Rapid urbanization affects microplastic communities in lake sediments: A case study of Lake Aha in southwest China

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.

Microplastic distribution in large shallow lake sediments: Variations with offshore distance and implications for microbial communities

Microplastics (MPs) are ubiquitous in global ecosystems and pose potential threats to the environment and biodiversity. However, the impact of MPs on microorganisms in real environments remains unclear. Our study focuses on the composition and distribution of MPs in sediments at different offshore distances in Taihu Lake. Our results indicated that MP abundance ranged from 240 to 1120 items/kg and decreased linearly with increasing offshore distance. Fibres dominated, with an average proportion of 47.58 %, and MPs within a particle size range of 0.5-1 mm (53.88 %) had the highest content. PA and PVC were the most abundant polymer types, accounting for 55.85 % and 17.94 %, respectively. The abundance of MPs in sediments was significantly positively correlated (P < 0.01) with the abundance of Firmicutes and significantly negatively correlated with the abundance of Planctomycetota. MPs account for 0.49 % of the variation in microbial alpha diversity and 1.88 % of the variation in microbial community composition. Our study demonstrates that environmental factor and MPs significantly affect microbial diversity and species composition. In summary, our research reveals the distribution patterns of MPs in sediments at different offshore distances in Taihu Lake, confirming the potential impact of MPs on microbial communities.

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.

Potential ecological risk of microplastics contamination to environment in protect area lakes

Microplastics (MPs) in freshwater have been extensively studied on a global scale. However, a deeper understanding is still required regarding the occurrence characteristics and ecological risks of MPs in protected area lakes(PAL). Here, the study investigated MPs pollution in PAL, outside protected areas lakes (OPAL), and ponds (OPAP) in the eastern Qinghai-Tibetan Plateau, and a comprehensive analysis was conducted comparing lakes or ponds from different income regions. The results showed that PAL has a single source of contamination, while OPAL and OPAP exhibited more diverse MP sources. The surface of all samples showed significant physicochemical changes like oxygen-containing functional groups and potential signs of biodegradation. Microbiome analysis identified potential plastic-degrading bacteria on MPs, which varied by polymer type. Ecological risk assessment revealed that OPAL and OPAP face higher ecological risks, particularly from polymers like PVC and PC, while PAL has low risk. However, we should also consider the environmental changes over the past 100 years of history in this region and emphasize the environmental health of PAL. Notably, MPs pollution is more severe in lower-middle-income regions, highlighting the urgent need for stricter controls.

The role of habitat preference and feeding strategy on exposure to microplastic pollution in freshwater fish species

Microplastic (MP) pollution has been observed in a variety of ecosystems, but there is a limited number of studies on reservoir ecosystems. The aim of this study was to determine the levels of MP contamination in sediment, water and commercially important fish species (Cyprinus carpio, Perca fluviatilis, Atherina boyeri and Sander lucioperca) collected from the Yamula Reservoir in Türkiye. Water samples were collectes at five stations. Four sediment samples were collected from the lake. As sediments from the lake represent a vital element of the lake ecosystem, they function as a historical archive that reflects alterations in land use and the characteristics of the lake over time. The average amounts of MPs observed in sediment and water samples were 0.12 MP/g and 0.58 MP/m3 respectively. The digestive systems of 30 individuals of each fish species were examined. The highest amount of MP was observed for C. carpio (6 ± 5.9 MP/individual), while the lowest amount of MP was observed for A. boyeri (1.8 ± 1.7 MP/individual). MP abundance in S. lucioperca and P. fluviatilis was 2 ± 2.8 and 4.6 ± 6.3 MP per individual. The most commonly observed polymer types were polypropylene (67%), polyvinyl alcohol (13%), polyethylene resin (13%) and high-density polyethylene (7%). The pollution load indexes determined for each fish species from the highest to the lowest were as follows: 1.83 (C. carpio) 1.6 (S. lucioperca) 1.05 (P. fluviatilis) and, 1 (A. boyeri). The findings of the study indicate that all sampling stations, including both sediment and water, are contaminated with MPs. Furthermore, the results demonstrate that all examined fish species ingest MPs. Additionally, the results indicate that fish inhabiting a wide range of habitats and consuming diverse diets are more susceptible to MP contamination.

