Occurrences and distribution of microplastic pollution and the control measures in China

Migration and transformation modes of microplastics in reclaimed wastewater treatment plant and sludge treatment center with thermal hydrolysis and anaerobic digestion

Microplastics in wastewater have been investigated globally, but less research on the migration and transformation of microplastics throughout wastewater and sludge treatment. This study investigated the fate of microplastics in a reclaimed wastewater treatment plant and a centralized sludge treatment center with thermal hydrolysis and anaerobic digestion. The results exhibited that the effluent microplastics of this reclaimed wastewater treatment plant were 0.75 ± 0.26 items/L. Approximately 98 % of microplastics were adsorbed and precipitated into sludge. After thermal hydrolysis, anaerobic digestion and plate and frame dewatering, the removal rate of microplastics was 41 %. Thermal hydrolysis was the most effective method for removing microplastics. Polypropylene, polyamide and polyethylene were widely detected in wastewater and sludge. 30 million microplastics were released into the downstream river and 51.80 billion microplastics entered soil through sludge cake daily. Therefore, substantial microplastics still entered the natural environment despite the high microplastics removal rate of reclaimed wastewater and sludge treatment.

Coagulation properties of magnetic magnesium hydroxide for removal of microplastics in the presence of kaolin and humic acid

Microplastics (MPs) is one of the most concerned emerging pollutants in recent years. Its widespread distribution has been shown to have potentially adverse effects on human health and ecosystems. Therefore, in this study, magnetic magnesium hydroxide coagulant (MMHC) was prepared by adding Fe3O4 magnetic micron particles in the Mg(OH)2 generation process, and it was used with PAM, a polymer flocculant, to remove polyethylene microplastics (≤270 μm) from water by coagulation. The removal efficiency of microplastics by MMHC reached 87.1%, which was 14.7% higher than that of traditional magnesium hydroxide coagulant (MHC). However, the Zeta potential of MMHC was lower than that of MHC, only 17.3 mV. In addition, the surface morphology of MMHC showed bubble-like clusters. The effect of PAM adding time on the microplastic removal efficiency was investigated. The best adding time of non-ionic PAM was 15s before the slow mixing started. The removal efficiency of organic matter and suspended particles in water by MMHC was determined by turbidity, ultraviolet spectrophotometry and three-dimensional fluorescence. The maximum removal efficiency was 98.5% and 93.3%, respectively. With the increase of the concentration of humic acid and kaolin in water, the removal efficiency of microplastics was basically not affected. MMHC can be reused after recycle, but it was found that the electrical neutralization mechanism was affected due to the transformation of its Zeta potential, and the adsorption effect of humic acid and kaolin particles in water became worse, the removal efficiency of microplastics, turbidity and UV254 decreased to 20.2%, 17.5% and 30%, respectively.

Combined toxic effects of polystyrene microplastics and 3,6-dibromocarbazole on zebrafish (Danio rerio) embryos

Microplastics (MPs) and polyhalogenated carbazoles (PHCZs) are widely detected in the aquatic environment, and their ecological risks have become a research focus. Although there is an extensive co-distribution of MPs and PHCZs, their combined toxicity to aquatic organisms is still unclear. This study investigated the toxic effects of polystyrene microplastics (PS-MPs) and 3,6-dibromocarbazole (3,6-DBCZ) on zebrafish embryos by individual/combined exposure. This study showed that individual or combined exposure of PS-MPs (10 mg/L) and 3,6-DBCZ (0.5 mg/L) could significantly increase the rate of zebrafish embryo deformity, whereas no significant effect was observed on mortality and hatching rate. Furthermore, exposure to 3,6-DBCZ or PS-MPs increased reactive oxygen species (ROS) levels in zebrafish embryos, and the resulting oxidative stress induced apoptosis. Comparably, the levels of oxidative stress and apoptosis in zebrafish embryos were significantly reduced with the combined exposure of 3,6-DBCZ and PS-MPs. These observations suggest that the combined exposure of 3,6-DBCZ and PS-MPs has an antagonistic effect on oxidative stress and apoptosis. Fluorescence PS-MPs tracing and 3,6-DBCZ enrichment analysis showed that, with the protection of chorion, the entry of PS-MPs (5 and 50 μm) into the embryonic stage (55 hpf) of zebrafish was prevented. Moreover, after exposure for 96-144 hpf, PS-MPs served as a carrier to promote the 3,6-DBCZ accumulation and its dioxin-like toxicity in zebrafish larvae through ingestion. Compared with 5-μm PS-MPs, 50-μm PS-MPs promoted higher accumulation and dioxin-like toxicity of 3,6-DBCZ in zebrafish larvae. These findings provide that MPs can be used as an important carrier of PHCZs, influencing their toxicity and bioaccumulation in the organisms.

Nanoplastics increase the adverse impacts of lead on the growth, morphological structure and photosynthesis of marine microalga Platymonashelgolandica

Nanoplastics and heavy metals are common pollutants in coastal environments with high concerns, but their joint ecological risk to marine primary productivity remains unclear. In this study, the effects of 7, 70, 700 μg/L lead (Pb) single exposure and in combination with 200 μg/L polystyrene nanoplastics (NPs, 70 nm) on marine microalga Platymonas helgolandica were investigated. Pb single exposure induced a dose-dependent inhibition on the growth of P. helgolandica, which was associated with the reduced photosynthetic efficiency and nutrient accumulation. Compared to Pb single exposure, the addition of NPs significantly reduced the photosynthetic efficiency and aggravated the damage to cell structure. Reduced esterase activity and increased membrane permeability also indicated that NPs exacerbated the adverse effects of Pb on P. helgolandica. Thus, co-exposure to NPs and Pb induced more severe impacts on marine microalgae, suggesting that the joint ecological risk of NPs and heavy metals to marine primary productivity merits more attention.

Nanoplastics induce neuroexcitatory symptoms in zebrafish (Danio rerio) larvae through a manner contrary to Parkinsonian's way in proteomics

Although nanoplastics (NPs) can penetrate the blood-brain barrier and accumulate in the brain, the neurotoxicity of these particles and the mechanisms associated with their unique physio-chemical properties have yet to be sufficiently ascertained. In this study, we assessed the neuroexcitatory symptoms of zebrafish (Danio rerio) larvae treated with polystyrene (PS) NPs based on an examination of locomotory behaviour, dopamine levels, and acetylcholinesterase activity. We found that PS NPs caused oxidative stress and inhibited atoh1a expression in the cerebellum of Tg(atoh1a:dTomato) transgenic zebrafish larvae, thereby indicating damage to the central nervous system. In contrast to the Parkinson's disease (PD) like effects induced by most types of nanoparticles, such as graphene oxide, we established that PS NPs influenced the neuronal proteomic profiles of zebrafish larvae in a manner contrary to the molecular pathways characteristic of PD-like effects, which could be explained by the molecular dynamic simulation. Unlike graphene oxide nanoparticles that promote significant change in the internal structure of neuroproteins, the complex macromolecular polymers of PS NPs promoted the coalescence and increased expression of neuroproteins, thereby plausibly contributing to the neuroexcitatory symptoms observed in treated zebrafish larvae. Consequently, compared with traditional nanoparticles, we believe that the unique physio-chemical properties of NPs could be a potential factor contributing to their toxicity.

