Size-selective microplastic uptake by freshwater organisms: Fish, mussel, and zooplankton

In vitro and in vivo effects of commercial and environmental microplastics on Unio delicatus

Microplastics (MPs) are ubiquitous pollutants in freshwater environments. In this study, freshwater mussels, Unio delicatus, were exposed to both environmental MPs (e-MP) and commercial MPs (c-MP) that include green fluorescent MP (gf-MP), polyethylene (c-PE) and polystyrene (c-PS) at environmental concentrations (5 mg/L and 50 mg/L) over duration of 7 and 30 days. According to in vivo experiment results, both e-MPs and c-MPs induced significant changes in the total hemocyte counts of mussels (p < 0.05). Exposure to high concentrations of e-MPs and c-MPs for 7 days led to decreased cellular glutathione levels in the mussels, while exposure to low concentrations of e-MPs and c-PS for 7 days resulted in increased advanced oxidation protein products (AOPP). Mussels exposed to high concentrations of e-MPs for 30 days exhibited decreases in both glutathione levels and AOPP values. Although no damage was observed in tissues other than gills and digestive gland, histopathological alterations were observed in these tissues following exposure to 50 mg/L c-MPs. Additionally, MPs were observed in the intestine tissues. In vitro experiments using the MTT assay showed no significant difference in cell viability between the MP-exposed group and the control group at tested concentrations, with no observed dose-response relationship (p > 0.05). Nevertheless, certain cells exhibited signs of cell death, such as disrupted cellular structures, condensed nuclei, and loss of cellular integrity. These observations were consistent with mechanical compression, indicating that physical contact with MPs may result in cell damage or death. These findings demonstrate that environmentally relevant concentrations of MPs have toxic effects on freshwater mussels and multiple parameters provide valuable insight for the evaluation of health risks of organisms.

Microplastics and microfibers contamination in the Arno River (Central Italy): Impact from urban areas and contribution to the Mediterranean Sea

Fluvial ecosystems are among the main drivers of microparticles (MPC) in the form of both synthetic polymers (i.e. microplastics; MPs) and natural-based textile fibers (MFTEX) to the seas. A wide dimensional range of MPC (5 to 5000 μm, hereafter MPCTOT) were investigated for the first time in the Arno River waters, one of the principal rivers of Central Italy, crossing a highly anthropized landscape. Fluxes of MPCTOT discharging to the Mediterranean Sea, one the most polluted Sea worldwide, were estimated as well. A specific sampling and analytical protocol was set up to distinguish between microplastics (MPs) and natural-based textile fibers (MFTEX) contribution for MPC larger than 60 μm (MPC>60), and investigate MPC smaller than 60 μm (MPC<60) as well. Results suggest extreme MPCTOT contamination all along the river (up to 6 × 104 particles/L), strongly driven by MPC<60, which account for >99 % of total particles found and whose abundance increases inversely with particle size. The MPC>60 fraction (<0.5 % of MPCTOT) highlighted a predominance (76 % of the total) of MFTEX and synthetic polymers microfibers (e.g., PET) suggesting strong contributions from laundry effluents. Specifically, MFTEX represent around 70 % of all MPC>60. The metropolitan area of Florence was identified as an MPCTOT hotspot as a consequence of the intense urbanization and possibly of over-tourism phenomenon affecting the city. The Arno River discharges approximately 4.6 × 1015 MPCTOT annually to the Mediterranean Sea. Fluxes are highly dependent on the seasonality, with a MPCTOT delivery of 2.4 × 1013 particles/day and 1.2 × 1012 particles/day during wet and dry season, respectively. The total mass of discharged MPCTOT is estimated at about 29 tons/year (t/y); the MPC>60 fraction amounts to about 8 t/y, and MFTEX to about 1 t/y.

Determination of Seasonal Microplastic pollutıon Variation in Aquatic Environments: Case Study from İskenderun Technical University Pond

Although microplastic (MP) pollution in aquatic ecosystems has been a critical issue, a significant portion of previous studies has been limited to marine environments. Few studies have evaluated MP abundance in inland waters, and those that exist often ignore seasonal variations. This study aimed to assess the seasonal variations in microplastic (MP) abundance in the İskenderun Technical University (İSTE) Pond. MP abundance ranged from 0.5 MPs/L to 10.8 MPs/L, with a mean of 3.7 MPs/L. Fiber-shaped, black-colored, small-sized (< 1000 μm) MPs were commonly found on the surface water. Statistical analysis confirmed significant variations in MP abundance across seasons. The abundance of MPs in the surface water correlated with the mean annual precipitation. Atmospheric deposition and storm water runoff were major contributors to microplastic pollution in the pond. PP and PET particles were identified. The findings of this study contains preliminary results that can be used in the development of future legislations and regulations.