Investigation of microplastic pollution index in the urban surface water: A case study in west Godavari district, Andhra Pradesh, India

Microplastics (MPs) are a growing environmental issue because of their widespread prevalence and their long-term effects on ecosystems and human health. Global studies have identified MPs in various aquatic environments, such as lake, rivers, estuaries, wastewater, and oceans. Although most MPs originate from urban surface water sources, the specific intensity, characteristics, and associated risk assessments remain unclear. This study focuses on west Godavari region of India, specifically analyzing MPs in surface water samples Godavari River and two water treatment plants (WTPs). A total of 330 MPs found in the surface water and 121 MPs in theWTP. In surface water, MPs were predominantly blue and transparent fibers, with the majority measuring less than 500 μm in size. Conversely, at the WTP, larger MPs, primarily in blue fiber form and exceeding 3000 μm, were observed. Additionally, μ-Raman spectroscopy analysis identified the presence of various polymers, including PP, PVC, PC, Nylon, and PET, among others. The risks associated with MPs, including their concentration and chemical composition, were assessed across all sample types using various indices such as Contamination Factor (CFi), Pollution Load Index (PLI), Polymer Risk Index (H), Potential Ecological Risk Index (RI), and Estimated Intake (EI) (daily, annually, and lifetime). The risk assessment revealed that the type of polymer poses a greater risk of MP pollution than the concentrations of MPs themselves. These findings provide critical insights into MP contamination patterns and risks, emphasizing the need for targeted mitigation strategies in this region.

Significant effects of rural wastewater treatment plants in reducing microplastic pollution: A perspective from China's southwest area

Sewage systems are a major source for microplastics in riverine exports to oceans. Urban areas are generally considered hotspots for microplastic discharge, whereas emissions from rural areas remain largely understudied. Hence, this study investigated the abundance, characteristics, and polymer types of microplastics in rural wastewater treatment plants (WWTPs) in Guiyang and estimated the annual microplastic emissions of China based on sewage discharge. The influent abundance of microplastics was 3.8-8.2 items/L, the effluent abundance was 3.1-5.9 items/L, with a lower removal rate of 14.4 %-54.6 %, which might be influenced by lower operating loads and influent concentrations. Raman spectroscopy analysis revealed that polyvinyl alcohol (PVA) was the predominant polymer type. Rural WWTPs were more effective at removing large-sized particles (> 0.1 mm) and films, resulting in higher removal effectiveness by weight (49.1 %) compared to urban WWTPs (30.8 %). Based on the abundance of microplastics in WWTPs within the study area and China's annual sewage discharge, this study estimated the microplastic emissions released through sewage in China in 2022. The annual microplastic emissions through sewage in China were estimated to be 2995.7 tons, with rural and urban areas contributing 25.1 % and 74.9 %, respectively. Approximately 724.8 tons and 1001.6 tons of microplastics were removed from rural and urban WWTPs, respectively. This work indicates the unignorable emissions of microplastics from rural sewage and highlights the crucial role of rural WWTPs in reducing microplastic pollution.

Dual carbon isotopes (δ13C and Δ14C) were used to reveal the main sources and input fluxes of dissolved inorganic carbon in a karst reservoir in winter

