From pollution to solutions: Insights into the sources, transport and management of plastic debris in pristine and urban rivers.

River systems are important recipients of environmental plastic pollution and have become key pathways for the transfer of mismanaged waste from the land to the ocean. Understanding the sources and fate of plastic debris, including plastic litter (>5 mm) and microplastics (MPs) (<5 mm), entering different riverine systems is essential to mitigate the ongoing environmental plastic pollution crisis. We comprehensively investigated the plastic pollution in the catchments of two rivers in the Yangtze River basin: an urban river, the Suzhou section of the Beijing-Hangzhou Grand Canal (SZ); and a pristine rural river, the Jingmen section of the Hanjiang River (JM). The abundance of plastic pollutants in SZ was significantly higher than in JM: 0.430 ± 0.450 items/m3 and 0.003 ± 0.003 items/m3 of plastic litter in the water; 23.47 ± 25.53 n/m3 and 2.78 ± 1.55 n/m3 MPs in the water; and 218.82 ± 77.40 items/kg and 5.30 ± 1.99 items/kg of MPs in the sediment, respectively. Plastic litter and MPs were closely correlated in abundance and polymer composition. Overall, the polymer type, shape and color of MPs were dominant by polypropylene (42.5%), fragment (60.4%) and transparent (40.0%), respectively. Source tracing analysis revealed that packaging, shipping, and wastewater were the primary sources of plastic pollutants. The mantel analysis indicated that socio-economic and geospatial factors play crucial roles in driving the hotspot formation of plastic pollution in river networks. The composition of the MP communities differed significantly between the sediments and the overlying water. The urban riverbed sediments had a more pronounced pollutant 'sink' effect compared with the pristine rivers. These findings suggested that the modification of natural streams during urbanization may influence the transport and fate of plastic pollutants in them. Our results offer pivotal insights into effective preventive measures.

Microplastic Pollution in Table Salts from China.

Microplastics have been found in seas all over the world. We hypothesize that sea salts might contain microplastics, because they are directly supplied by seawater. To test our hypothesis, we collected 15 brands of sea salts, lake salts, and rock/well salts from supermarkets throughout China. The microplastics content was 550-681 particles/kg in sea salts, 43-364 particles/kg in lake salts, and 7-204 particles/kg in rock/well salts. In sea salts, fragments and fibers were the prevalent types of particles compared with pellets and sheets. Microplastics measuring less than 200 µm represented the majority of the particles, accounting for 55% of the total microplastics, and the most common microplastics were polyethylene terephthalate, followed by polyethylene and cellophane in sea salts. The abundance of microplastics in sea salts was significantly higher than that in lake salts and rock/well salts. This result indicates that sea products, such as sea salts, are contaminated by microplastics. To the best of our knowledge, this is the first report on microplastic pollution in abiotic sea products.

Monthly variation and transport of microplastics from the Soan River into the Indus River.

The presence of plastic and microplastic pollution in freshwater systems receives extensive concerns for its accumulative trend and potential ecological impacts. This is the first annual study that investigated the monthly profile of plastic pollution in the mouth of the Soan River. Plastic pollutants comprising microplastic content up to 91.7 % were abundantly found during different seasons around the year, ranging from 132.7 items/m3 to 641.3 items/m3. The average abundance of plastics was significantly higher in August (641.3 ± 23.7 items/m3) than in other months. Overall, fibers, large microplastics (L-MPs), and transparent items were dominant by shape (57.7 %), size (61.9 %), and color (24.6 %), respectively. The highest average number of fibers (374.3/m3) and L-MPs (396 items/m3) were recorded during May and remained higher in the surface water from December to May. Fragments (432.3/m3) and S-MPs were observed higher (362.3 items/m3) during the peak rainy month of the summer monsoon season (August). Variations in the abundance and morphotypes were seemingly not only influenced by the seasonal change but also might be due to hydromorphological characteristics of the river, especially riverbed morphology, and the flow of the water. Only 5.2 % of the total items found were identified using µ-FTIR (micro-Fourier Transformed Infrared Spectroscope) which consisted of 70.7 % plastic items. Spectroscopy revealed that polyethylene terephthalate was an abundantly found polymer that largely prevailed in the form of fibers, followed by polypropylene and polyethylene. Most of the fragments, foams, and films were composed of polypropylene, polystyrene, and rayon respectively. Being an urban river, the polymeric profile demonstrated that anthropogenic activities had a significant impact on polluting the river. These findings are a very important source to understand the profile of plastic pollution in the Soan River and also a significant reference for policy-making in controlling plastic pollution among the riverine networks.

