Human activities affect the multidecadal microplastic deposition records in a subtropical urban lake, China

Molecular mechanisms by which polyethylene terephthalate (PET) microplastic and PET leachate promote the growth of benthic cyanobacteria

Toxic blooms of benthic cyanobacteria greatly threaten freshwater ecological health and drinking water safety. Meanwhile, microplastic pollution is becoming increasingly severe and microplastics accumulate in large quantities at the bottom of lakes and rivers, widely coexisting with algae. However, impacts of microplastics on benthic cyanobacteria are still unknown. This study investigated effects of microplastic polyethylene terephthalate (PET) - which is commonly found at the bottom of lakes and rivers - and its leachate at environmentally relevant concentration (0.3 mg/L) and high exposure concentration (3.0 mg/L) on typical benthic cyanobacteria (Oscillatoria sp. and Pseudanabaena sp.), and clarified the related molecular mechanisms through transcriptomic analysis. Results show that PET or PET leachate (PET-L) can promote benthic cyanobacterial growth and promotive effect of PET-L is more obvious than that of PET system. Promotion effect of PET or PET-L is more significant at environmentally relevant concentration (39-63 % increase compared with the control) compared with high exposure concentration (21-58 % increase compared with the control). In the presence of PET or PET-L, due to an increase in the number of cyanobacterial cells, concentrations of harmful metabolites (cylindrospermopsin, geosmin, and 2-methylisoborneol) in water also increased. Although PET particles may not be conducive to benthic cyanobacterial growth due to shading effect and mechanical damage, photosynthetic efficiency of algae was improved and dysregulated genes related to photosynthesis and extracellular transport of glycolipid were upregulated according to transcriptome analysis. Moreover, PET decomposition components, such as terephthalic acid and ethylene glycol, may be able to serve as carbon sources for cyanobacterial growth. Upregulation of genes associated with glycolysis, oxidative phosphorylation, and translation revealed that PET can promote the growth of benthic cyanobacteria. This study has important value in evaluating the impact of benthic cyanobacteria on aquatic ecological health and drinking water safety with the coexistence of microplastics.

Dissolved organic carbon and microplastics decrease the biodiversity effect on resource use efficiency of crustacean zooplankton

The relationship between biodiversity and ecosystem functioning has always been the focus of attention in ecology. Although many studies have indicated positive effects of species and functional diversity on ecosystem functioning, our understanding of how the relationships are altered in the face of environmental changes remains limited. In recent years, human activities such as urbanization have led to a significant influx of dissolved organic carbon (DOC) and microplastics into lake ecosystems, which altered the lake's water quality and ecosystem services. Here, by conducting a two-month mesocosm experiment, we found that increasing DOC concentration generally increased the crustacean zooplankton taxonomic species richness, functional richness, resource use efficiency (RUE) and body size. In addition, we found that species richness, functional richness and body size have a positive relationship with zooplankton RUE, indicating higher biodiversity and larger body size are essential for maintaining high ecosystem functions. More importantly, we found that increasing the pressure of DOC and microplastic reduced the biodiversity effect on trophic transfer efficiency, especially for the relationship between functional richness and zooplankton RUE. Our results suggested that biodiversity effects on ecosystem functioning could be probably reduced in the current global environment change context, indicating that we may underestimate the negative impact of diversity loss on ecosystem functions and services. Therefore, more efforts are needed to conserve biodiversity and to maintain the valuable services that the ecosystem provides.

Microplastics in lakes: Distribution patterns and influencing factors

As a kind of new pollutants, microplastics (MPs) have aroused public concern due to their widespread presence and potential ecological risks. Lakes, as crucial freshwater ecosystems and important water resources, are particularly vulnerable to MPs pollution. While MPs are known to be unevenly distributed within lakes, their distribution patterns and influencing factors have not been thoroughly understood. This review analyzes 84 field studies across 64 lakes worldwide to elucidate MPs distribution patterns and their driving mechanisms. Analysis reveals that MPs abundance is typically highest near areas of intense human activity and major water inflows, though hydrodynamics and wind conditions also influence spatial patterns. MPs characteristics (shape, size, color, polymer type) show distinct distribution patterns influenced by source types, transport mechanisms, and degradation processes. While surface water MPs concentrations vary seasonally due to precipitation, wind, and human activities, sediment cores indicate increasing MPs abundance in recent deposits. Integration of water and sediment sampling reveals that MPs characteristics affect their vertical distribution, with denser particles prone to sedimentation. This review identifies key knowledge gaps, including limited data on vertical distributions and temporal variations, and emphasizes the need for standardized methods and quantitative analysis of driving factors. These reviewed findings provide a foundation for understanding MPs fate in lake ecosystems and improving risk assessment capabilities, offering valuable insights for future surveys on MPs.

Exploring the response of bacterial community functions to microplastic features in lake ecosystems through interpretable machine learning

Microplastics (MPs) are ubiquitous and have various characteristics. However, their impacts on bacterial community functions in lakes remain elusive. In this study, we identified 33 different MPs features including their abundance, shape, color, size, and polymer type, from Taihu Lake, China. These features were used to construct 48 machine learning models, utilizing four types of machine learning regression algorithms, to investigate how different MP features influence human health, carbon/nitrogen cycling, and energy source-related functions of bacterial communities. The XGBoost models provided the best performance with an average R2 of 0.85 in explaining the abundance of functions. Yellow-, fragment-, and polyethylene terephthalate (PET) MPs were the most important features by Shapley values. Yellow- and PET-MPs mainly had primarily negative impacts on human pathogens pneumonia and chemoheterotrophy, respectively. Fragment-MPs had a primarily positive impact, which shifted from positive to negative at a proportion of 0.5 for methanol oxidation. Moreover, MPs may affect community structure by filtering for functional traits. These findings are important for understanding the effects of MP pollution on bacterial community function and its role in the global carbon and nitrogen cycling and human health and help us to determine the potential impacts of MP pollution on ecosystems.

