Microplastics In Freshwater Environments Research Articles

FTIR Spectroscopic Characterization And Identification Of Microplastics In Water Samples From Ashtamudi Lake, Kollam, Kerala FTIR Spectroscopic Characterization And Identification Of Microplastics In Water Samples From Ashtamudi Lake, Kollam, Kerala

Microplastics (MPs), defined as plastic particles under 5 mm, have garnered significant attention over the past 45 years, particularly in marine environments (Bergmann et al., 2015; Carpenter et al., 1972). Recently, research has expanded to freshwater systems, revealing their pervasive nature across aquatic, terrestrial, and atmospheric environments (Dris et al., 2015; Wagner and Lambert, 2018).MPs enter ecosystems either as primary MPs or as secondary MPs from the degradation of larger plastics. Major sources include plastic waste from households and industries, which can enter waterways directly or indirectly. This accumulation leads to detrimental effects on aquatic life (Merlin Issac & Kandasubramanian, 2021). Notably, fluvial systems are crucial pathways for transporting MPs from terrestrial sources to oceans, with studies indicating that rivers in Asia, particularly the Ganges, contribute significantly to ocean plastic pollution (Lebreton et al., 2017; Napper et al., 2021). Research indicates a wide range of MP concentrations in European rivers, from 0.03 to 187,000 particles per cubic meter, with diverse forms such as fibers, fragments, and spheres being identified (Heß et al., 2018; Leslie et al., 2017). In India, inadequate waste management and high population density contribute to elevated MP levels in freshwater systems, with the Ganges potentially releasing billions of MPs daily into the Indian Ocean (Napper et al., 2021).MPs pose risks not only to aquatic organisms through ingestion but also raise concerns about human health via the food web (Arthur et al., 2008; Andrady, 2011). Their physical characteristics can influence their behavior in aquatic environments, with studies exploring the analogy of plastic as sediment, indicating that MPs may behave similarly to natural sediment particles (Enders et al., 2019; Kane and Clare, 2019).Despite growing awareness, research on MPs in freshwater environments remains limited compared to marine studies. Understanding the fate of MPs, alongside their ecological impacts, is critical for effective management and mitigation strategies to combat plastic pollution in all ecosystems.

The Effect of Polyethylene Microplastics on Growth and Antioxydant Response of Oscillatoria Princeps and Chlorella Pyrenoidosa.

This study investigated the impacts of polyethylene microplastics (PE-MPs) with varying particle sizes (13μm and 6.5μm) on the growth and antioxidant responses of two freshwater algae species, Oscillatoria princeps (O. princeps) and Chlorella pyrenoidosa (C. pyrenoidosa). The results revealed a significant reduction in chlorophyll a content in both algal species upon exposure to PE-MPs, indicating a disruption of photosynthesis. Furthermore, Superoxide Dismutase (SOD) activity decreased in O. princeps, while Catalase (CAT) activity increased in both species, indicating complex physiological responses to microplastic stress. Notably, phycotoxin levels in O. princeps decreased with PE-MP exposure, while those in C. pyrenoidosa increased, particularly with 6.5μm PE-MPs. These findings underscore the potential toxic effects of PE-MPs on freshwater algal growth and metabolism, as well as their influence on toxin production. This study contributes valuable insights into the ecotoxicological impacts of microplastics in freshwater environments, highlighting the need for further research on their biological effects and environmental health implications.

Hydrodynamic driven microplastics in Dongting Lake, China: Quantification of the flux and transportation

Hydrodynamic conditions have a significant effect on the fate of microplastics (MPs). Moreover, research on the relation between hydrodynamic conditions and MPs in freshwater environments is critical and unquantified. In this regard, herein, a methodological framework integrating system monitoring with numerical simulation has been developed and successfully implemented for Dongting Lake, a large freshwater lake fed by multiple rivers. According to time-series monitoring and hydrological data, 199.29/128.50 trillion MP items entered or exited Dongting Lake in 2021. In addition, a coupled numerical model identified four key areas of MP accumulation, which overlap with nature reserves and agricultural zones, posing considerable risks to the ecological gene pool and food security. The quantitative results obtained using the developed framework enable calculation of MP inflow and outflow fluxes and facilitate analysis of MP transportation. Overall, this study provides a scientific basis for preventing and controlling MP pollution in Dongting Lake and offers valuable insights for future research on related issues in freshwater ecosystems.

