High Concentrations Of Microplastics Research Articles

Assessment of Brown Algae (Phaeophyceae) and Sediment Collected from Sanur Coastal Waters Based on Bioaccumulation Factors and Human Health Risks Related to Microplastic Ingestion Exposure

This study aimed to analyze Microplastics (MPs) contamination in brown algae and sediments, and their bioaccumulation factors, and estimate the risk to human health associated with exposure to ingested MPs collected from the water of the Sanur Beach, Bali Province. The samples were collected from three beaches which were determined using a purposive sampling method. The mean number of MPs found in P. australis was the same on all beaches, namely 17 items/seaweed, higher than S. aquifolium on all beaches. Line-shaped MPs were dominantly found in all algae (98.76%). A high percentage of line-shaped MPs was found in sediments at Mertasari and Semawang Beaches, but not at Sindhu Beach. The highest mean size of MPs in algae was found in P. australis at Semawang Beach, and sediments at Mertasari beach. The highest concentrations of MPs were also found in P. australis on the three coasts. The BAF value showed that the absorption of MPs in the sediment to brown algae was still low (<1). Values related to intake of brown algae consumption ranged from 190.58-1429.41 MPs item/week adjusted for calculation recommendations.

Growth inhibition and toxic effects of microplastics on Chlorella vulgaris

Microplastics (MPs) are new pollutants that severely threaten the water environment. This study investigated the effects of three microplastics, namely polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), and polystyrene (PS), on the growth, photosynthesis, biochemical composition, and antioxidant enzyme activity of Chlorella vulgaris. The results show that the average growth inhibition rate of PVC (1000 mg/l) is the highest (29.34 %), followed by PMMA (17.86 %), and PS (13.79 %). The small particle size and high concentration of microplastics are benefited to the inhibitory effect. The increase in soluble proteins within microalgae cells can enhance their water retention capacity and protect cell membranes from mechanical damage and lipid peroxidation caused by microplastics. The decrease in carbohydrate production can be attributed to a decrease in photosynthetic rate and overall physiological activity. The changes in superoxide dismutase and catalase activity can be seen as a defense mechanism for algae cells to maintain antioxidant system balance while removing excess reactive oxygen species.

Effects of groundwater sample volume on identified microplastics in groundwater of an agricultural area in Korea

Groundwater serves various purposes worldwide, including agricultural, drinking, domestic, and industrial uses. In the Republic of Korea, groundwater is used primarily for agricultural purpose. Understanding the quality of groundwater is crucial because microplastics (MPs) can enter groundwater through agricultural activities and potentially pose harm to humans. Therefore, groundwater sampling plays a vital role in determining the presence of MPs. However, the optimal volume of groundwater sampling required for accurate MP assessment remains uncertain. This study examined the optimal sample size for collecting MPs from groundwater in the heavy agricultural area of the Haean Basin, Korea. Groundwater sampling and MP analyses were conducted during the wet and dry seasons of 2022. A total of 500 L of groundwater was continuously sampled in increments of 100 L to 500 L (100, 200, 300, 400, and 500 L). Additionally, we investigated the land use surrounding the sampling wells and the predominant types of plastics used in agriculture. To ensure reliable MP analysis, precautions were taken to minimize plastic contact during sampling, pretreatment, and μ-FTIR analysis. The concentration of MPs in groundwater ranged from 0.04 to 17.77 particles/L during the wet season and from 0 to 0.56 particles/L during the dry season. The highest concentration of MPs was observed at the first 100 L sample volume, with concentrations decreasing as the sampling volume increased. Fragmented particles accounted for 86.3 % during the wet season and 91.5 % during the dry season, whereas fibers constituted 13.7 and 8.5 %, respectively. MPs in the size range of 20–100 μm were predominant in both seasons. The polymers identified in both seasons were polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), and polyamide (PA). While some studies suggest that 500 L is the optimal sample volume for assessing MPs in groundwater, the findings of this study indicate that a larger sample volume may be necessary. This study was the first attempt to determine the optimum sample volume required to collect MPs from groundwater, emphasizing the importance of conducting further research to validate these findings.