Effects of microplastics on polycyclic aromatic hydrocarbons migration in Baiyangdian Lake, northern China: Concentrations, sorption-desorption behavior, and multi-phase exchange

Microplastics (MPs) and polycyclic aromatic hydrocarbons (PAHs) have been found in all environment matrices and are of concern worldwide. In this study, PAHs were determined in Baiyangdian Lake, China, and the effects of MPs on the migration of PAHs at the lake interfaces were analyzed. The average abundances of detected MPs were 9595 items m-3 for water and 1023 items kg-1 for sediment. The detected MPs were polyamide 6, polypropylene, polyethylene, and polyethylene terephthalate. The average Σ16PAHs in the water, sediment, and air were 1338 ng L-1, 751 ng g-1 dry weight, and 395 ng m-3, respectively. At the air-water interface, naphthalene, and phenanthrene volatilized from water to air, whereas benzo(b)fluoranthene, benzo(k)fluoranthene, and dibenzo(a,h)anthracene deposited from air to water. The fugacity fraction between sediment and bottom water ranged from 0.88 to 0.99, which indicated net volatilization at the water-sediment interface. The adsorption capacities of the four MPs for the PAHs ranged from 39.4 to 99.8 μg g-1 with a desorption efficiency range of 0.01%-44.3% under oscillation. According to the distribution of PAHs on the MPs, the exchange fluxes of PAHs at the water-air and sediment-water interfaces were recalculated. The results showed that the MPs could increase deposition of the PAHs from air to the water (ΔFA-W: -221 × 10-2 to -0.01 × 10-2 ng m-2 d-1) and the volatilization of PAHs from sediment to water (ΔFW-S: -79.7 × 105 to 180 × 105 ng m-2 d-1), which suggests that MPs increase the risk of PAHs in water and to aquatic organisms.

Diversity, composition, and assembly processes of bacterial communities within per- and polyfluoroalkyl substances (PFAS)-contained urban lake sediments

Per- and polyfluoroalkyl substances (PFAS) are widespread, highly persistent, and bio-accumulative compounds that are increasingly found in the sediments of aquatic systems. Given this accumulation and concerns regarding the environmental impacts of PFAS, their influence on sedimentary bacterial communities remains inadequately studied. Here, we investigated the concentrations of 17 PFAS in sediments from six urban lakes in Nanjing, China, and assessed their effects on the diversity, composition, potential interactions, and assembly mechanisms of sedimentary bacterial communities. Sediment concentrations of PFAS ranged from 4.70 to 5.28 ng·g-1 dry weight. The high concentrations of the short-chain perfluorobutanesulfonic acid (PFBS) suggested its substitution for the long-chain perfluorooctanesulfonic acid (PFOS). As alternatives to long-chain PFAS, short-chain PFAS had similar effects on bacterial communities. The short-chain perfluoropentanoic acid (PFPeA) and the long-chain perfluorotridecanoic acid (PFTrDA) were the most important PFAS related to the ecological patterns of the co-occurrence network and may alter the composition of the sedimentary bacterial communities in the urban lakes. The Anaerolineaceae family represented as keystone bacteria within the PFAS-affected bacterial co-occurrence network. Deterministic processes (65.9 %), particularly homogeneous selection (63.2 %), were the dominant process driving bacterial community assembly. PFAS promoted the phylogenetic clustering and influenced the community dispersal capabilities to shape bacterial community assembly. This study provides a comprehensive analysis of PFAS distribution in sediments across six urban lakes in Nanjing and provides novel insights into the effects of PFAS on sedimentary bacterial communities. Further research is required to elucidate the mechanisms underlying the impacts of PFAS on microbial communities and to evaluate their broader ecological consequences.

Pollution status of microplastics in the sediments of warm monomictic Dal lake, India: Abundance, composition, and risk assessment

This report presents the first investigation of microplastic (MP) contamination in the shoreline sediments of Dal Lake, Jammu and Kashmir, India. The MP concentrations ranged from 503 to 3154 MP/kg, with a notable seasonal variation. The highest concentrations of microplastics occurred in the Spring, ranging from 467 to 3445 MP/kg. Microplastics were identified using optical microscopy, Fourier Transform Infrared spectroscopy, and thermogravimetric analysis. Polymer analysis revealed that the Gagribal basin was contaminated with polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyamide (PA), and polyethylene terephthalate (PET). In contrast, the Nigeen basin mainly comprises PE, PP, and PS. The significantly elevated Polymer Hazard Index (PHI) values, exceeding 1000 in the Gagribal basin, were attributed to the presence of PVC. Sediment quality was assessed using Pollution Load Index (PLI), Potential Ecological Risk Index (PERI), and PHI. Health risk metrics, such as estimated daily intake (EDI) and microplastic carcinogenic risks (MPCR), were also evaluated. There is a positive correlation between microplastic abundance and total organic carbon (TOC), total phosphorus (TP), and total nitrogen (TN). The Nigeen basin, characterized by a higher proportion of less hazardous polymers like PP, exhibited greater TOC levels due to enhanced microbial degradation of microplastics. Conversely, the Gagribal basin, with its higher presence of toxic polymers like PVC, had lower TOC levels, likely due to these compounds' inhibition of microbial activity. This study provides crucial insight into the spatial distribution and ecological impact of MPs in Dal Lake, setting the stage for future research on their effects on aquatic ecosystems.

Decadal changes in microplastic accumulation in freshwater sediments: Evaluating influencing factors

Microplastics are small plastic particles with sizes ranging between 1 μm and 5 mm. Microplastics can originate from macro plastics and degrade to a smaller size or be produced directly by manufacturers. Few studies have examined microplastic contamination in freshwater sediment cores to estimate changes in microplastic contamination over time. We present the results of a study that examined sediment cores from four watersheds, Kiskiminetas River, Blacklick Creek, Raystown Lake, and Darby Creek, in Pennsylvania, USA to reveal the history of microplastic accumulation and factors that contribute to microplastic distribution. The abundance and morphology of microplastics varied over time and between these four locations. The highest microplastic abundance was found in Raystown Lake, ranging from 704 to 5397 particles kg-1 with fiber as the dominant microplastic type, while Darby Creek (0-3000 particles kg-1), Kiskiminetas River (0-448 particles kg-1), and Blacklick Creek (0-156 particles kg-1) had lower microplastic concentration. Moreover, Darby Creek had the most diverse microplastic morphology and a trend of decreasing concentration with depth. Although the Darby Creek watershed has the most developed area and highest population density, it did not have the highest microplastic concentration. Averaged over the four cores, microplastic abundance increased as global plastics production increased from the 1950s-2010s. Our findings provide insights into the fate and transport of microplastic contamination in freshwater environments, which is vital to establishing sustainable mitigation strategies.