Presence of different microplastics promotes greenhouse gas emissions and alters the microbial community composition of farmland soil

Microplastics (MPs) are regarded as potential persistent organic pollutants owing to their small size and low degradability. However, the effect of MP pollution on greenhouse gas (GHG) emissions from farmland soil is yet unclear. Therefore, a series of microcosm experiments were set up using polyvinyl chloride (PVC), polypropylene (PP), polyethylene (PE), polystyrene (PS), and polyester (PET) at concentrations of 0.25 %, 2 %, and 7 % (w/w). Each treatment had three replicates. This experiment was carried out to verify the effect of MP pollution on greenhouse gas (GHG) emissions from farmland soil. The results showed that the addition of MPs significantly promoted the emissions of the three main GHGs, including nitrous oxide (N₂O), carbon dioxide (CO₂), and methane (CH₄). Especially, PE may cause most GHG emissions which would contribute to climate warming when its pollution concentration increased. In addition, different doses and types of MPs could affect microbial community structure. These findings of this present study may provide a scientific and practical reference for the prevention and control of MPs pollution and risk assessment of global climate change caused by MPs.

The unheeded inherent connections and overlap between microplastics and poly- and perfluoroalkyl substances: A comprehensive review

Microplastics (MPs) and poly- and perfluoroalkyl substances (PFASs) are receiving global attention due to their widespread presences and considerable level in the environment. Although the occurrence and fate of MPs and PFASs alone have been extensively studied, little was known about their unheeded connection and overlap between the two. Therefore, this review attempts to reveal it for the purpose of providing a new view from joint consideration of the two in the future studies. Initially, the critically examined data on the co-sources and existence of MPs and PFASs are summarized. Surprisingly, some products could be co-source of MPs and PFASs which are general in daily life while the distribution of the two is primary influenced by the human activity. Then, their interactions are reviewed based on the fact that PFASs can be sorbed onto MPs which are regarded as a vector of contaminations. The electrostatic interaction and hydrophobic contact are the predominant sorption mechanisms and could be influenced by environmental factors and properties of MPs and PFASs. The effects of MPs on the transport of PFASs in the environments, especially in aquatic environments are then discussed. Additionally, the current state of knowledge on the combined toxicity of MPs and PFASs are presented. Finally, the existing problems and future perspectives are outlined at the end of the review. This review provides an advanced understanding of the overlap, interaction and toxic effects of MPs and PFASs co-existing in the environment.

Tissue accumulation of polystyrene microplastics causes oxidative stress, hepatopancreatic injury and metabolome alterations in Litopenaeus vannamei

Microplastics (MPs) pose one of the major environmental threats to marine organisms and ecosystems on a global scale. Although many marine crustaceans are highly susceptible to MPs pollution, the toxicological effects and mechanisms of MPs on crustaceans are poorly understood. The current study focused on the impacts of MPs accumulation in shrimp Litopenaeus vannamei at the behavioral, histological and biochemical levels. The results demonstrated the accumulation of polystyrene MPs in various organs of L. vannamei, with highest MPs abundance in the hepatopancreas. The MPs accumulated in shrimp caused growth inhibition, abnormal swimming behavior and reduced swimming performance of L. vannamei. Following MPs exposure, oxidative stress and lipid peroxidation were also observed, which were strongly linked to attenuated swimming activity of L. vannamei. The above MPs-induced disruption in balance of antioxidant system triggered the hepatopancreatic damage in L. vannamei, which was exacerbated with increasing MPs concentrations (from 0.02 to 1 mg L^-1). Furthermore, metabolomics revealed that MPs exposure resulted in alterations of metabolic profiles and disturbed glycolysis, lipolysis and amino acid metabolism pathways in hepatopancreas of L. vannamei. This work confirms and expands the knowledge on the sublethal impacts and toxic modes of action of MPs in L. vannamei.

Abundance and characteristics of microplastics in the Wanquan River estuary, Hainan Island

As the nexus where rivers and oceans meet, estuaries are vulnerable to microplastic (MP) pollution derived from rivers. However, few studies have focused on the pollution status of MPs in small estuarine areas. Here, the abundance and characteristics of MPs in surface water and sediment samples from a small estuary, the Wanquan River estuary, were studied. The average abundance of MPs was 6573 ± 2659 n/m³ in surface water and 1065 ± 696 n/kg dw in sediment samples from the Wanquan River estuary. Most of the MPs in water samples and sediments were red (92.9 % and 88.1 %) fragments (87.4 % and 95.5 %) with sizes <1.0 mm (90.8 % and 92.4 %) made up of antifouling paint particles (APPs) (83.5 % and 89.8 %), respectively. A significant positive correlation (p < 0.01) was found between the concentration of Cu²⁺ and the abundance of APPs in sediment samples from the Wanquan River estuary. The APPs in the sediments can act as a continuous source of toxic chemicals (e.g., Cu²⁺) to marine environments. The results of this study expand our knowledge about MP pollution in small estuaries, and the ecological risk of APPs in the Wanquan River estuary to aquatic organisms should not be ignored.

