Seasonal variations of microplastics in surface water and sediment in an inland river drinking water source in southern China

Spatial and seasonal variations in abundance, distribution characteristics, and sources of microplastics in surface water of Mula river in Pune, India

Microplastics are one class of widely prevalent emerging contaminants that have a detrimental effect on ecosystems and human health. The status of microplastic pollution in rivers in Western India is not well documented, making it difficult for establishing monitoring policies and guidelines. Mula river in Pune is a lifeline for the numerous industries and residential establishments in the city and hence monitoring the health of the water of Mula river is of great societal relevance. This investigation elucidated the prevalence, abundance and characterization of microplastics in Mula River water, while it crosses Pune, one of the fastest developing cities in India. Season played a determinant role in microplastic abundance. During the pre-monsoon season, the average microplastic concentration at all the three selected locations was notably higher (1808 ± 697 particles/L) compared to the post-monsoon period (1561 ± 167 particles/L). Microplastics smaller than 100 μm were consistently dominant in both the seasons. Notably, the most common polymer found in the Mula River was Ethylene Vinyl Acetate (EVA), a copolymer of polyethylene (PE) and vinyl acetate, commonly used in plastic wraps and packaging material. Unregulated disposal of industrial waste emerged as the most potential source of microplastics in Mula river. This study addresses a critical knowledge gap about the distribution and sources of microplastics in rivers in India. This work provides baseline data that can be used to access accurate mitigation of microplastics and evaluate health and environmental impacts of microplastic pollution in Indian rivers.

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 pollution in the water and sediment of the Karnaphuli River, Bangladesh: An ecological risk assessment

Microplastics (MPs) have emerged as a new global pollutant, endangering marine ecosystems. Nonetheless, research on MP pollution in Bangladesh's estuaries and coastal environments is scare. Here, we carried out the experiment to evaluate the spatial and temporal variations of MPs along both bank of the Karnaphuli River in Chattogram city of Bangladesh, encompassing nearly all locations where the river traverses the city, while also accounting for the ecological risk assessment. The findings revealed that the potential MP content in surface water and bottom sediment varied from 14.24 to 26. 68 items m-3 and 75.63 to 272.45 items kg-1, respectively. MPs were detected in higher levels in sediment in winter but not in water until early summer. Furthermore, MPs were found at elevated levels in downstream surface water and sediment. MPs ranging from 0.3 to 0.5 mm were widespread, with fibers and fragments being the most common shapes and black and blue being the most common colors. The MPs' chemical composition includes polyethylene terephthalate (PET), high-density polyethylene (HDPE), acrylonitrile butadiene styrene (ABS), cellulose acetate (CA), ethylene-vinyl acetate (EVA), polystyrene (PS), and polyamide (PA). Surface water and bottom sediment showed a moderate correlation with MP abundance. The MP pollution's ecological danger in the Karnaphuli River was rated as Category I, suggesting a significant pollution load caused by MPs. This study sheds new light on the prevalence of MPs in the surface water and bottom sediment of the Karnaphuli River estuary, establishing the framework for future research and management of MP pollution.

Spatiotemporal distribution and ecological hazards of microplastic pollution in soil water resources around a wastewater treatment plant and municipal solid waste site

Research into the relative contributions of microplastic (MP) sources to aquatic and terrestrial environments is essential for understanding their fate and transport which is a prerequisite for designing effective pollution management strategies. This study explores the spatial distribution, seasonal variations, and ecological hazards of MPs in surface water, groundwater, soil, sediment, and leachate matrices adjacent to municipal solid waste (MSW) and sewage treatment plant (STP) sites in Northern India. Elevated MP concentrations were observed in leachate (283.22 ± 15.78 particles/L; pre-monsoon), whereas groundwater exhibited significantly reduced levels (10.75 ± 2.04 particles/L; pre-monsoon), indicating the attenuation efficiency and filtration potential of the subsurface zone. Seasonal variations revealed a dilution effect from monsoonal runoff, reducing MP concentrations. The identified MP shapes were predominantly fibers, followed by fragments, with transparent particles being the most common. The size distribution was dominated by smaller MPs (<0.3 mm), which exhibited a positive correlation with overall MP concentrations. The polymer types of MPs identified in the samples categorise the polymer hazard index (PHI) as a hazard level V (>1000) in all the samples indicating a high chemical risk in both the seasons. Similarly, the principal component analysis (PCA) revealed MP hotspots, particularly in soils near the MSW site, with concentrations reaching 53,580 ± 720 particles/kg emphasizing the vulnerability of terrestrial systems. This research highlights the importance of implementing effective waste management practices and provides valuable insights into the fate and transport of MPs by presenting strong evidence of MP movement from typical MSW/STP sites into adjacent land and water resources.