Microplastics in the sediments along the eastern Arabian Sea shelf: Distribution, governing factors and risk assessment

Despite the omnipresence of microplastics (MPs), the studies around the western continental shelf of Indian Ocean (Eastern Arabian Sea-EAS) are uncovered and understudied. Thus, the present study was focused to understand the spatial distribution, characterization and risk assessment of MPs in sediment across seven coastal transects (10 to 50 m) all along the EAS shelf. The highest MPs concentration (MPs/kg d.w.) was detected in the northern EAS (NEAS; 2260 ± 1050) followed by central (CEAS; 1550 ± 1012) and southern (SEAS; 1300 ± 513) shelves. Among all distinct locations, the highest concentration of MPs (2500 ± 1042) was detected in the north coastal sediments off Mumbai, followed by off Mangalore (1480 ± 1169) in the center and off Kochi (1350 ± 212) in the south. MPs were found in the form of fibres, fragments and films with a predominance of fibres (~70–80 %). Approximately 74.6 % of the total MPs were in the size range of 300 μm to 5 mm. The surface of detected MPs was rough, irregular, and mechanical weathering features such as pits, grooves also observed and spotted with bacterial community structures. Polypropylene (PP; 34 %), polyisoprene (PIP; 19 %), butyl rubber (18 %), and low-density polyethylene (LDPE; 13 %) were dominant polymers. The pollution load index highlighted minor risk while the polymer hazard index exhibited a hazard level of V. Litter discharge, fishing activities, and active marine navigation are among the many high-risk sources of plastic contamination in this region. Due to the prevailing winds, currents, low sea surface height, and high precipitation, the conditions in the EAS are favorable for the accumulation of both sea-based and land-based particles. Hence, this study provides novel insights into the potential risks posed by MP to the IO rim and associated marine ecosystem which will enhance our knowledge of the ecological implications and consequences of MP pollution, ultimately aiding in developing effective management and mitigation strategies.

Microplastics in commercial fish digestive tracts from freshwater habitats in Northern Thailand

Microplastics (MPs) contamination in fish species was one of the emerging environmental issues as a result of the widespread presence of plastic pollution in the environment. The presence of MPs in Thailand's freshwater was scant, and in contrast to other countries, little was known about the presence of this contaminant in freshwater fish. Hence, the purpose of this study was to examine the abundance, characteristics, and variation of MPs in various Thai commercial freshwater fish species. In order to compare the differences in MP ingestion rates across different feeding zones, 166 fish representing 24 species from various feeding zones were collected. MPs were found in the gastrointestinal tracts (GIT) of all fish samples tested, which was a substantially larger number than previously reported in other locations. Of all the fish species, Anabas testudineus, Labeo rohita, and Oreochromis mossambicus had the highest concentration of MPs (34.90 ± 21.43, 34.50 ± 7.78, 34.10 ± 11.15 items/individuals). Microscopical examinations showed that the majority of MPs were fiber-shaped and blue in color. Fourier transform infrared analysis (FTIR) showed that the polymers found in fish GIT were polyethylene, polypropylene, polyethylene terephthalate, polyvinyl acetate, poly (methyl vinyl ether), poly (methyl vinyl ether), polybutadiene, poly (ethylene-co-propylene), poly (ethylene glycol) tetrahydrofurfuryl ether, poly (methyl phenyl siloxane), poly (styrene-co-divinylbenzene), and polyvinylidene fluoride. The results of this study demonstrate that demersal fish had a higher concentration of MPs than benthopelagic and pelagic fish, indicating that plastic ingestion in fish may be related to the feeding habitat. However, it was not discovered that differences in the fish's body weight and length affected the MPs' ingestion. Our findings will help people in Thailand understand which freshwater fish and fish from which feeding zones are more contaminated with MPs for human consumption.

