Impact of coastal wastewater treatment plants on microplastic pollution in surface seawater and ecological risk assessment

Distribution characteristics and ecological risk analysis of microplastics in sediments and effluents related to offshore oil and gas activities in the Bohai Sea, China

Oil and gas activities are sources of marine microplastics (MPs) but have received less attention globally. This study assessed the distribution characteristics and ecological risks of MPs in 31 sediment samples and effluent samples of 5 oil and gas platforms related to offshore oil and gas activities in the Bohai Sea. The results showed that the mean abundance of MPs in sediment, produced water, and domestic sewage was 205.7 ± 151.5 items/kg d.w., 18 ± 11 items/L, and 26 ± 39 items/L, respectively. The MPs in sediments and effluents were dominated by transparent, rayon, and fibers <1 mm. Oil and gas activities may influence the abundance of MPs in the sediments. The sediments in the area were at a low level of risk, but some samples exhibited indexes beyond low levels. The mass of MPs carried by the effluents from oil and gas platforms in the Bohai Sea was less than that of other sources.

Treating wastewater for microplastics to a level on par with nearby marine waters

Retention of microplastics (MPs) at the third largest wastewater treatment plant (WWTP) in Sweden was investigated. The plant is one of the most modern and advanced of its kind, with rapid sand filter for tertiary treatment in combination with mechanical, biological, and chemical treatment. It achieved a significantly high treatment efficiency, which brought the MP concentration in its discharge on par with concentrations measured in marine waters of the same region. This novel data shows that properly designed modern WWTPs can reduce the MP content of sewage down to background levels measured in the receiving aquatic environment. Opposite to current understanding of the retention of MP by WWTPs, a modern and well-designed WWTP does not have to be a significant point source for MP. MPs were quantified at all major treatment steps, including digester inlet and outlet sludge. MPs sized 10-500 µm were analyzed by a focal plane array based micro-Fourier transform infrared (FPA-µFTIR) microscopy, a hyperspectral imaging technique, while MPs above 500 µm were analyzed by Attenuated Total Reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Mass was estimated from the hyperspectral images for MPs <500 µm and from microscope images >500 µm. The overall treatment efficiency was in terms of MP counts 99.98 %, with a daily input of 6.42 × 1010 and output of 1.04 × 107 particles. The mass removal efficiency was 99.99 %. The mechanical part of the treatment, the pre-treatment, and primary stages, reduced both the MP counts and mass by approximately 71 %. The combined biological treatment, secondary settling, and final polishing with rapid sand filtration removed nearly all the remaining 29 %. MPs became successively smaller as they passed the different treatment steps. The digester inlet received 1.04 × 1011 MPs daily, while it discharged 9.96 × 1010 MPs, causing a small but not significant decrease in MP counts, with a corresponding MP mass reduction of 9.56 %.

Evaluation of the coordinated development level in the coastal eco-environmental complex system: A case study of Jiaozhou Bay, China

Given the exponential population growth and remarkable socio-economic advancements, coastal areas face increasingly complex challenges in eco-environmental management due to anthropogenic pressures. With the current emphasis on high-quality economic development, there is an urgent need to establish and evaluate a comprehensive indicator system to ensure the sustainable development of the coastal eco-environment and to meet evolving management demands. Research on the coordinated development level of coastal eco-environmental complex system, based on the concept of land-sea coordination, plays a pivotal role in promoting the resolution of eco-environmental issues in coastal areas, achieving sustainable socio-economic development in these regions. In this study, we construct an indicator system for the eco-environmental complex system in Jiaozhou Bay (JZB) coastal zone, China, comprising six sub-systems and thirty indicators. The comprehensive development level and coupling coordination degree model (CCDM) are employed in this study to analyze the indicator system in 1980-2020, aiming to elucidate the processes involved in the improvements in this complex system. The findings indicate: (i) the system's comprehensive development level evaluation and coupling coordination degree (CCD) exhibit a two-stage pattern: a declining trend in 1980-2005, followed by a rising trend in 2005-2020. (ii) despite improvements, the comprehensive development level and the CCD of the system in 2020 still hold potential for further enhancement compared to 1980; and (iii) policymaking and changes in anthropogenic pressures in coastal areas are the primary factors influencing the performance of the system. In the future, policymaking can reduce anthropogenic pressures on the coastal eco-environment, improve the comprehensive development level and CCD of the complex system, and encourage a commitment to sustainable development.

