Microplastic emission trends in Turkish primary and secondary municipal wastewater treatment plant effluents discharged into the Sea of Marmara and Black Sea

The abundance, removal efficiency, and characteristics of microplastics in three urban wastewater treatment plants (WWTPs) on the southern coast of the Caspian Sea

Wastewater treatment plants (WWTPs) are one of the major collection points of microplastics (MPs). The MPs in influents and effluents of WWTPs were assessed for three cities on the southern coast of the Caspian Sea in the winter and spring seasons. The MP removal rate of WWTPs ranged between 71.12 and 88.13% depending on the season and treatment methods. The higher removal efficiency of MPs in the city of Sari compared to that in the other two cities might be attributed to the implementation of more effective treatment techniques at the Sari WWTP. Our findings showed that the presence of MPs in influents was greater in the spring than in the winter, attributed to the increased usage of personal care and washing products during the COVID-19 lockdown period. Conversely, in effluents, the abundance of MPs was higher in the winter than in the spring, likely due to precipitation and inadequate management of sewage overflows. On average, more than 50% of identified MPs had black/grey and white/transparent colours. The majority of the identified MPs that were found in both the influents and effluents of all three investigated WWTPs were smaller than 500 µm and had a fibre shape. Our findings indicate that removing plastics with a size smaller than 100 µm is more challenging compared to larger-sized plastics in WWTPs. Moreover, a strong correlation was observed between TSS and the abundance of MPs in influents. The predominant types of MP that were identified with spectroscopic analysis in most samples were polyamide (PA), acrylic, polyethylene (PE), polyethylene terephthalate (PET), polystyrene (PS), polyvinyl chloride (PVC), and polypropylene (PP). Based on the results of our study, it can be estimated that a total of 132 × 106 and 223 × 106 MPs are discharged per day from the three investigated WWTPs into aquatic environments that ultimately reach the Caspian Sea in the spring and winter, respectively. Our findings enhance our knowledge about the load of MPs from WWTPs into the Caspian Sea, and it provides a foundation for future discussions on management strategies and the reuse of wastewater.

Research advances of biodegradable microplastics in wastewater treatment plant: Current knowledge and future directions

Plastic and microplastic pollution in the environment has become a significant global concern. Biodegradable plastics (BPs), as environmentally friendly alternatives to conventional plastics, have also emerged as a crucial topic of global discussion. The successful application of BPs appears to offer a solution to the potential ecological risks posed by conventional plastics. However, BPs have negative impacts on the ecological environment and human health. BPs can gradually degrade into biodegradable microplastics (BMPs) in the environment. Wastewater treatment plants (WWTPs) have become an undeniable source and sink of microplastics. With the production and application of BPs, BMPs will inevitably enter WWTPs. This paper reviews the pollution status, degradation behavior of BMPs, and their potential impact on wastewater treatment performance. The focus is on the environmental behavior of BMPs in wastewater treatment systems. The influences of BMPs on microbial communities, sludge treatment, and disposal are thoroughly discussed. The results indicate that BMPs are more easily decomposed into micro/nanoplastics and release additives compared to conventional microplastics. The effects of BMPs on microbial communities and wastewater treatment depend on their characteristics. The numerous oxygen-containing functional groups on the surface of BMPs enable them to serve a dual purpose as transport media and potential sources of environmental pollutants. Finally, in light of existing knowledge gaps, suggestions and prospects for future research on BMPs are proposed.

Occurrence Characteristics and Ecotoxic Effects of Microplastics in Environmental Media: a Mini Review

The issue of environmental pollution caused by the widespread presence of microplastics (MPs) in environmental media has garnered significant attention. However, research on MPs pollution has mainly focused on aquatic ecosystems in recent years. The sources and pollution characteristics of MPs in the environment, especially in solid waste, have not been well-described. Additionally, there are few reports on the ecotoxicity of MPs, which highlights the need to fill this gap. This review first summarizes the occurrence characteristics of MPs in water, soil, and marine environments, and then provides an overview of their toxic effects on organisms and the relevant mechanisms. This paper also provides an outlook on the hotspots of research on pollution characterization and ecotoxicity of MPs. Finally, this review aims to provide insights for future ecotoxicity control of MPs. Overall, this paper expands our understanding of the pollution characteristics and ecological toxicity of MPs in current environmental media, providing forward-looking guidance for future research.