Physiological responses and molecular mechanism of Chlorella sorokiniana to surgical mask exudates in wastewater

Microalgae-based bioremediation is likely to be challenged by the microplastics (MPs) in wastewater induced by the widely use of surgical masks (SMs) during COVID-19. However, such toxic impact was generally evaluated under high exposure concentrations of MPs, which was not in agreement with the actual wastewater environments. Therefore, this study investigated the microalgal cellular responses to the surgical mask exudates (SMEs) in wastewater and explored the underlying inhibitory mechanism from the molecular perspective. Specifically, 390 items/L SMEs (including 200 items/L MPs which was the actual MP level in wastewater) significantly inhibited nutrient uptake and photosynthetic activities interrupted peroxisome biogenesis and induced oxidative stress which destroyed the structure of cell membrane. Moreover, the SMEs exposure also affected carbon fixation pathways, suppressed ABC transporters while promoted oxidative phosphorylation processes for the ATP accumulation These comprehensive processes led to an 8.5% reduced microalgae growth and variations of cellular biocomponents including lipid, carbohydrate, and protein. The increased carotenoids and consumed unsaturated fatty acid were considered to alleviate the SMEs-induced stress, and the enhanced EPS secretion facilitated the homogeneous aggregation. These findings will enhance current understandings of the SMEs effects in wastewater on microalgae and further improve the practical relevance of microalgae wastewater bioremediation technology.

Microplastic accumulation in oysters: Insights from aquaculture and laboratory conditions

Microplastics, emerging pollutants, are present in seafood and pose a potential health risk to consumers. The objective of this study was to assess microplastic concentrations in the surface water, sediments, and oysters of the Cha Va River, an aquaculture production area in southern Vietnam. Laboratory experiments were also conducted to examine rates of ingestion by and bioconcentration of microplastics in oysters. Microparticles including microplastics were measured in all samples collected from the field, and presented 9–27 items m−3 in surface water, 3300–8000 items kg−1 dry weight in sediments, and 0.67–8.33 items ind−1 or 0.02–0.33 items g−1 wet weight in oysters. Fibre shapes and blue colour were the most common while polypropylene, polyester, polyethylene, and polyethylene terephthalate acrylate, alkyd were identified. The presence of microparticles in surface water and sediment was influenced by the complex vertical motion characteristic of tidal environments whereas the microparticles in natural oysters seemed to be closer related to those in sediment than in the surface water. Laboratory experiments showed that oysters incubated in 10 and 1000 microplastics L−1 tanks accumulated 4.1 ± 2.0 and 19.0 ± 11.0 microplastics per individual, respectively. However, bioconcentration of microplastics in oysters was higher (12.37 ± 6.95) in tanks with lower microplastic concentrations than in tanks with higher microplastic concentrations (0.62 ± 0.35). It is a high potential human health risk to the local oyster-consumers because of the annually microparticle ingestion from 657 to 3942 items per person. We suggested further studies on the severity of this potential health risk and policies for minimising microplastic emissions into the environment in Vietnam.

Assessing stress responses in potherb mustard (Brassica juncea var. multiceps) exposed to a synergy of microplastics and cadmium: Insights from physiology, oxidative damage, and metabolomics