Microplastics monitoring in freshwater systems: A review of global efforts, knowledge gaps, and research priorities

The escalating production of synthetic plastics and inadequate waste management have led to pervasive microplastic (MP) contamination in aquatic ecosystems. MPs, typically defined as particles smaller than 5 mm, have become an emerging pollutant in freshwater environments. While significant concern about MPs has risen since 2014, research has predominantly concentrated on marine settings, there is an urgent need for a more in-depth critical review to systematically summarize the current global efforts, knowledge gaps, and research priorities for MP monitoring in freshwater systems. This review evaluates the current understanding of MP monitoring in freshwater environments by examining the distribution, characteristics, and sources of MPs, alongside the progression of analytical methods with quantitative evidence. Our findings suggest that MPs are widely distributed in global freshwater systems, with higher abundances found in areas with intense human economic activities, such as the United States, Europe, and China. MP abundance distributions vary across different water bodies (e.g., rivers, lakes, estuaries, and wetlands), with sampling methods and size range selections significantly influencing reported MP abundances. Despite great global efforts, there is still a lack of harmonized analyzing framework and understanding of MP pollution in specific regions and facilities. Future research should prioritize the development of standardized analysis protocols and open-source MP datasets to facilitate data comparison. Additionally, exploring the potential of state-of-the-art artificial intelligence for rapid, accurate, and large-scale modeling and characterization of MPs is crucial to inform effective strategies for managing MP pollution in freshwater ecosystems.

Travertine deposition rather than tourism activity is the primary contributor to the microplastic risks in alpine karst lakes

Microplastics (MPs) are emerging as anthropogenic vectors to form plastisphere, facilitating microbiome colonization and pathogenic dissemination, thus contributing to environmental and health crises across various ecosystems. However, a knowledge gap persists regarding MPs risks and their driving factors in certain unique and vulnerable ecosystems, such as Karst travertine lakes, some of which are renowned World Natural Heritage Sites under ever-increasing tourism pressure. We hypothesized that tourism activities serve as the most important factor of MPs pollution, whereas intrinsic features, including travertine deposition can exacerbate potential environmental risks. Thus, metagenomic approaches were employed to investigate the geographical distribution of the microbiome, antibiotic resistance genes (ARGs), virulence factor genes (VFGs), and their combined environmental risks in Jiuzhaigou and Huanglong, two famous tourism destinations in Southwest China. The plastisphere risks were higher in Huanglong, contradicting our hypothesis that Jiuzhaigou would face more crucial antibiotic risks due to its higher tourist activities. Specifically, the levels of Lipopolysaccharide Lewis and fosD increased by sevenfold and 20-fold, respectively, from upstream to downstream in Huanglong, whereas in Jiuzhaigou, no significant accrual was observed. Structural equation modeling results showed that travertine deposition was the primary contributor to MPs risks in alpine karstic lakes. Our findings suggest that tourism has low impact on MPs risks, possibly because of proper management, and that travertine deposition might act as an MPs hotspot, emphasizing the importance of considering the unique aspects of travertine lakes in mitigating MPs pollution and promoting the sustainable development of World Natural Heritage Sites.

Vertical distribution of microplastics in sediment columns along the coastline of China

At present, there has been relatively less coverage of microplastics (MPs) pollution in sediment columns, especially across a large geographical span. This study collected sediment columns across 11 provinces along the coastline of China for MPs pollution investigation. The study found higher MPs diversity (Simpson diversity index) in sediment columns than in surface sediments, mostly comprising fiber MPs with dominant transparent and blue colors. Lower MPs pollution was noted in mangrove reserves, while estuarine and coastal areas showed higher pollution levels. Spearman correlation analysis shows that vertical of MPs abundance significantly decreased with depth at 6 of 11 sites. Large-sized MPs with diverse colors in deeper sediments (>40 cm) suggests that burial processes may render MPs more resistant to degradation. Our research highlights varied MPs distribution in coastal sediment, aiding future marine MPs pollution prediction and assessment.

Centennial Records of Microplastics in Lake Cores in Huguangyan Maar Lake, China

Microplastic records from lake cores can reconstruct the plastic pollution history. However, the associations between anthropogenic activities and microplastic accumulation are not well understood. Huguangyan Maar Lake (HML) is a deep-enclosed lake without inlets and outlets, where the sedimentary environment is ideal for preserving a stable and historical microplastic record. Microplastic (size: 10-500 μm) characteristics in the HML core were identified using the Laser Direct Infrared Imaging system. The earliest detectable microplastics appeared unit in 1955 (1.1 items g-1). The microplastic abundance ranged from n.d. to 615.2 items g-1 in 1955-2019 with an average of 134.9 items g-1. The abundance declined slightly during the 1970s and then increased rapidly after China's Reform and Opening Up in 1978. Sixteen polymer types were detectable, with polyethylene and polypropylene dominating, accounting for 23.5 and 23.3% of the total abundance, and the size at 10-100 μm accounted for 80%. Socioeconomic factors dominated the microplastic accumulation based on the random forest modeling, and the contributions of GDP per capita, plastic-related industry yield, and total crop yield were, respectively, 13.9, 35.1, and 9.3% between 1955-2019. The total crop yield contribution further increased by 1.7% after 1978. Coarse sediment particles increased with soil erosion exacerbated microplastics discharging into the sediment.

Simulation of the dynamic processes of microplastic suspension and deposition in a lake sediment-water system

The occurrence of microplastics in aquatic environments has attracted increasing interest from both the public and scientists, especially their migration behaviors. Although several environmental behaviors of microplastics have been studied, the issue of microplastic suspension and deposition in lake sediment-water systems remains to be elucidated. In this study, we built an indoor sediment-water system with input and output rivers that simulated the actual situations in lakes, and aimed to explore the suspension and deposition behavior of microplastics using eight group experiments. The abundance of microplastics in overlying water and sediments in different periods was analyzed, and the characteristics of hydrodynamic disturbance on microplastic suspension and deposition were identified. Importantly, the exchange of microplastics in sediments and water under dynamic flow conditions was assessed. The results showed that the middle-scale experiment designed in this study effectively simulated the dynamic transport process of microplastics in lakes, and the hydrodynamic force had a significant impact on the suspension and deposition behaviors of microplastics. The average abundance of polystyrene, polyethylene terephthalate and polyamide microplastics was 1.07, 0.60 and 0.83 particles/L in overlying water during the suspension experiments, respectively. This showed a pattern of first rising and then falling with the extension of suspension time. Even in the environment with the maximum input water volume (8000 ml/min) in this study, only microplastics at a depth of 0 to 2 cm from the sediment were suspended. The average abundance of microplastics was 313.02 particles/kg during the deposition experiments, which gradually increased with the extension of deposition time in sediments. Finally, microplastic sizes in water of the suspension experiments and in sediments of the deposition experiments were concentrated in the range of 500 to 1500 μm and 300 to 1000 μm, respectively.