A review of microplastics in wastewater treatment plants in Türkiye: Characteristics, removal efficiency, mitigation strategies for microplastic pollution and future perspective

The effluent of WWTPs is an important source of microplastics (MP) for the aquatic environment. In this review study, MPs in wastewater treatment plants (WWTP) in Türkiye and their removal from WWTPs are reviewed for the first time. First, MP characteristics in the influent and effluent of WWTPs in Türkiye are discussed. In the next section, the abundance of MPs in the influent and effluent of WWTPs in Türkiye and the MP removal efficiency of WWTPs in Türkiye are evaluated. Then, the results of studies on MP abundance and characteristics in Türkiye's aquatic environments are presented and suggestions are made to reduce MPs released from WWTPs into the receiving environments. Strategies for reducing MPs released to the receiving environment from WWTPs of Türkiye are summarized. In the last section, research gaps regarding MPs in WWTPs in Türkiye are identified and suggestions are made for future studies. This review paper provides a comprehensive assessment of the abundance, dominant characteristics, and removal of MPs in WWTPs in Türkiye, as well as the current status and deficiencies in Türkiye. Therefore, this review can serve as a scientific guide to improve the MP removal efficiency of WWTPs in Türkiye.

Monitoring of microplastic pollution in sediments along the Çoruh River Basin, NE Türkiye

Microplastic (MP) pollution has become a research issue on the world agenda. Monitoring studies are essential for MP content in aquatic environments since it is the final accumulation point. The present study focused on MP characterizations in sediment samples taken from 20 different stations on the Çoruh River, the major river in the North East of Türkiye. Accordingly, the potential anthropogenic pollution from settlements near the four stations (2, 15, 18, and 20) exceeding 400 MP kg-1 was estimated. On the other hand, stations (1, 3, 9, 11, and 13) far from settlements with quite low MP abundance were also observed. The polymer structures of the detected MPs are generally PE and PET, and their shapes are mostly fiber. This situation raises suspicion that MPs originate from primary use waste such as water bottles and packaging materials. In general, the fiber MPs are smaller than the fragments because of the river's high water flow rate and the low strength of the fiber MPs. In light of these results, the current monitoring data in the region will create awareness and guidance regarding MP pollution in settlements.

Microplastics in rocky shore mollusks of different feeding habits: An assessment of sentinel performance

Microplastics (MPs) accumulation in rocky shore organisms has limited knowledge. This study investigated MPs accumulation in filter-feeding oysters, herbivorous limpets and carnivorous snails to assess their performance as sentinel species in the MPs trophic transfer. The samples were obtained along a contamination gradient in the Santos Estuarine System, Brazil. All three studied species showed MPs concentrations related to the contamination gradient, being the oysters the species that showed the highest levels, followed by limpets and snails (average of less and most contaminated sites of 1.06-8.90, 2.28-5.69 and 0.44-2.10 MP g-1, respectively), suggesting that MPs ingestion rates are linked to feeding habits. MPs were mainly polystyrene and polyacetal. The polymer types did not vary among sites nor species. Despite minor differences in percentages and diversity of size, shape, and color classes, the analyzed species were equally able to demonstrate dominance of small, fiber, transparent, black and blue MPs. Thus, oysters, limpets, and snails are proposed as sentinels of MPs in monitoring assessments.

Microplastic pollution in stream sediments discharging from Türkiye's eastern Black sea basin

Rivers are the principal route for terrestrial microplastics to reach the marine environment. The Black Sea exhibits a notable representation because it has a drainage zone almost six times the surface area and is semi-closed, meaning that microplastics tend to gather there. To mitigate MP pollution, it is necessary to identify the contamination sources and then raise public awareness. Thus, the current study focused on the MP presence in the sediment of streams running into the SE Black Sea. 594 MPs were observed in sediment samples from 16 stations along the 350 km coastline. The abundance of MP was higher, particularly in streams that pass through locations with high tourism and industrial activity levels. Detected MPs ranged between 0.1 and 5 mm, while the overall density was smaller than 1 mm. Fragments and fiber MPs were regularly detected, although the presence of films was rarely recorded. The polymer structures that were most commonly observed in the analyzed pollutants were PET and PE. The current study uncovered MP contamination in stream sediments originating from Türkiye's Eastern Black Sea basin and might be a baseline work for future inland water studies.