Both microplastics (MPs) and cadmium (Cd) are common contaminants in farmland systems, is crucial for assessing their risks for human health and environment, and little research has focused on stress responses mechanisms of crops exposed to the combined pollution. The present study investigated the impact of polyethylene (PE) and polypropylene (PP) microplastics (MPs), in combination with Cd, on the physiological and metabolomic changes as well as rhizosphere soil of potherb mustard. Elevated levels of PEMPs and PPMPs were found to impede nutrient uptake in plants while promoting premature flowering, and the concomitant effect is lower crop yields. The substantial improvement in Cd bioavailability facilitated by MPs in rhizosphere soil, especially in high concentrations of MPs, then elevated bioavailability of Cd contributed to promoted Cd accumulation in plants, with distinct effects depending on the type and concentration of MPs. The presence of MPs Combined exposure to high concentrations of MPs and Cd resulted in alterations in plant physiology and metabolomics, including decreased biomass and photosynthetic parameters, elevated levels of reactive oxygen species primarily H2O2, increased antioxidant enzyme activities, and modifications in metabolite profiles. Overall, our study assessed the potential impact on food security (the availability of cadmium to plant) and crops stress responses regarding the contamination of MPs and Cd, providing new insights for future risk assessment in agriculture.

Microplastic in long-term soil monitoring: first spatial and temporal data on plastics in agricultural topsoils

PurposeWithin the emerging field of soil related microplastic (MP) research, little is known about spatio-temporal variations of MP concentrations in soils. To overcome this current knowledge gap, we suggest the exploitation of long-term soil monitoring programmes (LTSM) and its archived soil samples, to gain first data on spatio-temporal variations within soil MP contamination.MethodsWe analysed 32 archived topsoil samples of 13 cropland and 3 control sites, including grassland and forest sites, which are part of the LTSM programme of the German federal state of Hesse. Analysed samples cover a time span of 10–16 years. MP (>300 µm) have been extracted via sodium chloride (NaCl, 1.2 g cm−3) density separation, Nile Red staining and fluorescent optical identification followed by ATR-FTIR analysis of individual MP.ResultsWe found MP contamination (mean 34.66 ± 24.08 p kg−1) from mainly PE and synthetic rubber polymers. Furthermore, we were able to detect spatial MP contamination hotspots, with unexpected high MP concentrations in control grassland and forest LTSM sites. In case of temporal trends, we cannot conclude a general increase of MP concentrations over time. However, as we found MP in older and newer samples, MP contamination is likely to be ubiquitous in topsoils and has already been present in the environment for several decades.ConclusionOur findings underline the role of cropland topsoils as MP reservoirs, but raise questions on the MP storage in grassland and forest soils. Applying MP analytical tools to archived LTSM samples enables first insights within non-targeted spatial source analysis and temporal trends of soils MP pollution. If enhanced analytical methods will be applied to LTSM samples, it will be possible to gain more detailed insights within spatio-temporal MP dynamics in soils.

Distribution and major driving elements of antibiotic resistance genes in the soil-vegetable system under microplastic stress

Microplastics (MPs) and antibiotic resistance genes (ARGs) are both enriched in soil-vegetable systems as a consequence of the prolonged use of agricultural mulches. MPs can form unique bacterial communities and provide potential hosts for ARGs. Therefore, MPs stress may promote the spread of ARGs from soil to crops. Increasing ARGs pollution in soil-vegetable system. In our research, we investigated the distribution and major driving elements of antibiotic resistance genes in the soil-vegetable system under microplastic stress. The results showed that MPs treatment decreased the relative abundance of ARGs in non-rhizosphere soil. High concentrations of MPs promoted the enrichment of tetracycline antibiotic resistance genes in rhizosphere soil. MPs treatment promoted the enrichment of ARGs and mobile genetic elements (MGEs) in lettuce tissues, and the overall abundance of ARGs in root after 0.5 %, 1 %, and 2 % (w/w, dry weight) polyethylene (PE) administration was considerably higher compared to that in the untreated group (p < 0.05). At the same time, high PE concentrations promoted the spread of sulfa ARGs from root to leaf. MPs also impacted the bacterial communities in the soil-plant system, and the changes in ARGs as well as MGEs in each part of the soil-vegetable system were significantly correlated with the bacterial diversity index (p < 0.05). Correlation analysis and network analysis showed that bacterial communities and MGEs were the main drivers of ARGs variation in soil-lettuce systems.