Unravelling land-based discharge of microplastics in River Basantar of Jammu & Kashmir, India: Understanding sinking behaviors and risk assessments

Microplastics (MPs) are ubiquitous and are increasing globally, but there is limited information available on their presence in freshwater ecosystems. This research work aims to investigate the abundance, sinking behavior, and risk assessment of MPs in the freshwater River Basantar, Jammu & Kashmir, India. Microplastic abundance in sediments was recorded in the range of 1-6 items g-1, with a mean abundance of 3 ± 1.594 item g-1, whereas MPs in surface water ranged from 200 to 850 items L-1 with a mean abundance of 530 ± 218.4 items L-1 among 12 sites for sediments and 10 sites for surface water. Besides, the sinking behavior of MPs was analyzed through portioning coefficients (Kd) at sediments-surface water interface, which ranges from 0.71 to 2.50 L Kg-1 for River Basantar. The most common shapes identified were fragments, fibres, and films, followed by pellets, foams, and lines. ATR-FTIR polymeric characterization reported polyethylene, polypropylene, polystyrene, polyethylene terephthalate, and polyvinyl chloride, and thus, polymeric risk assessment analysis was also evaluated and normally distributed in the River Basantar. Polymer Hazard Index was calculated across all the sites which observed to be polluted under risk categories "III" and "IV" for both the sediments and surface water samples. Pollution Load Index (PLI) calculated across all the sites was >1 depicting all the sites for both sediments and surface water sampling to be polluted. Pollution Risk Index was assessed and majority of surface water and sediment samples were observed to be under "Very high" risk category. The study, using principal component analysis and heatmap analysis, found that MPs are primarily a result of urbanization and anthropogenic actions, like industrial discharges, household wastes, and agricultural runoffs. This study highlights the significance of more investigation and coordinated efforts to solve the worldwide problem of plastic pollution in freshwater environments. Results data provide insight into the current state of MP contamination and will help government authorities implement strict rules and perform management interventions to reduce and monitor pollution levels in River Basantar. Future studies on the partitioning of MPs in sediments and surface water must be focused on aggregation, biofouling, plastic density & size, salinity, and flow behaviors to understand transport and deposition in rivers.

Distribution and risk assessment of microplastics in a source water reservoir, Central China

The current researches on microplastics in different water layers of reservoirs remains limited. This study aims to investigate the microplastics in different water layers within a source water reservoir. Results revealed that the abundance of microplastics ranged from 2.07 n/L to 14.28 n/L (reservoir, water) and 3 to 7.02 n/L (river, water), while varied from 350 to 714 n/kg(dw) (reservoir, sediment) and 299 to 1360 n/kg(dw) (river, sediment). The average abundance in surface, middle, and bottom water were 6.83 n/L, 6.30 n/L, and 6.91 n/L respectively. Transparent fibrous smaller than < 0.5 mm were identified as the predominant fraction with Polypropylene and Polyethylene being the prevalent polymer types. Additionally, the pollution load index, hazard index, and pollution risk index were calculated for different layers and sediments. Results showed that surface water exhibited a moderate level of risk while the sediments posed a low level of risk. Both the middle and bottom water showed elevated levels of risk due to higher concentrations of polymers with significant toxicity indices. This study presents novel findings on the distribution of microplastics in different water layers, providing crucial data support for understanding the migration patterns of microplastics in source water reservoirs and facilitating pollution prevention efforts.

Review of mayflies (Insecta Ephemeroptera) as a bioindicator of heavy metals and microplastics in freshwater

Heavy metal and microplastic pollutions are prevalent in freshwater ecosystems, with many freshwater bodies being contaminated by one or both of these pollutants. Recent studies reported extreme detections of Cd, Pb and Zn, high concentrations of Cr, Pb and Cu and microplastics acting as vectors of pollutants, including heavy metals. Mayflies can serve as bioindicators of heavy metal contamination in freshwater ecosystems because changes in their community structure, physiology, and behaviour can reflect and help predict the concentrations of metals in these environments. This review discusses the ecological alterations induced by tissue metal concentration in mayflies and other macroinvertebrates. As sensitive taxa to heavy metal contamination, mayflies can reflect the impacts of this pollution through their ethology and relationship to the substrate, highlighting issues such as eutrophication, alterations in community structure, inhibitory effects and sediment toxicity. Mayflies are also highly affected by microplastic exposure, which leads to ingestion, bioaccumulation, biomagnification, habitat and community alteration, behavioural changes, physiology alteration and toxicity. Mayflies bioindication metrics for assessing the impact of heavy metals and microplastics include the examination of community alteration, functional feeding behaviour, molecular structure, dietary and toxicity impacts, bioaccumulation and biomagnification and biomarkers. Current challenges for the utilization of mayflies as bioindicators include temporal variations in sensitivity, lack of universally recognised protocols and need for standardised protocols for microplastic analysis. Additionally, the applicability of mayflies as bioindicators may vary across different ecosystems, emphasising the need for selecting suitable indicators that align with the unique characteristics of the ecosystem.