Characteristics, distribution patterns and sources of atmospheric microplastics in the Bohai and Yellow Seas, China

Although the prevalence of microplastics in the atmosphere has recently received considerable attention, there is little information available regarding the distribution of atmospheric microplastics over oceanic regions. In this study, during the summer and autumn months of 2022, we investigated atmospheric microplastics in four marine regions off the eastern coast of mainland China, namely, the southern, middle, and northern regions of the Yellow Sea, and the Bohai Sea. The abundance of atmospheric microplastics in these regions ranged from 1.65 to 16.80 items/100 m3 during summer and from 0.38 to 14.58 items/100 m3 during autumn, although we detected no significant differences in abundance among these regions. Polyamide, chlorinated polyethylene, and polyethylene terephthalate were identified as the main types of plastic polymer. On the basis of meteorological data and backward trajectory model analyses, we established that the atmospheric microplastics detected during summer were mainly derived from the adjacent marine atmosphere and that over the continental landmass in the vicinity of the sampling area, whereas microplastics detected during autumn appear to have originated mainly from the northeast of China. By influencing the settlement and migration of microplastics, meteorological factors, such as relative humidity and wind speed, were identified as potential factors determining the distribution and characteristics of the detected microplastics. Our findings in this study, revealing the origin and fate of marine atmospheric microplastics, make an important contribution to our current understanding of the distribution and transmission of microplastics within the surveyed region and potentially worldwide.

Influencing factors of microplastic generation and microplastic contamination in urban freshwater

This research analyzes data on the microplastic (MP) contamination in the environmental systems (atmosphere, lithosphere, hydrosphere) and the levels of MPs in freshwater of cities with different levels of national income. This study investigates the influencing factors of MP generation, i.e., mismanaged plastic waste, untreated wastewater, number of registered motor vehicles, and stormwater runoff. The statistical correlations between the MP contamination in urban freshwater and the four influencing factors of MP generation are determined by linear regression. The results indicate that MPs are most abundant in aquatic systems (i.e., hydrosphere) and pose a serious threat to the human food chain. The regression analysis shows a strong correlation between mismanaged plastic waste and microfragment smaller than 300 μm in particle size in urban freshwater with high goodness-of-fit (R2 = 0.8091). A strong relationship with high goodness-of-fit also exists between untreated wastewater and microfragment of 1000-5000 μm in particle size (R2 = 0.9522). The key to mitigate the MP contamination in urban freshwater is to replace improper plastic waste management and wastewater treatment with proper management practices.

An evaluation on microplastic accumulations in Turkish soils under different land uses

Microplastic (MP) pollution is now widely reported in soil ecosystems. However, the level of this pollution in soil ecosystems has not been sufficiently elucidated. Moreover, there is little understanding of how land use conditions affect the occurrence and distribution of MPs in soils. Therefore, this study examined 55 soil samples (44 agricultural and 11 urban) from the Mediterranean, Aegean, and Marmara regions of Türkiye, representing both agricultural and urban land uses. The samples were analyzed for MP distribution characteristics, such as abundance, shape, size, color, and type. Different types of MPs were detected in the soil samples, and their averages in agricultural and urban soils were 192.7 ± 14.2 and 127.3 ± 21.6 particles kg-1, respectively. MP abundance in the soil exhibited variations between different land uses, with agricultural areas showing higher levels compared to urban areas. In agricultural soils, MPs were predominantly blue-colored (44.6 %), in the form of fibers (74.9 %), smaller than 1000 μm (66.1 %), and primarily constituted polyethylene (90.8 %). In urban areas, MPs were also blue-colored (54.7 %), had a fiber shape (64.2 %), smaller than 1000 μm (70.6 %), and mostly belonged to the polyethylene category (78.5 %). A significant difference in MP concentrations was observed between agricultural and urban areas, reflecting the influence of distinct land uses on MP levels. Moreover, Principal Component Analysis (PCA) revealed that soil properties, including pH, electrical conductivity, organic matter, aggregate stability, average weight diameter, sand, clay, and silt, emerged as the primary determinants influencing the abundance and size of MPs within the soil. These findings contribute valuable insights into the origins of soil MPs and the intricate connections between MPs and varying soil characteristics across diverse land use categories.

A review of microplastic threat mitigation in Asian lentic environments

Microplastic (MP) pollution has evolved into a significant worldwide environmental concern due to its widespread sources, enduring presence, and adverse effects on lentic ecosystems and human well-being. The growing awareness of the hidden threat posed by MPs in lentic ecosystems has emphasized the need for more in-depth research. Unlike marine environments, there remain unanswered questions about MP hotspots, ecotoxic effects, transport mechanisms, and fragmentation in lentic ecosystems. The introduction of MPs represents a novel threat to long-term environmental health, posing unresolved challenges for sustainable management. While MP pollution in lentic ecosystems has garnered global attention due to its ecotoxicity, our understanding of MP hotspots in lakes from an Asian perspective remains limited. Hence, the aim of this review is to provide a comprehensive analysis of MP hotspots, morphological attributes, ecotoxic impacts, sustainable solutions, and future challenges across Asia. The review summarizes the methods employed in previous studies and the techniques for sampling and analyzing microplastics in lake water and sediment. Notably, most studies concerning lake microplastics tend to follow the order of China > India > Pakistan > Nepal > Turkey > Bangladesh. Additionally, this review critically addresses the analysis of microplastics in lake water and sediment, shedding light on the prevalent net-based sampling methods. Ultimately, this study emphasizes the existing research gaps and suggests new research directions, taking into account recent advancements in the study of microplastics in lentic environments. In conclusion, the review advocates for sustainable interventions to mitigate MP pollution in the future, highlighting the presence of MPs in Asian lakes, water, and sediment, and their potential ecotoxicological repercussions on both the environment and human health.