Probabilistic risk assessment of microplastics on aquatic biota in coastal sediments

As an emerging form of pollution, microplastic contamination of the coastal ecosystems is one of the world's most pressing environmental concerns. Coastal sediments have been polluted to varying degrees by microplastics, and their ubiquitous presence in sediments poses a threat to marine organisms. However, there is currently no ecological risk assessment of microplastics on aquatic biota in sediments. This study, for the first time, established a new procedure to evaluate the toxicity of microplastics on aquatic biota in sediments, based on the probabilistic risk assessment (PRA) concept. The choice of Zhelin Bay as the case study site was based on its severe pollution status. The average content of microplastics in the sediments of Zhelin Bay was 2054.17 items kg-1 dry weight, and these microplastics consisted of 46 different species. Microplastics in sediments exist in five different forms, with the film form being the main composition, and the majority of microplastics have particle sizes ranging from 100 to 500 μm. Correlation analysis (CA) reveals significant negative correlations between microplastic abundance, and Al2O3 and SiO2. The toxicity of microplastics, based on the PRA concept, suggests that Zhelin Bay surface sediments had a low probability (3.43%) of toxic effects on aquatic biota.

Effects of microplastics on microbial community dynamics in sediments from the Volturno River ecosystem, Italy

In this study, the sources, abundance, and ecological implications of microplastic (MP) pollution in Volturno, one of the main rivers in southern Italy, were explored by investigating the MP concentration levels in sediments collected along the watercourse. The samples were sieved through 5- and 2-mm sieves and treated with selective organic solvents. The polymer classes polystyrene (PS), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polycarbonate (PC), nylon 6 (PA6), and nylon 6,6 (PA66) were quantified using pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) and high-performance liquid chromatography (HPLC). Furthermore, a 16S rRNA metagenomic analysis was performed using next-generation sequencing in Ion Torrent™ to explore the bacterial taxonomy and ecological dynamics of sediment samples. The MPs were detected in all samples collected from the study area. PP and PET were the most abundant and frequently detected polymer types in the analysed samples. The total MP concentration ranged from 1.05 to 14.55 ppm (parts per million), identifying two distinct data populations: high- and low-MP-contaminated sediments. According to the Polymer Hazard Index (PHI), MP pollution was categorised as hazard levels III and IV (corresponding to the danger category). Metagenomic data revealed that the presence of MPs significantly affected the abundance of bacterial taxa; Flavobacteraceae and Nocardiaceae, which are known to degrade polymeric substances, were present in high-MP-contaminated sediments. This study provides new insights into the ecological relevance of MP pollution and suggests that microorganisms may serve as biomarkers of MP pollution.

Analysis of microplastics in ships ballast water and its ecological risk assessment studies from the Persian Gulf

Transport of ballast water is considered a significant vector for dispersion of different pollutants, including microplastics (MPs), throughout the world's oceans. However, there is limited information on MPs in ballast water. Size distribution, polymer type, and ecological risks of MPs in ballast water were investigated for the first time in this study. The mean levels of MPs in ballast water and seawater samples were 12.53 and 11.80 items/L, respectively. MPs with a size category of 50-300 μm was the most abundant. Fiber, black, and polycarbonate (PC) were the predominant shape, color, and polymer type of identified MPs in ballast water and seawater, respectively. The pollution load index (PLI), hazard index (HI), and risk quotient (RQ) indicated high levels of MP pollution, potentially indicating an ecological risk. These findings increase our understanding of the major sources (such as ballast water), transportation routes, and related ecological risks of MPs to marine ecosystems.

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.

