Occurrence and distribution of microplastics in an urban river: A case study in the Pearl River along Guangzhou City, China

Freshwater microplastics pollution: Detecting and visualizing emerging trends based on Citespace II

Microplastic particles with less than 5 mm in diameter has been detected in human feces and freshwater systems. Microplastics could cause serious physical and chemical harm to humans and organisms. Some previous studies on microplastics mainly concentrate on the marine environment, but few have focused on freshwater microplastics. Therefore, Citespace II is used to systematically analyze the related literature in order to comprehensively understand the research state of freshwater microplastics. The results show that there is still a large gap between research on freshwater and marine microplastics. Studies on freshwater microplastics have mainly been undertaken in developed countries such as the United States and Germany, while fewer studies have been conducted in the developing countries which face the most serious plastic pollution. Most studies focus on the rivers and lakes, but other freshwater sources with microplastic pollution, such as groundwater and reservoirs, have received less attention. This study also explored the possible opportunities and challenges that may be faced in freshwater research in order to introduce specific policies and measures to mitigate this emerging pollutant.

Occurrence and pollution characteristics of microplastics in surface water of the Manas River Basin, China

Microplastics, as a new type of pollutant, are widely found in various environmental media, and their effects on organisms are of great concern to society. However, research on the characteristics of microplastic pollution in inland rivers in China is still rare. The Manas River, which is located in the interior of Northeast China, was selected as the research object. The occurrence and pollution characteristics of microplastics in the surface water of the river were explored. The range of abundance of microplastics in the Manas River Basin was 21 ± 3-49 ± 3 items/L. Fibrous microplastics were dominant in all sites (88.0%); their size was mainly distributed between 0.1 and 1.0 mm (82.6%), and white and black were the dominant colours (82.9%). In addition, the size range of flaky-type microplastics were investigated in this study, which was principally between 2.5 × 10³-9.0 × 10⁴ μm² (84.5%). Infrared spectral analysis revealed that most of the selected particles were identified as microplastics, and polymer types of microplastics were dominated by polypropylene and polyethylene terephthalate (48.3%). This study can be used as a reference to better understand the contamination features of microplastics in inland rivers.

Occurrence of microplastics in the Han River and riverine fish in South Korea

Microplastic pollution has been paid attention due to the possibly global threat to human health and ecosystem in recent years. In this study, we investigated the distribution of microplastics in the Han River and its tributaries, South Korea, and in six species of inhabiting fish, namely carp (C. carpio), crucian carp (C. cuvieri), bluegill (L. macrochirus), bass (M. salmoides), catfish (S. asotus), and snakehead (C. argus). We found that the concentration of microplastics in the surface waters (0 m) was 0-42.9 particles/m³ (mean: 7.0 ± 12.9 particles/m³) compared to 20.0-180.0 particles/m³ (mean: 102.0 ± 50.3 particles/m³) at a depth of 2 m. Concentrations in the river tributaries ranged from 1.2 to 234.5 particles/m³ (mean: 91.1 ± 72.3 particles/m³). The most common types the plastic identified were polyethylene (PE), silicone, and polystyrene, while polytetrafluoroethylene (PTFE), polyethylene, and polyester dominated in the tributaries. With respect to shape, >73% of the recovered microplastics were fragments and the rest were fibers in the water. We also measured the concentration of microplastics in the intestines of fish, which ranged from 4 to 48 particles/fish (mean: 22.0 ± 16.0 particles/fish). The most common types of plastic found in the sampled fish were polytetrafluoroethylene (PFTE), polyethylene (PE), and rayon, and >94% of all the microplastic found in fish was in the form of fragments with the remainder being fibers. The concentrations of microplastic in the gills of fish ranged from 1 to 16 particles/fish (mean: 8.3 ± 6.0 particles/fish). In contrast, no microplastic was found in the flesh of the sampled fish. Our results imply that the ingestion of microplastics by fish is more closely related to habitat rather than feeding habits.