Microplastic contamination in water and sediments of Mahanadi River, India: An assessment of ecological risk along rural-urban area

Worldwide, environmental concerns about MPs pollution have increased. Microplastic contamination that pollutes the ocean is mostly caused by terrestrial transfer from close proximity locations. A study of MPs pollution near coastal locations becomes necessary to address the MPs transit, fate, and mitigation. In the current study MPs pollution in the surface water and sediment of the Mahanadi River estuary was assessed during Pre-MS and MS. The size, shape, and colour of the MPs were determined using a stereomicroscope, and the MPs polymer composition was identified by Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) spectroscopy. The mean concentration of MPs that were potentially discovered in water was 16.6 ± 5.2 and sediments 197.3 ± 5.4 during Pre-MS. In the MS observed mean abundance of MPs was 15.1 ± 5.4 in water and 164.6 ± 76.9 in sediments. The highest abundant size was smaller than 1 mm; the most prevalent shape were fibers followed by film and fragments; black and white was a prominent colour in water and sediments respectively. Polyesters (PEs), polyethylene (PE), polyvinyl chloride (PVC), polypropylene (PP), polyamide (PA), Polystyrene (PS), and Polycarbonates (PC) were found in the analysis of the chemical composition of MPs in water and sediments samples. The calculated PLI value shows pollution load at category I, with polymer hazard levels at categories III, IV, and V, indicating very high risk. The current research results show that river inflows and fishing-related actions are probably the main causes of MPs pollution.

Depth profiles of microplastics in sediments from inland water to coast and their influential factors

Microplastics, plastic particles with a size smaller than 5 mm, are widely observed in the global environments and pose a growing threat as they accumulate and affect the environments in numerous ways. These particles can be transported from inland water to coast and disperse from surface water to deep sediments, especially the latter, while knowledge of the hidden microplastics in sediment layers is still lacking. Understanding the characteristics and behavior of microplastics in deep sediments from inland water to coast is crucial for estimating the present and future global plastic budget from land to seas. Herein, present knowledge of microplastic sedimentation from inland water to coast is reviewed, with a focus on the physical characteristics of microplastics and environmental factors that affect sedimentation. The abundance, shape, composition, and timeline of microplastics in sediment layers in rivers, floodplains, lakes, estuaries and coastal wetlands are presented. The abundance of microplastics in sediment layers varies across sites and may exhibit opposite trends along depth, and generally the proportion of relatively small microplastics increases with depth, while less is known about the vertical trends in the shape and composition of microplastics. Timeline of microplastics is generally linked to the sedimentation rate, which varies from millimeters to centimeters per year in the reviewed studies. The spatiotemporal characteristics of microplastic sedimentation depend on the settling and erosion of microplastics, which are determined by two aspects, microplastic characteristics and environmental factors. The former aspect includes size, shape and density influenced by aggregation and biofouling, and the latter includes dynamic forces, topographic features, bioturbation and human activities. The comprehensive review of these factors highlights the needs to further quantify the characteristics of microplastic sedimentation and explore the role of these factors in microplastic sedimentation on various spatiotemporal scales.

Interplay of compound pollutants with microplastics transported in saturated porous media: Effect of co-existing graphene oxide and tetracycline

Co-existence of microplastics, nanomaterials, and antibiotics may lead to intensified multifaceted pollution, which may influence their fate in soils. This study investigated the co-transport behavior of polystyrene microplastics (PS) and compound pollutants of graphene oxide (GO) and tetracycline (TC). Packed column experiments for microplastic with or without combined pollutants were performed in KCl (10 and 30 mM) and CaCl2 solutions (0.3 and 1 mM). The results showed transport of PS was facilitated at low ionic strengths and inhibited at high ionic strengths by GO with or without TC under examined conditions. Carrier effect of GO as well as the aggregation of PS in the presence of co-exiting GO or GO-TC could be the contributor. Although the existence of TC relieved the ripening phenomenon of PS and GO deposition due to enhanced electronegativity of sand media, the effect of GO on the PS transport has not been significantly impacted, indicating the dominant role of GO during cotransport process. Furthermore, the transport of PS was increased by TC owing to competition for deposition sites on sand surfaces. In turn, the transport of TC was mainly affected by PS whether graphene was present or not. The increase in electrostatic repulsive force (transport-promoting) and addition adsorption sites (transport-inhibiting) may be responsible for the observations. Our findings could improve understandings of complex environmental behaviors of microplastics and provide insight into investigation on cotransport of emerging contaminants under various conditions relevant to the subsurface environment.

Water quality variation and driving factors quantitatively evaluation of urban lakes during quick socioeconomic development

Rapid urbanisation has caused a significant impact on the ecological environment of urban lakes in the world. To maintain the harmonious development of urban progress and water quality, it is essential to evaluate water quality variation and explore the driving factors quantitatively. A comprehensive evaluation method with cluster analysis and Kriging interpolation was used to explore the spatiotemporal variation in a typical urban lake in China, Chaohu Lake, from 2011 to 2020. The correlation between water quality and socioeconomic factors was evaluated by Pearson correlation analysis. Results indicated that: total phosphorus (TP) and total nitrogen (TN) were the key pollution parameters of Chaohu Lake. The pollution situation was gradually improving, however, and the improvement in chemical oxygen demand (COD) is more evident due to anthropogenic control. The spatial heterogeneity of water quality in Chaohu Lake is remarkable, and the water quality is poor in the west but better in the east. Natural attributes of lakes and external load were the main reasons for the spatial heterogeneity. The western residential areas of Chaohu Lake Basin (CLB) are concentrated, and a large amount of industrial and domestic sewage exacerbates water pollution in the west of tributaries. In contrast, the implementation of water environmental governance policies in recent years has alleviated water pollution. From 2011 to 2020, water quality has improved by 23%-35% in the west and 7%-14% in the east. This study provided a framework for quantitatively assessing water quality variation and its driving forces in urban lakes.