Evaluation of the migration behaviour of microplastics as emerging pollutants in freshwater environments.

Microplastics, as an emerging pollutant, are widely distributed in freshwater environments such as rivers and lakes, posing immeasurable potential risks to aquatic ecosystems and human health. The migration behaviour of microplastics can exacerbate the degree or scope of risk. A complete understanding of the migration behaviour of microplastics in freshwater environments, such as rivers and lakes, can help assess the state of occurrence and environmental risk of microplastics and provide a theoretical basis for microplastic pollution control. Firstly, this review presents the hazards of microplastics in freshwater environments and the current research focus. Then, this review systematically describes the migration behaviours of microplastics, such as aggregation, horizontal transport, sedimentation, infiltration, stranding, resuspension, bed load, and the affecting factors. These migration behaviours are influenced by the nature of the microplastics themselves (shape, size, density, surface modifications, ageing), environmental conditions (ionic strength, cation type, pH, co-existing pollutants, rainfall, flow regime), biology (vegetation, microbes, fish), etc. They can occur cyclically or can end spontaneously. Finally, an outlook for future research is given.

From Origins to Impacts: A Comprehensive Review of Microplastics in Freshwater Environments

Microplastics are plastic particles of dimensions less than 5mm, increasingly recognized as omnipresent contaminants in freshwater systems. These small particles are sourced from microbeads provided by personal care products, industrial abrasives, and other secondary sources formed by the degradation of larger plastic items. The microplastics are contaminated in freshwater environments through runoff, atmospheric deposition, and the discharge of water treatment processes. The presence of microplastics in freshwater has greater potential to cause harm to aquatic environments and human health. The primary objective of this paper is to identify the microplastic pollution in freshwater resources and classify the sources of this pollution in freshwater resources, including both primary and secondary microplastics, and to evaluate the ecological impact of microplastics and their potential health risks to humans through food chain transfer. This review synthesizes the most recent findings on sources, impacts, and potential mitigation measures of microplastic pollution in freshwater ecosystems to emphasize the attentive work needed urgently in our efforts to conquer the environmental challenge. The mitigation strategies in practice thus focus on policy implementation and correct technology in wastewater treatment, raising public awareness to minimize the use of plastics and encourage good waste management. However, studies with much detail are still required to develop systematic methodologies for microplastic analysis and go far enough to find long-term solutions

Research and Trends of Filtration for Removing Microplastics in Freshwater Environments

ABSTRACTMicroplastics (MPs) are a pollutant that increasingly threatens freshwater ecosystems and requires effective solutions for their removal. The aim of this study is to review current filtration methods used to remove MPs from freshwater environments. This study uses a systematic review method of existing literature regarding filtration techniques for removing MPs. Data were collected from various scientific sources published between 2015 and 2023. The filtration techniques analyzed include traditional filtration and advanced filtration technology. The study results show that advanced filtration technologies such as nanofiltration and biofiltration have a high potential in removing MPs from freshwater. However, each technique has its own challenges, including removal efficiency and implementation cost. The conclusion is that filtration is an effective method for dealing with MP pollution in freshwater ecosystems; however, further study is needed to address the existing challenges. This study provides in‐depth insights that can help develop more efficient policies and technologies for managing MP pollution in the future.

Response of Relationship Between Microplastic Abundance and Nitrogen Metabolism Function Microorganisms and Genes in Water