Long-term investigation of microplastic abundance in Squalius species in Turkish inland waters

Examining the enduring alterations in microplastic (MP) concentrations within fish in inland waters is of utmost importance in understanding the historical trajectory of plastic waste and formulating consequential predictions regarding upcoming pollution levels. This study includes the collection of fish samples from 22 different river basins in Türkiye and all Squalius species distributed in Türkiye, covering the years 2004-2018, and examined the presence of MP in museum specimens' gastrointestinal tracts (GITs). 331 specimens were examined, and microplastic was observed in 20.8% (69). A mean value of 0.27 ± 0.19 MP per individual was observed, resulting in a cumulative score of 91 MP. Most observed MPs were composed of fiber, representing 79.1% of the total. The polymer types identified were mostly polyethylene (PE) at 38.5% and polyethylene terephthalate (PET) at 29.7%. The black color was prominent among MPs, and MP length ranged between 101 and 4963 μm. The analysis revealed no statistically significant difference in the mean MP values across different years and basins. There is no substantial correlation between the abundance of MP and the sizes of fish, population density, or quantities of plastic production. The data indicate that MP has persistently acted as a contaminant in freshwater ecosystems over an extended period. It is projected that the laundering of synthetic textiles serves as the primary contributor to MP contamination in freshwater bodies. Our results offer significant baseline data on the pervasive issue of MP pollution in the freshwater environment. These findings enable us to gain profound insights into the current state of MP contamination in fish residing in lotic systems while empowering us to make accurate predictions about its future trajectory.

A characterization and an exposure risk assessment of microplastics in settled house floor dust in Istanbul, Turkey

The presence of microplastics in the indoor environment presents growing environmental and human health risks because of their physicochemical and toxic characteristics. Therefore, we aimed to isolate, identify, and characterize plastic debris in settled house floor dusts. This study is a rare study which assess the risks of plastic debris in settled house dust through multiple approaches including the estimated daily intake, pollution loading index, and polymer hazard index. The results indicated that polyethylene and polypropylene were the predominate polymer type of plastic debris in settled house dust with various shapes and colors. The risk assessment results also indicated the serious impact of microplastics in terms of extremely dangerous contamination as well as the fact that they present a polymer hazard. Results indicated that humans have a higher risk of exposure to microplastics via ingestion rather than inhalation. In addition, infants had a higher risk of potential intake compared to other age groups.

Monthly microplastics change in European anchovy's (Engraulis encrasicolus) gastrointestinal tract in the Black Sea

To contribute to a better understanding of the regional dynamics of MP pollution and its potential effects on the anchovy population and human health, here we assessed the presence and characterization of microplastics (MPs) in European anchovy (Engraulis encrasicolus), which is the most caught/consumed species in the Black Sea and is of vital importance to the ecosystem. A total of 360 individuals (30 per month) were sampled from the eastern Black Sea continental shelf all year round (monthly from September 20 to Aug 21). We extracted and digested the gastrointestinal tracts (GITs) of the samples with H2O2 and characterized the MPs in the GITs by stereomicroscope and ATR-FTIR. MPs varied between 0 and 0.43 MP individual-1. The morphological structure of MPs was composed of 51 % fiber > fragment (32.7 %) > film (12.2 %) > foam (4.1 %) and polymer types as PP (42.9 %) and PE (22.4 %). In the prevalence of MP colors, black (26.5 %) > white (24.5 %) > red (22.5 %) was observed. The mean MP size was 735.32 ± 836.62 μm, with no significant correlation between the abundance and size of ingested MPs and anchovy height/weight and GIT weight. We determined that MP abundance showed substantial differences between the fishing season (0.18 ± 0.05 MP ind-1) and the banned season (0.05 ± 0.03 MP ind-1). It is essential to develop effective waste management strategies to protect the vulnerable marine ecosystems of the Black Sea and ensure sustainable exploitation of living resources in this region. These strategies should be accompanied by robust monitoring and enforcement measures to guarantee their effectiveness and compliance.