Distribution of microplastics in surface water and sediments of Qin river in Beibu Gulf, China

As a series of pollutants, microplastics have recently attracted widespread attention worldwide. In this study, different surface water and sediment samples were collected at 12 sampling sites along the urban section of Qin River in Guangxi Province, China. Water samples were collected using plankton nets with two different pore sizes (75 μm and 300 μm) and Teflon pump system with 25 μm mesh screen. The results showed that there was no significant difference in the abundance, particle size, and type of microplastics (F = 0.302, P = 0.588) between the two plankton nets, but the microplastic abundance in the samples collected by the Teflon pump was significantly higher (F = 9.12, P = 0.001), especially for microplastic fibers (F = 9.525, P = 0.001). Compared with the plankton net sampling method, the Teflon pump sampling had a smaller sample volume, resulting in a higher estimate of microplastic abundance in the water column. The microplastic abundance in the sediments was 0-97 items·kg^-1 dry weight. PE and PP were the main types of microplastics in Qin River, accounting for 67.2% and 72.3% in the water column and sediments, respectively. The microplastics in the water column and sediments were dominated by large-sized particles in the range of 1-5 mm. The sources of microplastic pollution in Qin River may be affected by many factors, including population density, industrial structure, and aquaculture activities. However, aquaculture activities were generally the main source of microplastic pollution in Qin River estuary. Wastewater treatment plants (WWTPs) could effectively decrease the microplastic abundance in urban sewage, reducing the impact of urban sewage discharge on microplastic accumulation in Qin River.

Development of a digestion method for determining microplastic pollution in vegetal-rich clayey mangrove sediments

Microplastics are ubiquitous pollutants found in environments. Mangrove sediments containing vegetal litter are different from other environmental matrices such as river and marine sediments. The presence of vegetal litter leads to an under-estimation of microplastic pollution, particularly classical digestion methods are not suitable for removing this type of organic matter. The present study aims to develop a digestion method to remove vegetal litter and improve the determination of microplastic pollution in mangrove sediments. Results showed that our three-stage method with repeatedly addition of hydrogen peroxide had the highest efficiency in removing mangrove vegetal litter when compared with the three classical digestion methods. The high match scores of Fourier Transform Infrared Spectroscopy proved that the developed method had little impacts on the integrity of five polymer types of microplastics. The developed method also achieved high efficiency in extracting microplastics from mangrove sediments containing different content of vegetal litter. CAPSULE: A digestion method was developed for extracting microplastics in clayey mangrove sediments rich in vegetal litter.

Distribution of microplastics in surface water of the lower Yellow River near estuary

The composition and distribution of microplastics in surface water of the Yellow River lower reach near estuary were investigated in this work. The major shape types of microplastics can be classified to fibers, fragments and particles, and 93.12% of microplastics in the surface water were fibers. The microplastics <200 μm were most abundant at all sample sites, which accounted for 87.94% of microplastics. The composition of microplastics was identified as polyethylene, polypropylene, and polystyrene according to infrared spectrometer analysis. The amounts of primary microplastics accounted for approximately three-fourths according to scanning electron microscope and microscope photo observing. The microplastics at different weathering processes could be also observed. The average abundances of microplastics in the dry and wet seasons were 930 and 497 item/L, respectively. The abundances of microplastics in the dry season all higher than that in the wet season. The microplastic concentrations in the surface water decreased linearly with the distances from the estuary of Yellow River with rather high positive correlation coefficients at wet season (r = 0.8104, p < .01) and at dry season (r = 0.8333, p < .01). The distribution of microplastics in the river section and the density of microplastics may be the primary factors to influence the microplastic concentrations in the surface water. The researches about distribution of microplastics in the river section might provide useful information that could be used for calculating either mass fluxes or inventories of microplastics.

Microplastics in stormwater runoff in a semiarid region, Tijuana, Mexico

Land-based sources are considered the most important source of microplastic pollution to marine environment. Stormwater runoff has been identified as one of the main pollutant contributors to water bodies. Seven sites were sampled to identify and quantify microplastics in stormwater runoff in Tijuana, Mexico. The median microplastic abundance found in the samples was between 66 and 191 particles L^-1, the highest abundance being recorded in an industrial land use site. The estimated annual total microplastic loads were between 8 × 10⁵ and 3 × 10⁶ particles ha^-1. The most abundant microplastic shape and identified polymer type were fibers and polyethylene, respectively. The highest microplastic abundances were observed in events with higher rainfall. The results have shown that stormwater runoff is an important source of microplastic to water bodies.

