Global Riverine Plastic Outflows

Microplastics in Flathead Lake, a large oligotrophic mountain lake in the USA

Microplastics are contaminants that are closely associated with human activity and are often abundant even in remote areas. As the largest natural freshwater lake in the western USA, Flathead Lake is a suitable site to study microplastics in lakes in less-populated areas of North America. Our assessment of microplastics in lake surface water samples showed that microplastic densities and concentrations in Flathead Lake were similar to those in other lakes located in less-populated areas around the world, with densities ranging from 8.00 × 10⁴ to 4.22 × 10⁵ particles/km² with a mean concentration of 1.89 × 10⁵ particles/km². Dry deposition rates for microplastics ranged from 4 to 140 particles/m²/day with an average of 69 particles/m²/day and were significantly higher in the fall. Microplastic concentrations in wet deposition ranged from 0.006 particles/mL to 0.050 particles/mL with highest concentrations in winter and lowest in summer. Fibrous microplastics were predominant in both lake water and atmospheric deposition. The high densities of microplastics in the sample sites located near the Flathead River inlet suggests that the river is an important source of microplastics to Flathead Lake. The high densities of microplastics and high proportions of non-fibrous microplastics near populated areas of the lake imply that local human activities also affect microplastics in Flathead Lake. Although the annual flux of microplastics in dry deposition was higher than that in wet deposition, the relatively modest difference suggests that precipitation might enhance the deposition of microplastics. The results of this study indicate that instituting increased control measures that target both reducing the microfibers generated by laundry and improving the overall level of plastic waste management in the watershed may help in controlling microplastic levels in Flathead Lake.

Impact of waste of COVID-19 protective equipment on the environment, animals and human health: a review

During the Corona Virus Disease 2019 (COVID-19) pandemic, protective equipment, such as masks, gloves and shields, has become mandatory to prevent person-to-person transmission of coronavirus. However, the excessive use and abandoned protective equipment is aggravating the world's growing plastic problem. Moreover, above protective equipment can eventually break down into microplastics and enter the environment. Here we review the threat of protective equipment associated plastic and microplastic wastes to environments, animals and human health, and reveal the protective equipment associated microplastic cycle. The major points are the following:1) COVID-19 protective equipment is the emerging source of plastic and microplastic wastes in the environment. 2) protective equipment associated plastic and microplastic wastes are polluting aquatic, terrestrial, and atmospheric environments. 3) Discarded protective equipment can harm animals by entrapment, entanglement and ingestion, and derived microplastics can also cause adverse implications on animals and human health. 4) We also provide several recommendations and future research priority for the sustainable environment. Therefore, much importance should be attached to potential protective equipment associated plastic and microplastic pollution to protect the environment, animals and humans.

Microplastics in the surface waters of the South China sea and the western Pacific Ocean: Different size classes reflecting various sources and transport

Microplastic transport in the marginal seas is a key process influencing their ultimate fate in the open oceans. In the present study, we collected seawater samples from the western Pacific Ocean (WP) and the South China Sea (SCS) to investigate the distribution, transport, and possible sources for microplastics. Generally, the range of microplastic levels were 187-1816, 146-1563, and 34.2-622 particles/m³ (averaged in 797 ± 512, 744 ± 330, and 201 ± 134 particles/m³) for the northern SCS, the western SCS, and the WP, respectively. Based on the size distribution, the highest value (390 ± 288 particles/m³) was found for 100-200 μm, followed by 200-500 μm (131 ± 155 particles/m³), and 500-1000 μm (29.7 ± 39.2 particles/m³), with the lowest for 1-5 mm (13.6 ± 14.2 particles/m³). Granule, yellow, and size <1000 μm were their most prevalent characteristics. The main polymer types of microplastics were polyester, rayon, and nylon. A negative correlation between microplastic proportion and particle size was observed in the SCS and the WP. Furthermore, the main sources of microplastics in the northern SCS probably came from the Pearl River. Surface currents and the vertical mixing processes might be two different mechanisms that affect microplastic transport from the WP and the SCS. Future comparison to measured particle size distributions data allows us to explain size-selective microplastic transport in the marine environment, and probably provide guidance on microplastic longevity.

Adsorption of Different Pollutants by Using Microplastic with Different Influencing Factors and Mechanisms in Wastewater: A Review

The studies on microplastics are significant in the world. According to the literature, microplastics have greatly specific surface areas, indicating high adsorption capacities for highly toxic pollutants in aquatic and soil environments, and these could be used as adsorbents. The influencing factors of microplastic adsorption, classification of microplastics, and adsorption mechanisms using microplastics for adsorbing organic, inorganic, and mixed pollutants are summarized in the paper. Furthermore, the influence of pH, temperature, functional groups, aging, and other factors related to the adsorption performances of plastics are discussed in detail. We found that microplastics have greater advantages in efficient adsorption performance and cost-effectiveness. In this paper, the adsorptions of pollutants by microplastics and their performance is proposed, which provides significant guidance for future research in this field.

Catchment-wide flooding significantly altered microplastics organization in the hydro-fluctuation belt of the reservoir

Hydro-fluctuation belt (HFB) is the most sensitive area of a large reservoir. This research aimed to identify the impact of catastrophic flooding on the local microplastics organization in the HFB soil of the Three Gorges Reservoir, the largest reservoir in China. We found that the catchment-wide flooding efficiently alleviated the local microplastics abundance from 7,633 to 4,875 items/kg (from 44 to 18 mg/kg) but added to the pollution risk in the reservoir body. After flooding, the overall size distribution of local microplastics was minimally altered. Interestingly, the preferential retention of the small-sized polyethylene was found in HFB after flooding. Approximately 5.0×10¹⁴ items (∼2,360 tons) of microplastics were evacuated into the reservoir, equivalent to 15.8 wt% of the plastic flux of the Yangtze River into the ocean. We observed that HFB is a significant source of local microplastics in reservoir, and the long-term source–sink transformation mechanism in the HFB should be further investigated.

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Microplastics were detected across all sites in hydro-fluctuation belt (HFB) soil

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Flooding efficiently reduced local microplastics in HFB soil

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Catastrophic flooding induced selective retention of microplastics in HFB soil

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HFB soil was a significant source of microplastics in the reservoir basin

Exposure to polystyrene microplastics reduces regeneration and growth in planarians

The potential adverse effects of microplastics (MPs) on ecosystems and human health have received much attention in recent years. However, only limited data are available on the mechanisms for the uptake, distribution, and effects of MPs in freshwater organisms, especially with respect to tissue repair, regeneration and impairment of stem cell functions. To address this knowledge gap, we conducted exposure experiments in which planarians (Dugesia japonica) were exposed to polystyrene (PS)-MPs mixed in liver homogenate and examined the tissue growth and regeneration, stem cell functions, and oxidative stress. The body and blastema areas decreased upon exposure to PS-MPs, indicating that the growth and regeneration of planarians were delayed. The proliferation and differentiation processes of stem cells were inhibited, and the proportion of mitotic stem cells decreased, which may be related to the activation of the TGFβ/SMAD4 and Notch signaling pathways. The enhancement of antioxidant enzyme activities and malondialdehyde on the first day of exposure to PS-MPs confirmed the oxidative stress response of planarians to PS-MPs. The present study demonstrated the likelihood of biotoxicity induced by PS-MPs. These results will provide clues for further investigations into the potential risks of PS-MPs to human stem cells.

