. Rivers provide livelihood to approximately 40 % of the global population through food and potable water. Hence, assessment of emerging contaminants like microplastics in rivers and the associated fauna is crucial. This study assessed microplastics (MPs) in fish, sediment and freshwater samples across the third largest riverine system of peninsular India, the Mahanadi River. The number concentrations of MPs measured in water, sediment and fish ranged from 337.5 ± 54.4-1333.3 ± 557.2 MPs/m3, 14.7 ± 3.7-69.3 ± 10.1 MPs/kg. Dry weight and 0.4-3.2 MPs/Fish, respectively. Surprisingly, MPs were found in every second fish sample, with a higher MP number in the gut than in the gills. Black and blue coloured filaments with <0.5 mm size were the dominant MPs with polypropylene and polyethylene polymers in abundance. The Polymer Hazard Index (PHI) and the Potential Ecological Risk Index (PERI) studies revealed that the majority of the sampling sites fell in Risk category V (dangerous category). An irregular trend in the MP concentration was observed downstream of the river, though relatively elevated MP concentrations in water and fish samples were observed downstream of the river. t-Distributed Stochastic Neighbour Embedding (t-SNE) unveiled distinct patterns in MP distribution with a higher similarity exhibited in the MPs found in fish gill and gut samples, unlike water and sediment, which shared certain characteristics. The findings in the current study contribute to filling the knowledge gap of MP assessment and accumulation in global freshwater systems and highlight the microplastic contamination and accumulation in fish with its potential implications on human health.

Distribution, mobilization, risk assessment and source identification of heavy metals and nutrients in surface sediments of three urban-rural rivers after long-term water pollution treatment

Sediments are critical pollution carriers in urban-rural rivers, which can threaten the water quality of the river and downstream lakes for a long time. However, it is still not clear whether conventional water pollution treatments could abate sediment pollution or not. In this study, heavy metals (HMs) and nutrient salts in the surface sediments and overlying water were investigated after decades' water pollution treatment in three urban-rural rivers. HM speciation was determined by the sequential extraction; diffusion fluxes were estimated using Fick's first law; HM ecological risk and nutrient pollution were evaluated; and pollution sources were identified by statistical analysis and GIS. The results showed that the HMs and nutrients were extremely serious in the urban regions. The accumulation level of Pb, Cu and Cd in the sediments of the three rivers were all much higher than the soil background value, and the labile fractions accounted for high proportions (57 % for Pb, 55 % for Cu and 43 % for Cd), which could be easily eluate from the sediments and caused hazards to the aquatic environment. The sediment diffusion fluxes of HMs and ammonia nitrogen were mostly positive, which indicated these sites currently released these pollutants from sediment to overlying water. Cd, Pb, Cu and Cr may mainly originate from industrial discharge and domestic sewage, while Cr was also greatly affected by crustal weathering; nutrient pollution may originate from agricultural activities and domestic sewage. Our study demonstrated that after decades' conventional water treatment in these rivers, the sediment pollution was still in a serious level with high ecological risk, and Cd was the dominant pollutant. At present, the external point source pollution has been effectively controlled, thus, the in-depth understanding of the sediment pollution characteristics after long-term water treatment could provide a scientific basis for the accurate elimination of river pollution.

Microplastic prevalence and human exposure in the bottled drinking water in the west Godavari region of Andhra Pradesh, India

Microplastics (MPs) are widespread, minute plastic particles present in various aquatic environments, raising concerns about their effect on human health and ecosystems. The detrimental effects of MPs on the environment, include the contamination of ecosystems, harm to aquatic life through ingestion, potential disruption of food chains, and long-term ecological consequences. Despite numerous studies confirming the MP's presence in aquatic environments, research specifically focused on MPs in bottled drinking water (BDW) is limited. Research on MPs in drinking water is vital to assess potential health risks and develop strategies for ensuring water safety and quality. This study fills a research gap by investigating microplastics (MPs) in nine brands of BDW in the West Godavari region of Andhra Pradesh, India. The average MP concentration in BDW was found to be 2.89 ± 0.48 items/L, with fibers being the predominant shape and sizes ranging from 500 to 1000 μm. Transparent and blue were the most common colors. From ATR-FTIR analysis, the dominant polymer found was polypropylene (PP) followed by polyethylene terephthalate (PET). The human risk assessment was also calculated using the formula of Estimated daily intake (EDI) and Lifetime intake (LTI). The calculation found that the EDI of MPs for children and adults ranged from 0.041 to 0.291 MPs per kilogram per day and 0.019 to 0.133 MPs per kilogram per day, respectively. The mean LTI of MP consumption of an individual, ranged from 17,958 to 2,54,861 MPs, considering an average age of 75 years. The current findings offer valuable information for ongoing evaluations of the potential human risks linked to MP exposure.

Microplastics in beach sediments of the Azores archipelago, NE Atlantic

Oceanic islands are exposed to plastic debris that has accumulated in the open ocean, particularly in the subtropical gyres. This study investigates the abundance and typology of microplastics (from 0.1 to 5 mm) on 19 sandy beaches spread across 8 oceanic islands of the Azores archipelago. Between January and April 2016, a total of 341 particles retrieved from all beaches, were identified as microplastics. The highest concentration (50.19 ± 21.93 particles kg-1 dw) was found in Terceira Island. Beach morphology and grain size were important factors explaining microplastic concentration. Fibres were the most dominant morphology recovered (80.9 %), followed by fragments (12.3 %). Fourier transform infrared spectroscopy (FTIR) revealed that 41 % of the fibres consisted of polyester and 60 % of the fragments were polyethylene. This research underlines the widespread contamination of microplastics in oceanic islands of the Atlantic Ocean.