Microplastics in aquatic environments: Occurrence, accumulation, and biological effects

Microplastics, whether originating directly from industrial and household products or from the degradation of larger plastics, are currently of intense global concern. These particles are present in aquatic environments in high concentrations and may adversely affect aquatic organisms. An additional concern is the ability of microplastics to adsorb inorganic and organic pollutants and subsequently liberate them into marine and freshwater systems. In this review, we report on the occurrence and abundance of microplastics in the global aquatic environment. We then consider the accumulation (uptake, distribution, and elimination) of microplastics in aquatic organisms and the important factors that lead to bioaccumulation. The effects of microplastics on aquatic organisms of different trophic levels are also discussed. Several studies have shown that the size, shape, and surface physicochemical characteristics of microplastics are essential determinants of their biological effects. Finally, we examine the combined effects of microplastics and other pollutants, including persistent organic pollutants and heavy metals. Our review concludes by suggesting future lines of research based on the remaining knowledge gaps in microplastic research.

Occurrence, Fate and Fluxes of Plastics and Microplastics in Terrestrial and Freshwater Ecosystems

Plastics and microplastics are nowadays ubiquitously found in the environment. This has raised concerns on possible adverse effects for human health and the environment. To date, extensive information exists on their occurrence in the marine environment. However, information on their different sources and their transport within and across different freshwater and terrestrial ecosystems is still limited. Therefore, we assessed the current knowledge regarding the industrial sources of plastics and microplastics, their environmental pathways and load rates and their occurrence and fate in different environmental compartments, thereby highlighting important data gaps which are needed to better describe their global environmental cycle and exposure. This study shows that the quantitative assessment of the contribution of the different major sources of plastics, microplastics and nanoplastics to aquatic and terrestrial ecosystems is challenged by some data limitations. While the presence of microplastics in wastewater and freshwater is relatively well studied, data on sediments and especially soil ecosystems are too limited. Moreover, the overall occurrence of large-sized plastics, the patterns of microplastic and nanoplastic formation from them, the presence and deposition of plastic particles from the atmosphere and the fluxes of all kinds of plastics from soils towards aquatic environments (e.g. by surface water runoff, soil infiltration) are still poorly understood. Finally, this study discusses several research areas that need urgent development in order to better understand the potential ecological risks of plastic pollution and provides some recommendations to better manage and control plastic and microplastic inputs into the environment.

The accumulation of microplastics in fish from an important fish farm and mariculture area, Haizhou Bay, China

Marine fisheries and aquaculture can match growing demand for marine protein from an increasing population. However, the microplastics (MPs) in marine environments may pose a threat to human health through food chains by seafood consumption. The MPs have been found lodged in the digestive tracts and other tissues of various sea animals, nevertheless, little is known in regard to the accumulation of MPs in fish from major fish farms and mariculture areas, especially in non-digestive tissues of fishes. This study investigated the accumulation of MPs in six major wild fish species (including Thryssa kammalensis, Amblychaeturichthys hexanema, Odontamblyopus rubicundus, Cynoglossus semilaevis, Chaeturichthys stigmatias and Collichthys lucidus), both in digestive and non-digestive tissues, from an important fish farm and mariculture area, Haizhou Bay, China. All fishes had items that were identified as MPs. The highest abundance of MPs was 22.21±1.70items/individual or 11.19±1.28items/g in T. kammalensis, which is filter-feeding and usually inhabits in estuary. The lowest abundance of MPs was observed in C. semilaevis (13.54±2.09items/individual) and C. stigmatias (1.61±0.56items/g). The abundance of MPs exponentially increased with the decrease of MPs size. The MPs were dominated by fiber in shape, black or grey in colour and cellophane in composition. As to different tissues, the total number of MPs on skin (800) or in gills (746) was higher than that in gut (514). In terms of skin, the abundances of MPs in three species of scaleless fish with mucus (A. hexanema, C. stigmatias and O. rubicundus) were generally higher than other three fishes with scales (C. lucidus, C. semilaevis and T. kammalensis), implying the potential high risk of scaleless fish consumption for human health in Haizhou Bay. More in-depth studies need to focus on the scaleless fish through mucus adsorbing enormous MPs.