Spatial and temporal distributions of microplastics and their macroscopic relationship with algal blooms in Chaohu Lake, China

Microplastics are emerging pollutants with sizes less than 5 mm, and they are ubiquitous. The occurrence of algal blooms has become a major problem affecting water quality in Chaohu Lake. To understand the relationship between the microplastic distribution and algal bloom density from a macroscopic point of view in Chaohu Lake, we collected microplastic samples from water and sediments during the wet and dry seasons and collected satellite remote sensing images of the algae density in recent years. The research results showed that the spatial and temporal distributions of microplastics were uneven and varied greatly. The average abundances of microplastics in the water samples were 2133 ± 1534 n•m^-3 in the dry season and 1679 ± 1577 n•m^-3 in the wet season, and the average abundance of microplastics in sediments was 308 ± 231 n•kg^-1. The abundance of microplastics in the estuaries was higher than those in other locations, and it was higher in the western part of the lake than in the eastern part. The microplastics in water and sediments presented different sizes, colors, shapes and compositions. The abundance, distribution and migration of microplastics were mainly affected by population density, rainfall, runoff, hydrodynamic force and wind direction. At a more macroscopic level, the distribution of microplastics was similar to that of algal blooms, TN and TP to some extent, especially in the early stage of algal bloom outbreaks, and the algal density was significantly positively correlated with the flux of microplastics into the lake. Microplastics, as carriers of algae, could promote the growth of algae blooms in the early stage, while in the later stage, microplastics and algal blooms could aggregate and coprecipitate through adsorption or adhesion and then inhibit the growth of algae.

Migration characteristics of microplastics based on source-sink investigation in a typical urban wetland

Although urban wetlands are key transition sub-ecosystems connecting urban microplastic pollution sources to freshwater environments, few studies have reported microplastic migration characteristics in urban wetlands. Recent studies have only focused on the occurrence of microplastics in wetlands. Thus, this study investigated the occurrence of microplastics in sources and sinks (surface water, sediment, effluent, and agricultural waste) and analyzed the migration characteristics of microplastics in a typical urban wetland, namely the Huixian Wetland, Guilin. The abundance of microplastics was in the ranges of 16.5-89.0 items/L, 16.8 × 103-52.8 × 103 items/kg, and 172.0-605.0 items/L in the surface water, sediment, and effluent, respectively. Most of the microplastic settlement at 1-2 km downstream of the source of pollution in this wetland presented with a total decrease of 53.7-61.4% for microplastics in the surface water, whereas microplastics of smaller sizes (100-500 µm) were retained more in surface water than the smallest (50-100 µm) and large (500-5000 µm) microplastics. Clustering analysis and principal component analysis showed that effluent was the major source of microplastics in the urban section of this wetland, and agricultural wastes also played a role in the suburbs. This first quantification of small-sized (50-500 µm) microplastic removal throughout an urban wetland provides key reference information for controlling the environmental risk of microplastics in aquatic environments.

Source and Distribution of Emerging and Legacy Persistent Organic Pollutants in the Basins of the Eastern Indian Ocean

Persistent organic pollutants (POPs) have received significant and ongoing attention. To establish favorable regulatory policies, it is vital to investigate the occurrence, source, and budgets of POPs worldwide. POPs including phthalic acid esters (PAEs), organophosphate esters (OPEs), brominated flame retardants (BFRs), and highly chlorinated flame retardants (HFRs) have not yet been examined in the Eastern Indian Ocean (EIO). In this study, the distribution of POPs has been investigated from surface sediments with the depth of 4369-5742 m in the Central Indian Ocean Basin (CIOB) and Wharton Basin (WB) of EIO. The average (±SD) concentrations of ∑₁₁PAEs, ∑₁₁OPEs, ∑₄ BFRs, and ∑₅HFRs were 1202.0 ± 274.36 ng g^-1 dw, 15.3 ± 7.23 ng g^-1 dw, 327.6 ± 211.74 pg g^-1 dw, and 7.9 ± 7.45 pg g^-1 dw, respectively. The high abundance of low-molecular-weight (LMW) PAEs, chlorinated OPEs, LMW BDEs, and anti-Dechlorane Plus indicated the pollution characteristics in the EIO. Correlation analysis demonstrated that LMW compounds may be derived from the high-molecular-weight compounds. The monsoon circulation, currents, and Antarctic Bottom Water may be the main drivers. POP accumulation rate, depositional flux, and mass inventory in the Indian Ocean were also estimated.

Transcriptomic and metabolic responses of earthworms to contaminated soil with polypropylene and polyethylene microplastics at environmentally relevant concentrations

Examining transcriptomic and metabolic responses of earthworms to microplastic-contaminated soil is critical for understanding molecular-level toxicity of microplastics; yet very little research on this topic exists. We investigated influences of environmentally relevant concentrations (ERC) of polypropylene (PP) and polyethylene (PE) microplastic-contaminated soil on earthworms at the transcriptomic, metabolic, tissue and whole-body levels to study their molecular toxicity. The addition of PP and PE at ERC induced oxidative stress on earthworms, as indicated by the high enrichment of glutathione metabolism and increased glutamine at the transcriptomic and metabolic levels. Digestive and immune systems of earthworms were damaged according to the injuries of the intestinal epithelium, partial shedding of chloragogenous tissues and unclear structure of coelom tissues, which were confirmed by pathway analysis at the transcriptomic level. Significant enrichment of arachidonic acid and glycerolipid metabolisms indicated that PP and PE disturbed the lipid metabolism in earthworms. Significantly increased betaine and myo-inositol, and decreased 2-hexyl-5-ethyl-3-furansulfonate suggested that PP and PE caused differences in osmoregulation extent. In conclusion, most similar responses of earthworm might result from special size rather than type effects of PP and PE microplastics. Contamination of soils with microplastics even at ERC has health risks to earthworms; therefore, proper management of microplastics to reduce their input to the environment is key to reducing the health risks to soil fauna.

Viral diversity and potential environmental risk in microplastic at watershed scale: Evidence from metagenomic analysis of plastisphere

Microplastics (MPs) have been considered as a new vector for the long-distance transport of pathogens in aquatic ecosystems. However, the composition of viral communities attached on MPs and their environmental risk are largely unknown. Here, we profiled the viral diversity and potential risk in five different MPs collected from the Beilun River based on metagenomic analysis. Nearly 2863 million raw reads were produced and assembled, and annotation resulted in the identification of 1719 different species of viruses in MPs. Viruses in polypropylene (PP) displayed the highest diversity, with about 250 specific viruses detected. Source tracking of viruses in MPs by the fast expectation-maximization microbial source tracking method (FEAST) demonstrated that viruses in upstream and downstream MPs are two major sources of viruses in estuary. Furthermore, the MP-type-dependent potential environmental risk of viruses was significant based on both antibiotic resistance genes (ARGs) and virulence factors (VFs) detected in viral metagenomes, and PP was confirmed with the highest potential environmental risk. This study reveals the high diversity and potential environmental risk of viruses in different MPs, and provides an important guidance for future environmental monitoring and understanding the potential risks associated with both viral transmission and MPs pollution.

Impact of intensive mariculture activities on microplastic pollution in a typical semi-enclosed bay: Zhanjiang Bay

Microplastic (MP) was investigated in Zhanjiang Bay, a semi-enclosed bay in south China and famous for considerable mariculture industry, to evaluate whether mariculture activities accelerated MP pollution. The MP abundances ranged from 0 to 2.65 n/m³ (number/m³), showing seasonal variances with higher levels in May and September and lower levels in January. In the inner part of the bay, a significantly high MP abundance and predominance of foam were found during the oyster breeding period, and pollution sources were prone to be single and extensive. This suggested that MPs were strongly influenced by the intensive plastic products for oyster culturing, especially during breeding. Moreover, plastic cages used for culturing were the main source of MPs in the central part of the bay. By conducting statistical analysis for eight representative bays, the economic growth, social development, agriculture structure, and aquaculture development were supposed to influence the local MP pollution level.