Zooplankton-microplastic exposure in Delaware coastal waters: Atlantic blue crab (Callinectes sapidus) larvae case study

High microplastic concentrations in the Delaware Bay have prompted concern regarding harm to local species. We consider the extent to which the zooplankton is exposed to bay-derived microplastics, focusing on Atlantic blue crabs (Callinectes sapidus) during offshore larval migration. We simulate regional flow fields for a spawning season in the Delaware coastal system to advect passive Lagrangian microplastic and zooplankton tracers. Microplastic exposure levels are estimated from tracer distributions. Field sampling of zooplankton and microplastic concentrations for the Delaware Bay mouth and the adjacent shelf in August 2020 is utilized to appraise model performance. Three mechanisms elevating microplastics exposure are identified: zooplankton transport into microplastic-laden tidelines, displacement of microplastics into the buoyant outflow current, and aggregation in offshore plume fronts. Organization via the above mechanisms substantially enhance microplastic exposures over zooplankton migrations (by an average factor of at least 3.8).

Application of Infrared and Near-Infrared Microspectroscopy to Microplastic Human Exposure Measurements.

Microplastic pollution is a global issue for the environment and human health. The potential for human exposure to microplastic through drinking water, dust, food, and air raises concern, since experimental in vitro and in vivo toxicology studies suggest there is a level of hazard associated with high microplastic concentrations. However, to infer the likelihood of hazards manifesting in the human population, a robust understanding of exposure concentrations is needed. Infrared and near-infrared microspectroscopies have routinely been used to analyze microplastic in different exposure matrices (air, dust, food, and water), with technological advances coupling multivariate and machine learning algorithms to spectral data. This focal point article will highlight the application of infrared and Raman modes of spectroscopy to detect, characterize, and quantify microplastic particles, with a focus on human exposure to microplastic. Methodologies and state-of-the-art approaches will be reported and potential confounding variables and challenges in microplastic analysis discussed. The article provides an up-to-date review of the literature on microplastic exposure measurement using (near) infrared spectroscopies as an analytical tool, highlighting the recent advances in this rapidly advancing field.

Spatiotemporal distribution of microplastics in Miri coastal area, NW Borneo: inference from a periodical observation

The current study aims to investigate the spatiotemporal distribution of microplastics (MPs) in the Miri coast, targeting their occurrences, characterisation, and potential sources. For a periodical study, coastal sediments were collected from three different time intervals (monsoon, post-monsoon, and post-COVID) and subjected to stereomicroscope, ATR-FTIR, and SEM-EDX analyses. These results show a significant increase of MPs in post-COVID samples by approximately 218% and 148% comparatively with monsoon and post-monsoon samples, respectively. The highest concentration of MPs was detected near the river mouths and industrial areas where the waste discharge rate and anthropogenic activities dominate. Fibre-type MPs are the most abundant, with an average of nearly 64%, followed by fragments, films, microbeads, and foams. The most dominant polymer types were polytetrafluoroethylene (PTFE), polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyester (PET). Overall, the current study shows a better understanding of MPs occurrence and potential sources in the Miri coastal area.

Efektivitas Ferrofluid dalam Penurunan Parameter Limbah Laundri

One of the new applications of ferrofluid, a colloidal compound containing magnetic nanoparticles, is the removal of microplastics from water. Laundry waste has a high concentration of microplastics, but this wastewater contains other substances besides microplastics, such as TSS, COD, surfactants, etc. Therefore, it is necessary to analyze the effectiveness of this method directly from wastewater to determine the total amount. The following is the highest percentage reduction obtained for each parameter: microplastic content of 66.16% is reduced. Then for the TSS parameter, ferrofluid reduces TSS by 70%. As for TDS, the ferrofluid method has the highest percentage reduction of 50.3%. Furthermore, for surfactants or detergents, the highest decrease in ferrofluid was only 10.37%. Lastly, in COD, the biggest decline reached 30%.