Recent developments in microplastic contaminated water treatment: Progress and prospects of carbon-based two-dimensional materials for membranes separation

Micro (nano)plastics pollution is a noxious menace not only for mankind but also for marine life, as removing microplastics (MPs) is challenging due to their physiochemical properties, composition, and response toward salinity and pH. This review provides a detailed assessment of the MPs pollution in different water types, environmental implications, and corresponding treatment strategies. With the advancement in nanotechnology, mitigation strategies for aqueous pollution are seen, especially due to the fabrication of nanosheets/membranes mostly utilized as a filtration process. Two-dimensional (2D) materials are increasingly used for membranes due to their diverse structure, affinity, cost-effectiveness, and, most importantly, removal efficiency. The popular 2D materials used for membrane-based organic and inorganic pollutants from water mainly include graphene and MXenes however their effectiveness for MPs removal is still in its infancy. Albeit, the available literature asserts a 70- 99% success rate in micro/nano plastics removal achieved through membranes fabricated via graphene oxide (GO), reduced graphene oxide (rGO) and MXene membranes. This review examined existing membrane separation strategies for MPs removal, focusing on the structural properties of 2D materials, composite, and how they adsorb pollutants and underlying physicochemical mechanisms. Since MPs and other contaminants commonly coexist in the natural environment, a brief examination of the response of 2D membranes to MPs removal was also conducted. In addition, the influencing factors regulate MPs removal performance of membranes by impacting their two main operating routes (filtration and adsorption). Finally, significant limitations, research gaps, and future prospects of 2D material-based membranes for effectively removing MPs are also proposed. The conclusion is that the success of 2D material is strongly linked to the types, size of MPs, and characteristics of aqueous media. Future perspectives talk about the problems that need to be solved to get 2D material-based membranes out of the lab and onto the market.

High Heterotrophic Plasticity of Massive Coral Porites pukoensis Contributes to Its Tolerance to Bioaccumulated Microplastics

Scleractinian corals have been observed to be capable of accumulating microplastics from reef environments; however, the tolerant mechanism is poorly known. Here, we examined the response of Porites pukoensis to microplastic pollution by analyzing algal symbiont density, energetic metabolism, and caspase3 activities (representing the apoptosis level) in the coral-Symbiodiniaceae association. The environments of three fringing reef regions along the south coast of Sanya City, Hainan Province of China, were polluted by microplastics (for example, microplastic concentrations in the seawater ranged from 3.3 to 46.6 particles L^-1), resulting in microplastic accumulation in P. pukoensis (0.4-2.4 particles cm^-2). The accumulation of microplastics was negatively correlated to algal symbiont density in the corals but not to caspase3 activities in the two symbiotic partners, demonstrating that P. pukoensis could tolerate accumulated microplastics despite the decrease of algal symbiont density. Furthermore, results from the carbon stable isotope and cellular energy allocation assay indicated that P. pukoensis obtained energy availability (mainly as lipid reserves) using the switch between heterotrophy and autotrophy to maintain energy balance and cope with accumulated microplastics. Collectively, P. pukoensis achieved tolerance to microplastic pollution by maintaining energy availability, which was largely attributed to its high heterotrophic plasticity.

The occurrence, speciation, and ecological effect of plastic pollution in the bay ecosystems

Bay is a unique part of the ecosystem, acting as the intersection for marine and terrestrial systems and hosting diverse biological organisms. The ubiquitous application of plastics has resulted in a massive amount of plastic waste released and accumulated in the bay ecosystem, posing significant ecological effects. Thus, thoroughly understanding plastic pollution's occurrence, speciation, and ecological effect in the bay ecosystems is of vital importance. We conducted a comprehensive review on the sources and distribution of plastics in the bay ecosystem, and the associate ecological effects, from individual toxicity to trophic transfer in ecosystems. Among bay areas around the world, the concentrations of microplastics vary from 0.01 to 3.62 × 10⁵ item/m³ in seawater and 0 to 6.75 × 10⁵ item/kg in sediment. Small-sized plastic particles (mostly <2 mm) were widely reported in bay organisms with the concentration range of 0 to 22.5 item/ind. Besides, the toxicity of plastics on marine organisms has been documented in terms of mortality, growth, development, reproduction, enzyme activity and transcription. Since abundance of small plastic particles (e.g., micro- and nano-scale) is far greater than large plastic debris in the bay ecosystems, in-depth risk assessment of small-sized plastics needs to be conducted under environmentally realistic conditions. Our review could provide a better understanding on the occurrence, speciation, and ecological effect of plastic pollution in the bay ecosystems.

Adsorption mechanism of trace heavy metals on microplastics and simulating their effect on microalgae in river

Microplastics (MPs) and heavy-metal contamination in freshwater is an increasing concern. Fe, Mn, Pb, Zn, Cr, and Cd are common heavy metals that can easily flow into rivers causing water pollution. Microplastics act as carriers for heavy metals and increase the transport of contaminants in freshwater systems. We investigated the adsorption mechanisms of three kinds of MPs having similar particle sizes, namely polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC), with respect to trace heavy metals of Pb, Cu, Cr, and Cd under different temperature and salinity conditions. The reaction kinetics of the adsorption of different trace heavy metals on different MPs were consistent with both the quasi primary and quasi secondary kinetic models, indicating the complexity of heavy metal adsorption by MPs. The adsorption rate of heavy metal on MPs was mainly controlled by intra-particle diffusion, and the isotherm model indicated that the adsorption of Pb, Cu, Cr, and Cd by MPs occurred in the form of monolayer physical adsorption. Additionally, an increase in temperature and decrease in salinity were favourable to improve the affinity of MPs toward heavy metals (through adsorption). Zeta potential measurements and Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses indicated that electrostatic force interaction was the main mechanism of the adsorption process; oxygen-containing functional groups, π-π interaction, and halogen bonds played important roles in the process of adsorption. Furthermore, the growth inhibition and oxidative stress of microalgae Chlorella vulgaris (GY-D27) due to PP, PS, and PVC were analysed; notably, MPs or Pb inhibited the growth of Chlorella vulgaris. However, the reduced toxicity to Chlorella vulgaris, with respect to a mixture of Pb and MPs, was confirmed using superoxide dismutase and catalase enzyme activities. Our results can be applied for the risk assessment of heavy metals and MPs in aquatic environments.

A review of sources, status, and risks of microplastics in the largest semi-enclosed sea of China, the Bohai Sea

The largest semi-enclosed sea of China, the Bohai Sea, serves as an important sink of microplastics (MPs) originated from terrestrial and marine sources. This study summarized potential sources and migration pathways of MPs in the Bohai Sea and reviewed the abundance and characteristics of MPs in water, sediments, and organisms. Coastal anthropogenic activities (i.e., plastic production, agricultural activities, and industrial and domestic sewage discharge) and marine origins (i.e., aquaculture, marine litters, and transportation) might accelerate the MPs enrichment in the Bohai Sea. The abundance of MPs ranged from 0.07 to 5200 items/m³ in the seawater, mainly influenced by the application of different trawl nets/sieves with different sizes (0.005-0.33 mm). Sediments of coastal rivers contained the MPs ranging from 56.7 to 1795 items/kg, significantly higher than that of the Bohai Sea (6.24-461.6 items/kg). Among organisms, the average abundance of MPs was the lowest in zooplanktons (0.03 items/animal), significantly lower than that in invertebrates (1.39 items/animal) and fish (2.12 items/animal), but no biomagnification of MPs was observed. The preliminary risk assessment indicated that seawater in the Liaodong Bay had medium ecological risk of MPs while other bays of the Bohai Sea had minor risks. To make the ecological risk of MPs quantifiable and comparable, future research priorities are recommended to focus on more frequent field surveys, standardization of sampling methods, and establishment of toxicity database of common polymer types of MPs in the Bohai Sea.