Environmental fate of microplastics in the world's third-largest river: Basin-wide investigation and microplastic community analysis

Rivers have been recognized as major transport pathways for microplastics into the sea but large-scale quantitative data on the environmental fate of riverine microplastics remains limited, hindering proper risk assessment and development of regulatory measures. Microplastics in the whole Yangtze River Basin of China were systematically investigated by sampling the water, sediment, and soil. Microplastics were detected in all samples, with an average abundance of 1.27 items/L, 286.20 items/kg, and 338.09 items/kg for water, sediments, and soils, respectively, with polypropylene and polyethylene being the most abundant polymers. A generally increasing trend of microplastic abundance from upstream to downstream was identified, which were co-attributed by geographical and anthropogenic factors including elevation, longitude, distance from the nearest city, population density, urbanization rate, and land use. Microplastics in the sediments showed more prominent vertical migration than those in the soils, and the density and size of microplastics may be the key factors governing the migration of microplastics across different compartments. Community analysis showed that microplastics in different compartments were significantly different and highly correlated with geographical distance. Major cities at the middle and lower reaches were considered pivotal nodes of microplastic pollution in the Yangtze River Basin. Policy recommendations were also proposed towards better remediation of microplastic pollution involving riverine systems.

Microbial adaptation to co-occurring vanadium and microplastics in marine and riverine environments

Vanadium (V) and microplastics have been respectively detected in environmental media, posing threats to ecosystem and human health. However, their co-existence situations in environment with microbial adaptation have been poorly understood. In this study, water and sediments collected from potential V polluted marine and riverine ecosystems were analyzed to reveal the distribution of V and microplastics with microbial responses. High concentrations of V (1.65-6.92 μg/L in water and 6.16-347.92 mg/kg in sediment) and microplastics (800-15600 item/m³ in water and 20-700 item/kg in sediment) co-occurred in aquatic environment. Less rich and diverse bacterial communities were colonized on microplastics compared to surrounding environment. Plastic-degrading taxa (e.g., Ralstonia, Rhodococcus) and V(V) reducers (e.g., Bacillus, Pseudomonas) were enriched in microplastic biofilms. Redundancy analysis showed that V, together with nutrients, ambient conditions and Cr, contributed significantly to the compositions of microbial community on microplastics. Besides directly acting on microbial community, V could also alter it by influencing environmental factors (e.g., pH), as indicated through structural equation model. This study advances understanding the previously ignored interactions of biogeochemical processes of V and microplastics in aquatic environment.

Aggregate exposure pathways for microplastics (mpAEP): An evidence-based framework to identify research and regulatory needs

Microplastics as emerging contaminants have been detected from peaks to poles. High concerns on the risks of microplastic pollution to humans and ecosystems have therefore been raised in the past decade. While a large number of studies have been conducted to investigate the environmental levels and toxicity of microplastics, the information generated to support risk assessment is fragmented and the coherence between different types of study is largely lacking. Here we introduced the Aggregate Exposure Pathway (AEP), a conceptual framework originally proposed for chemical exposure assessment, to facilitate organization, visualization and evaluation of existing information generated from microplastic research, and to efficiently identify future knowledge and regulatory needs. A putative microplastic AEP network (mpAEP) was developed to demonstrate the concept and model development strategies. Two mpAEP case studies, with polyethylene (PE) as a prototype, were then presented based on existing environmental exposure data collected from the Changjiang Estuary and the East China Sea (Case I), and the Oslo Fjord (Case II), respectively. Weight of evidence (WoE) assessment of the mpAEPs were performed for evaluating the essentiality, theoretical plausibility, empirical evidence and quantitative understanding of the evidence and relationships in the AEPs. Both cases showed moderate/high WoE to support the strength of the models, whereas also displayed clear knowledge gaps, thus providing guidance for future investigations and regulations. The mpAEP framework introduced herein presents a novel strategy for organizing fragmented information from diverse types of microplastic research, enhancing mechanistic understanding of causal relationships and facilitating the development of quantitative prediction models for research and regulation in the future.

Interactive effects of polymethyl methacrylate (PMMA) microplastics and salinity variation on a marine diatom Phaeodactylum tricornutum

Until now, knowledge about the interactive effects of microplastics and environmental factors on primary producers is quite limited. In this work, a marine diatom (Phaeodactylum tricornutum) was exposed to polymethyl methacrylate (PMMA) microplastics at different salinities (25, 35, and 45‰) for 10 days in order to study their interactive effects. Results showed that growth of P. tricornutum was negatively affected by PMMA microplastics and salinity variation with a minimum EC₅₀ value of 91.75 mg L^-1. Photosynthetic activity of P. tricornutum was also inhibited by the two factors, and their interactive effects on chlorophyll fluorescence parameters (F_v/F_m and Φ_PSII) were significant. In the algal cells, soluble protein accumulated, activities of two antioxidant enzymes changed, and malondialdehyde (MDA) content increased when this diatom was exposed to the microplastics at different salinities. These data would help to evaluate the risks of microplastics to primary producers under different environmental factors.

Dog poop bags: A non-negligible source of plastic pollution

Plastic pollution derived from the disposal of plastic bags in the environment is clearly evidenced. However, little attention has been directed towards plastic waste derived from plastic dog poop bags (DPBs), which are widely used and can never be recycled. Herein, we raise concerns about the contribution of DPBs to plastic pollution in the environment. Combining the weight of each DPB, the number of bags daily used for a dog, and the number of pet dogs around the world, we estimated the number of annual consumed and disposed DPBs at more than 415 billion, or equivalently 0.76-1.23 million tons of plastics based on various weights of different DPBs. Although plastic waste produced by DPBs only accounts for a small fraction (0.6%) of the total plastic waste generation, the extremely short life cycle of DPBs has made them a non-negligible source of plastic pollution in the environment.

Plastic Pollution, Waste Management Issues, and Circular Economy Opportunities in Rural Communities

Rural areas are exposed to severe environmental pollution issues fed by industrial and agricultural activities combined with poor waste and sanitation management practices, struggling to achieve the United Nations’ Sustainable Development Goals (SDGs) in line with Agenda 2030. Rural communities are examined through a “dual approach” as both contributors and receivers of plastic pollution leakage into the natural environment (through the air–water–soil–biota nexus). Despite the emerging trend of plastic pollution research, in this paper, we identify few studies investigating rural communities. Therefore, proxy analysis of peer-reviewed literature is required to outline the significant gaps related to plastic pollution and plastic waste management issues in rural regions. This work focuses on key stages such as (i) plastic pollution effects on rural communities, (ii) plastic pollution generated by rural communities, (iii) the development of a rural waste management sector in low- and middle-income countries in line with the SDGs, and (iv) circular economy opportunities to reduce plastic pollution in rural areas. We conclude that rural communities must be involved in both future plastic pollution and circular economy research to help decision makers reduce environmental and public health threats, and to catalyze circular initiatives in rural areas around the world, including less developed communities.