Microplastic pollution in water and fish samples around Nanxun Reef in Nansha Islands, South China Sea

Nanxun Reef is one of the typical reefs in Nansha Islands, South China Sea. As the Nansha Islands are surrounded by certain developing countries, the economic and population growth have resulted in increased surface runoff of persistent organic pollutants in offshore areas. Microplastic has been found in many freshwaters and sea areas in recent years. However, the levels of microplastics contamination in Nansha Islands are still uncharted. In this study, 15 water and 35 fish samples were collected around the Nanxun Reef. The average concentration of microplastics was 1733 items/m³ for surface water samples and 3.1 items per individual for fish samples. The majority of ingested microplastics by fish were fibers, mostly transparent or blue. In surface water samples, blue microbeads were the main types of microplastics, accounting for 76.5% of all the detected particles. The main size of microplastics was <0.5 mm both in water and fish samples. Our results demonstrated that fishery activities and human domestic sewage might be the dominant sources of microplastic pollution in the Nansha Island, South China Sea.

Plastic Particle Ingestion by Wild Freshwater Fish: A Critical Review

Plastic pollution, especially microplastics (MP) pollution, is a hot topic in both mainstream media and scientific literature. Although rivers are potentially the major transport pathway of this pollution to the sea, plastic contamination in freshwater bodies is comparatively understudied. Microplastic pollution in freshwater fish is of growing interest, and while few studies exist, discrepancies do occur in the sampling, extraction, and identification of MP and in the expression of the results. Even though those differences hamper comparisons between some studies, a comparative work has been performed to identify the factors influencing MP ingestion by fish and consequently to target potential ecological traits that can be used to monitor species. Monitoring plastic ingested by fish will give relevant ecological information on MP pollution. This review focuses on MP ingestion by wild freshwater and estuarine fish. In addition to providing an overview of the existing data concerning contamination levels in wild freshwater fish, we aimed to (1) propose several overall recommendations on the methodologies applicable to all biota, (2) compare MP contamination levels in fish and in their environment, and (3) determine which parameters could help to define fish species for monitoring.

Current practices and future perspectives of microplastic pollution in freshwater ecosystems in China

The pollution of marine and freshwater environments by plastic waste has attracted increasing public attention worldwide in recent years. China is the world's second largest economy and contributes the largest mass of mismanaged plastic waste. In this review, we collected accessible data on the abundance of microplastics in China's freshwater ecosystems, analyzing this pollutant in the samples of waters, sediments and biota. The results showed that microplastics are pervasive in surveyed freshwater environments, and a high abundance of microplastics was found in estuaries and inland waters located in populated urban areas. Moreover, many freshwater bivalve and fish have been found to uptake microplastics. Although similar sampling and laboratory processing methods were applied for microplastic research in different aquatic ecosystems, methods of investigation and units reported by different authors should be standardized. The characteristics of the detected microplastics showed that small size (<1 mm), fibers and transparency were the most common features in China's freshwater ecosystems and that PP and PE were the most common types of microplastics. The current situation of microplastic pollution in China is largely caused by inefficient administration and lack of applicable legislation and regulations. Therefore, we suggest that the Chinese government need to be more active in dealing with the plastic pollution issues, and increase education and publicity to promote people's awareness of environmental pollution caused by microplastics.

A method for extracting soil microplastics through circulation of sodium bromide solutions

Microplastics (MP) have been recently found in soil environments. These MP might have adverse effects at high concentrations and thus efficient extraction and analysis of MP from soil is needed. Here we propose a new method of NaBr solution circulation for extracting soil MP. A device for the circular extraction of soil MP was developed. This device included a separation, vacuum filtration, and solution recovery system. It was then utilized to test separation efficiency of soil MP with three economic and environmentally friendly extraction reagents: NaCl, CaCl₂ and NaBr solutions. The separation was tested with ten different types of polymers, three different size classes and three different shapes of MP. Extraction with NaBr showed the highest recovery rates ranging from 85% to 100%. After extraction the samples were treated with H₂O₂ and analyzed by micro-Fourier transform infrared spectroscopy. The developed method was assessed for its potential influence on MP and no significant changes in the integrity of multiple MP were found. Finally, the established method was used to analyze MP in four types of soil: farmland, yellow-brown, paddy and floodplain soil from the suburb of Shanghai. Results showed that the mean abundance of MP was 136.6-256.7 item kg^-1. Various MP including PP (40%), PE (35.5%), Acrylic (15.6%), PET (6.7%) and PA (2.2%) were found. With this paper, we provide an alternative method through NaBr solution circulation for the extraction of soil MP.