Microplastics in the Arctic: a transect through the Barents Sea

Globally, the abundance of microplastics in our oceans is increasing, including within the remote locations of the polar regions. The Barents Sea, which adjoins the Arctic Ocean, is an area of high primary productivity that, owing to the convergence of regional currents, has been mooted as a potential sixth ocean gyre that may coalesce high concentrations of plastic debris. This study aimed to explore data collected from large volume samples of sub-surface water collected from transects through the Barents Sea to quantify and characterise microplastics in this region, with a focus on potential impacts to zooplankton. Overall, the mean microplastic abundance in the Barents Sea was 0.011 microplastics m-3 (range: 0.007 – 0.015 m-3). Microplastics were found in higher abundances nearer land mass at the southern end of the transect and northwards towards the ice edge, recording 0.015 microplastics m-3 during both transect legs. Microplastics were predominantly fibrous (92.1%) and typically blue (79%) or red (17%) in colour. A range of polymers were identified including polyester (3.8%), copolymer blends (2.7%), elastomers (7.1%) and acrylics (10.6%), however semi-synthetic polymers dominated, comprising 74.4% of particles found. Higher microplastic concentrations in the northernmost transect may stem from melting sea-ice, while the higher concentrations in the southernmost transect likely derive from the long-range transport of microplastics via currents from Europe.

Effects of elevated temperature and microplastic exposure on growth and predatory performance of a freshwater fish

AbstractFreshwater ecosystems are increasingly exposed to co‐occurring anthropogenic stressors that can alter food web interactions and organismal life histories. We examined the individual and combined effects of climate warming and microplastic pollution on the growth rate and predatory performance of an invasive freshwater fish, the round goby (Neogobius melanostomus). In temperature‐controlled chambers, we exposed 160 juvenile gobies to one of six scenarios over 37 d, combining three environmentally relevant concentrations of microplastics (63–75 μm polyethylene microbeads) with two temperature regimes representing contemporary (18°C) and projected mean summer maxima (26°C) in their current range in the Great Lakes–St. Lawrence River basin. Exposure to elevated temperature reduced the growth and predatory performance of round gobies. Their decline in predatory performance was greatest at the highest microplastic concentration, regardless of temperature. The effects of environmentally relevant microplastic concentrations on the growth and performance of gobies were weaker than the effects of thermal stress. Given that the round goby is an abundant and widely distributed bottom‐dwelling fish in nearshore areas of the Great Lakes–St. Lawrence River basin, its responses to these co‐occurring stressors could have cascading effects on food webs.

Microplastic and associated polyaromatic hydrocarbons in surface waters feeding Beyşehir Lake in Türkiye

&lt;p&gt;The detection of microplastics, defined as tiny plastics particles having a size from 1 µm to 5 mm, in aquatic environments has become a serious concern worldwide. Microplastics may be introduced either directly to water bodies or indirectly to the aquatic systems. In particular, microplastics may interact with persistent organic pollutants and inorganic contaminants and they transfer these pollutants to organisms in the aquatic environment. In this study, microplastics and their sorbed polyaromatic hydrocarbons (PAHs) in the surface water feeding Beyşehir Lake in Türkiye were investigated. The abundance of microplastics in the surface water was determined in the range of 2830-6860 particles/m3. While five shapes (fiber, foam, film, fragment, pellet) of microplastics were determined in surface waters, fiber and fragment form microplastics were predominantly observed. The detected polymer types were cellophane, polyethylene, polypropylene. The transparent/white color microplastics were the most dominant (42-81%). The total concentration of the seventeen PAHs associated with microplastics in surface waters ranged from 1924 to 7970 ng/g. According to the diagnostic ratios of the PAH isomers (fluoranthane/pyrene &amp;lt; 1 and phenanthrene/antracene &amp;gt;10), the source of the PAHs all surface waters can be pyrogenic and petrogenic origins. These findings indicate that high concentrations of microplastics and PAHs sorbed microplastics were carried into the lake by the surface waters feeding Beyşehir Lake. These pollutants may pose a risk to the use of water for irrigation and potable purposes and to aquatic organisms in the lake.&lt;/p&gt;&#x0D;