Characteristics and seasonal variation of microplastics in the wastewater treatment plant: The case of Bursa deep sea discharge

Microplastics (MPs) are an emerging pollutant that can be detected in all ecosystems, especially aquatic ecosystems. Wastewater treatment plants (WWTPs) are important point sources of MP release into the sea. In this study, the characteristics of MPs in wastewater and sludge samples taken from different units of WWTP in Bursa-Gemlik district for 12 months were investigated. Wastewater and sludge samples collected from 7 different points were classified as size, shape, color, and counted. The amount of MP in the influent and effluent of the WWTP, respectively; 107.1 ± 40.2 MP/L and 4.1 ± 1.1 MP/L. Although the MP removal efficiency of the WWTP is 96.17 %, approximately 74,825,000 MP is discharged into the Marmara Sea every day. The amount of MP in the sludge is 14.3 ± 7.1 MP/g. The amount of MP accumulated in 22tons of waste sludge formed daily in WWTP was calculated as 314,600,000 MP, and the annual accumulated amount was calculated as approximately 1.15 × 1011 MP. The MPs in the WWTP were mainly 1-0.5 mm in size. Fibers were the dominant MP shape in both the wastewater and sludge samples. Black and transparent were the dominant MP colors. Seven different polymer types of MPs were detected, which were mainly types of polyethylene, polypropylene, and polyethylene terephthalate. Despite the high removal efficiency in the investigated WWTP, it has been shown that it acts as an important source of MPs to the sea ecosystem due to the high discharge rates.

Risk assessment of microplastic pollution in an industrial region of Bangladesh

Despite the high potential for microplastics (MPs) pollution in Bangladesh, the presence of MPs in the industrial region has largely been unexplored in Bangladesh. So, this study was conducted to determine whether MP pollution is prevalent in the industrial soil of Bangladesh and the extent of its toxicity. To examine MPs, a total of 12 soil samples were collected from the industrial region of Narayanganj, and a stereoscopic microscope was used to visually identify the MPs. Prior to that the technique of density separation and sieving was applied to extract MPs from those 12 soil samples. Among the twelve investigated samples, a total of 151 MPs (Mean: 12.6 ± 7.9 particles kg^-1) were identified, which were mostly white and ranged in size from 0.5 to 1 mm. Different types of MPs according to their shapes such as fibers (60.3%), fragments (19.2%), films (10.6%), and foam (9.9%) have been detected. 7 MPs (Mean: 0.58 ± 0.79) have been found in 3 urban farmland sites, 15 MPs (Mean: 1.87 ± 1.81) in two near metropolitan areas, and 129 MPs (Mean: 4.6 ± 4.39) in 7 industrial locations. Five polymers were identified by μ-FTIR, among which Polyamide predominated, followed by Polypropylene. According to risk assessments, the region falls under hazard categories II and III, suggesting a moderate to high risk. This paper gives thorough information on the toxicity of MP in an industrial location; therefore, it may be useful in the development of effective methods to address environmental issues.

Kıyı Lagün Sedimentlerinde Mikroplastiklerin Oluşumları ve Mekansal Dağılımları: Küçükçekmece Lagünü Örneği

Nehir, haliç ve lagünler, karasal ve deniz ekosistemleri arasında bağlantıyı sağlarken, tıpkı diğer kirleticilerde olduğu gibi sediment yapılarında da mikroplastik kirliliği hakkında kapsamlı bir profil ortaya koymaktadır. Bu çalışmada, Küçükçekmece Lagünü’nün üç farklı sucul alanından (deniz, kanal ve göl) alınan sediment örneklerinde mikroplastik bolluğu ve karakterizasyonunun belirlenmesi amaçlanmıştır. Bu kapsamda, lagünde belirlenen 5 istasyondan 12 aylık (Mart 2019 – Şubat 2020) sediment örnekleri alınmıştır. Mikroplastik ön işlemlerine tabi tutulan sediment örneklerinde, stereomikroskop ile mikroplastik bolluğu sayımı ve kategorizasyonu (boyut, tip ve renk) yapılmıştır. Ortalama mikroplastik bolluğu 2922,32±517,35 MP/kg olarak belirlenmiş olup, tespit edilen ortalama mikroplastik bolluğu değeri, ülkemizde daha önce yapılmış benzer çalışmalara kıyasla 2,4 kat daha yüksek bulunmuştur. Liflerin (%59) baskın mikroplastik tipi olduğu, baskın mikroplastik renginin siyah (%42) olduğu ve MP boyutlarının %50’sinin 1-100 μm arasında olduğu belirlenmiştir. Mevsimsel mikroplastik dağılımı irdelendiğinde ise, en yüksek bolluk değerlerinin yağışlı sezon olan kış aylarında olduğu tespit edilmiştir. Çalışma alanında en yüksek ortalama mikroplastik bolluğuna sahip L1 istasyonu, Küçükçekmece Lagünü Bağlantı Alanı temsil etmekte olup, lagündeki tüm antropojenik baskıların hissedildiği istasyon olarak ortaya çıkmaktadır. Bu çalışma, dünyanın diğer bölgelerindeki benzer sediment alanları için mikroplastik bolluğu ve dağılımı hakkında temsili veriler sağlamayı amaçlamaktadır.