Microplastics in Seawater, Sediment, and Organisms from Hangzhou Bay

Microplastics (MPs) are widely present in global oceans, and can pose a threat to marine organisms. This study examined the abundance and characteristics of MPs in seawater, sediment, and organism samples collected from Hangzhou Bay. Abundance of MPs in seawater (n = 26) and sediment (n = 26) were 0.77-9.6 items/m³ and 44-208 items/kg dw, respectively. Size of MPs in sediment (mean 2.5 mm, range 0.21-5.3 mm) was significantly (p < 0.05) larger than that in seawater (1.1 mm, 0.13-4.9 mm). Fiber was consistently the predominant shape of MPs in seawater and sediment. The major polymer composition of MPs was polyethylene (PE; mean 47 %) in seawater, but textile cellulose (60 %) was the main polymer type of MPs in sediment. Average abundance of MPs in marine organisms (n = 388) ranged from 0.064 (zooplankton) to 2.9 (Harpodon nehereus) items/ind, with the mean size of 0.19-1.4 mm. MP abundance in marine organisms was not significantly correlated with their trophic level. Fiber was always the predominant shape of MPs in different marine organisms, contributing mean 67 (fish)-93 % (zooplankton) of total MPs. MPs in crustacean (mean 58 %), shellfish (64 %), and cephalopod (29 %) were dominated by textile cellulose. Whereas, PE (mean 44 %) and polypropylene (43 %) were the major polymer compositions of MPs in fish and zooplankton, respectively. To our knowledge, this is the most comprehensive study investigating the occurrence of MPs in environmental matrixes from Hangzhou Bay, which contributes to the better understanding of environmental behaviors of MPs in estuarine sea environment.

Concurrent water- and foodborne exposure to microplastics leads to differential microplastic ingestion and neurotoxic effects in zebrafish

Organisms constantly ingest microplastics directly from the environment or indirectly via trophic transfer due to the pervasiveness of microplastic pollution. However, most previous studies have only focused on waterborne exposure at the individual level, while few studies have investigated the contribution of trophic transfer to the exposure in organisms. We comprehensively evaluated the differences in microplastic ingestion and toxic effects in zebrafish exposed to microplastics via two concurrent routes (waterborne and foodborne). The polyethylene microplastics (40-47 μm, 0.1-10 mg/L) concentration used here was set in a range closed to the environmentally relevant microplastic concentrations, especially considering the extreme high concentration scenarios in wastewater. The concentration of microplastics resulting from foodborne exposure (0.01±0.01 μg/mg; 0.1±0.1 particles/mg) was significantly lower than that through waterborne exposure (0.06±0.02 μg/mg; 0.8±0.3 particles/mg), suggesting the ingestion of microplastics in their tissues occurs mainly through direct environmental uptake rather than food chain transfer (though the initial microplastic concentration was 1000 folds lower). However, more sublethal impacts, including the significant abnormal hyperactive swimming behaviour (107±5% induction; p< 0.05), were observed in the foodborne group than waterborne group. Additionally, ingenuity pathway analysis predicted both exposure routes caused obvious nervous system interference but through opposite modes of action. This was further verified by the alteration of neurotransmitter biomarkers that neurotoxicity mechanisms were completely different for the two exposure routes. The neurotoxic effects of microplastics are non-negligible and can exert together through both water- and foodborne exposure routes, which deserves further attention.

Microplastic occurrence in the northern South China Sea, A case for Pre and Post cyclone analysis

Microplastics (MPs) have become a great concern owing to their persistence and ecotoxicity in various environmental compartments. MPs can be transported from land to oceans via the aquatic system, and the oceans are believed to be the final sink for MPs. To resolve the lack of data concerning MP contamination in the northern South China Sea (NSCS), coastal seawater and sediments were investigated. The sample sites included the coastal area from Hong Kong to western Guangdong Province, which provided a representative coverage of variable distance to the shore. MP particles were observed in all samples, suggesting a widespread MP pollution in NSCS. The average MP abundance was relatively high in South China Sea, but it was lower than that in other Chinese coastal areas. In all samples, the dominant MP polymer was polyethylene terephthalate fibers. No statistically significant correlation was found between the abundances of MPs in seawater and sediment. The MP distribution in surface water affected by the monsoon exhibited high abundance in the east and low in the west, and MPs were more abundant near the shore than away from it. The tropical cyclone had no obvious effect on the overall MP abundance except in the Hong Kong west marine water (R4), which may attribute to proximity to Hong Kong and other islands.

Microplastics impacts in seven flagellate microalgae: Role of size and cell wall

The toxicity of microplastic particles (MPs) on aquatic environments has been widely reported; however, their effects on protists are still contradictory. For example, it is unclear if cell size and cell wall have a role in shaping the response of flagellates to MPs. In this study, seven marine flagellated microalgae (six Dinoflagellates and one Raphidophyceae) were incubated with 10 mg L^-1 MPs (polystyrene plastic micro-spheres, 1 μm diameter) to address the above question by measuring different response variables, i.e., growth, optimal photochemical efficiency (F_v/F_m), chlorophyll-a (Chl-a) content, superoxide dismutase (SOD) activity, and cell morphology. The effect of MPs on growth and F_v/F_m showed species-specificity effects. Maximum and minimum MPs-induced inhibitions were detected in Karenia mikimotoi (76.43%) and Akashiwo sanguinea (10.16%), respectively, while the rest of the species showed intermediate responses. The presence of MPs was associated with an average reduction of Chl-a content in most cases and with a higher superoxide dismutase activity in all cases. Seven species were classified into two groups by the variation of Chl-a under MPs treatment. One group (Prorocentrum minimum and Karenia mikimotoi) showed increased Chl-a, while the other (P. donghaiense, P. micans, Alexandrium tamarense, Akashiwo sanguinea, Heterosigma akashiwo) showed decreased Chl-a content. The MPs-induced growth inhibition was negatively correlated with cell size in the latter group. SEM images further indicated that MPs-induced malformation in the smaller cells (e.g., P. donghaiense and K. mikimotoi) was more severe than the bigger cells (e.g., A. sanguinea and P. micans), probably due to a relatively higher ratio of the cell surface to cell volume in the former. These results implicate that the effect of MPs on marine flagellated microalgae was related to the cell size among most species but not cell wall. Thus plastic pollution may have size-dependent effects on phytoplankton in future scenarios.