The impact of microplastics (MPs) as a new type of pollutant on water pollution has become a research hotspot. To explore the response relationship between the abundance of MPs and nitrogen metabolism function in a freshwater environment, Lake Ulansuhai was used as the research object; the abundance of MPs in the water was detected using a Zeiss microscope, and the distribution characteristics of nitrogen metabolism functional bacteria and functional genes in the water were analyzed using metagenomics sequencing. The correlation analysis method was used to explore the relationship between the abundance of MPs and nitrogen metabolism functional microorganisms and nitrogen metabolism functional genes. The results showed that the presence of MPs in freshwater environments had a higher impact on Cyanobacteria and Firmicutes as the dominant phyla, and the presence of MPs promoted their enrichment and growth. Among the dominant bacterial genera, MPs promoted the growth of Mycobacterium and inhibited Candidatus_Planktopila more significantly, further indicating that in freshwater environments, MPs affected normal nitrogen metabolism by affecting microbial communities, and pathways such as carbon and nitrogen fixation and denitrification were important pathways for MPs to affect nitrogen metabolism. From the perspective of nitrogen metabolism functional genes, it was found that the abundance of MPs significantly affected some functional genes during nitrification (pmoA-amoA, pmoB-amoB, and pmoC-amoC), denitrification (nirK and napA), and dissimilatory nitrate reduction (nrfA) processes (P < 0.05). Moreover, the influence of MPs abundance on different functional genes in the same pathway of nitrogen metabolism varied, making the impact of MPs on aquatic environments very complex; thus, its harm to the water environment cannot be underestimated.

Ceratophyllum demersum alleviates microplastics uptake and physiological stress responses in aquatic organisms, an overlooked ability

It has been demonstrated that microplastics (MPs) may be inadvertently ingested by aquatic animals, causing harm to their physiological functions and potentially entering the food chain, thereby posing risks to human food safety. To achieve an environmentally friendly and efficient reduction of MPs in freshwater environments, this experiment investigates the depuration effect of C. demersum on MPs using three common aquatic animals: Macrobrachium nipponense, Corbicula fluminea, and Bellamya aeruginosa as research subjects. The amounts of MPs, digestive enzyme activity, oxidative stress index, and energy metabolism enzyme activity in the digestive and non-digestive systems of three aquatic animals were measured on exposure days 1, 3, and 7 and on depuration days 1 and 3. The results indicated that the depuration effect of C. demersum and the species interaction were significant for the whole individual. Concerning digestive tissue, C. demersum was the most effective in purifying B. aeruginosa. When subjected to short-term exposure to MPs, C. demersum displayed a superior depuration effect. Among non-digestive tissues, C. demersum exhibited the earliest purifying effect on C. fluminea. Additionally, C. demersum alleviated physiological responses caused by MPs. In conclusion, this study underscores C. demersum as a promising new method for removing MPs from aquatic organisms.

Freshwater algal biofilm assemblages are more effective than invertebrate assemblages at aggregating microplastics

Microplastics, plastic particles less than 5 mm in length, are a ubiquitous pollutant in the environment, but research on freshwater microplastic contamination is lacking. A possible fate of microplastics in freshwater environments is to become entangled or aggregated in biofilms, which are matrices of algae, bacteria, and micro invertebrates that grow on underwater surfaces, following a progression of settling algae, periphyton, and finally invertebrate colonization. This in-situ study at the Oasis Marina at National Harbor in Oxon Hill, Maryland, examined how the taxonomic assemblages of freshwater biofilms in the Potomac River are associated with the number of microplastics aggregated within them. Aluminum discs, acting as artificial substrate for biofilm growth, were deployed at the water's surface and at 2 m depth to survey biofilm assemblage and were sampled monthly from October 2021–October 2022. Microplastic abundances in the water column were measured every 2 weeks over the same period. Spatial and temporal trends in trapped and suspended microplastics, water quality parameters (temperature, dissolved oxygen, pH, salinity, conductivity, turbidity, ammonia, nitrate, and phosphate), and biofilm assemblages were measured and compared to explore factors affecting the abundance of microplastics and their partitioning between the water column and biofilms. Water quality had no measurable impact on microplastic abundance in the water column at either depth, but temperature was negatively correlated to microplastic abundance in biofilms. As the weather warmed and biofilms progressed to invertebrate settling, they tended to contain fewer microplastics. This may have occurred because less biologically rich biofilms, primarily composed of unicellular algal colonies, provide a favorable surface for microplastic deposition. Understanding seasonal changes in biofilm assemblage and microplastic abundance may help track the fate of microplastics in freshwater systems, particularly in their interactions with lower trophic organisms.

Microplastic contamination in bathing areas in the Central Amazon, Itacoatiara, Brazil.