The dual role of coastal mangroves: Sinks and sources of microplastics in rapidly urbanizing areas

Mangrove ecosystems are vital for coastal protection, biodiversity, and pollution interception, yet their interactions with microplastics in rapidly urbanizing regions remain underexplored. This study investigated the microplastic dynamics in the Maozhou River and Dasha River, along with the coastal Xiwan Mangrove Park in the Pearl River Estuary, the second largest estuary in China. Samples were collected from mangrove and surrounding areas, identifying microplastics using Fourier-transform infrared spectroscopy (FTIR) and Laser Direct Infrared (LDIR) techniques. Microplastic concentrations ranged from 245.8 to 1562.4 n/m³ in water and 374.3 to 7475.3 n/kg in sediments. The Maozhou River exhibited consistent microplastic levels across varying hydrological conditions, while the Dasha River and Xiwan Mangrove showed greater sensitivity to water flow changes influenced by urban land use. During high-flow periods, urban river microplastic concentrations decreased due to dilution, whereas mangrove areas experienced elevated levels in water from urban runoff, upstream retention, and sediment resuspension, suggesting a potential for outward release. Weaker water dynamics led to increased microplastic accumulation in mangrove sediments. The distribution of microplastic types was influenced by multiple urban pollution sources, with synthetic rubbers linked to urban transportation comprising over 50 % of some samples, peaking at 79 %. These findings underscore the dual role of mangroves as microplastic sinks and potential sources, highlighting the significant impact of hydrological conditions on their function. This study offers new insights into microplastic pollution in urban mangrove ecosystems and emphasizes the urgent need for improved management strategies in coastal areas facing rapid urbanization.

Estimation of the uptake of polycyclic aromatic hydrocarbons desorbed from polyethylene microplastics in the digestive tract of the red seabream (Pagrus major) and mummichog (Fundulus heteroclitus)

The vector effects of microplastics (MPs) in natural marine environments and their contribution to polycyclic aromatic hydrocarbon (PAH) bioaccumulation in fish are still unknown. This study, therefore, aimed to evaluate the effects of MPs on carrying PAHs under conditions close to the actual marine environments. The PAH content sorbed onto MPs from seawater positively correlated with the octanol/water partition coefficient (log KOW) in both polyethylene and polystyrene MPs. The desorption rate constant (k2) of PAHs sorbed onto MPs from seawater in the digestive tract was calculated using two marine teleost fish in an in vitro desorption experiment. A negative correlation was observed between the log KOW and k2 of the PAHs. The PAHs with larger log KOW and lower water solubility are easier to sorb onto MPs and less likely to desorb in the digestive tract of marine fish species. The estimation of PAH uptake into the fish body using the k2 of three selected PAHs (phenanthrene, pyrene, and chrysene) indicated that >95 % of the chemicals were uptaken from seawater via gills. It was presumed that there was an additional uptake of PAHs into the fish body (vector effect) due to desorption from MPs in the digestive tract when marine fish ingested MP that was sorbed and concentrated with PAHs. The degree of uptake was, however, much lower than that from seawater via gills. The vector effect of PAHs by MPs in the actual sea may be negligible, and the risk is presently considered to be low.

First occurrence and risk assessment of microplastics in enteral nutrition formulas

Occurrence and characteristics of microplastics were evaluated in enteral nutrition formulas, for the first time. A total of 30 samples belonging to 9 brands were analysed. Physical and chemical characteristics of microplastics were identified by stereomicroscopy and micro-raman spectroscopy, respectively. The mean number of microplastics was 45 ± 63 MP/L. Two different shapes of microplastics were detected with fibres (62%) being the most common microplastics followed by fragments (38%). The most common color of microplastics was black (37%) followed by blue (26%), orange (15%), green (7%), red (7%), grey (4%) and multicolor (4%). The length of microplastics ranged from 10 to 2086 μm with an average of 548 ± 526 μm. Estimated mean daily microplastic intake for four different scenarios varied between 24 to 61 and 30 to 76 MPs/day for women and men, respectively. The mean polymer hazard index and microplastic load index levels were calculated as 380 and 1.30, respectively. The results of this study showed that microplastics are prevalent in enteral nutrition products. The presence of polymers with high hazard risk scores in enteral nutrition formulas may pose a risk to the health of patients with special nutritional needs.