In karst areas, the dissolved inorganic carbon (DIC) concentrations in aquatic systems are typically higher than that in non-karst areas due to intensive carbonate rock weathering. Understanding the sources and input fluxes of DIC in karst reservoirs is crucial for regional carbon cycle studies. This study utilized dual carbon isotopes (δ13CDIC and Δ14CDIC) to estimate the contribution rates and input fluxes of DIC from various sources in Aha Reservoir (AHR), located in southwestern China. Our results indicated that the DIC concentrations (22.33-32.79 mg L-1) and δ13CDIC values (-10.02‰ to -8.55‰) were nearly homogeneous both vertically and laterally in the reservoir (p > 0.05). The Δ14CDIC values (-246.31‰ to -137.86‰) were homogeneous along the vertical profile (p > 0.05), but showed significant horizontal variation (p < 0.05), with values decreasing from -149.57 ± 10.27‰ to -232.85 ± 2.37‰ at the mouths of the inflowing rivers. We found that the inflowing rivers were the primary DIC sources to AHR, contributing 70% of the total input, while groundwater and atmospheric CO2 contributions were relatively minor, at 18% and 12%, respectively. The Jinzhong River (JZR), influenced by industrial and domestic wastewater discharge, contributed the largest DIC input flux at 2.01 t/(km2·mon). In contrast, the Youyu River (YYR), influenced by acidic mine drainage, and the Baiyan River (BYR), influenced by agricultural activities, contributed relatively smaller DIC input fluxes of 1.29 t/(km2·mon) and 1.03 t/(km2·mon), respectively. This study highlights the significant impact of anthropogenic activities on DIC input in AHR, with industrial and domestic wastewater discharges having a greater influence than agricultural activities and acidic mine wastewater inputs. These findings underscore the critical need to manage and mitigate the impacts of human activities on karst reservoir ecosystems.

Deciphering pollution sources and mechanisms controlling groundwater chemistry in a typical dense agricultural plain on Yungui Plateau

Groundwater is a critical resource for economic growth and livelihoods in the dense agricultural plains of plateaus. However, contaminations from various sources pose significant threats to groundwater quality. Understanding the sources of groundwater contamination and the mechanisms of hydrochemical control is essential for the sustainable development of agriculturally intensive plains. This research utilizes 23 datasets of groundwater chemical measurements to apply hierarchical clustering analysis, positive matrix factorization, and hydrochemical analysis techniques. Through these methods, the study identifies the sources of groundwater contamination and deciphers the hydrochemical control mechanisms within a representative intensive agricultural plain region of Yungui Plateau. The finds indicate that groundwater in the plain primarily derives from the rainfall occurred in the surrounding mountains. During the long underground flow process, groundwater undergoes water-rock interactions and ion exchanges with various lithological strata, resulting in the formation of distinct hydrochemical types. As it traverses regions influenced by human activities, groundwater encounters varying levels and types of contamination. Consequently, there is a notable variation in groundwater quality across different areas of the plain. Groundwater is dominated by the hydrochemical faces of HCO3-Ca type in the southern part of the plain. Groundwater in the piedmont region of this part exhibits the highest quality, acting as the baseline for the overall groundwater quality of the plain. Groundwater in agricultural areas of this part is severely polluted by nitrate-rich agricultural wastewater. In the central urban area, under the control of municipal wastewater discharge and denitrification, groundwater is to some extent polluted by NH4 +. In the northern sector of the plain, groundwater chemistry exhibits greater diversity due to variations in geological strata and exposure to a range of pollution sources. The majority of the regions are contaminated with SO4 2- and Cl- and present a predominance of Cl-Na type for groundwater hydrochemical facies. Groundwater at the northernmost end is polluted by NO2 -, NH4 +, and P. In addition, there is also a small amount of groundwater near the lake that is heavily polluted by fertilizers. This study provides valuable insights for the development of sound groundwater management strategies, applicable not only to the current agricultural plain but also to analogous regions worldwide. PRACTITIONER POINTS: This study probed the impact of agricultural pollution on the groundwater hydrochemistry in a cultivated plain. The research pinpointed the origins and contributions of groundwater chemicals in the cultivated agricultural plain. A conceptual model was established to illustrate groundwater chemistry formation in an intensive agricultural irrigation plain on Yungui Plateau.

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.