Using Data-Driven Methods and Aging Information to Quantitatively Identify Microplastic Environmental Sources and Establish a Comprehensive Discrimination Index

The global distribution of microplastics (MPs) across various environmental compartments has garnered significant attention. However, the differences in the characteristics of MPs in different environments remain unclear, and there is still a lack of quantitative analysis of their environmental sources. In addition, the inclusion of aging in source apportionment is a novel approach that has not been widely explored. In this study, we conducted a meta-analysis of the literature from the past 10 years and extracted conventional and aging characteristic data of MPs from 321 sampling points across 7 environmental compartments worldwide. We established a data-driven analysis framework using these data sets to identify different MP communities across environmental compartments, screen key MP features, and develop an environmental source analysis model for MPs. Our results indicate significant differences in the characteristics of MP communities across environments. The key features of differentiation were identified using the LEfSe method and include the carbonyl index, hydroxyl index, fouling index, proportions of polypropylene, white, black/gray, and film/sheet. These features were screened for each environmental compartment. An environmental source identification model was established based on these features with an accuracy of 75.1%. In order to accurately represent the single/multisource case in a more probabilistic manner, we proposed the MP environmental source index (MESI) to provide a probability estimation of the sample having multiple sources. Our findings contribute to a better understanding of MP migration trends and fluxes in the plastic cycle and inform effective prevention and control strategies for MP pollution.

Multidecadal heavy metals and microplastic deposition records in an urban lake: the ecological risk assessments and influencing factors

With the development of urbanization and economic growth, the urban lake ecosystem faces many challenges derived from external factors. As pollutants in the aquatic environment, heavy metals and microplastics negatively influence the urban lake ecosystem due to their intrinsic properties. To understand the distribution patterns and multidecadal deposition characteristics of heavy metals and microplastics, six sediment cores were collected in March 2021 from a Chinese urban lake, Xinghu Lake, and the isotopic composition of cesium-137 and lead-210 was analyzed for the chronology of the sediment core. Here, the classifications of comprehensive ecological risk evaluation methods for heavy metals and microplastics were adjusted further. Meanwhile, the correlations among heavy metals, microplastics, sediment grains, and natural and social factors were further analyzed. The results showed that the sediments of Xinghu Lake were mainly fine silt (39%), and the average surface area of sediment was 1.82 ± 0.60 m²/g. The average concentrations of cadmium, chromium, copper, nickel, lead, vanadium, and zinc were 0.268 ± 0.077, 59.91 ± 16.98, 23.29 ± 6.48, 52.16 ± 13.11, 36.83 ± 11.78, 119.57 ± 26.91, and 88.44 ± 29.68 mg/kg, respectively. The average comprehensive potential ecological risk indexes of heavy metals and microplastics in sediment cores were 46.59 ± 9.98 and 105.78 ± 23.32 in Xinghu Lake, and their risks were projected to reach high and very high levels by 2030 and 2050. The annual average temperature was the key natural factor for the abundances of heavy metals and microplastics, and the small sediment grain had a significant correlation with these. Agricultural activities were major pollution sources of heavy metals and microplastics, while the chemical fibers and plastic products were closely related to the abundance of microplastics.

Source or sink role of an urban lake for microplastics from Guangdong-Hong Kong-Macao greater bay area, China

Plastic production and consumption in China are larger than others in the world, and the challenge of microplastic pollution is widespread. With the development of urbanization in the Guangdong-Hong Kong-Macao Greater Bay Area, China, the environmental pollution of microplastics is becoming an increasingly prominent issue. Here, the spatial and temporal distribution characteristics, sources, and ecological risks of microplastics were analyzed in water from an urban lake, Xinghu Lake, as well as the contribution of rivers. Importantly, the roles of urban lakes for microplastics were demonstrated through the investigations of contributions and fluxes for microplastic in rivers. The results showed that the average abundances of microplastics in water of Xinghu Lake were 4.8 ± 2.2 and 10.1 ± 7.6 particles/m³ in wet and dry seasons, and the average contribution degree of the inflow rivers was 75%. The size of microplastics in water from Xinghu Lake and its tributaries was concentrated in the range of 200-1000 μm. In general, the average comprehensive potential ecological risk indexes of microplastics in water were 247 ± 120.6 and 273.1 ± 353.7 in wet and dry seasons, which the high ecological risks of them were found through the adjusted evaluation method. There were also mutual effects among microplastic abundance, the concentrations of total nitrogen and organic carbon. Finally, Xinghu Lake has been a sink for microplastics both in wet and dry seasons, and it would be a source of microplastics under the influence of extreme weather and anthropogenic factors.

The spatial distribution and abundance of microplastics in lake waters and ice during ice-free and ice-covered periods

Understanding the spatial distribution and characteristics of microplastics (MPs) in lake waters is essential to assessing and addressing lacustrine MP pollution. This study investigated how lake ice affects the abundance, spatial distribution, and characteristics (size, shape) of MPs in Lake Ulansuhai by analyzing samples collected at ten sites uniformly distributed throughout the lake during ice-free and ice-covered periods. The abundance of MPs ranged between 204 ± 28 and 1224 ± 185 n·L^-1 in lake waters during the ice-free period, and from 34 ± 8 to 216 ± 21 n·L^-1 and 269 ± 84 to 915 ± 117 n·L^-1 in water and ice during the ice-covered period, respectively. During the ice-covered period, MPs were 2.74-8.14 times higher in the ice than in water beneath the ice. Ice formation decreased MP abundance in lake waters, in part, by incorporating a relatively high percentage of MPs into the ice mass during freezing and by inhibiting atmospheric MPs from reaching the lake waters. The abundance of MPs in the water during the ice-free period was 4.50-11.30 times greater than during the ice-covered period. Seasonal variations in MP shape also occurred; the proportion of fibrous MPs in water decreased during the ice-covered period. Variations in MP abundance were partly due to differences in sedimentation rates; the settling of fibrous MPs is slower, making it easier for them to be captured during the formation of surface ice. Spatially, MPs were uniformly distributed during the ice-free period, but exhibited a spatially distinct pattern during ice-covered periods, when MPs in lake waters were higher in the northeast and lower in the southwest portions of the lake. During the ice-free period, small MPs (0.05-0.5 mm) were more likely to move with currents in the lake, whereas water velocities were reduced by ice formation, allowing small MPs to accumulate near the lake inlet.