Due to the visible abundance of plastic improperly disposed of in the environment, the number of investigations has increased worldwide in different water bodies and biota. Despite this, studies of contamination by microplastics in freshwater environments in the Amazon are scarce. This study investigated microplastic contamination in sediment samples of bathing areas in the Central Amazon, in Itacoatiara, Amazonas, Brazil. A total of 202 microplastic particles were recorded in the five investigated areas that are used for recreation. These results indicate no significant difference in the number of microplastic particles among the establishments; however, the size of the microplastic particles differed significantly between the establishments. Both blue and red microplastic particles were recorded, with blue particles being the most abundant. The microplastic particles were in the form of fibers and fragments. The number of microplastic particles was significantly different between the areas within and adjacent to the bathing areas, though the size of the microplastic particles was not significantly different in the areas within and adjacent to the bathing areas. There was no significant correlation in the establishments in regard to their frequency of use and contamination (number of microplastic particles). This is the first study that indicates the anthropogenic impacts associated with microplastic contamination in recreation areas within the Amazon Forest, an area considered by the world to be of vital importance for conservation. The results of this study indicate that microplastics are present in these bathing areas of the Central Amazon and that contamination in areas used for recreation may be significantly higher than in areas not used for this purpose.

Synergistic adverse effects of microfibers and freshwater acidification on host-microbiota interactions in the water flea Daphnia magna

Microfibers are the most common type of microplastics in freshwater environments. Anthropogenic climate stressors, such as freshwater acidification (FA), can interact with plastic pollution to disrupt freshwater ecosystems. However, the underlying mechanisms responsible for the interactive effects of microfibers and FA on aquatic organisms remain poorly understood. In this study, we investigated individual Daphnia magna–microbiota interactions affected by interactions between microfibers and FA (MFA). We found that the accumulated amount of microfibers in pH-treatment groups was significantly higher than in the control groups, resulting in negative consequences on reproduction, growth, and sex ratio. We also observed that MFA interactions induced immunity- and reproduction-related biological processes. In particular, the abundance of pathogenic bacteria increased only in MFA groups, indicating that MFA interactions can cause intestinal damage. Our integrated analysis of microbiomes and host transcriptomes revealed that synergistic adverse effects of MFAs are closely related to changes in microbial communities, suggesting that D. magna fitness and the microbial community are causally linked. These finding may help elucidate the toxicity mechanisms governing the responses of D. magna to microfibers and acidification interactions, and to host-microbiome-environment interactions.

An Assessment of Microplastic Pollution in Several Streams of Gyeonggi-do

In recent years, there has been a growing interest in the environmental effects of microplastics, leading to active research efforts worldwide. However, most of these studies have focused on microplastic pollution in marine environments, resulting in a lack of information on the levels of microplastics in freshwater environments. To address this gap, this study investigated types and concentrations of microplastics in four rivers and two effluents from wastewater treatment plants in Gyeonggi-do, Korea, to determine the extent of microplastic contamination in relation to the surrounding environment and seasons. Microplastic concentrations were higher in the Gyeongan Stream (1.8~9.9 ea/L), Bokha Stream (0.47~2.6 ea/L), Osan Stream (0.5~6.6 ea/L), and Tan Stream (0.2~11.4 ea/L) than in the Tan Stream or Nakdong River, which were investigated in the past. However, due to spatial limitations, it is unclear whether the wastewater effluent had any downstream effects. The most commonly detected microplastic types were polypropylene, polyethylene, and polyester, comprising 58–90% of total microplastics, likely due to the influence of the surrounding environment (industries and human habitation). Moreover, types and concentrations of microplastics were found to reflect seasonal characteristics, particularly rainfall, suggesting that continuous monitoring is necessary to accurately assess the situation. The findings of this study can aid in the development of management strategies for reducing microplastic pollution in freshwater sources in the future.