Effects of cooking methods on microplastics in dried shellfish.

Many studies have reported the occurrence of microplastics in live shellfish intended for human consumption. However, far fewer studies have been conducted on dried shellfish from supermarkets or fishery markets. In this study, the characteristics of microplastics in six kinds of dried shellfish products following different cooking treatments were investigated. Dietary exposure to microplastics in dried shellfish was estimated using the consumption rate of seafood among different age groups. Microplastics were detected in all the uncooked, dried shellfish products, ranging from 0.3 to 4.2 items/g. Fibres accounted for more than 80% of microplastics in razor clams, winkles, and scallops. The proportion of microplastics smaller than 1 mm in size ranged from 57.1% to 89.7% of the total microplastics found in dried shellfish. The polymer types included polyethylene terephthalate (PET), rayon, polyester, nylon, polypropylene (PP), cellophane (CP), and polyethylene (PE). Principal component analysis (PCA) showed that the sizes and shapes of microplastics in scallops were more susceptible to alteration by different cooking methods. Steaming and frying significantly reduced the abundance of microplastics in razor clams. In addition, significantly fewer microplastics were found in scallop products after boiling and steaming than were found in fried scallop products. The estimated dietary intake of microplastics for infants was the highest among the age groups considered (3.05 items/kg(bw)/day). Accordingly, frying was suggested for cooking mussels, boiling for clams and winkles, and steaming for scallops. Combining risks from ingesting plastics and plastic additives, steaming is suggested as the best method to cook shellfish.

Microplastic contamination of fish gills and the assessment of both quality assurance and quality control during laboratory analyses.

Microplastic pollution has received substantial international attention in terrestrial and marine environments and in the atmosphere. In this study, we assessed microplastic pollution and analyzed the accumulation of microplastics in the gills of fish caught in the Zhoushan fishing ground from September 2017 to March 2018. The average abundance of microplastics was 0.49 ± 0.54 particles/gill and frequently found chemical polymers was polyethylene terephthalate. We also conducted experiments on microplastic pollution in the water and the working solutions used during the analytical process and found that the source of microplastic contamination was the solutions used. Moreover, we evaluated and scored experimental quality control and quality assurance adapted from the 'Total Accumulated Score' method. Valuable steps are recommended in order to produce reliable results and improve the quality of results in microplastic analyses.

Seasonal distributions of microplastics and estimation of the microplastic load ingested by wild caught fish in the East China Sea.

Microplastic (MP) pollution in marine environments and organisms has received substantial international attention. However, long-term field studies of MPs are scarce. Here, we assessed the seasonal variation in MP abundance in the Zhoushan fishing ground (ZFG), one of the most abundant and productive fishing grounds worldwide, and analyzed the long-term MP accumulation in fish gastrointestinal tracts from September 2017 to June 2018. The most common MP particles in the ZFG were polyethylene terephthalate and polypropylene. After four seasons of continuous monitoring, we did not find accumulation of MPs in the fish after 10% KOH digestion. In total, 254 MP particles were removed from the gastrointestinal tracts of all fish. The average number of particles per fish was lower than that reported in previous global marine studies. There were significant differences among species. Moreover, this study provides the calculation of the weight of MPs ingested by fish and an estimate of the load of accumulated MPs in fish. According to the estimation, the load of MPs ingested by fish annually was approximately 3 kg in ZFG. These findings provide the long-term evidence of MP contamination in biota from the ZFG. The amounts of MPs ingested by fish require more detailed and improved investigation and estimation in further studies.

Adherence of microplastics to soft tissue of mussels: A novel way to uptake microplastics beyond ingestion.