Separation and identification of microplastics from soil and sewage sludge

Soil and sludge are important pools for microplastics (MPs), however standard separation methods for MPs from these pools are still missing. We tested the widely used methods for MPs extraction from water and sediment to six agriculture surface soils and three sewage sludges from municipal wastewater treatment plants and included an additional pre-digestion procedure with 30% H₂O₂ before floatation to remove soil or sludge organic matter (OM). Extraction efficiency of MPs were evaluated under different separation conditions, including floatation solution (NaCl, ZnCl₂, and NaI), filtration membrane, and oxidation solution. Results showed that H₂O₂ pre-digestion significantly increased MPs extraction in soil and sludge, especially the samples with high OM contents, particularly sludge. Floatation solution with higher densities recovered more MPs. The extra released MPs were mainly small fibrous MPs, probably because they are easily retained by aggregates. Our results provide an feasible separation method for MPs in soil and sludge, i.e., pre-digestion with 30% H₂O₂ at 70 °C, floatation with NaI solution, filtration through nylon membrane, and further oxidation with 30% H₂O₂ + H₂SO₄ or 30% H₂O₂ at 70 °C. About 420-1290 MP items/kg soil were detected in soil samples, while much higher numbers (5553-13460 MP items/kg) were found in sludge samples. The dominate morphology of MPs was white fiber with a size of 0.02-0.25 mm, while the main types of MPs, identified by a micro-Fourier transformed infrared spectroscopy (μ-FTIR), were polyethylene and polypropylene in soil samples and polyethylene, polyethylene terephthalate, and polyacrylonitrile in sludge samples.

Riverine Microplastic Pollution in the Pearl River Delta, China: Are Modeled Estimates Accurate?

Plastic pollution has caused increasing global concern. Currently, model estimates of the riverine plastic inputs to the global oceans based on the concept of Mismanaged Plastic Waste (MPW) varied substantially, and no field measurements of riverine inputs were available. We conducted sampling at the eight major river outlets of the Pearl River Delta, South China with rapid economic growth and urbanization to provide field measured data for fine-tuning modeling results. Floating microplastics (MPs) were collected with a Manta net (mesh size of 0.33 mm) five times during 2018. Microplastic particles (0.3-5.0 mm) widely occurred in all sampling sites. The number and mass concentrations of MPs were in the ranges of 0.005-0.7 particles m^-3 and 0.004-1.28 mg m^-3 and were positively correlated with water discharges. The annual riverine input of MPs from the Pearl River Delta was estimated at 39 billion particles or 66 tons, which converts to 2400-3800 tons of plastic debris based on calculations described in Text S2. These values were substantially below the MPW-based model estimates (91,000-170,000 tons). The large difference between measured and modeling results may have derived from the large uncertainty in the MPW values assigned to the world's countries/regions.

River Deltas as hotspots of microplastic accumulation: The case study of the Ebro River (NW Mediterranean)

Microplastics (MPs) are considered pollutants that are ubiquitously distributed in aquatic environments. One of the key hotspot areas to understand fluxes of MPs entering into the oceans are transitional systems, between fresh and marine waters, where river estuaries in particular play an important role. In this study we analyzed MPs occurrence in the Ebro River Delta, Northeastern Iberian Peninsula, one of the largest wetland areas in the NW Mediterranean Basin. Microplastic profile, abundance, distribution, and characteristics were screened across different environmental matrices. MPs were collected in sandy beaches on the northern edge of the delta, in estuarine benthic sediments, and in surface waters of the Ebro River, with a mean abundance of 422 ± 119 MPs·kg^-1 DW, 2052 ± 746 MPs·kg^-1 DW and 3.5 ± 1.4 MPs·m^-3, respectively. Fibers were found to be the largest class (70 ± 22%) of the three different environmental matrices investigated. We estimated that the Ebro surface water represents an input of 2.14 × 10⁹ MPs·yr^-1 to the Mediterranean Sea. The main contribution of this study is a new insight on the distribution of MPs across different environmental matrices in river estuaries, where estuarine benthic sediments were identified as a potential important sink for MPs.