Water transfer projects and microplastics: Analyzing changes in lake environments with a focus on Wabu Lake, China

Microplastics are widespread in freshwaters, yet their interaction with navigational structures remains unclear. This study compared the distribution and characteristics of microplastics before and after navigation in Wabu Lake. Microplastic concentrations decreased significantly in both surface water and sediment due to navigation opened, from 13.7 ± 6.56 to 3.12 ± 1.8 p L-1 (p < 0.001) and from 568 ± 286 to 174 ± 60.2 p kg-1 (p < 0.001), respectively. Acrylates copolymer was frequently detected in surface water and sediment before navigation, whereas the dominant polymer after navigation was chlorinated polyisoprene in surface water and chlorinated polyethylene in sediment. The results showed that three-years dredging induced relatively severe microplastic pollution before navigation, however, these microplastics were apparently eliminated after navigation, as the distribution and characteristics of microplastics thoroughly varied. This study provides a valuable finding that microplastic transport process can be facilitated by water transfer project, which should be considered for preventing microplastic pollution.

Microplastics in multi-environmental compartments: Research advances, media, and global management scenarios

During the past decades, microplastics (MPs) have become an emerging concern due to their persistence and potential environmental threat. MP pollution has become so drastic that it has been found in the human food chain, breast milk, polar regions, and even the Himalayan basin, lake, etc. Inflammation, pulmonary hypertension, vascular occlusions, increased coagulability and blood cell cytotoxicity, disruption of immune function, neurotoxicity, and neurodegenerative diseases can all be brought on by severe microplastic exposure. Although many MPs studies have been performed on single environmental compartments, MPs in multi-environmental compartments have yet to be explored fully. This review aims to summarize the muti-environmental media, detection tools, and global management scenarios of MPs. The study revealed that MPs could significantly alter C flow through the soil-plant system, the structure and metabolic status of the microbial community, soil pH value, biomass of plant shoots and roots, chlorophyll, leaf C and N contents, and root N contents. This review reveals that MPs may negatively affect many C-dependent soil functions. Different methods have been developed to detect the MPs from these various environmental sources, including microscopic observation, density separation, Raman, and FT-IR analysis. Several articles have focused on MPs in individual environmental sources with a developed evaluation technique. This review revealed the extensive impacts of MPs on soil-plant systems, microbial communities, and soil functions, especially on water, suggesting possible disturbances to vital ecological processes. Furthermore, the broad range of detection methods explored emphasizes the significance of reliable analytical techniques in precisely evaluating levels of MP contamination in various environmental media. This paper critically discusses MPs' sources, occurrences, and global management scenarios in all possible environmental media and ecological health impacts. Future research opportunities and required sustainable strategies have also been suggested from Bangladesh and international perspectives based on challenges faced due to MP's pollution.

Unveiling microplastics pollution in a subtropical rural recreational lake: A novel insight

While global attention has been primarily focused on the occurrence and persistence of microplastics (MP) in urban lakes, relatively little attention has been paid to the problem of MP pollution in rural recreational lakes. This pioneering study aims to shed light on MP size, composition, abundance, spatial distribution, and contributing factors in a rural recreational lake, 'Nikli Lake' in Kishoreganj, Bangladesh. Using density separation, MPs were extracted from 30 water and 30 sediment samples taken from ten different locations in the lake. Subsequent characterization was carried out using a combination of techniques, including a stereomicroscope, Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FE-SEM). The results showed a significant prevalence of MPs in all samples, with an average amount of 109.667 ± 10.892 pieces/kg3 (dw) in the sediment and 98.167 ± 12.849 pieces/m3 in the water. Small MPs (<0.5 mm), fragments and transparent colored particles formed the majority, accounting for 80.2%, 64.5% and 55.3% in water and 78.9%, 66.4% and 64.3% in sediment, respectively. In line with global trends, polypropylene (PP) (53%) and polyethylene (PE) (43%) emerged as the predominant polymers within the MPs. MP contents in water and sediment showed positive correlations with outflow, while they correlated negatively with inflow and lake depth (p > 0.05). Local activities such as the discharge of domestic sewage, fishing waste and agricultural runoff significantly influence the distribution of polypropylene. Assessment of pollution factor, pollution risk index and pollution load index values at the sampling sites confirmed the presence of MPs, with values above 1. This study is a baseline database that provides a comprehensive understanding of MP pollution in the freshwater ecosystem of Bangladesh, particularly in a rural recreational lake. A crucial next step is to explore ecotoxicological mechanisms, legislative measures and future research challenges triggered by MP pollution.