Prevalence of microplastics in commercially sold soft drinks and human risk assessment

Due to the increasing global plastic production and use in recent years, the amount of microplastic (MP) accumulating in the environment has also increased. This microplastic pollution potential has been documented mostly in studies of the sea or seafood. The presence of microplastics in terrestrial foods has therefore attracted less attention, despite the potential for future major environmental risks. Some of these researches are related to bottled water, tap water, honey, table salt, milk, and soft drinks. However, the presence of microplastics in soft drinks has not yet been evaluated in the European continent, including Türkiye. Hence, the current study focused on the presence and distribution of microplastics in ten soft drink brands in Türkiye since the water utilized in the bottling process of soft drinks originates from different water supply sources. Using FTIR stereoscopy and stereomicroscope examination, MPs were detected in all of these brands. According to the microplastic contamination factor (MPCF) classification, 80% of the soft drink samples indicated a high level of contamination with microplastics. The study's findings showed that each liter of consumed soft drinks exposes people to about nine microplastic particles, which is a moderate dose when compared to exposure levels in earlier research. It has been determined that bottle-production processes and the substrates used for food production may be the main sources of these microplastics. The chemical components of these microplastic polymers were polyamide (PA), polyethylene terephthalate (PET) and polyethylene (PE), and fibers were the dominant shape. Compared to adults, children were subjected to higher microplastic loads. The study's preliminary data on MP contamination of soft drinks may be useful for further evaluating the risks exposure to microplastics poses to human health.

Plastic occurrence in fish caught in the highly industrialized Gulf of İzmit (Eastern Sea of Marmara, Türkiye)

Occurrence of micro- (<5 mm) and mesoplastics (5-25 mm) in twelve fish species caught off Gulf of İzmit in the Sea of Marmara was investigated. Plastics were found in the gastrointestinal tracks of all the analysed species: Trachurus mediterraneus, Chelon auratus, Merlangius merlangus, Mullus barbatus, Symphodus cinereus, Gobius niger, Chelidonichthys lastoviza, Chelidonichthys lucerna, Trachinus draco, Scorpaena porcus, Scorpaena porcus, Pegusa lascaris, Platichthys flesus. From a total of 374 individuals examined plastics were found in 147 individuals (39%). The average plastic ingestion was 1.14 ± 1.03 MP. fish^-1 (considering all the analysed fish) and 1.77 ± 0.95 MP. fish^-1 (considering only the fish with plastic). Fibres were the primary plastic types found in GITs (74%), followed by films (18%) and fragments (7%), no foams and microbeads were found. A total of ten different colours of plastics were found with blue (62%) being the most common colour. Length of plastics ranged from 0.13 to 11.76 mm with an average of 1.82 ± 1.59 mm. A total of 95.5% of plastics were microplastics, and 4.5% as mesoplastics. The mean frequency of plastic occurrence was higher in pelagic fish species (42%), followed by demersal (38%) and bentho-pelagic species (10%). Fourier-transform infrared spectroscopy confirmed that 75% of polymers were synthetic with polyethylene terephthalate being the most common polymer. Our results indicated that carnivore species with a preference for fish and decapods were the highest impacted trophic group in the area. Fish species in the Gulf of İzmit are contaminated with plastics, representing a potential risk to ecosystem and human health. Further research is needed to understand the effects of plastic ingestion on biota and possible pathways. Results of this study also provide baseline data for the implementation of the Marine Strategy Framework Directive Descriptor 10 in the Sea of Marmara.