Microplastic pollution is recognized as an emerging threat to aquatic ecosystems. One of the main environmental risks associated with microplastics is their bioavailability to marine organisms. Up to date, ingestion has been widely accepted as the sole way for the animals to uptake microplastics. Nevertheless, microplastics have also been found in some organs which are not involved in the process of ingestion. We hypothesize that the animal might uptake microplastics through adherence in addition to ingestion. To test this hypothesis, we collected mussels from the fishery farms, conducted exposure/clearance experiments and analyzed the accumulation of microplastics in specific organ of mussels. Our studies clearly showed the uptake of microplastic in multiple organs of mussels. In the field investigations, we found that the abundance of microplastic by weight but not by individual showed significant difference among organs, and the intestine contained the highest level of microplastics (9.2items/g). In the uptake and clearance experiment, the accumulation and retention of microfibers could also be observed in all tested organs of mussels including foot and mantle. Our results strongly suggest that adherence rather than ingestion led to the accumulation of microplastics in those organs which are not involved in ingestion process. To our best knowledge, it is the first time to propose that adherence is a novel way for animals to uptake microplastics beyond ingestion. This new finding makes us rethink about the bioavailability, accumulation and toxicity of microplastics to aquatic animals.

Effects of virgin microplastics on goldfish (Carassius auratus).

Microplastics (MPs) are abundant in freshwater and marine environments. They are diverse shape and size and are ingested by organisms. In this study, goldfish (Carassius auratus) were exposed via diet to three types of virgin MPs material types and shapes including fibers, fragments, and pellets. After six weeks of exposure, various sub-lethal effects, but no mortality, was observed. Fish exposed to plastic showed significant weight loss compared with the control. Fibers were found in the gills, gastrointestinal tract (GIT), and feces were not likely to accumulate in the GIT. Pronounced and severe alterations were found in the livers of fish exposed to fibers. The distal intestine showed more pronounced and severe changes compared to the proximal intestine, likely due to an intake of fibers. The ingestion of fibers caused the highest frequencies of progressive and inflammatory changes in the livers and intestines. This is in accordance with the higher organ index in these organs compared to other texa. Conversely, fragments and pellets were not ingested but chewed and expelled. Chewing process resulted in damages to the jaws as ranging from slight exfoliation to deep incisions. The highest frequency of regressive and circulatory (e.g., dilated sinusoids) changes was found in fish exposed to fragments, specifically in the upper and lower jaw, and in lower jaw and liver, respectively. Together, these results demonstrate that ingestion and chewing of MPs lead to damages in various organs and tissues of the gastrointestinal system, and suggest that different materials can have drastically different impacts on fish.

Microplastics and mesoplastics in fish from coastal and fresh waters of China.

Plastic pollution is a growing global concern. In the present study, we investigated plastic pollution in 21 species of sea fish and 6 species of freshwater fish from China. All of the species were found to ingest micro- or mesoplastics. The average abundance of microplastics varied from 1.1 to 7.2 items by individual and 0.2-17.2 items by gram. The average abundance of mesoplastics varied from 0.2 to 3.0 items by individual and 0.1-3.9 items by gram. Microplastics were abundant in 26 species, accounting for 55.9-92.3% of the total number of plastics items in each species. Thamnaconus septentrionalis contained the highest abundance of microplastics (7.2 items/individual). The average abundance of plastics in sea benthopelagic fishes was significantly higher than in freshwater benthopelagic fishes by items/individual. The plastics were dominanted by fiber in shape, transparent in color and cellophane in composition. The proportion of plastics in the stomach to the intestines showed great variation in different species, ranging from 0.5 to 1.9 by items/individual. The stomach of Harpodon nehereus and intestines of Pampus cinereus contained the highest number of plastics, (3.3) and (2.7), respectively, by items/individual. Our results suggested that plastic pollution was widespread in the investigated fish species and showed higher abundance in comparison with worldwide studies. The ingestion of plastics in fish was closely related to the habitat and gastrointestinal tract structure. We highly recommend that the entire gastrointestinal tract and digestion process be used in future investigations of plastic pollution in fish.

Microplastics in commercial bivalves from China.

We investigated microplastic pollution in 9 commercial bivalves from a fishery market in China. Multiple types of microplastics, including fibers, fragments and pellets, occurred in the tissue of all bivalves. The number of total microplastics varied from 2.1 to 10.5 items/g and from 4.3 to 57.2 items/individual for bivalves. Scapharca subcrenata contained on average 10.5 items/g and exhibited the highest levels of microplastics by weight. Fibers were the most common microplastics and consisted of more than half of the total microplastics in each of the 8 species. In Alectryonella plicatula, pellets accounted for 60% of the total microplastics. The most common size class was less than 250 µm and accounted for 33-84% of the total microplastics calculated by species. Our results suggest that microplastic pollution was widespread and exhibited a relatively high level in commercial bivalves from China. More intensive investigations on microplastics should be conducted in seafood.