Microplastics pollution in the Surma River, Bangladesh: A rising hazard to upstream water quality and aquatic life

The ecological health of freshwater rivers is deteriorating globally due to careless human activities, for instance, the emission of plastic garbage into the river. The current research was the first assessment of microplastics (MPs) pollution in water, sediment, and representative organisms (fish, crustacean, and bivalve) from the Surma River. Water, sediment, and organisms were sampled from six river sites (Site 1: Charkhai; Site 2: Golapganj; Site 3: Alampur; Site 4: Kazir Bazar; Site 5: Kanishail and Site 6: Lamakazi), and major water quality parameters were recorded during sampling. Thereafter, MPs in water, sediment, and organism samples were extracted, and then microscopically examined to categorize selected MPs types. The abundance of MPs, as well as size, and color distribution, were estimated. Polymer types were analyzed by ATR-FTIR, the color loss of MPs was recorded, the Pollution Load Index (PLI) was calculated, and the relationship between MPs and water quality parameters was analyzed. Sites 4 and 5 had comparatively poorer water quality than other sites. Microplastic fibers, fragments, and microbeads were consistently observed in water, sediment, and organisms. A substantial range of MPs in water, sediment, and organisms (37.33-686.67 items/L, 0.89-15.12 items/g, and 0.66-48.93 items/g, respectively) was recorded. There was a diverse color range, and MPs of <200 μm were prevalent in sampling areas. Six polymer types were identified by ATR-FTIR, namely Polyethylene (PE), Polyamide (PA), Polypropylene (PP), Cellulose acetate (CA), Polyethylene terephthalate (PET), and Polystyrene (PS), where PE (41%) was recognized as highly abundant. The highest PLI was documented in Site 4 followed by Site 5 both in water and sediment. Likewise, Sites 4 and 5 were substantially different from other study areas according to PCA. Overall, the pervasiveness of MPs was evident in the Surma River, which requires further attention and prompt actions.

Effects of microplastics on the structure and function of bacterial communities in sediments of a freshwater lake

As an emerging pollutant, microplastics (MPs) cause widespread concern around the world owing to the serious threat they pose to ecosystems. In particular, sediments are thought to be the long-term sink for the continual accumulation of MPs in freshwater ecosystems. Polyethylene (PE) and polyethylene terephthalate (PET) have been frequently detected with large concentration variations in freshwater sediments from the lower reaches of the Yangtze River, one of the most economically developed regions in China, characterized by accelerated urbanization and industrialization, high population density and high plastics consumption. However, the impact of PE and PET on the sedimental bacterial community composition and its function has not been well reported for this specific region. Herein, PE and PET particles were added to freshwater sediments to assess the effects of different MP types on the bacterial community and its function, using three concentrations (500, 1500 and 2500 items/kg) per MP and incubations of 35, 105 and 175 days, respectively. This study identified a total of 68 phyla, 211 classes, 518 orders, 853 families and 1745 genera. Specifically, Proteobacteria, Chloroflexi, Acidobacteriota, Actinobacteriota and Firmicutes were the top five phyla. A higher bacterial diversity was obtained in control sediments than in the MP-treated sediments. The presence of MPs, whether PET or PE, had significant impact on the bacterial diversity, community structure and community composition. PICRUSt2 and FAPOTAX predictions demonstrated that MPs could potentially affect the metabolic pathways and ecologically functional groups of bacteria in the sediment. Besides the MP-related factors, such as the type, concentration and incubation time, the physicochemical parameters had an effect on the structure and function of the bacterial community in the freshwater sediment. Taken together, this study provides useful information for further understanding how MPs affect bacterial communities in the freshwater sediment of the lower reaches of the Yangtze River, China.