Dynamic characteristics of microplastics under tidal influence and potential indirect monitoring methods

Rivers are an important channel for the transport of microplastics from inland areas to the ocean. It is of great significance to explore the dynamic changes in microplastic pollution characteristics under tidal fluctuations to understand the exchange of microplastics between rivers and oceans. In this study, the occurrence of microplastics in typical tidal channels in the lower reaches of the Dong River was investigated during the wet and dry weather seasons, and high frequency continuous dynamic monitoring of microplastics was carried out in a typical tidal cross section during a tidal cycle. The abundances of microplastics during wet and dry weather seasons were 3.97-102.87 ± 28.63 item/m³ and 5.43-56.43 ± 14.32 item/m³, respectively. The microplastics generally exhibited a fluctuating growth pattern, with low contents in the upstream area and high contents in the downstream area, and the abundance of microplastics differed greatly in the different functional zones. The dynamic monitoring results showed that the abundance of microplastics was clearly affected by the tides, in that it increased during the flood tide and decreased during the ebb tide, with abundances ranging from 11.15 to 95.26 item/m³. In addition, there was a significant linear relationship between the abundance of microplastics and flow in the typical tidal cross section. The relationship between the response of microplastic pollution characteristics and tides combined with local hydrometeorological factors may be a potentially effective real-time monitoring method for assessing microplastic pollution indirectly.

The spatial distribution of microplastics in topsoils of an urban environment - Coimbra city case-study

Due to their seemingly ubiquitous nature and links to environmental and human health problems, microplastics are quickly becoming a major concern worldwide. Artificial environments, such as those found in urban environments, represent some of the main sources of microplastic. However, very few studies have focused on the occurrence of microplastics in urban soils. The aim of the current research was to evaluate the microplastic contamination in urban soils from artificial and natural land uses throughout Coimbra city, Portugal. Sixty-seven spaces and ten land use areas were evaluated. The artificial land use areas were dumps, landfills, parking lots, industries and construction areas, and the natural land use areas were forests, urban parks, moors (wetlands), pastures and urban agricultural areas. Microplastic extraction was done by density separation. Quantification and size measurements of microplastics was carried out using a microscope. Polymer types were identified by μ-FTIR for 25% of the samples. The microplastic content ranged from 5 × 10³ to 571 × 10³ particles·kg^-1, with a mean of 106 × 10³ particle·kg^-1. The green park was the land use with the highest concentration of microplastics (158 × 10³ particle·kg^-1) and the forest was the one with the lowest concentration (55 × 10³ particle·kg^-1). The landfill (150 × 10³ particle·kg^-1), industry (127 × 10³ particle·kg^-1) and dump (126 × 10³ particle·kg^-1) were the artificial spaces with the highest levels of microplastics. The main polymers detected were polypropylene and polyethylene, followed by polyvinyl chloride and rubber, and the main sizes measured between 50 and 250 μm. Our results indicate that natural spaces can contain higher amounts of microplastics as compared to artificial spaces in the urban environment. This suggests that microplastics are easily transported through the urban landscape and that urban green spaces can retain microplastics in their soils. Land use planning may present an opportunity to better control the levels of microplastics in urban environments.

Microplastics pollution in freshwater sediments: The pollution status assessment and sustainable management measures

Microplastics (MPs) pollution in freshwater sediments has brought hidden dangers to food and drinking water supply. Implementing sustainable management measures for MPs pollution in freshwater sediments has become an inevitable trend for sustainable development of society. Existing studies still lacked sufficient discussion in sustainable management of MPs pollution in freshwater sediments. This makes it difficult to formulate sustainable management measures for MPs pollution in freshwater sediments. This study analyzed the pollution status of MPs in freshwater sediments from 84 study areas. The results showed that current studies on MPs pollution in freshwater sediments were mainly concentrated in densely populated and economically developed areas. The average abundance of MPs in freshwater sediments from collected study areas was 1290.88 items/kg, this brought a potential threat to sustainable development in surrounding areas. The pollution load level and potential ecological risk level of MPs in freshwater sediments from these study areas were low. Reducing MPs discharge and restricting the use of high-risk polymers are effective ways to prevent the deterioration of MPs pollution status in freshwater sediments. The abundance and types of MPs in freshwater sediments from these study areas were affected by human activities. Sustainable management of MPs pollution in freshwater sediments from collected study areas requires establishing a lifecycle management system for plastic products, and the industrial structures should be optimized. In addition, legislation and market regulation are effective ways to restrict the discharge of plastic wastes. Sustainable management of MPs in freshwater sediments requires the synergy of legislation and market regulation.

Long-term deposition records of microplastics in a plateau lake under the influence of multiple natural and anthropogenic factors

Microplastic accumulation in the lake aquatic environment has attracted worldwide attention, but the long-term deposition characteristics and influencing factors of microplastics are not clear. Hence, we attempted to analyze the factors that influence the accumulation of microplastics during the process of natural environmental change and social development through the method of the sedimentological approach. In this investigation, the chronological sequence of sediment core was set up based on lead-210 composition to study microplastic accumulation rates in a plateau lake, Jianhu Lake. For the first time, the records of microplastic deposition were analyzed combined with multiple anthropogenic and natural factors, including 4 natural and 17 social factors to reveal the influence of natural processes and social development on microplastic abundances. The results showed that sediments were highly contaminated by microplastics, and the mean abundance of microplastics in the sediment cores of Jianhu Lake was 924 ± 427 particles/kg, and showed a gradually increasing trend from the bottom (25 to 30 cm) to surface layer (0 to 5 cm). Blue and black were the main colors of microplastics, and the average proportion of wirelike microplastics was 63 %. Additionally, the polymer type of microplastic was mainly rayon, the surface morphology of different polymer types was disparate, and various elements enriched on the surface of microplastics were also detected. In the past 70 years, the deposition rate of microplastics in Jianhu Lake maintained the trend of continuous growth, and the abundance of microplastics is projected to be 448 to 3017 and 513 to 3670 particles/kg by 2035 and 2050, respectively. What is more, there are significant correlations among multiple natural and anthropogenic factors and microplastic deposition, as well as microplastic polymer species.

Experiment on monitoring leakage of landfill leachate by parallel potentiometric monitoring method

The accumulation of municipal solid waste (MSW) in landfills often becomes a serious pollution source of geological environment and groundwater. The geological environment is the carrier of the landfill, and also the main pollution object of the landfill. The main pollution modes of the landfill site to the surrounding geological environment are purging, flushing, leachate, etc. If the leachate leakage cannot be found and repaired in time, it will cause serious harm to the geological environment and groundwater. The cost of geological environment and groundwater sampling through borehole surveys is high. Therefore, monitoring the seepage path and migration law of leachate is of great significance for determining the pollution range of the landfill site. In this study, by adjusting the grids of different sizes and changing the flow rate of leachate, the monitoring of fluid migration of different types of leachate was strengthened. The results show that the parallel potential monitoring method can quickly reflect the location and number of leachate points and the migration law of leachate. It provides effective reference data for landfill leachate monitoring.