Occurrence of tire wear particles and other microplastics within the tributaries of the Charleston Harbor Estuary, South Carolina, USA

Microplastics (<5 mm) are ubiquitous in the marine environment, occurring in both sediments and surface waters worldwide. However, few studies have documented the presence of microplastics and tire wear particles in coastal rivers. A survey of microplastics and low-density tire wear particles (≥63 μm) in the sediment and surface water of the three major tributaries within the Charleston Harbor estuary was conducted. Intertidal sediment, subtidal sediment, and sea surface microlayer concentrations ranged from 0 to 652 microplastics/m², 3-4,375 microplastics/kg wet weight, and 3-36 microplastics/L, respectively. Blue fibers and tire wear particles were the two most abundant microplastic types observed, constituting 26.2% and 17.1%, respectively, of total microplastics. Tire wear particles were primarily identified by morphology, and ATR-FTIR analysis was conducted for a small subset (n = 5) of larger particles (≥500 μm). The present study provides the first microplastic field assessment of low-density tire wear particles in estuarine tributaries.

Distribution, sedimentary record, and persistence of microplastics in the Pearl River catchment, China

Microplastics (MPs) in the environment have become an issue worldwide. However, data about MPs in freshwater systems are still limited so far. This study investigated sources, fate, and seasonal and spatial distribution of MPs in the main stream Pearl River and its tributaries, as well as in the Pearl River Estuary (PRE), China. MPs were widely detected in the river water, river bed sediment, and estuarine sediment, with abundances of 0.57 ± 0.71 items L^-1, 685 ± 342 items kg^-1 dry weight (dw), and 258 ± 133 items kg^-1 dw, respectively. Sheet, fragmental, and fibrous polyethylene, polypropylene, and ethylene-propylene copolymers were predominant, suggesting that MPs in the Pearl River catchment be mainly derived from fragmentation of discarded plastic wastes. In addition, municipal wastewater was also an important MPs source, especially for polyethylene terephthalate (PET) fibers. Polymers of higher density, such as PET and polyvinyl alcohol were relatively more abundant in the sediment than in the river water, especially in the estuarine sediment. Upward increase of the MP abundance was observed in the sedimentary core, probably indicating increasing release of plastic wastes due to growing production and uses of plastic products. On the other hand, percentage of finer MPs increased with increasing depth. The results revealed persistence and potential downward dispersion of the fine MPs. The MPs abundance was positively related with population density and gross domestic product, demonstrating impacts of human activities and economic development on the MPs contamination. Higher MPs abundance was detected in dry season than in wet season in the river water, suggesting dilution effect of precipitation. It's estimated that 15963 tons of MPs could be released annually into the PRE from the main stream Pearl River and its tributaries.

Municipal solid waste (MSW) landfill: A source of microplastics? -Evidence of microplastics in landfill leachate

Although landfill is suspected to be releasing microplastics to the environment, there is few empirical researches carried out. To clarify suspicions of landfills as potential sources of microplastics, twelve leachate samples from four active and two closed municipal solid waste landfills were investigated. Microplastics were found in all the landfill leachate samples. In total, seventeen different types of plastics were identified in the leachate samples with calculated concentration ranging from 0.42 to 24.58 items/L. Polyethylene and polypropylene were the predominant polymer types. 99.36% microplastics were derived from the fragmentation of plastic waste buried in landfills. The size of 77.48% microplastics was between 100 and 1000 μm. The study shows that the generation, accumulation and release of microplastic in landfills is a long-term process. The results of our study provide preliminary evidence and validate that landfill isn't the final sink of plastics, but a potential source of microplastics.