Microplastic in clams: An extensive spatial assessment in south Brazil

Microplastic pollution is becoming a continuously growing environmental concern, while bivalve mollusks are particularly vulnerable due to their sessile habits and feeding through water filtration processes. Microplastic incidence in soft tissues of the clam Amarilladesma mactroides was assessed along unconsolidated substrates distributed in extensive coastal regions of southern Brazil. Influence of urbanization levels, distance to rivers and local hydrodynamics on microplastic accumulation by the clam was tested. The average concentration of microplastics was high (3.09 ± 2.11 particles.g-1), considering 16 sampled sites. Particles were mainly composed by polyamide, polyethylene and polyethylene terephthalate, while were mainly smaller, fibrous and colorless. High urbanization and closer proximity to rivers insured higher contamination, which is a trend observed globally. No influence of coastal hydrodynamics was seen. Considering obtained findings, A. mactroides presents good potential to be used as a valuable tool to assess microplastic contamination in unconsolidated substrates of beach areas.

Chemical evolution of rainfall in China's first eco-civilization demonstration city: Implication for the provenance identification of pollutants and rainwater acid neutralization

Rainfall chemistry is a vital indicator for reflecting anthropogenic/natural input on atmospheric quality, and the rainfall process is also the main sink of air contaminants, which has received widely concerns by all walks of life. However, the chemical compositions, sources of major solutes, historical evolution, and their determinants of rainwater in Chinese urban area, which is hotspot of atmospheric pollutant emission, are unclear under the dual background of fast economic development and eco-civilization construction. To decipher these issues, the latest year data of observation-based rainwater chemistry and the historical rainwater data, and air pollution data of China's first eco-civilization demonstration city were integrated and studied. The results presented that SO42- (53.4 %) and NO3- (28.8 %), Ca2+ (46.5 %) and NH4+ (37.9 %) dominated the present rainwater anions and cations. The historical changes in the relative proportion of rainwater ions (e.g., the holistic decreasing trend of SO42-) revealed the reduction and management achievement of atmospheric pollutant emission driven by different stages of eco-civilization city construction. The atmospheric components were well removed by rainfall scouring and all the rainwater ions showed obvious temporal variations. The concentrations of most of ions were higher in winter but lower in summer due to the key factors of meteorological factor (mainly rainfall amount) and the seasonal variations of source contribution. The stoichiometry-based source identification and relative contribution calculation reflected that anthropogenic input was the most primary contributor of NO3- (99.4 %) and SO42- (95.4 %), and the contribution of fixed emission source was relatively higher than that of traffic sources. The NH4+ was defined as the anthropogenic input ion (urban wastes and fuel combustion), while all Cl- and Na+ were from oceanic input. In contrast, terrigenous input represented the most important origin of Ca2+, K+, and Mg2+, with relative contribution of 99.5 %, 97.0 %, and 90.7 %, respectively. The high neutralization factor (NF, about 2.0) values and neutralizing to acidifying potential (NP/AP, about 1.7) ratios and their increasing trend in past few decades revealed the fact of rainwater acid being highly neutralized under the background of eco-civilization city construction.

Biodegradation of microplastics: Advancement in the strategic approaches towards prevention of its accumulation and harmful effects

Microplastics (MPs) are plastic particles in a size ranging from 1 mm to 5 mm in diameter, and are formed by the breakdown of plastics from different sources. They are emerging environmental pollutants, and pose a great threat to living organisms. Improper disposal, inadequate recycling, and excessive use of plastic led to the accumulation of MP in the environment. The degradation of MP can be done either biotically or abiotically. In view of that, this article discusses the molecular mechanisms that involve bacteria, fungi, and enzymes to degrade the MP polymers as the primary objective. As per as abiotic degradation is concerned, two different modes of MP degradation were discussed in order to justify the effectiveness of biotic degradation. Finally, this review is concluded with the challenges and future perspectives of MP biodegradation based on the existing research gaps. The main objective of this article is to provide the readers with clear insight, and ideas about the recent advancements in MP biodegradation.