Research Progress on Trojan-horse Effect of Microplastics and Heavy Metals in Freshwater Environment

As an emerging pollutant of global concern, microplastics (plastics with size<5 mm) and heavy metals are widely found in freshwater environments. Microplastics migrate easily, are difficult to degrade, and have large specific surface areas. They can enrich a variety of pollutants such as heavy metals and greatly increase their potential harm to the environment and ecology. Firstly, the special environmental behavior of microplastics carrying heavy metals and migrating together in freshwater environments was defined as the "Trojan-horse effect." Then, the Trojan-horse effect and its mechanism of microplastics and heavy metals in the freshwater environment were summarized and expounded from four aspects:the source and distribution of microplastics in the freshwater environment, the enrichment effect of microplastics on heavy metals, the impact of microplastics and the heavy metal Trojan-horse effect on its migration behavior, and the biological impact of microplastics and the heavy metal Trojan-horse effect. The results showed that, as a wide range of non-point source pollutants, microplastics widely existed in freshwater environments. In freshwater environments, the adsorption degree of single metals was different in different environments. It was mainly affected by microplastics, metals, and environmental factors. There was competitive adsorption in the presence of multiple metal ions. The Trojan-horse effect of microplastics and heavy metals could also affect their co-transport behavior. The Trojan-horse effect of microplastics and heavy metals in the freshwater environment frequently exacerbated their toxicity to aquatic organisms. This study provides references for comprehensively understanding the Trojan-horse effect and its mechanism in microplastics and heavy metals in the freshwater environment, which could effectively reduce the ecological risk and impact on human health of microplastics and heavy metals in the freshwater environment.

Multilevel Toxicity Evaluations of Polyethylene Microplastics in Zebrafish (Danio rerio).

Microplastics in freshwater environments pose a serious threat to living beings. Polyethylene microplastics (PE-MP) are the type most used around the world as microbeads in personal care products, and they have been found in aquatic organisms. The behavior and toxicity of fluorescent PE-MP spheres with an average diameter of 58.9 μm were studied in adult, juvenile and embryo zebrafish (Danio rerio). The adults were studied for genotoxicity, cytotoxicity, histology and biochemical markers. Juveniles underwent a follow-up in the gastrointestinal (GI) tract with histologic observations, and embryos were studied for embryotoxicity with the FET-test. In adults, micronucleus test and comet assays found neither genotoxicity after acute exposure for 96 h at concentrations of 0.0, 12.5, 50 and 100 mg.L-1, nor cytotoxicity through the nuclear abnormalities test. Acetylcholinesterase (AChE), Glutathione-S-Transferase (GST) and Lactate Dehydrogenase (LDH) activities were measured in adults exposed for 96 h. The AChE and GST activities were significantly changed, while no changes occurred for LDH. In conclusion, these PE-MP spheres did not cause serious toxic effects in zebrafish because there was no internalization. The observed biochemical changes in AChE and GST may be associated with GI microbiological dysbiosis, previously reported. The PE-MP spheres in the intestine of juveniles remained present for 12-15 days on average after the post-exposure clearance study, showing a slow depuration. The histological analysis, in adults, found no internalization of these microbeads, with complete depuration. The PE-MP spheres did not cross the chorion barrier, showing no embryotoxic effects after exposures at 0.0, 6.25, 12.5, 50.0 or 100.0 mg.L-1 for 96 h.

Polystyrene microplastics induced inflammation with activating the TLR2 signal by excessive accumulation of ROS in hepatopancreas of carp (Cyprinus carpio)

Polystyrene microplastics (PS-MPs) affect the immune defense function on carp (Cyprinus carpio). The PS-MPs model of carp was established by feeding with PS-MPs particle size of 8 µm and concentration of 1000 ng/L water. Hepatopancreas function test revealed the activities of AKP, ALT, AST and LDH abnormal increase. PS-MPs induced tissue damage and lead to abnormal hepatopancreas function. The PS-MPs also induced a oxidative stress with the antioxidant enzymes SOD, CAT, GSH-PX, and T-AOC activities decreasing and reactive oxygen species (ROS) excessive accumulation. PS-MPs activated the Toll like receptor-2 (TLR2) signaling pathway. The mRNA and protein expressions of TLR2, Myeloid differentiation primary response 88 (MyD88), tumor necrosis factor receptor-associated factor 6 (TRAF6), NF-κB p65, Tumor necrosis factor (TNF-α), Interleukin-1β (IL-1β), Inducible Nitric Oxide Synthase (iNOS), and cycooxygenase 2(COX2) was revealed increased in both hepatopancreas and hepatocytes with the qPCR and Western blotting analysis mode. ELISA showed the expressions of TNF-α, IL-1β, iNOS, and COX2 inflammatory molecule were increased in both hepatopancreas and hepatocytes. The results showed that PS-MPs caused a serious injure in the hepatopancreas and brought serious effects on the inflammatory response of carp. The present study displayed the harm caused by PS-MPs in freshwater fish, and provided some suggestions and references for toxicological studies of microplastics in freshwater environment.