Effect of microplastics exposure on the photosynthesis system of freshwater algae

Microplastics are widely distributed in freshwater environments. At present, most of the studies on the toxicity of microplastics are concentrated on aquatic feeding animals, but relatively few have addressed freshwater algae. This study investigated the effect of microplastics (polypropylene (PP) and polyvinyl chloride (PVC)) exposure on the photosynthetic system of freshwater algae over the logarithmic growth period. The results showed that both PVC and PP had a negative effect on chlorophyll a concentrations of Chlorella (C.) pyrenoidosa and Microcystis (M.) flos-aquae; among them, when the concentration of PVC exceeded 250 mg/L, compared with the control group, the chlorophyll a content of C. pyrenoidosa was reduced by 55.23%. For photosynthetic activity, higher concentrations of PVC and PP can induce lower values of F_v/F_m, F_v/F₀, and F_v'/F_m', suggesting a larger impact in algae. However, algae were able to adjust, with increased values of F_v/F_m, F_v/F₀, and F_v'/F_m'. This dose-negative effect phenomenon also exists in the study of the rapid light-response curves. In addition, comparing the two microplastics, we could see that PVC greatly inhibits the photosynthesis system of freshwater algae. Our study confirmed that microplastics can affect algae growth under certain concentrations, which provides evidence for understanding the risks of microplastics.

Development and Validation of an Efficient Method for Processing Microplastics in Biota Samples

The impacts of microplastics on aquatic ecosystems and biota are gaining attention globally. Although microplastics have been widely detected in biota, there currently are few standardized detection and identification methods. The present study developed a novel one-step digestion method which was evaluated with mussel and fish samples. This method employed nitric acid and hydrogen peroxide (HNO₃ :H₂ O₂ = 4:1 by volume) as digestion reagents, which completely digested biota samples <5 g weight within 30 min at 50 °C. A density separation step was subsequently used to remove organic residues as necessary. The efficiency and suitability of this method were tested by spiking microplastics of 7 different types and of various sizes (1000, 900, 675, 300, 250, and 150 μm) into mussel and gastrointestinal tracts of fish. The recoveries of microplastics ranged from 90 to 100%. No significant changes in weight, surface area, and particle size (t test, p > 0.05) were observed for all tested polymers. Fourier transform infrared spectral analyses demonstrated that the method did not degrade any of the polymers except for polyethylene terephthalate. The method was demonstrated with mussel and fish samples collected from the Pearl River delta, south China, and was able to recover microplastics effectively. Overall, the present method is time-saving and easy to operate, with low procedural cross-contamination. The properties of microplastics recovered by the present method remained largely intact, greatly benefiting subsequent qualitative and quantitative analyses. Environ Toxicol Chem 2019;38:1400-1408. © 2019 SETAC.

Microplastic distribution in surface water and sediment river around slum and industrial area (case study: Ciwalengke River, Majalaya district, Indonesia)

Microplastic research in urban and industrial areas, including remote areas, have been conducted recently. However, there is still a lack of research about microplastic abundances in slum area. Ciwalengke River is located in Majalaya, Indonesia, which is dominated by slum and industrial areas that probably generate microplastics. This research was conducted to investigate the distribution of microplastic around the slum area for the first time. Surface water and sediment samples of the river were obtained at ten locations and grouped into six segments location based on different land use at the riverbank. Microplastic particles were identified using binocular microscope and categorized by shape and size. The average microplastic concentration were 5.85 ± 3.28 particles per liter of surface water and 3.03 ± 1.59 microplastic particles per 100 g of dry sediments. Microplastic concentration in the sediment samples were found to have significant differences in location segment (Kruskal Wallis test, p-value = 0.01165 < 0.05), but no significant differences were found in the water samples (Kruskal Wallis test; p-value = 0.654 > 0.05). In addition, microplastic distribution was dominated by fiber particle. More fiber shape might be derived from the direct clothing of residents in the river and fabric washing process in the textile industries. This was also revealed by Raman spectroscopy test of several microplastic particles indicating that the type of microplastic were polyester and nylon.