The Value of China's Legislation on Plastic Pollution Prevention in 2020

It has taken 12 years since 2008, but China is finally strengthening plastic pollution prevention and control through legislation. In an effort to regulate and control plastic products, China's government amended and released a series of laws and regulations in 2020, possibly heralding the end of China's plastic pollution. China's plastic pollution legislation, while late, is a viable and right response to the severe environmental and ecology problem. Legislative progress in plastic pollution prevention has extended beyond China government's administrative capability but has also been an important step in the protection of the environment in the world.

The Value of China's Legislation on Plastic Pollution Prevention in 2020

It has taken 12 years since 2008, but China is finally strengthening plastic pollution prevention and control through legislation. In an effort to regulate and control plastic products, China's government amended and released a series of laws and regulations in 2020, possibly heralding the end of China's plastic pollution. China's plastic pollution legislation, while late, is a viable and right response to the severe environmental and ecology problem. Legislative progress in plastic pollution prevention has extended beyond China government's administrative capability but has also been an important step in the protection of the environment in the world.

Review of Current Issues and Management Strategies of Microplastics in Groundwater Environments

Microplastic contamination has become widespread in natural ecosystems around the globe as a result of the tremendous rise in plastic production over the last 70 years. However, microplastic pollution in marine and riverine habitats has received more attention than that of terrestrial environments or even groundwater. This manuscript reviews the current issues, potential occurrences, and sources of the emerging problem of microplastic contamination in groundwater systems. The most prevalent types of plastic detected in groundwater are polyethylene and polyethylene terephthalate, and fibers and fragments represent the most commonly found shapes. The vertical transportation of microplastics in agricultural soils can affect groundwater aquifer systems, which is detrimental to those who use groundwater for drinking as well as to microorganisms present in the aquifers. Moreover, this review sheds light on the interlinkage between sustainable development goals and groundwater microplastic contamination issues as part of the strategies for the management of microplastic contamination in groundwater. Overall, this review reveals a lack of interest and a gap in knowledge regarding groundwater microplastic pollution and highlights future perspectives for research in this area.

Release of microplastics from typical rainwater facilities during aging process

As the demand for urban flood prevention and drainage increases, a large number of plastic rainwater facilities are in use. Microplastics will be released inevitably into stormwater systems during aging and hydraulic scouring processes, which could cause potential pollution risk. This study simulated the release behavior of microplastics from three typical plastic rainwater facilities including a rainwater inspection well, rainwater storage module, and rainwater pipe (mainly composed of high-density polyethylene, polypropylene, and polyvinyl chloride, respectively) under the effects of aging and hydraulic scouring. After 15-45 days of UV aging and 72 h of hydraulic scouring, the surfaces of the three facilities were found to exhibit increases in roughness, cracks, folds, and cavities, with the most pronounced changes occurring in the rainwater storage module. As the aging time increased, oxygen-containing functional groups formed and led to carbon chain scission. Fourier transform infrared spectroscopy (FTIR), two-dimensional correlation spectroscopy (2D-COS) and X-ray photoelectron spectroscopy (XPS) of facility surfaces showed that the formation of oxygen-containing functional groups was an important factor affecting the release of microplastics. The amount of microplastics released from the three facilities ranged from 160 to 1905 items/g (microplastics/facilities), following in the order of rainwater inspection well > rainwater storage module > rainwater pipe. The particle size of the released microplastics ranged from 3 to 1363 μm, with 10-30 μm accounting for the greatest proportion of particles, 50.10%. The size of microplastics released from the rainwater inspection well and rainwater storage module increased with the aging degree, while the release from the rainwater pipe decreased. The release behavior depends mainly on the composition of the materials and the aging time. Thus, microplastics can be released from plastic rainwater facilities under suitable conditions. The results can be used to further evaluate microplastic pollution caused by urban rainwater facilities.

Distribution and possible sources of atmospheric microplastic deposition in a valley basin city (Lanzhou, China)

The deposition is an important process of microplastics transporting from atmosphere to water and soil. But the spatial and temporal distribution of microplastics in urban atmospheric deposition and its influencing factors are poorly understood. The current study investigated the possible sources, spatial and temporal distribution, and potential ecological risk of microplastics in deposition from the valley basin of Lanzhou city during the COVID-19 pandemic (from February to August, 2020). The deposition flux of microplastics was 353.83 n m^-2 d^-1. Most plastic samples were small sized (50～500 µm) and transparent. The dominant chemical composition and shapes were PET, fragments and fibers, respectively. A modified method was conducted to identify the sources of microplastics, and the local sources were suggested as the main possible sources. The distribution of microplastics investigated through the inverse distance weight interpolation showed spatial variation and temporal differentiation which was dominated by the human activity. The rainfall also affected the temporal distribution. The preliminary assessment indicated higher potential ecological risk of microplastics in deposition. This study suggested the dominant effect of human activity on the source and distribution of atmospheric microplastic deposition in city.

Ecological risk assessment of marine microplastics using the analytic hierarchy process: A case study in the Yangtze River Estuary and adjacent marine areas

Microplastic (MP) pollution is ubiquitous in the terrestrial and marine environments, even in the air. However, ecological risk assessment studies of microplastics are scarce. In the present study, an ecological risk assessment model was built to evaluate the risks of microplastics in the Yangtze River Estuary and adjacent marine areas. A basic index database of the impacts of MP pollution on the ecosystem was constructed around three types of indices, namely, the pressure, status, and response indices. While the expert scoring method was used to determine the weights of these indices, in view of the complexity of the ecosystem in the Yangtze River Estuary, the fuzzy comprehensive evaluation method was used to evaluate its ecological risk. According to the model, microplastic pollution in the Yangtze River Estuary and adjacent marine areas was within a lower risk state, indicating that its risks for the marine ecosystem were still within a controllable range.

Current status of microplastics pollution in the aquatic environment, interaction with other pollutants, and effects on aquatic organisms

Microplastics, as emerging pollutants, have received great attention in the past few decades due to its adverse effects on the environment. Microplastics are ubiquitous in the atmosphere, soil, and water bodies, and mostly reported in aqueous environment. This paper summarizes the abundance and types of microplastics in different aqueous environments and discusses the interactions of microplastics with other contaminants such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), antibiotics, and heavy metals. The toxicity of microplastics to aquatic organisms and microorganisms is addressed. Particularly, the combined toxic effects of microplastics and other pollutants are discussed, demonstrating either synergetic or antagonistic effects. Future prospectives should be focused on the characterization of different types and shapes of microplastics, the standardization of microplastic units, exploring the interaction and toxicity of microplastics with other pollutants, and the degradation of microplastics, for a better understanding of the ecological risks of microplastics.