Recycle or Not? An Exploration of Microplastic Generation During Plastic Processing via a Local Case Study

Microplastic (MP), an emerging pollutant, has been identified as a critical target in tackling plastic pollution. Although a plethora of studies have explored MP generation from various sources, limited attention has been paid to plastic processing. This study investigated MP (10 μm-5 mm) generation in virgin and waste plastic extrusion processing. MPs at a density of 2.13 × 105-9.79 × 107 (approximately 0.01-10.85 g) were generated when processing 1 t of plastic. Feedstock sources, polymer types, and pelletizing techniques were found to influence the process. With a moderate weight (270.58-527.34 t) but enormous amount (1.34 × 1016-2.63 × 1016) of MPs generated globally in 2022, plastic processing is an underestimated but vital source of MPs, emphasizing the need for MP inspection and appropriate removal technologies in the industry, especially for virgin plastic processing and water ring pelletizing. Further simulation indicated that up to 84.35% of MPs could be removed using commonly available materials in the investigated plastic processing facility, with a higher removal efficiency for larger-sized particles. In this regard, plastic recycling was superior to virgin plastic processing with fewer and larger-sized MPs generated, which could facilitate MP removal and should be fostered.

Enrichment characteristics of microplastics in Antarctic benthic and pelagic fish and krill near the Antarctic Peninsula

Global microplastic pollution has garnered widespread attention from researchers both domestically and internationally. However, compared to other regions worldwide, little is known about microplastic pollution in the marine ecosystems of the Antarctic region. This study investigated the abundance and characteristics of microplastics (MPs) in the gills and intestines of 15 species of Antarctic fish and Antarctic krill (Euphausia superba). The results indicate that the abundance of MPs in Antarctic fish and E. superba ranged from 0.625 to 2.0 items/individual and 0.17 to 0.27 items/individual, with mean abundances of 0.93 ± 0.96 items/individual and 0.23 ± 0.44 items/individual, respectively. Antarctic fish ingested significantly more MPs than E. superba. There was no significant difference in the abundance of MPs between the gills and intestines of Antarctic fish. However, the quantity of pellet-shaped MPs in the gills was significantly higher than in the intestines. The depth of fish habitat influenced the quantity and size of MPs in their bodies, with benthic fish ingesting significantly fewer MPs than pelagic fish. Pelagic fish ingested significantly more MPs sized 1-5 mm than benthic fish. Additionally, analysis of the characteristics of MPs revealed that fiber-shaped MPs were predominant in shape, with sizes generally smaller than 0.25 mm and 0.25-0.5 mm. The predominant colors of MPs were transparent, red, and black, while the main materials were polypropylene (PP), polystyrene (PS), polyamide (PA), and polyvinyl chloride (PVC). Compared to organisms from other regions, the levels of MPs in Antarctic fish and E. superba were relatively low. This study contributes to a better understanding of the extent of MP pollution in Antarctic fish and E. superba, aiding human efforts to mitigate its impact on the environment.

From the highway to receiving water bodies: identification and simultaneous quantification of small microplastics (< 100 µm) in highway stormwater runoff

Highway stormwater (HSW) runoff is among the environment's most important sources of microplastics. This study aimed to characterize via vibrational spectroscopy and quantify SMPs (small microplastics < 100 µm) in HSW runoff from a trafficked highway entering a facility equipped with a filtration system and in those flowing out to the receiving water body near agricultural activities. Samples of the inlet runoff (from the highway) and outlet runoff (the discharge into the environment) were collected in different periods to investigate potential seasonal and spatial differences. The sampling, methodology, and analysis were thoroughly carried out to quantify and simultaneously identify SMPs via Micro-FTIR to obtain a specific novel dataset to assess the environmental quality of highway pollution. A significant difference between inlet and outlet samples was reported; the highest abundance in inlet samples was 39813 ± 277 SMPs L.1 (SW10 IN; average length of 77 µm), while the highest one in outlet samples was 15173 ± 171 SMPs L-1 (SW10 OUT; SMPs' average length of 63 µm). Polyamide 6 (PA 6) and High-Density Polyethylene (HDPE) were predominant. Our results show that these HSW treatment plants, designed for managing regulated pollutants, can intercept SMPs, improving the quality of HSW runoff discharged into the environment.