Microplastic pollution in rice-fish co-culture system: A report of three farmland stations in Shanghai, China

Microplastics are emerging contaminants of increasing concern. Despite the occurrence of microplastics in farmland soils, the knowledge on microplastics in rice-fish co-culture ecosystems is limited. In this study, we investigated the distribution of microplastics in three rice-fish culture stations in Shanghai. During non-rice and rice-planting periods, microplastics in water, soils and aquatic animals (eel, loach and crayfish) were systematically assayed using methods of NaCl density extraction, H₂O₂ digestion and micro-fourier transform infrared spectroscopy. Results showed that average microplastic abundances were 0.4 ± 0.1 items L^-1, 10.3 ± 2.2 items kg^-1, 1.7 ± 0.5 items individual^-1 in water, soils and aquatic animal samples, respectively. We found an increasing trend in microplastic abundances in water, soil and animal samples from non-rice period to rice-planting period. Almost all of microplastics were found in digestive tracts of animals. Major microplastics were small (<1 mm) polyethylene and polypropylene fibers, with color of white and translucent. Size, shape, color and polymer type distributions of microplastics were similarly found in environmental and animal samples. Moreover, microplastic abundances in aquatic animals correlated to abundance in farmland soils. This study, for the first time, reveals the occurrence and characteristics of microplastic pollution in rice-fish culture ecosystem which suggests the potential ecological risks of microplastics in the agroecosystem.

Microplastic abundance, distribution and composition in the Pearl River along Guangzhou city and Pearl River estuary, China

Like many urban rivers, the Pearl River in China is contaminated with microplastics. Compared with marine environments, microplastic pollution in freshwater is less understood, especially in urban rivers. In the present study, the abundance and distribution of microplastics in water from the Pearl River was investigated, including the estuary and the urban section along Guangzhou. The average abundance of microplastics was 19,860 items/m³ and 8902 items/m³ in the urban section and estuary, respectively. Wastewater effluents from cities might be a main source of microplastics in the Pearl River, and the urban tributaries might act as retention systems for microplastics. Among these microplastics, over 80% of them were less than 0.5 mm. The main shapes of microplastics were film, fragment, and fiber, mostly blue or transparent. Moreover, the most common polymer types of these microplastics were polyamide (26.2%) and cellophane (23.1%). This study reveals the contamination and characteristics of microplastics in the Pearl River, and provides important data for further research on microplastics in freshwater ecosystems.

Interactive effects of polystyrene microplastics and roxithromycin on bioaccumulation and biochemical status in the freshwater fish red tilapia (Oreochromis niloticus)

There are hundreds of thousands metric tons of microplastics (MPs) present in aquatic environments. The MPs coexist with other pollutants in water bodies, such as pharmaceuticals, and may carry and transfer them into aquatic organisms, consequently causing unpredictable ecological risks. The purpose of the present study was to evaluate the effect of the presence of polystyrene microplastics (PS-MPs) on the distribution and bioaccumulation of roxithromycin (ROX) in freshwater fish red tilapia (Oreochromis niloticus) as well as their interactive biochemical effects in red tilapia. PS-MPs were found to enhance the bioaccumulation of ROX in fish tissues compared to ROX-alone exposure. In the treatment of PS-MPs (100 μg L^-1) combined with ROX (50 μg L^-1), the highest concentrations of ROX reached 39,672.9 ± 6311.4, 1767.9 ± 277.8, 2907.5 ± 225.0, and 4307.1 ± 186.5 μg kg^-1 in gut, gills, brain, and liver, respectively. Furthermore, compared to the ROX alone, the neurotoxicity caused by ROX was alleviated due to the presence of MPs after 14 d of exposure. The activities of cytochrome P450 (CYP) enzymes [7-ethoxyresorufin O-deethylase (EROD) and 7-benzyloxy-4-trifluoromethyl-coumarin O-dibenzyloxylase (BFCOD)] in fish livers exposed to all co-exposure treatments exhibited great variability compared to ROX alone after 14 d of exposure, suggesting that the presence of MPs may affect the metabolism of ROX in tilapia. Compared with ROX alone, the superoxide dismutase (SOD) activity increased significantly, and malondialdehyde (MDA) contents decreased in the co-exposure treatments, showing that oxidative damage in situations of co-exposure to MPs and ROX was mitigated in fish livers after 14 d of exposure. Collectively, the presence of MPs could affect the fate and toxicity of other organic pollutants in fish. The results emphasize the importance to study the interactions between MPs and other organic pollutants in aquatic environments.