Microplastic abundance and distribution in a Central Asian desert

Microplastic pollution is widespread, affecting even the remotest places on Earth. However, observational data on microplastic deposition in deserts, which comprise 21% of the total land area, are relatively rare. The current study aims to address the knowledge gap in terms of microplastic distribution in Asian deserts. The Badain Jaran Desert in Central Asia is the second largest desert in China. We investigated microplastic distribution and deposition on dunes and lakes of this desert. Microplastics were extracted from surface sediments to determine their characteristics and polymer types by microscopic inspection and μ-FTIR. The abundance of microplastics (detection limit is approximately 40 μm) in the uninhabited area ranged from 0.7 ± 1.5 to 11.7 ± 15.5 items/kg, with an average of 6.0 ± 15.4 items/kg. Fragments and fibers accounted for 77% and 23% of the total microplastics, respectively. Epoxy resin (28%), polyethylene terephthalate (25%), phenoxy resin (25%), and polyamide (9%) were the main polymer components, whose sizes were concentrated at 50-200 μm. Back-trajectory modeling was then performed to explore the possible source direction of the microplastics. The results showed that the microplastics mainly originated from the populated areas southeast of the desert, indicating long-distance atmospheric transport and deposition in deserts. The desert-edge zone with some tourism activity contained more microplastics (8.2 ± 17.9 items/kg) than the non-tourism zone (0.9 ± 1.6 items/kg), indicating a potential contribution from tourism. The abundance in the non-tourism zone (0.9 items/kg) can be used as a reference for microplastic background values in the Central Asian deserts, as this value is critical for simulating and predicting global microplastic yields.

Interactions between microplastics/nanoplastics and vascular plants

Microplastics and nanoplastics are distributed in the environments universally. The interrelationship between vascular plants and micro/nanoplastics began to attract attention in recent years. Based on the relevant literatures collected from various databases, this review focuses on two topics: 1) the effect of vascular plants on the fate of micro/nanoplastics; 2) the effects of micro/nanoplastics on vascular plants. The review of the available studies reveals that vascular plants can act as sinks for microplastics and nanoplastics as their surfaces can adsorb these plastics; moreover, nanoplastics can be internalized by plants. Plastics on the surfaces and in the interiors of vascular plants can cause various phytotoxicity effects, including impacts on growth, photosynthesis, and oxidative stress. Furthermore, the results and mechanisms of phytotoxicity effects caused by microplastics or nanoplastics can be very different. However, knowledge gaps still exist in the relationships between micro/nanoplastics and vascular plants based on the analysis of available studies; thus, potential subjects for future studies were proposed, including the fates, analysis methods, influencing factors, mechanisms of phytotoxicity, and further influences of microplastics and nanoplastics in the vascular plant ecosystems. This study presents a review of micro/nanoplastics-vascular plant research and reaches a basis for future research.

Microplastic pollution in Larimichthys polyactis in the coastal area of Jiangsu, China

We investigated microplastics (MPs) pollution in 349 Larimichthys polyactis specimens from the coastal area of Jiangsu Province, China. The MP abundance in L. polyactis was 1.03 ± 1.04 items/individual and 0.95 ± 0.92 items/10 g (wet weight). The MP abundance in specimens from the Haizhou Bay fishing ground was slightly higher than that in specimens from the Lvsi fishing ground. Spearman's correlation showed that MP abundance was positively correlated with body length when expressed as items/individual, but not items/10 g. The abundance in the gastrointestinal tract was slightly higher than that in the gills, but the differences were not significant for either measurement index. The MPs predominantly ingested by L. polyactis were <1 mm, fibrous, blue and had a cellophane composition. The MP pollution in L. polyactis in the coast of Jiangsu Province is at a medium to low level, as compared with other regions of China.

Field to laboratory comparison of metal accumulation on aged microplastics in coastal waters

The ubiquity of microplastics in the environment has attracted much attention on their risks. Though newly produced plastics were considered inert to aqueous metals, a few studies suggest aged microplastics can accumulate metals. Still, knowledge gap exists on the comparability of metal accumulation in field condition and that acquired in controlled laboratory settings. Accordingly, we comparatively assessed the field accumulation and laboratory adsorption of metals on aged microplastics in coastal waters. Microplastics of different polymeric types were aged for 8 weeks at three coastal sites with different contamination levels. Microplastics accumulated metals to substantial concentrations during ageing (median concentrations, μg g^-1: Fe = 950, Mn = 94, Zn = 19, Cu = 2.8, Ni = 1.7, Pb = 1.6, and Cd = 0.005). Adsorption capacity of (aged) microplastics was evaluated in laboratory using a stable isotope tracer method. At environmentally realistic concentrations (μg L^-1, ¹¹⁴Cd = 1.7, ⁶⁵Cu = 4.4, ⁶²Ni = 5.4, ²⁰⁶Pb = 0.5, and ⁶⁸Zn = 13), the median concentrations of newly adsorbed isotopes on the aged microplastics were 0.01, 1.4, 0.07, 0.56, and 1.1 μg g^-1, respectively, one to two orders of magnitude higher than those adsorbed on pristine microplastics. However, the composition pattern of metals accumulated on aged microplastics differed from the composition of metals newly adsorbed in laboratory: the prior one reflected the contamination status of ageing sites and varied by polymeric types; whereas the laboratory newly adsorbed metals on aged microplastics were uniformly correlated to particulate Fe and Mn concentrations, suggesting Fe and Mn mineral coatings mediated the ensuing metal adsorption. Such discrepancy unveiled the complexity of metal accumulation behavior in the real environment and highlighted that cares should be taken when translating laboratory findings to risk assessment of metal contaminated microplastics in the real environment.

Research progresses of microplastic pollution in freshwater systems

Microplastics (MPs) have received widespread attention as an emerging environmental pollutant. They are ubiquitous in the freshwater system, causing a global environmental issue. The current features and perspectives of MPs in the freshwater systems can provide the concerns of their ecological effects, which has not been addressed widely. Therefore, in this study, we reviewed the characteristics of MPs in freshwater environments and discussed their sources and potential impacts. The abundance of MPs in freshwater system ranged from approximately 3-6 orders of magnitude in different regions. There colors were mainly white and transparent, with polypropylene (PP) and polyethylene (PE) as the major polymers. The main shape of these MPs was fibers with dominant size of less than 1 mm. Analysis indicated MPs in freshwater system mostly originated from human activities such as sewage discharge in highly contaminated areas, while atmospheric long-distance transport and precipitation deposition played an important role in remote areas. Freshwater MPs pollutants also affected drinking water and aquatic organisms. Because the abundance of MPs in organisms was relatively balanced, the pollution level of biological MP pollution cannot accurately characterize the pollution status in the watershed currently. Future research should focus and strengthen on periodic monitoring to characterize the temporal and spatial changes of MPs, and enhance toxicological research to explore MPs pollution impact on biota and humans.

Microplastics in the western Pacific and South China Sea: Spatial variations reveal the impact of Kuroshio intrusion

Surface currents play an essential role in the worldwide distribution of microplastics in the coastal seas and open oceans. As a branch of the western boundary currents (WBCs), Kuroshio changes seawater properties and pollutant levels of the South China Sea (SCS) during its intrusion process. To study the impact of Kuroshio intrusion on microplastics, we conducted field observations on surface water from the western Pacific (WP) and SCS. Microplastic abundances in the surface water of WP (0.02-0.10 particles m^-3) were generally lower than those in the SCS (0.05-0.26 particles m^-3). Fragments and granules dominated their apparent characteristics, and showed spatial classifications in different areas. The abundance of fragment, granule and foam showed a similar unimodal trend, as they peaked when the Kuroshio fraction was 0.1, implying the effect of Kuroshio intrusion was a combination of the dilution and biogeochemical influence. The polymer types of microplastics, dominated by polypropylene (PP), polyethylene (PE), polyester (PES), polymethacrylate (PMA) and phenoxy resin (PR), showed complicated compositions in the northern SCS, and Kuroshio intrusion was not the dominant influencing factor. Further study is needed to discover the comprehensive effect of Kuroshio intrusion on the fate of microplastics and is expected for the whole WBC system.