Microplastics in different tissues of historical and live samples of endangered mega-fish (Acipenser sinensis) and their potential relevance to exposure pathways

The Chinese sturgeon (Acipenser sinensis) is an endangered freshwater mega-fish (IUCN-red listed) that survives in the Yangtze River Basin, but the population of which has declined significantly in response to environmental pressures generated by human activities. In order to evaluate the interaction between Chinese sturgeon and microplastics (MPs) for the first time, we examined the gut and gills of historical samples (n = 27), in conjunction with the blood and mucus of live samples (n = 10), to explore the potential pathways involved in MP uptake. We detected MPs in 62.9 % of the field fish, with no significant difference between guts (mean=0.9 items/individual) and gills (mean=0.8 items/individual). The abundance of MPs in fish from 2017 was significantly higher than that from 2015 to 2016 with regards to both gills and gut samples. The size of MPs in gills was significantly smaller than those in guts, yet both contained mostly fibers (90.2 %). No MPs were confirmed in blood, however 62.5 % of mucus samples contained MPs. The MPs in mucus indicated the possibility of MPs entering Chinese sturgeons if their skins were damaged. The body size of Chinese sturgeons affected their MPs uptake by ingestion and inhalation, as less MPs were detected in the gut and gills of smaller individuals. Combining the evidence from historical and live samples, we revealed the presence of MPs in different tissues of Chinese sturgeon and their potential relevance to exposure pathways. Our work expands the understanding of multiple exposure pathways between MPs and long-lived mega-fish, while emphasizing the potential risks of long-term exposure in the field.

Effects of different concentrations and particle sizes of nanoplastics on gut microbiology, metabolism, and immunity in Chiromantes dehaani

This study investigated the effects of nanoplastics (NPs) of varying particle sizes (75, 500, and 1000 nm) and concentrations (2.5 and 10 mg/L) on the gut health of Chiromantes dehaani. The experimental groups included a control (Cg0), and varying combinations of particle size and concentration. Our results showed that 75 nm NPs were more likely to enhance pathogenic bacterial growth than other sized NPs. Compared with CK, Low NPs concentrations (2.5 mg/L) raised total cholesterol (T-CHO) levels in the gut, while high concentrations significantly decreased both triglyceride (TG) and T-CHO levels (p < 0.05). The enzymatic activities of intestinal lipase and amylase were inhibited by NPs exposure, with greater inhibition at higher NPs concentrations. The 500 nm NPs exhibited a notably higher inhibitory effect than the 75 and 1000 nm NPs (P < 0.05). In terms of apoptosis, NPs exposure led to reduced mRNA expression of Bcl2 and increased expression of Caspase-3, Caspase-8, and Caspase-9, indicating an induction of apoptosis. This effect was more pronounced at higher NPs concentrations, with 75 nm NPs more likely to induce apoptosis in intestinal cells than 500 nm and 1000 nm NPs. Moreover, NPs triggered intestinal inflammatory responses, evidenced by the increased mRNA expression of TNF-β, TNF-α, IL1β, IL6, and IL8, and the decreased expression of IL10. High NPs concentrations were more likely to induce intestinal inflammation, with 500 nm NPs imparting the strongest effect. In summary, the study demonstrated that NPs, and particularly those at higher concentrations, disrupted the gut environment of C. dehaani by altering the microflora, reducing microbial diversity, inhibiting digestion and metabolism, inducing apoptosis, and triggering inflammation. Among the sizes of NPs tested, 500 nm NPs had the most significant adverse impact on digestion, metabolism, and inflammation, while 75 nm NPs most strongly induced apoptosis in C. dehaani's intestinal cells.

Distribution and characteristics of microplastics in 16 benthic organisms in Haizhou Bay, China: Influence of habitat, feeding habits and trophic level

Microplastics (MPs) are widely found in the ocean and cause a serious risk to marine organisms. However, fewer studies have been conducted on benthic organisms. This study conducted a case study on the pollution characteristics of MPs on 16 marine benthic organisms in Haizhou Bay, and analyzed the effects of habitat, trophic level, and feeding mode on the MPs pollution characters. The results showed that MPs were detected in all 16 organisms with an average abundance of 8.84 ± 9.14 items/individual, which is in the middle-high level in the international scale. Among the detected MPs, the main material was cellophane. This study showed that benthic organisms can be used as indicator organisms for MPs pollution. MPs in organisms can be affected by their habitat, trophic level, and feeding mode. Comprehensive analysis of MPs in benthic organisms will contribute to fully understand the characterization and source resolution of MPs pollution.