Variation of microplastics in the shore sediment of high-altitude lakes of the Indian Himalaya using different pretreatment methods

Microplastics pollution is a growing environmental concern. However, microplastics studies in high altitude remote lakes are scarce. In this study, microplastics pollution was assessed in the shore sediment of three high altitude lakes in Ladakh of the Indian Himalaya, namely Pangong Lake, Tsomoriri Lake and Tsokar Lake. Sampling of lakes shore sediment was performed in August 2019. Two different pretreatment methods were implemented with sediment samples from same sites, resulting two sets of samples. One set of samples was pretreated utilizing enzymatic degradation together with Fenton reactions. Another set of samples from the same sites were pretreated with 30 % hydrogen peroxide (H₂O₂) and Fenton reaction. Enzymatically pretreated samples resulted in higher microplastics concentrations than the set of H₂O₂ pretreated samples, which indicated that microplastics concentrations in sediment samples varies even among samples from the same site and that the pretreatment procedure may impact on the reported microplastics concentrations. Considering both sets of samples, microplastic concentration was 160-1000 MP/kg dw in Pangong Lake, 960-3800 MP/kg dw in Tsomoriri Lake, and 160-1000 MP/kg dw in Tsokar Lake. Blank correction based on the limit of detection and the limit of quantification indicated that microplastics concentrations at some sites of the studied lakes are higher than the limit of detection and the limit of quantification. The findings of this study indicated that the studied lakes in the Indian Himalaya are contaminated with microplastics. In addition, the comparison of microplastics using different pretreatment methods illustrated the importance of harmonization of microplastics studies to enable a reliable comparison among microplastics data. Therefore, this study contributes towards an assessment of microplastics in the high-altitude lakes in Indian Himalaya. The findings attributed towards clearer understanding regarding the need of harmonization of pretreatment methods and demonstrated the importance of reporting complete information in microplastics research.

Microplastics in urban runoff: Global occurrence and fate

Public concerns on microplastic (MP) pollution and its prevalence in urban runoff have grown exponentially. Huge amounts of MPs are transported from urban environments via surface runoff to different environment compartments, including rivers, lakes, reservoirs, estuaries, and oceans. The global concentrations of MPs in urban runoff range from 0 to 8580 particles/L. Understanding the sources, abundance, composition and characteristics of MPs in urban runoff on a global scale is a critical challenge because of the existence of multiple sources and spatiotemporal heterogeneity. Additionally, dynamic processes in the mobilization, aging, fragmentation, transport, and retention of MPs in urban runoff have been largely overlooked. Furthermore, the MP flux through urban runoff into rivers, lakes and even oceans is largely unknown, which is very important for better understanding the fate and transport of MPs in urban environments. Here, we provide a critical review of the global occurrence, transport, retention process, and sinks of MPs in urban runoff. Relevant policies, regulations and measures are put forward. Future global investigations and mitigation efforts will require us to address this issue cautiously, cooperating globally, nationally and regionally, and acting locally.

Application of a microplastic trap to the determination of the factors controlling the lakebed deposition of microplastics

Microplastics (MPs) in aquatic environments are hard to degrade, easy to transport, and potentially hazardous to biota. Previous studies of MPs in lakes have shown that their deposition is a significant process controlling both their lateral dispersal from a source, and their concentration within the water column. However, the lakebed depositional rates of MPs have predominantly been determined using laboratory experiments and/or through model simulations that may not fully reflect field conditions. In this paper, lacustrine depositional rates in Lake Ulansuhai were documented using an MP trap that allowed for the assessment and quantification of the depositional rates of MPs of differing size, density, and shape at three sampling sites over five different time periods. The results showed that the downward flux for all types of MPs near the lakebed was correlated with wind speed. Higher wind speeds led to the resuspension of greater amounts of MPs in the lakebed sediments and the transport of greater amounts of MPs from the lake inlet to the lake interior and outlet along the hydrologic flow directions. Consequently, higher wind speeds increased the abundance of MPs at the sediment-water interface and intensified the vertical mixing of MPs in the lake water, resulting in a higher depositional flux of MPs. Particles of differing size, shape, and density exhibited different depositional rates. In general, fragmentary, larger size, and higher density MPs were more likely to be deposited. Thus, size and shape have a strong effect on the migration and deposition of HDMPs in Lake Ulansuhai.

Spatial distribution of microplastics pollution in sediments and surface waters of the Aras River and reservoir: An international river in Northwestern Iran

Microplastics (MPs) in freshwater environments have been recognized as one of the important sources of plastic contamination in marine ecosystems. Reducing the amount and spatial distribution of MPs reaching the sea through accumulation behind dams remains unclear. In this study we analyzed the spatial distribution of sediment and surface water MPs in the Aras Dam and from nineteen upstream and downstream locations of the Dam in the Aras River. The MPs abundance ranged from 32 to 528 items/kg dry weight (mean 217.8 ± 132.6) and 1 to 43 items/m³ (mean 12.8 ± 10.5) in the sediment and surface water stations, respectively. MPs abundance in surface waters collected within the Dam reservoir was significantly higher than those found either upstream or downstream (P < 0.05). For sediments, reservoir MPs concentration was generally higher than upstream and downstream, although their differences were not significant. High MPs concentration was observed in the vicinity of urban areas. Moreover, MPs abundance was positively correlated with total organic carbon (TOC) and clay content (P < 0.01). GAM analysis revealed that clay is the most important variable with lowest Akaike information criterion (AIC) and explained 61.3 % of deviance (R-sq.(adj) = 0.344) in MPs abundance. MP particles ranged from 0.1 to 5 mm in size and were dominated by fibers (53.5 %), black color (24 %) and PE polymer (36.6 %). Our results highlight the high MPs distribution in the Aras River and demonstrate that they accumulate in the surface waters behind the Dam. Consequently, the fate and effects of MPs in international rivers is one of the most politicized issues between countries with a common boundary and therefore needs joint management policies that help mitigate this insidious problem.