Microplastic ingestion by Atlantic horse mackerel (Trachurus trachurus) in the North and central Moroccan Atlantic coast between Larache (35°30'N) and Boujdour (26°30'N)

Horse mackerel is a semi-pelagic species found in abundance in the Moroccan coasts and occupies the first ranks in the catches landed by the coastal fleet. In this study, we investigated the ingestion of Polyamide, Acrylic and Polystyrene by Atlantic horse mackerel, in the Moroccan Atlantic coastal area located between Larache (35°30'N) and Boujdour (26°30'N). The objective is to map the spatial distribution of horse Mackerel containing microplastics (MPs) in their stomachs and identify hot spot areas. We also aim to verify the most ingested polymer by this fish characterized by significant daily vertical migrations. The results show that the three studied polymers were detected in the stomach contents of more than 73% of studied fishes. The hot spot areas are located more in the northern part where urbanization and fishing activity are important. Polyamide, the densest polymer, is the most abundant (86% of cases), followed by acrylic. These two polymers were found in association in 47% of cases. No correlation between the presence of MPs in the stomach contents and the size of the individual fishes was noted. Interestingly, the group of mature specimens ingested more MPs than the immature group.

Microplastics on beaches and mangrove sediments along the coast of South China

Accumulation of microplastics (MPs) data on a global scale is key to supporting plastic waste management for protecting ecosystems. To respond this call, a sampling campaign was conducted in the summer and winter seasons of 2018 to collect beach and mangrove sediment samples from 32 sites along the coastline of South China. The MPs concentrations in the intertidal zone along the coast of South China were comparable to those in other regions around the world. Polystyrene foams and fibers were the most abundant debris in the 0.2-5 mm and 0.02-2 mm MPs, respectively. Principal component and correlation analyses indicated that the abundances of MPs were related to wind direction, wastewater discharge amount, and tourist and fishing activities. Risk assessments suggested that potential ecological risks induced by MPs on beaches and mangrove forest along the coast of South China should not be overlooked.

Comparison of Detection Methods of Microplastics in Landfill Mineralized Refuse and Selection of Degradation Degree Indexes

A landfill is an important sink of plastic waste and potential sources of microplastics (MPs) when mineralized refuse is reused. However, limitations are still present in quantifying MPs in mineralized refuse and assessing their degradation degree. In this study, laser direct infrared spectroscopy and liquid chromatography-tandem mass spectrometry (LC-MS/MS) were used to identify MPs of mineralized refuse from a landfill. Although 25-113 items/g MPs were detected in particles subjected to flotation, 37.9-674 μg/g polyethylene terephthalate (PET) and 0.0716-1.01 μg/g polycarbonate (PC) were detected in the residual solids by LC-MS/MS, indicating a great amount of plastic polymers still presented in the residue. This suggests that the commonly used flotation-counting method will lead to significant underestimation of MP pollution in mineralized refuse, which might be due to the aging and aggregation process caused by the long-term landfill process. The ratio of "bisphenol A/PC" and "plasticizer/MPs" was found to be positively correlated and negatively correlated with the landfill age, respectively. Therefore, in addition to the spectral index such as the carbonyl index, new indexes based on the concentrations of polymers, free monomers, and plasticizers were proposed to characterize the degradation degree of MPs in a landfill.

The life of a plastic butter tub in riverine environments

Plastic pollution in the world's ocean is one of the major environmental challenges that affects the society today, due to their persistence at sea, adverse consequences to marine life and being potentially harmful to human health. Rivers are now widely recognized as being the major input source of land-based plastic waste into the seas. Despite their key role in plastic transportation, riverine plastic pollution research is still in its infancy and plastic sources, hot-spots and degradation processes in riverine systems are to date poorly understood. In this contribution, we introduce a novel concept of following the aging of polypropylene based post-consumer goods placed in known trapping and mobility zones of macroplastics on a fluvial point bar, which was determined through repeated field surveys of macroplastic densities on this bar. As a proof-of-concept, we followed the degradation of 5 identical plastic butter tubs in 5 different locations on a riverbank and significant differences in the aging of the tubs were observed. The degree of aging of the tubs can to some extent be correlated to their proximity to the main river channel, exposure to natural conditions, such as solar radiation, and its storage time on land.

Microplastics in a Remote Lake Basin of the Tibetan Plateau: Impacts of Atmospheric Transport and Glacial Melting

Plastic pollution is fast becoming one of the most pressing global issues that we currently face. Remote areas, such as the polar regions and the Tibetan Plateau, are now also exposed to microplastic contamination. However, with the impact of global warming, the transport of microplastics within the glacier-lake basins in such regions remains unclear. In this work, the Nam Co Basin in the Tibetan Plateau was selected to study the characteristics of microplastics in the rain fallout, lake water, glacial runoff, and non-glacial runoff. Fiber and films were the most common microplastic morphologies in all water samples; a higher proportion (37%) of light-weighing polypropylene and small-size (50-300 μm, ∼30%) microplastics were found in the glacial runoff. Air mass trajectory analysis showed that microplastics could be transported through the atmosphere over a distance of up to 800 km. For microplastic loading in lakes, the atmospheric fallout was estimated to be 3.3 tons during the monsoon season, whereas the contributions of glacial runoff (∼41 kg) and non-glacial runoff (∼522 kg) were relatively low. For the microplastic loading in glaciers, the atmospheric deposition was ∼500 kg/yr, and the output caused by glacial melting only accounted 8% of the total atmospheric input. All these results suggested that the dominant pathway through which microplastics enter remote mountainous lake basins is atmospheric deposition, and once deposited on glaciers, microplastics will be stored for a long time. This work provides quantitative evidence elucidating the fate of microplastics in alpine lake environments.

Uncertainties in global estimates of plastic waste highlight the need for monitoring frameworks

Several studies have estimated global inputs of plastic into the environment, relying on national statistics and modeling approaches. However, these estimates exhibit uncertainty driven by limited primary municipal solid waste management data. We compare mismanaged plastic estimates from three global studies (Jambeck et al. (2015), Lebreton and Andrady (2019), and Borrelle et al. (2020)), finding significant differences. Specifically, 58 countries show at least a 25 percentage point difference in estimated mismanagement rates, 27 countries show at least a 50 percentage point difference, and 9 countries show at least a 75 percentage point difference. Further, several top plastic generators exhibit large discrepancies in mismanagement estimates, including China, Russia, and Indonesia. The limitations of global plastic pollution estimates are well-known in the scientific community, and some variation is expected. However, these discrepancies limit policy design and mitigation. Thus, municipal, national, and international monitoring of plastic management and pollution must be improved.

Simultaneous sorption behaviors of UV filters on the virgin and aged micro-high-density polyethylene under environmental conditions

The simultaneous sorption behaviors of four analytes from the UV filters group, benzophenone (BPh), 4-methylbenzylidene camphor (4MBC), benzophenone 3 (BPh3), and benzophenone 2 (BPh2) on virgin and aged high-density polyethylene (HDPE) with a particle size of 125 μm in milliQ and river water were examined in this study. The aging processes of HDPE particles were carried out with the use of simulated sunlight. Conducted research revealed that the sorption of UV filters on HDPE particles follows pseudo-second-order kinetics. A Temkin isothermal model best described the adsorption process for 4BMC, BPh, BPh3, BPh2 on aged HDPE in river water, and 4MBC, BPh, BPh3 on virgin HDPE in milliQ water. The adsorption of BPh2 onto virgin MPs in milliQ water was consistent with the Langmuir isothermal model. Environmental conditions and physicochemical properties of analytes influenced the sorption mechanism between UV filters and MPs particles. It was observed that the main mechanisms responsible for the sorption of BPh, 4MBC, BPh3, and BPh2 on the surface of HDPE are hydrophobic interactions, that may change through the involvement of electrostatic interactions.