Fate and effects of microplastics in combination with pharmaceuticals and endocrine disruptors in freshwaters: Insights from a microcosm experiment

Microplastic contamination of freshwater ecosystems has become an increasing environmental concern. To advance the hazard assessment of microplastics, we conducted a microcosm experiment in which we exposed a simplified aquatic ecosystem consisting of moss and caddisflies to microplastics (polyethylene, polystyrene and polypropylene) and pharmaceuticals and personal care products (1H-benzotriazole, bisphenol A, caffeine, gemfibrozil, ketoprofen, methylparaben, estriol, diphenhydramine, tris (1-chloro-2-propyl) phosphate) over the course of 60 days. We monitored the flux of microplastics within the microcosm, as well as the metabolic and total protein variation of organisms. This study offers evidence highlighting the capacity of moss to act as a sink for free-floating microplastics in freshwater environments. Moss is also shown to serve as a source and pathway for microplastic particles to enter aquatic food webs via caddisflies feeding off of the moss. Although most ingested microparticles were eliminated between caddisflies life stages, a small fraction of microplastics was transferred from aquatic to terrestrial ecosystem by emergence. While moss exhibited a mild response to microplastic stress, caddisflies ingesting microplastics showed stress comparable to that caused by exposure to pharmaceuticals. The molecular responses that the stressors triggered were tentatively identified and related to phenotypic responses, such as the delayed development manifested through the delayed emergence of caddisflies exposed to stress. Overall, our study provides valuable insights into the adverse effects of microplastics on aquatic species, compares the impacts of microplastics on freshwater biota to those of pharmaceuticals and endocrine disrupting compounds, and demonstrates the role aquatic organisms have in redistributing microplastics between aquatic and terrestrial ecosystems.

Exposure to microplastics induces lower survival, oxidative stress, disordered microbiota and altered metabolism in the intestines of grass carp (Ctenopharyngodon idella)

There are major gaps in illustrating the risk to freshwater fish that are exposed to environmental microplastics (MPs), even though MPs in freshwater environments has drawn much concern. To explore the potentially negative effects of microplastics on freshwater fish, grass carp (averaging 9.215 ± 0.035g) were exposed to microplastics (32–40 μm in diameter) at two environmental concentrations (100 and 1000 μg/L) for 21 days, and evaluated for physio-biochemical performance, gut microbiome, and metabolome responses. After exposure, microplastics were detected in the intestine and within basal nuclei and goblet cells hyperplasia. Antioxidant enzyme activities (superoxide dismutase and catalase) also significantly decreased within the intestines (P < 0.05). Through 16S rRNA gene sequencing analysis, a decrease in diversity and richness was observed in the MPs-H and MPs-L groups. The abundance of opportunistic pathogens increased and beneficial bacteria decreased in both MP treatments. For example, Acinetobacter and Bosea proportions were higher in the MPs-L group, while Bacteroides and Shewanella increased in the MPs-H group. Furthermore, abundance of Lactobacillus decreased both in the MPs-H and MPs-L groups. Metabolomics analysis revealed primary bile acid biosynthesis metabolism upregulated in the MPs-L and purine metabolism downregulated in the MPs-H group. Additionally, an integration analysis of the gut microbiome and metabolomics identified significant associations between several bacteria taxa and metabolites related to intestinal repair. Taken together, these results highlighted the negative effects on intestinal morphology, oxidative stress, and microbiome and emphasized the relationship between microbiota and metabolites in response to microplastics, which could provide comprehensive insights into the potential risks of MPs on freshwater fish intestines.