Mathematical modeling of microplastic abundance, distribution, and transport in water environments: A review

Microplastic pollution in marine and riverine environments is a threat not only for the aquatic ecosystem itself but also for human activity and life. Although there are reviews regarding microplastic debris in environments, most of them focus on the studies on their type, occurrence, and distribution. Only a limited number of these studies focus on the modeling methods, usually concentrating on particular aspects, such as settling or bioaccumulation. In this paper, physically-based existing microplastics modeling studies are classified and reviewed according to the environment, modeling methodology, and input-output relationships. Considering the strengths and weaknesses of all modeling methodologies, it is deduced that more reliable results are obtained using hybrid methods, especially the coupling of hydrodynamic and process-based models, and hydrodynamics and statistical models. The significance of having much more consideration and knowledge on the microplastics' physical properties and the environmental processes affecting their fate and transport in the aquatic environments is revealed for future research. It has also been recommended that a standardized method for data calibration, validation, and verification is necessary to be able to compare the modeling results with field investigations more efficiently than it is currently.

Occurrence and spatial distribution of microplastics, and their correlation with petroleum in coastal waters of Hainan Island, China

In this study, the distribution, abundance, morphology, and composition of microplastics (MPs) in surface seawater and sediment of Hainan Island were systematically investigated. Seawater and sediment samples were collected from six functional zones, including harbor, industrial district, sparsely populated area, tourist area, residential area, and aquaculture area. The abundance of MPs in seawater was 0.46-19.32 items/L, with an average of 2.59 ± 0.43 items/L, which were similar to those detected in the South China Sea (e.g., Nansha (1.25-3.20 items/L) and Xisha (2.57 ± 1.78 items/L)). The highest level was detected in Qinglan Bay Estuary, and the lowest was in Sanya West Island. The abundance of MPs in sediment was 41.18-750.63 items/kg, with an average of 372.47 ± 62.10 items/kg; the highest concentration was detected at Tanmen Port, and the lowest was in Lingao sea area. It was detected that the MPs with smaller size exhibited a higher concentration in seawater. MPs were commonly black and white, and predominantly linear and fragmented in shape. Polyethylene terephthalate (PET) was the dominant polymer, which might be derived from laundry wastewater. The petroleum concentration was 0.02-0.21 mg/L in the investigated area, with harbors being the most severely polluted areas. Furthermore, this study also found that MPs pollution was positively correlated with petroleum in seawater, indicating similarities between MPs and petroleum-based sources of pollution. This study identifies the contamination and characteristics of MPs and their correlation with petroleum in Hainan Island, the biggest island in the South China Sea, providing important data for further research on protecting marine ecosystems.

Photocatalytic and biological technologies for elimination of microplastics in water: Current status

Water pollution by microplastics (MPs) has emerged as a significant environmental and public health concern. Several conventional technologies in drinking water and wastewater treatment facilities are capable of capturing a substantial portion of microplastics from surface water; however, only limited methods are available for actual destruction of microplastics. Rate of success is highly variable, and actual mechanisms which result in MP destruction are only partly known. Photocatalysis and microbial degradation technologies show promise at laboratory scale for the transformation of microplastics to water-soluble hydrocarbons, carbon dioxide and, in limited cases, useful fuels. Both photocatalytic and microbial technologies offer the potential for long-term water security and ecological stability and deserve further attention by scientists. Additional research is necessary, however, in identifying more effective semiconductors for photocatalysis, and optimal effective microbial consortia and environmental conditions to optimize microplastic biodegradation. Many more polymer types beyond polyethylene must be studied for degradation, and laboratory-scale research must be expanded to field-scale. This paper provides a comprehensive overview of processes and mechanisms for removing MPs by photocatalysis and microbial technologies. It provides useful data for research dedicated to improved removal of MPs from surface waters.

Environmental emission, fate and transformation of microplastics in biotic and abiotic compartments: Global status, recent advances and future perspectives

The intensive use and wide-ranging application of plastic- and plastic-derived products have resulted in alarming levels of plastic pollution in different environmental compartments worldwide. As a result of various biogeochemical mechanisms, this plastic litter is converted into small, ubiquitous and persistent fragments called microplastics (<5 mm), which are of significant and increasing concern to the scientific community. Microplastics have spread across the globe and now exist in virtually all environmental compartments (the soil, atmosphere, and water). Although these compartments are often considered to be independent environments, in reality, they are very closely linked. Ample research has been done on microplastics, but there are still questions and knowledge gaps regarding the emission, occurrence, distribution, detection, environmental fate and transport of MPs in different environmental compartments. The current article is intended to provide a systematic overview of MP emissions, pollution conditions, sampling and analytical approaches, transport, fates and transformation mechanisms in different environmental compartments. It also identifies research gaps and future research directions and perspectives.

Microplastics (MPs) Act as Sources and Vector of Pollutants-Impact Hazards and Preventive Measures

Currently, people are paying more and more attention to the interaction between microplastics (MPs) and chemical substances (including metals and organic substances), so it is necessary to understand the relationship between MPs and chemical substances. In this review, we explored (1) MPs may become a source of chemical substances. (2) MPs can also be used as a carrier for attaching pollutants. (3) No matter what role MPs play, MPs and the attached chemical substances will have harmful effects on biological systems. However, because the current research is not deep enough, more experimental areas are needed to explore the interaction mechanism and the principle of toxicity. In addition, laws and policies need to be developed that actively promote and strive to develop biodegradable alternative microplastics to reduce the harm of microplastics and their additives to the environment.

Taking a mass-balance approach to assess marine plastics in the South China Sea

The South China Sea (SCS) is recognised as a global hotspot for plastic pollution. We review available field studies and identify a significant lack of data needed to construct a simple mass balance box model for plastic pollution in the SCS. Fundamental information on plastic mass input, transfer and sink terms are simply not available. Also unknown are the rates of accumulation in different environments, the dispersal pathways of plastic particles of different density, the residence times of plastic in the water column and the rate at which macroplastics are transformed into microplastics in different environments. Filling these information gaps is critical for states to determine adequate response measures, including developing and tracking impact of policies to deal with the problem of plastic pollution in the SCS.