Investigation of microplastics in urban rivers of Eastern China in summer: abundance, characteristics and ecological risk assessment

Microplastics (MPs) are increasingly becoming recognized as worldwide environmental contaminants, exerting a substantial impact on the safety of city rivers. This study explored the abundance and characteristics of MPs in summer 2023, including June and August, representing plum rain and typhoon rain seasons. The Qinhuai River exhibits more spatial fluctuations in six sampling sites with average concentrations of 470 ± 119.56 items per L, and the abundance increases with the water flows in the river. Downstream had the highest MP abundance of 484 ± 121.34 items per L, which were positive with the concentration of suspended solids (SS). Transparent and green MPs were more even in the sampling sites, and the shapes of fragments were predominant in the summer. Interestingly, the proportion of fiber and small-sized (38-75 μm) microplastics was predominant in the plum rain seasons, while the percentage of large-sized (270-5000 μm) and polymers of PE occurred in the typhoon rain seasons. The index of hazard scores of plastic polymers (H) revealed that the studied river had a severe pollution level (IV), which was highly influenced by PVC and PC. Besides, the pollution load index PLI value of different rain seasons was slightly polluted (I), while the PLI in autumn rain seasons was relatively higher than that in other seasons due to the higher variance of MPs. Therefore, the ecological risk of microplastics of PVC and PC in the Qinhuai River during varying seasons should be seriously considered. Our research is expected to provide valuable assistance in improving the management of urban rivers.

Distribution patterns and environmental risk assessments of microplastics in the lake waters and sediments from eight typical wetland parks in Changsha city, China

The quality of water in urban parks is closely related to people's daily lives, but the pollution caused by microplastics in park water and sediments has not been comprehensively studied. Therefore, eight typical parks in the urban area of Changsha, China, were selected, and Raman spectroscopy was used to explore the spatial distributions and compositions of the microplastics in the water and sediments, analyze their influencing factors, and evaluate their environmental risks. The results showed that the abundances of surface water microplastics in all parks ranged from 150 to 525 n L-1, and the abundances of sediment microplastics ranged from 120 to 585 n kg-1. The microplastics in the surface water included polyethylene terephthalate (PET), chlorinated polyethylene (CPE), and fluororubber (FLU), while those in the sediments included polyvinyl chloride (PVC), wp-acrylate copolymer (ACR), and CPE. Regression analyses revealed significant positive correlations between human activities and the abundances of microplastics in the parks. Among them, the correlations of population, industrial discharge and domestic wastewater discharge with the abundance of microplastics in park water were the strongest. However, the correlations of car flow and tourists with the abundance of microplastics in park water were the weakest. Based on the potential ecological risk indices (PERI) classification assessment method, the levels of microplastics in the waters and sediments of the eight parks were all within the II-level risk zone (53-8,549), among which the risk indices for Meixi Lake and Yudai Lake were within the IV risk zone (1,365-8,549), which may have been caused by the high population density near the park. This study provides new insights into the characteristics of microplastics in urban park water and sediment.

Exploring correlations between microplastics, microorganisms, and water quality in an urban drinking water source

The microplastic pollution in freshwater system is gradually becoming more severe, which has led to increasing attention on the distribution and potential harmful effects of microplastics. Moreover, microplastics may have an impact on river ecology and pose risks to ecosystems. Therefore, it is important to reveal this process. This study aimed to explore correlations between microplastics and free-living microorganisms in an urban drinking water source of Xiangjiang River by using multivariate statistical analysis. The results indicated that the abundance of microplastics (size 50 μm to 5 mm) in surface water and sediments ranged from 0.72 to 18.6 (mean ± SD: 7.32 ± 2.36) items L-1 and 26.3-302 (150 ± 75.6) items kg-1 dry weight (dw), respectively, suggesting potential microplastic pollution despite the protected status as a drinking water source. Higher microplastic abundances were observed in urban areas and the downstream of wastewater plants, with mostly granular shape, transparent and black color as well as 50-100 μm in size. The multivariate statistical analysis presented that the abundance of microplastics is not significantly correlated with water indicators, due to the complexity of the abundance data. The water indicators showed an obvious correlation with microplastics in colors of transparent and black, and smaller sizes of 50-100 μm. This is also true for microplastics and microorganisms in water and sediment. Proteobacteria was the main prokaryote in water and sediments, being positively correlated with 50-100 μm microplastics; while Chloroplastida was the dominated eukaryotes, presenting a weak correlation with smaller-size microplastics. Overall, when considering the properties of microplastics such as shape, color and size, the potential correlations with water indicators and microorganisms were more evident than abundance. This study provides new insights into the multivariate statistical analysis, explaining the potential correlations among microplastic properties, microorganisms and environmental factors in a river system.