Behavior of Microplastics in Inland Waters: Aggregation, Settlement, and Transport

Inland waters are the main medium transporting microplastics to the ocean. Aggregation, vertical settlement, and horizontal transport will occur when microplastics enter the inland waterbodies. This paper reviews these behaviors of microplastics in inland waters and their influencing factors. The aggregation of microplastics were divided into homogeneous aggregation and heterogeneous aggregation, which are critical for the settlement of microplastics. The settlement of microplastics in inland water bodies is influenced by microplastic properties (size, density, and shapes) and environmental conditions (microorganisms, sedimental properties, hydraulic conditions, and so on). Horizontal transport of microplastics in water is influenced by hydrologic conditions, rainfall, river morphologies, dams, vegetation, etc. Future perspectives including laboratory simulations and numerical models involving multiple factors, the behaviors of degradable plastics, and the influence of hydrologic conditions have been proposed.

Agricultural Plastic Pollution in China: Generation of Plastic Debris and Emission of Phthalic Acid Esters from Agricultural Films

Agricultural plastic films have been proven highly advantageous, but they also cause pollution of plastic debris and associated chemicals. Phthalates (phthalic acid esters, PAEs), an important additive of agricultural films, can be released and contaminate the environment. Here, we analyzed the agricultural plastic usage and assessed plastic debris in China and developed a method to estimate PAE emissions from agricultural films. Additionally, the environmental fate of PAEs was evaluated using a fugacity-based multimedia model. The agricultural plastic film usage in China in 2017 was 2,528,600 tons. After agricultural film recycling and water erosion, the plastic debris amount was estimated as 465,016 tons. The water erosion process carried 4329 tons of plastic debris into the aquatic environment. During its lifetime, the agricultural film released a total of 91.5 tons of two typical types of PAEs. PAEs from the mulching film would mostly be removed through degradation, while those from the greenhouse film accumulate in vegetables. Populated regions exhibited more serious PAE pollution in vegetables but with no immediate health risks. The model was well evaluated using comparable measured concentrations and uncertainty analysis based on the Monte Carlo method. The findings from this study demonstrate the serious agricultural plastic pollution problem and associated PAE contamination in China.

Microplastic pollution in aquatic environments with special emphasis on riverine systems: Current understanding and way forward

Microplastics (MPs) are emerging as a severe threat in our environment. Their diverse existence in marine environments is being researched globally and thus a widely known fact; however, their presence in the freshwater counterpart has gained attention lately only. Riverine systems, the most critical freshwater resources serve as an essential link between terrestrial and marine environments and their contamination with MPs is going to create severe environmental issues. Because of their small size and unique morphology, these polymers can exhibit variable toxicity to the interacting biota and alter their habitat properties; thus, causing serious impacts on the environment and health of living beings, including humans. These microplastics can also interact with pollutants like heavy metals and organic pollutants, which further augment their harming potential. Inefficient and poor plastic waste disposal practices play an important role in the generation of microplastic pollutants. In the present COVID 19 pandemics, the excessive use of plastic to contain the spread of infection has further added the plastic load in the environment which will eventually lead to the generation of microplastic particles. Also, a significant amount of microplastic pollutants in riverine systems are delivered through wastewater treatment plant effluents. These trade-offs create a distress situation in the environment. The present study connects these key issues for a better understanding of the diverse existence of microplastic pollutants, their sources, and fate, with a special emphasis on riverine systems. A critical appraisal of the knowledge gaps and proposal of suitable solutions through this review might open up avenues for further research and effective management of the microplastics in aquatic environments.

Source- and polymer-specific size distributions of fine microplastics in surface water in an urban river

There is increasing concern about the environmental behaviors of microplastics (MPs), in particular fine MPs (FMPs), such as their concentrations, sources, size distributions, and fragmentation by weathering in waters. However, there is little information about size distributions of MP polymer types and their relationships to their sources. Here, we analyzed concentrations, compositions, and size distributions of 18 polymer types of MPs of >20 μm by micro-Fourier transform infrared spectroscopy with a novel pretreatment method in surface waters at five sites from the headwaters to the mouth of a Japanese river, and in influent and effluent from a sewage treatment plant (STP). The microplastic concentrations ranged from 300 to 1240 particles/m³ in surface waters. Cluster analysis identified two primary sources of MPs: residential wastewater at the headwater site and non-point sources from urban areas at downstream sites; concentrations of chemical contaminants from STPs were much higher at the downstream sites. The median particle sizes (D₅₀) of MPs increased in urban areas at the downstream sites and were larger than those in influent and effluent. These results imply the release of larger MPs from non-point sources in urban areas. The size distributions of each polymer and all MPs could be fitted significantly to the Weibull distribution function. Values of D₅₀, shape parameters, and scale parameters estimated from the functions were useful indicators for evaluating size distributions in detail. A significant positive correlation of D₅₀ with the tensile strengths of virgin polymers among 13 dominant polymers detected in the surface water suggests that the fragmentation properties of each polymer are influenced by its physical strength. Multidimensional analysis with concentrations, polymeric compositions, and size distributions of MPs, including FMPs, could provide useful information about their sources and their environmental behaviors.

Commodity plastic burning as a source of inhaled toxic aerosols

Commodity plastic is ubiquitous in daily life and commonly disposed of via unregulated burning, particularly in developing regions. We report here the much higher emission factors (13.1 ± 7.5 g/kg) and toxicities of inhalable aerosols emitted from the unregulated burning of plastic waste based on field measurements and cellular experiments, including oxidative stress and cytotoxic tests in A549 cells. Plastic foam burning emitted aerosols possesses the highest EFs (34.8 ± 4.5 g/kg) and toxicities, which are 4.2- to 13.4-fold and 1.1- to 2.7-fold higher than those emitted from the burning of other waste types. These quantified toxicities are mainly attributed to aerosols containing carbonaceous matter, especially persistent organic pollutants, including polycyclic aromatic hydrocarbons and dioxins, which originate from incomplete combustion processes. The aerosol emission amounts were estimated from the obtained experimental results. Approximately 70.2 million tons (29%) of plastic waste was burned without regulation worldwide in 2016, leading to 0.92 ± 0.53 million tons of toxic aerosols being released into the air, a majority of which occurred in developing regions. The results indicate improved combustion technology and control strategies are urgently needed in developing regions for discarded plastic -waste to mitigate toxic exposure risks and achieve sustainable development.

Microplastics in seawater and two sides of the Taiwan Strait: Reflection of the social-economic development

Microplastic abundance, distribution and source characteristics were investigated for the surface seawaters from the Taiwan Strait as well as those of sediments along its west and east coasts. The microplastic abundances were in the range of 28-208 (mean 90) and 10-246 (mean 69) items/kg (d.w.) along the west and east coasts respectively. The higher microplastic abundance on the west coast might be related to the different local economic development, population, land-use and other human activities. Combined with microplastic pollution and socio-economic development, regression analysis results showed that urbanization level is negatively correlated with foams while positively correlated with fibers. This study, as the first report of microplastics in the Taiwan Strait, suggested further research on microplastics cross-strait transportation and the relationship with economic developments.

Microplastics in soil: A review on methods, occurrence, sources, and potential risk

Microplastic is an emerging contaminant of concern in soil globally due to its widespread and potential risks on the ecological system. Some basic issues such as the occurrence, source, and potential risks of microplastics in the soil are still open questions. These problems arise due to the lack of systematic and comprehensive analysis of microplastic in soils. Therefore, we comprehensively reviewed the current status of knowledge on microplastics in soil on detection, occurrence, characterization, source, and potential risk. Our review suggests that microplastics are ubiquitous in soil matrices globally. However, the research progress of microplastics in the soil is restricted by inherent technological inconsistencies and difficulties in analyzing particles in complex matrices, and studies on the occurrence and distribution of microplastics in soil environments remain very scarce, especially in Africa, South America, and Oceania. The consistency of the characteristics and composition of the microplastics in the aquatic environment and soil demonstrate they may share sources and exchange microplastics. Wide and varied sources of microplastic are constantly filling the soil, which causes the accumulation of microplastics in the soil. Studies on the effects and potential risks of microplastics in soil ecosystems are also reviewed. Limited research has shown that the combination and interaction of microplastics with contaminants they absorbed may affect soil health and function, and even migration along the food chain. The occurrence and impact of microplastic on the soil depend on the morphology, chemical components, and natural factors. We conclude that large research gaps exist in the quantification and estimation of regional emissions of microplastics in soil, factors affecting the concentration of microplastics, and microplastic disguising as soil carbon storage, which need more effort.