Aged microplastics decrease the bioavailability of coexisting heavy metals to microalga Chlorella vulgaris

Environmental aging of ubiquitous microplastics (MP) occurs through the action of biotic and abiotic factors, and aged MP exhibit different physicochemical properties and environmental behavior from virgin MP. This study aimed to investigate the aged micro-sized polystyrene (mPS) and polyvinyl chloride (mPVC), and the heavy metals copper (Cu) and cadmium (Cd), and examine the effects of their combined toxicities on microalga Chlorella vulgaris. Results showed that the presence of MP inhibited cell growth as compared with the control, the inhibition rate (I) decreased as concentrations of MP rose and aged MP exhibited stronger inhibition of cells than did virgin MP. The largest I was achieved in each culture with the MP concentration of 0.01 g/L, in which aged mPS with the maximal of 36.84% (I_{aged mPS}) followed by aged mPVC (I_{aged mPVC} = 30.03%), virgin mPS (I_{virgin mPS} = 29.10%) and virgin mPVC (I_{virgin mPVC} = 16.72%). Addition of the heavy metals Cu²⁺ and Cd²⁺ significantly inhibited cell growth, and toxicity increased with concentrations in a range of 0.5-2.0 mg/L; the maximum I values were 19.50% (I_Cu) and 85.14% (I_Cd), respectively. The combined toxicity of aged MP + Cu or aged MP + Cd was less than that of individual heavy metals. In particular, as compared with the maximal I_Cd of 85.14% achieved by single Cd²⁺, the toxicity of Cd²⁺ was greatly reduced when combined with aged mPS and mPVC, with the I value decreased to 27.55% (I_{aged mPS}) and 32.51% (I_{aged mPVC}), respectively. Both single and combined treatments caused cell damage to the microalga, accompanied by increased superoxide dismutase (SOD) and intracellular malonaldehyde (MDA) content.

Size-dependent adverse effects of microplastics on intestinal microbiota and metabolic homeostasis in the marine medaka (Oryzias melastigma)

Microplastic (MP) is an emerging environmental pollutant and exposure to MPs has been associated with numerous adverse health outcomes in both wild and laboratory animals. The toxicity of MPs depends on concentration, exposure time, chemical composition and size distribution, but the impacts of particle size remain inconclusive yet. In this study, adult marine medaka (Oryzias melastigma) were exposed to different size of polystyrene MPs (PS-MPs) with concentration of 10 mg/L for 60 days and the growth performance, lipid metabolism, immune parameters and gut microbiome were determined. Results indicated that particle size is a dominant factor causing lipid metabolism disorders and hepatic toxicity in PS-MPs-exposed fish. The bodyweight, adipocyte size and hepatic lipid contents were significantly increased in 200 μm PS-MPs-exposed fish, while 2 and 10 μm PS-MPs-exposed fish exhibited liver injury principally manifested asthepresence oflittlefibrosis and inflammation. Given that larger particles could not enter the circulatory system, the impacts of PS-MPs on intestinal microbial biota homeostasis were further investigated. The results not only showed the characterization of gut microbial communities in Oryzias melastigma, but also indicated that microbial diversity and composition were altered in gut of fish exposed to PS-MPs, in particular 200 μm PS-MPs. The differentially abundant bacterial taxa in PS-MPs-exposed fish mainly belonged to the phylum Verrucomicrobia, Firmicutes and Fusobacteria. And furthermore, increased abundance of Verrucomicrobia and Firmicutes/Bacteroidetes ratio and decreased Fusobacteria were correlated with the increased bodyweight. Intestinal microbiome should play a critical role in regulating host lipid metabolism in fish exposed to lager size of PS-MPs.

Microplastics in the endangered Indo-Pacific humpback dolphins (Sousa chinensis) from the Pearl River Estuary, China

Microplastic pollution is a growing concern worldwide. Despite numerous studies showing the occurrence of microplastics in low-trophic level aquatic organisms, microplastic ingestion and contamination in cetaceans, especially those from Asian waters, has been rarely recorded. Here, we investigated stomach microplastic pollution in twelve Indo-Pacific humpback dolphins stranded along the Pearl River Estuary (PRE), China. We also compared microplastic abundances in dolphins stranded near populated urban areas (ZH, n = 6) with those stranded near rural areas (JM, n = 6). Microplastics were detected in all samples, with abundance ranging widely from 11 to 145 items individual^-1 (mean ± SD, 53 ± 35.2). Major microplastics were polypropylene and polyethylene fibers, with the size mostly ranging from 1 to 5 mm and the dominant colors of white or transparent. Humpback dolphins from ZH (73 ± 36.8 items individual^-1) exhibited a significantly higher average microplastic abundance than those from JM (33 ± 18.3 items individual^-1, p < 0.05). In particular, the highest microplastic concentration was identified in the dolphin (SC-ZH01) stranded near the mouth of the Pearl River, whereas the dolphin (SC-JM04) collected at the rural site contained the lowest concentration of microplastics, suggesting the important influence of land-based human activities on the accumulation of microplastics in the PRE. The identification of varied microplastic polymers indicated their complex source scenarios. This study suggests that, as one of top predators in the potential microplastic food chains, this cetacean species could likely serve as an endpoint biomonitoring species of microplastic pollution in the PRE or other similar estuarine ecosystems. Our results highlight the need for more studies towards better understanding the potential impacts of microplastics on this endangered species.

Microplastics physicochemical properties, specific adsorption modeling and their interaction with pharmaceuticals and other emerging contaminants

This review discusses the imminent threat that microplastics (MPs) associated with pharmaceuticals represent to the aquatic environment and public health. We initially focused upon recognizing and stressing that MPs are ubiquitous pollutants. The influence of environmental factors, such as pH, mechanical stress, and photodegradation, are examined, aiming to elucidate how both substances might associate, what are their simultaneous degradation pathways and, to understand the interactions between MPs and pharmaceuticals. Mathematical tools, such as modeling and simulations, are presented in detail, aiming to improve how information is interpreted. Furthermore, it is exhibited that MPs sorption and interaction behavior towards organic contaminants play an important role in understanding its dynamics in the environment, as well as their possible interactions with pharmaceuticals that are summarized. At last, MPs and pharmaceuticals toxicity and bioaccumulation are presented.