Distribution and characteristics of microplastics in an urban river: The response to urban waste management

The rivers have been proven to be potential sources and the major transport pathways of microplastic (MP) in natural aquatic eco-systems, yet there is an absence of understanding the provenances and distribution dynamics of MP in fluvial water body of urban regions. The present investigation aimed to characterize the distribution and accumulation of MPs in both surface water and riverine bed sediments in a typical urban river (Nanming River, southwest China), during the dry and wet seasons of 2021. MP were detected throughout the entire sample set, with average surface water abundances of 750 ± 53 n/m3 and 693.3 ± 40 n/m3 in dry and wet seasons, respectively, and 2250 ± 496.7 n/kg (dw) in surface sediments. Furthermore, the composition of 25 polymer types MPs were analyzed. The sediment of the Nanming River is a sink for MPs, recording their long-term accumulation. Multivariate statistical analysis-based results indicated that urban littering and agricultural input were the major contributors of non-point MP in the Nanming River, while the discharged effluent was another factor influencing the distribution of MPs in urban fluvial system. The average abundance of MPs was negatively correlated with purchase power parity (PPP), demonstrating that the poorly waste management results in a higher abundance of MPs in municipal river systems. The present study systematically characterized the distribution of MPs in medium-sized urban rivers systems in Southwest China. These findings can inform policy and management decisions to reduce MPs pollution in urban rivers and protect aquatic ecosystems.

Impact of separate concentrations of polyethylene microplastics on the ability of pollutants removal during the operation of constructed wetland-microbial fuel cell

Microplastics (MPs) in water pose a great threat to the ecological environment, but the impact of MPs on constructed wetland microbial fuel cells (CW-MFCs) has not been studied, so in order to fill the research gap and enrich the research in the field of microplastics, a 360-day experiment was designed to determine the operating status of CW-MFCs at different concentrations (0, 10, 100 and 1000 μg/L) polyethylene microplastics (PE-MPs) at different times, focusing on the changes of the CW-MFCs' ability to handle pollutants, power production performance and microbial composition. The results showed that with the accumulation of PE-MPs, the removal effect of COD and TP did not change significantly, and that the removal rate was maintained at around 90% and 77.9% respectively, within 120 d of operation. What's more, the denitrification efficiency increased (from 4.1% to 19.6%), but with the passage of time, it decreased significantly (from 7.16% to 31.9%) at the end of the experiment, while oxygen mass transfer rate was significantly increased. Further analysis showed that the accumulation of PE-MPs did not affect the current power density significantly with the changes of time and concentration, but the accumulation of PE-MPs would inhibit the exogenous electrical biofilm and increase the internal resistance, thereby affecting the electrochemical performance of the system. In addition, the results of microbial PCA showed that the composition and the activity of the microorganisms were changed under the action of PE-MPs, that the microbial community in CW-MFC showed a dose effect on the input of PE-MPs, and that the relative abundance of nitrifying bacteria with time was significantly affected by PE-MPs concentration. The relative abundance of denitrifying bacteria decreased over time, but PE-MPs promoted the reproduction of denitrifying bacteria, which was consistent with the changes in nitrification and denitrification rates. The removal modes of EP-MPs by CW-MFC include the adsorption and the electrochemical degradation, with two isothermal adsorption models of Langmuir and Freundlich being constructed in the experiment, and the electrochemical degradation process of EP-MPs being simulated. In summary, the results show that the accumulation of PE-MPs can induce a series of changes in substrate, microbial species and activity of CW-MFCs, which in turn affects the pollutant removal efficiency and power generation performance during its operation.