Influence of the co-exposure of microplastics and tetrabromobisphenol A on human gut: Simulation in vitro with human cell Caco-2 and gut microbiota

Microplastics (MPs) pollution becomes an emergent threat to the ecosystem, and its joint effect with organic contaminants will cause more severe consequences. Recently, MPs has been observed in human feces, suggesting that we are exposed to an uncertain danger. In this study, the joint effect of polyethylene microplastics particles (PEMPs) and Tetrabromobisphenol A (TBBPA) on human gut was explored through the simulation experiment in vitro with human cell Caco-2 and gut microbiota. The toxicity of TBBPA and PEMPs on Caco-2 human cells was considered by physiological and biochemical indexes such as cell proliferation, cell cycle, reactive oxygen species, lactate dehydrogenase release, and mitochondrial membrane potential. Besides, microbial community diversity, community structure, and function changes of gut microbiota were investigated using Illumina 16S rRNA gene MiSeq sequencing to reveal the influence of TBBPA and PEMPs on human gut microbiota. The results indicated that both PEMPs and TBBPA would deteriorate the status of Caco-2 cells, and TBBPA played a major role in it; meanwhile, PEMPs affected Caco-2 cells at high concentrations. Particularly, TBBPA and PEMPs exhibited a joint effect on Caco-2 cells to a certain degree. TBBPA selectivity inhibited the growth of gram-positive bacteria such as Enterococcus and Lactobacillus, contributing to the thriving of gram-negative bacteria such as Escherichia and Bacteroides. The existence of PEMPs would enhance the proportion of Clostridium, Bacteroides, and Escherichia. Community composition changed dramatically with the interference of PEMPs and TBBPA; this was undesirable to the healthy homeostasis of the human gut. PICRUSt analysis determined both PEMPs and TBBPA interfered with the metabolism pathways of gut microbiota. Hence, the threat of MPs and TBBPA to humans should arouse vigilance.

The missing ocean plastic sink: Gone with the rivers

Plastic floating at the ocean surface, estimated at tens to hundreds of thousands of metric tons, represents only a small fraction of the estimated several million metric tons annually discharged by rivers. Such an imbalance promoted the search for a missing plastic sink that could explain the rapid removal of river-sourced plastics from the ocean surface. On the basis of an in-depth statistical reanalysis of updated data on microplastics-a size fraction for which both ocean and river sampling rely on equal techniques-we demonstrate that current river flux assessments are overestimated by two to three orders of magnitude. Accordingly, the average residence time of microplastics at the ocean surface rises from a few days to several years, strongly reducing the theoretical need for a missing sink.

Lifetime bioaccumulation, gender difference, tissue distribution, and parental transfer of organophosphorus plastic additives in freshwater fish

Plastic pollution has been a growing global issue. Various plastic additives may enter the environment with plastic debris, which could also become contaminants. Lifetime bioaccumulation, gender difference, tissue distribution, and parental transfer potential of commonly applied organophosphorus plastic additives (OPPAs) were investigated in wildlife fish of the Pearl River system, China. The OPPAs were widely detected in 7 consumable fish species. Tris (2-chloropropyl) phosphate was the predominant compound, with a median concentration of 18.8 ng/g lipid weight. The total OPPA concentrations (ΣOPPAs) were higher in the livers and swimming bladders, suggesting important roles of lipophilicity on the OPPAs accumulation in the fish. Besides, the livers were more abundant in the non-chlorinated OPPAs relative to the other tissues, indicating potentially stronger metabolism of the chlorinated OPPAs in the livers. Redbelly tilapia contained obviously lower ΣOPPAs than the other species. On the other hand, proportions of the chlorinated OPPAs were obviously lower in barbel chub and Guangdong black bream. For an individual species, higher ΣOPPAs were usually detected in the female than in the male fish. Furthermore, the females contained higher proportions of the non-chlorinated OPPAs. These results suggested potentially more accumulation of the OPPAs, particularly the non-chlorinated OPPAs in the female than in the male fish. Body weight dependence of the OPPAs accumulation showed varied patterns depending on species, tissue, and compound. Species-specific characteristics affected by both ecology and organisms' physiology should be considered in combination in assessing bioaccumulation of the OPPAs. The OPPAs were slightly bioaccumulative with LogBAFs of 1.2-3.3. The OPPAs did not show obvious inclination to be partitioned to biota from sediment. Omnipresence of the OPPAs in both egg/ovary and testis of the fish suggested potential transgenerational transfer of these chemicals, which can be a serious ecological issue and warrants further research.

The fate of plastic litter within estuarine compartments: An overview of current knowledge for the transboundary issue to guide future assessments

Plastics can enter biogeochemical cycles and thus be found in most ecosystems. Most studies emphasize plastic pollution in oceanic ecosystems even though rivers and estuaries are acknowledged as the main sources of plastics to the oceans. This review detected few studies approaching the transboundary issue, as well as patterns of estuarine gradients in predicting plastic distribution and accumulation in water, sediments, and organisms. Quantities of plastics in estuaries reach up to 45,500 items m^-3 in water, 567,000 items m^-3 in sediment, and 131 items per individual in the biota. The role of rivers and estuaries in the transport of plastics to the ocean is far from fully understood due to small sample sizes, short-term approaches, sampling techniques that underestimate small plastics, and the use of site-specific sampling rather than covering environmental gradients. Microfibres are the most commonly found plastic type in all environmental matrices but efforts to re-calculate pathways using novel sampling techniques and estimates are incipient. Microplastic availability to estuarine organisms and rising/sinking is determined by polymer characteristics and spatio-temporal fluctuations in physicochemical, biological, and mineralogical factors. Key processes governing plastic contamination along estuarine trophic webs remain unclear, as most studies used "species" as an ecological unit rather than trophic/functional guilds and ontogenetic shifts in feeding behaviour to understand communities and intraspecific relationships, respectively. Efforts to understand contamination at the tissue level and the contribution of biofouling organisms as vectors of contaminants onto plastic surfaces are increasing. In conclusion, rivers and estuaries still require attention with regards to accurate sampling and conclusions. Multivariate analysis and robust models are necessary to predict the fate of micro- and macroplastics in estuarine environments; and the inclusion of the socio-economic aspects in modelling techniques seems to be relevant regarding management approaches.

Prediction Models on pKa and Base-Catalyzed Hydrolysis Kinetics of Parabens: Experimental and Quantum Chemical Studies

Parabens for which the molecules contain hydrolytic and ionizable groups, are emerging pollutants due to their ubiquity in the environment. However, lack of pK_a and second-order base-catalyzed hydrolysis kinetics (k_B) values limits their environmental persistence assessment. Herein, six parabens were selected as reference compounds for which the pK_a and k_B values were measured experimentally. A semiempirical quantum chemical (QC) method was selected to calculate pK_a of the parabens, and density functional theory (DFT) methods were selected to calculate k_B for neutral and anionic forms of the parabens, by comparing the QC-calculated and determined values. Combining the QC-calculated and experimental pK_a and k_B values, quantitative structure-activity relationships with determination coefficients (R²) being 0.947 and 0.842 for the pK_a and k_B models, respectively, were developed, which were validated and could be employed to efficiently fill the k_B and pK_a data gaps of parabens within applicability domains. The base-catalyzed hydrolysis half-lives were estimated to range from 6 h to 1.52 × 10⁶ years (pH 7-9, 25 °C), further necessitating the in silico models due to the tedious and onerous experimental determination, and the huge number of hydrolyzable and ionizable chemicals that may be released into the environment.