Removal of polystyrene and polyethylene microplastics using PAC and FeCl3 coagulation: Performance and mechanism

As a new type of potentially threatening pollutant, microplastics are widely distributed in water and may come into contact with the humans through tap water. The removal behaviors of microplastics in water treatment plants coagulation are not completely clear. In this paper, the removal performance and mechanism of polystyrene (PS) and polyethylene (PE) microplastics using PAC and FeCl₃ coagulation were studied. Results showed that PAC was better than FeCl₃ in removal efficiency of PS and PE microplastics. Charge neutralization occurred in the coagulation process. The figures of scanning electron microscope (SEM) illustrate that agglomeration adsorption occurred in PS system, and the Fourier transform infrared spectroscope (FTIR) spectra demonstrates that new bonds were formed during the interaction between PS microplastics and coagulants. In addition, the hydrolysis products of coagulants played a major role rather than the hydrolysis process in both PS system and PE system. The removal efficiency of microplastics in alkaline conditions was higher than that in acidic conditions. Cl^- had little effect on the removal efficiency of microplastics, while SO₄^2- and CO₃^2- had inhibitory and promoting effects respectively. The increase of stirring speed could improve the removal efficiency of microplastics. This paper can provide a reference for the study of microplastics treated by coagulation.

Hazardous microplastic characteristics and its role as a vector of heavy metal in groundwater and surface water of coastal south India

Study of hazardous microplastics in the natural water resources is minimal compared to the sea salt, seafood and even packaged water. We presented results of the first baseline research of microplastics in groundwater and surface water from the coastal south India (Tamil Nadu state) and evaluated the heavy metal adsorption capacities of different polymers. The microplastics (up to 19.9 particles/L) were of relatively larger size in surface water (0.34-4.30 mm) compared to the groundwater (0.12-2.50 mm). Polyamide (nylon), polyester, polypropylene, polyethylene, polyvinyl chloride and cellulose were the common polymers and all of them showed different capacities of heavy metal adsorption. In two different experimental sites, the polypropylene showed higher capacity of adsorption compared to other polymers in the following orders: (i) cadmium > manganese > lead > arsenic and (ii) manganese > zinc > arsenic > lead > copper. The polyamide, however, exhibited better adsorption only for manganese. Similar to other recent findings, our results associate microplastics as a major vector to transport heavy metals in the water system. Formulation of strategies to reduce the environmental risks of particulate plastics as a potent vector for transportation of the toxic trace elements and subsequent, impact on human health through the OSPRC framework (Origins, Sources, Pathways, Receptors and Consequence) in the study area would require future research.

Environmental fate, toxicity and risk management strategies of nanoplastics in the environment: Current status and future perspectives

Tiny plastic particles considered as emerging contaminants have attracted considerable interest in the last few years. Mechanical abrasion, photochemical oxidation and biological degradation of larger plastic debris result in the formation of microplastics (MPs, 1 μm to 5 mm) and nanoplastics (NPs, 1 nm to 1000 nm). Compared with MPs, the environmental fate, ecosystem toxicity and potential risks associated with NPs have so far been less explored. This review provides a state-of-the-art overview of current research on NPs with focus on currently less-investigated fields, such as the environmental fate in agroecosystems, migration in porous media, weathering, and toxic effects on plants. The co-transport of NPs with organic contaminants and heavy metals threaten human health and ecosystems. Furthermore, NPs may serve as a novel habitat for microbial colonization, and may act as carriers for pathogens (i.e., bacteria and viruses). An integrated framework is proposed to better understand the interrelationships between NPs, ecosystems and the human society. In order to fully understand the sources and sinks of NPs, more studies should focus on the total environment, including freshwater, ocean, groundwater, soil and air, and more attempts should be made to explore the aging and aggregation of NPs in environmentally relevant conditions. Considering the fact that naturally-weathered plastic debris may have distinct physicochemical characteristics, future studies should explore the environmental behavior of naturally-aged NPs rather than synthetic polystyrene nanobeads.

High levels of microplastic pollution in aquaculture water of fish ponds in the Pearl River Estuary of Guangzhou, China

Microplastics (MPs) have caused great concern worldwide recently due to their ubiquity in the aquatic environment. The current knowledge on the occurrence of MPs in aquaculture fish ponds in a typical estuary system remains meagre. This study investigated the abundance and characteristics (shape, color, size and composition) of MPs in aquaculture water and pond influents in the Pearl River Estuary of Guangzhou, China, using an improved separation method. The bulk sampling and improved separation method by the combination of ethanol and polyaluminum chloride (PAC) significantly increased the MP separation efficiency, especially for particles with size less than <333 μm. The investigation results showed that MPs were detected in all water samples of fish ponds at two experimental stations with abundances of 10.3-60.5 particles/L (S1) and 33.0-87.5 particles/L (S2), respectively. Moreover, the average abundance of MPs in aquaculture water (42.1 particles/L) exhibited higher value than that in pond influents (32.1 particles/L). Most of MPs were colored and fibrous in appearance. MPs with the size range of <1000 μm (56.3-87.7%) prevailed in aquaculture water. MPs with size <333 μm that usually ignored in most studies were detected with percentage of 43.7% at S1station and 33.2% at S2 station, respectively. The small-sized MPs (<100 μm) in aquaculture water (23.7% at S1 station and 14.6% at S2 station) were more abundant than those in pond influents (7.2% at S1 station and 2.5% at S2 station). The main composition of MPs was polypropylene (PP) and polyethylene (PE). These findings indicated a high level of MP pollution in aquaculture fish ponds. The MPs originated from the Pearl River Estuary were accumulated in aquaculture fish ponds. This study provides an insight into MP pollution in aquaculture fish ponds at a typical estuarine system and highlights the load of MPs in the pond influents.

Microplastics profile in a typical urban river in Beijing

Municipal wastewater treatment plants (WWTPs) are known to be important point sources of microplastic pollution in the environment because they discharge large volumes of microplastic-containing effluents into nearby rivers. However, the fate of these microplastics once they enter the urban rivers is not well understood. The present study focused on the Qing River, a typical urban river in Beijing that receives effluents from four nearby WWTPs. We investigated the microplastic pollution profile both at the effluent outfalls from the WWTPs and in the river. Using micro Fourier-transform infrared spectroscopy, we identified and confirmed a total of 18 polymers from the river and effluent outfalls. The microplastics were then separated into four categories based on their shapes with the fragment group being the most abundant, followed by the fiber, film, and pellet groups. Abundance of microplastics was found to be slightly higher in the main body of the Qing River when sampled in November than in July. However, abundance levels from the effluent outfalls were similar in November and in July. Significant amounts of microplastics in the Qing river, up to 80%, were retained upstream of dams that are used for water storage. This result was also confirmed by a decrease in the polymer-diversity index downstream of the dams compared to upstream. A preliminary conclusion could be drawn that the microplastics in the Qing River are mainly released from the WWTPs and that most of these microplastics are retained in the river by dams.