Microplastics in freshwater environment: the first evaluation in sediment of the Vaal River, South Africa

Microplastic pollution has become an environmental concern worldwide. In this study, the occurrence, abundance, and composition of microplastics (MPs) in sediment of the Vaal River, South Africa were assessed. Twenty-five sediment samples were collected from the Vaal River using a Van Veen grab sampler, samples underwent digestion, density separation, and filtration prior to physical and chemical analysis. Following the extraction, potential MPs were visually identified under a Nikon stereomicroscope, aided by chemical characterization using Raman spectroscopy. The results revealed 100% prevalence in sediment samples, with an average abundance of 463.28 ± 284.08 particles/kg_dw. Small-sized MPs of 2 mm and less were the most abundant, representing more than 82% of the total particles. Fragments and coloured MPs were the most dominant compared to other shapes and transparent particles, accounting for 63% and 60%, respectively. Microplastics were identified as polyethylene (PE) (both high and low density), polypropylene (PP), and polyethylene co-vinyl acetate (PEVA), polyester (PES), polyurethane foam (PU), and polyethylene/hexene-1-copolymer (PEH). These findings reveal elevated levels of MP contamination within the Vaal from secondary sources. Potential sources include wastewater effluent, anthropogenic activities, surface run-off from urban centres, inflow from tributaries, and recreational activities.

Assessment of microplastic contamination in the urban lower Chao Phraya River of Bangkok city, Thailand.

Rivers are one of the major pathways for the transportation of microplastics (MPs) from land-based sources to the ocean. However, there are only a few studies on MPs in freshwater environments, particularly in Asian countries. In this study, MP contamination in the Chao Phraya River in selected locations distributed throughout Bangkok, Thailand was investigated. MPs were collected using a Manta net with a mesh size of 335 μm. After digestion and distinction based on density, MPs were observed using a stereomicroscope, and polymer types were identified using Fourier Transform Infrared Spectroscopy. MP concentrations detected in the five sampling locations of the river water from upstream to downstream were 11, 35, 40, 15, and 4 particles/m3, with an average concentration of 21±16 particles/m3. Most MPs were identified as either fragments or sheets/films. Polypropylene was the dominant polymer type. The number of MPs increases as their size decreases. Potential sources of MPs may include the degradation of single-use plastic products, especially containers and plastic packaging. MP concentrations and characteristics varied for different locations, indicating different sources and pathways of MPs in urban contexts. Further investigation on the different pathways of the transportation of MPs to river water from land-based sources is required.

Distribution and migration characteristics of microplastics in farmland soils, surface water and sediments in Caohai Lake, southwestern plateau of China

Microplastics (MPs) have become a new environmental pollution problem of global concern, and there are relatively few studies on the migration pattern of MPs in farmland soils, water and sediments in lake ecosystems. To address the abovementioned issues, the present study investigated the relative abundances and morphological distributions of MPs in water, sediments and farmland soils in the Caohai Lake region. The order of the relative MP abundance distribution in the Caohai Lake region was farmland soils (3000–8640 n/kg), freshwater estuarine sediments (3300–4260 n/kg), lake sediments (1320–4260 n/kg), freshwater estuarine water (3.4–12 n/L) and lake water (4.6–10.1 n/L). It was indicated that the estuary in study area, as a key point in the whole transportation process of MPs, and was considered as a "potential sink" of MPs. The MPs that were detected in this study were divided into four types, inclusive of fibers, pellets, fragments and films. Transparent and black MPs accounted for large proportions of the MPs in the five environments, and their possible sources were mulching films, greenhouse films, shopping bags and woven bags. The proportions of MPs with particle sizes of 0–0.5 mm for the studied locations was farmland soils (85.74% ± 6.10%) > lake sediments (84.70% ± 7.04%) > freshwater estuarine sediments (79.12% ± 2.99%) > freshwater estuarine water (73.52% ± 14.41%) > lake water (73.46% ± 11.00%), and it was exhibited that most of MPs cracking occurs in the farmland. In the present study, the relative abundance of MPs was a weak correlation with the physical and chemical indices in farmland soils and water bodies in the Caohai Lake region. The relative abundance of MPs was positively correlated with total organic carbon, total nitrogen, total phosphorus and alkali hydrolysed nitrogen in the sediments. Our investigation suggested that the MPs in farmland soils were mainly derived from plastic film and domestic sewage and that estuarine water is the first temporary carrier of MPs after they enter the water environment. These findings provide a theoretical reference for the treatment of MPs in freshwater environments.