An ecotoxicological approach to microplastics on terrestrial and aquatic organisms: A systematic review in assessment, monitoring and biological impact

Marine and land plastic debris biodegrades at micro- and nanoscales through progressive fragmentation. Oceanographic model studies confirm the presence of up to ∼2.41 million tons of microplastics across the Atlantic, Pacific, and Indian subtropical gyres. Microplastics distribute from primary (e.g., exfoliating cleansers) and secondary (e.g., chemical deterioration) sources in the environment. This anthropogenic phenomenon poses a threat to the flora and fauna of terrestrial and aquatic ecosystems as ingestion and entanglement cases increase over time. This review focuses on the impact of microplastics across taxa at suggested environmentally relevant concentrations, and advances the groundwork for future ecotoxicological-based research on microplastics including the main points: (i) adhesion of chemical pollutants (e.g., PCBs); (ii) biological effects (e.g., bioaccumulation, biomagnification, biotransportation) in terrestrial and aquatic organisms; (iii) physico-chemical properties (e.g., polybrominated diphenyl ethers) and biodegradation pathways in the environment (e.g., chemical stress, heat stress); and (iv) an ecotoxicological prospect for optimized impact assessments.

Environmental factors-mediated behavior of microplastics and nanoplastics in water: A review

The release of plastics in nature is an increasing global concern due to their degradation from microplastics (MPs) and even to nanoplastics (NPs), which are being recognized as a potential global threat to humans and environment. This paper summarizes the current knowledge on the effect of different environmental factors on the aggregation of MPs and NPs in aquatic environment. Stability (or extent of aggregation) of MPs and NPs varies with pH, ionic strength, ion type (monovalent, divalent, and trivalent), kind of minerals, and natural organic matter (NOM) of the aquatic environment. Electrostatic interactions between particles at different pH and ionic strength caused by salts of different valents govern the aggregation. In the presence of minerals (or inorganic colloids), net surface charge of mineral and surface potential of MPs and NPs (i.e., positive or negative surface functionality) play important roles in the heteroaggregation of MPs and NPs. In the presence of NOM, additional complex interactions including hydrophobic interactions and bridging are also involved in the aggregation of particles. Understanding the interactions of MPs and NPs of different surface charge with diverse environmental factors at a wide range of environmental conditions is pivotal to assess the mobility and the fate of degraded plastic particles and their risk to human health and ecological systems.

Combined effect of microplastics and DDT on microbial growth: A bacteriological and metabolomics investigation in Escherichia coli

Microplastics (MPs) can adsorb toxic chemicals in biological or environmental matrixes and thus influence their behavior and availability. In order to investigate how the combined pollution of MPs and toxic organic chemical influence microbial growth and metabolism, Escherichia coli (E. coli) was grown in a complex, well-defined media and treated with polystyrene microplastics (PS MPs) and dichloro-diphenyl-tricgloroethane (DDT) at human relevant concentration levels. In vivo metabolites captured by a novel solid phase microextraction (SPME) probe, were used to reflect the metabolic dysregulation of E. coli under different pollution stresses. Results showed that the toxic effect of DDT displayed a distinct dose-dependent phenomenon while the existence of PS decreased the growth and metabolic interference effect of DDT on E. coli. Adsorption results revealed a mechanism that PS weakened the adverse impact of DDT by decreasing its free concentration in the treated culture media. Tricarboxylic acid (TCA) cycle related enzymes activities and antioxidant defense related substances of E. coli also proved the mechanism. The current study is believed to broaden our understanding of the ecotoxicity of MPs with toxic organic chemicals on microorganism.

Macroplastics in rivers: present knowledge, issues and challenges

Macroplastics are the primary contributor to riverine plastic pollution by mass, posing a wide range of serious threats for riverine systems, from adversely affecting various life forms within the riverine system, to potentially increasing flood risk, and generally resulting in adverse effects on any livelihoods. Compared to other river-related research disciplines, research into riverine macroplastics and their effects has not yet featured prominently. Various quantification methods are presently used to assess the presence of macroplastics at different locations within river systems; however, overcoming limitations and unifying methods remain an essential need. Macroplastic dynamics in rivers are subject to various factors, including both material and river characteristics. We review the diverse factors that potentially influence macroplastic dynamics in rivers, and highlight our knowledge limits. We advocate for future research that enables synergies between improved field quantification techniques, use of global protocols and data sharing, and laboratory experiments. This is needed to obtain a riverine macroplastic budget model, required for the implementation of targeted management practices. Finally, a multilayer potential management strategy is presented: (i) reducing the macroplastic supply into rivers; (ii) removing effectively and safely macroplastics from within rivers; and (iii) treating macroplastics once removed from the riverine system.

A critical review on marine litter in the Adriatic Sea: Focus on plastic pollution

Marine litter affects various habitats across the world. This review focuses on the Adriatic region, considering the presence of marine litter as well as microplastics (mPs) and macroplastics (MPs) in different environments (water, beach, seabed and biota). Data from 53 scientific papers were critically analysed, providing a snapshot of this type of contamination, and evidencing critical issues. The final part of the review provides considerations on spatial and temporal trends, comparing data with the available information provided by transport forecasting models. It emerges that the most investigated areas are those most subjected to the contribution of rivers, tourism or have the greatest relevance to nature conservation. Our analysis also reveals that, even though many international research projects have played a fundamental role in the creation of shared methods and protocols, currently available data are difficult to compare. Nevertheless, our results enhance knowledge of the state of the art in the research carried out so far, and on the situation regarding pollution due to the marine litter in the Adriatic Sea, as well as highlighting avenues for future investigation.

Plastics Are an Insignificant Carrier of Riverine Organic Pollutants to the Coastal Oceans

Global rivers act as a dominant transport pathway for land-based plastic debris to the marine environment. Organic pollutants (OPs) affiliated with riverine plastics can also enter the global oceans, but their amounts remain unknown. Microplastic (MP) samples were collected in a one-year sampling event from the surface water of the eight main riverine outlets in the Pearl River Delta (PRD), China, and analyzed for OPs affiliated with MPs, including 16 polycyclic aromatic hydrocarbons (PAHs), eight polybrominated diphenyl ethers (PBDEs), and 14 polychlorinated biphenyls (PCBs). The mean concentrations of MP-affiliated ∑₁₆PAH, ∑₈PBDE, and ∑₁₄PCB were 2010 (range: 25-40,100), 412 (range: 0.84-14,800), and 67.7 (range: 1.86-456) ng g^-1, respectively. Based on these and previous results, the annual riverine outflows of MP-affiliated OPs were 148, 83, and 8.03 g for ∑₁₆PAH, ∑₈PBDE, and ∑₁₄PCB, respectively. Assuming that plastic debris of different sizes contained the same concentrations of the target pollutants as MPs, the mean riverine outflows of plastic-bound ∑₁₆PAH, ∑₈PBDE, and ∑₁₄PCB were 6.75, 3.77, and 0.37 kg year^-1, respectively, which were insignificant compared with the riverine outflows of OPs through riverine water discharge (up to hundred tons per year). Apparently, plastics are an insignificant carrier of riverine OPs to the coastal oceans.