Effect of PET microplastics on the growth, digestive enzymes, and intestinal flora of the sea cucumber Apostichopus japonicus

Marine microplastic (MP) pollution is becoming a serious problem and their potentially toxic effects on marine organisms have attracted much attention. Sea cucumber is very important for the safety and health of marine ecosystems. However, there have been relatively few studies on the effects of microplastic pollution on sea cucumbers at environmentally-related concentrations and under controlled conditions. Therefore, this study evaluated the effects of polyethylene terephthalate (PET) microplastics (particle sizes: 0.5–45 μm, 2–200 μm, and 20–300 μm; and three concentration levels for each particle size, approximately 103, 104, and 105 particles/kg) on the basic biological indicators, intestinal digestive enzymes, and intestinal flora of Apostichopus japonicus after a 28-day feeding experiment. This study showed that environmentally-related and high concentrations of microplastics had little effect on A. japonicus. This study provides valuable reference information about the effects of marine microplastic pollution on sea cucumbers.

Metagenomic analysis reveals the responses of microbial communities and nitrogen metabolic pathways to polystyrene micro(nano)plastics in activated sludge systems.

Microplastics (MPs) and nanoplastics (NPs) are prevalent in sewage and pose a potential threat to nitrogen biotransformation in wastewater treatment systems. However, investigations on how MPs and NPs affect the microbial nitrogen conversion and metabolism of the activated sludge are still scanty. Herein, the responses of microbiomes and functional genes to polystyrene MPs and NPs in activated sludge systems were investigated by metagenomic analysis. Results indicated that 1mg/L MPs and NPs had marginal impacts on the nitrogen removal performance of the activated sludge systems, whereas high concentrations of MPs and NPs (20 and 100mg/L) decreased the total nitrogen removal efficiency (13.4%-30.6%) by suppressing the nitrogen transformation processes. Excessive reactive oxygen species induced by MPs and NPs caused cytotoxicity, as evidenced by impaired cytomembranes and decreased bioactivity. Metagenomic analysis revealed that MPs and NPs diminished the abundance of denitrifiers (e.g. Mesorhizobium, Rhodobacter and Thauera), and concurrently reduced the abundance of functional genes (e.g. napA, napB and nirS) encoding for key enzymes involved in the nitrogen transformations, as well as the genes (e.g. mdh) related to the electron donor production, thereby declining the nitrogen removal efficiency. Network analysis further clarified the attenuate association between denitrifiers and denitrification-related genes in the plastic-exposed systems, elucidating that MPs and NPs restrained the nitrogen removal by inhibiting the contributions of microorganisms to nitrogen transformation processes. This study provides vital insights into the responses of the microbial community structure and nitrogen conversion processes to micro(nano)plastics disturbance in activated sludge systems.

Characterization and Quantification of Surficial Sediment Microplastics and Its Correlation with Heavy Metals, Soil Texture, and Flow Velocity

Investigating the presence of microplastics in the Pasig River, the highest plastic-emitting river in the Philippines and one of the ocean’s leading contributors of these materials, is highly relevant. In this study, surficial sediments in eight stations along the main channel of the Pasig River were analyzed for microplastic content, heavy metals, and soil texture. The microplastics were categorized according to shape, color, and size. The polymer type was determined using infrared spectroscopy. The number of microplastics was correlated with heavy metals, soil texture, and flow velocity. The results show that the dominant shape, color, size, and polymer type were fragment, color white, size range from 0 to 500 μm, and polyvinyl alcohol, respectively. Downstream stations 5 and 8 had the highest microplastic concentration. The number of microplastics showed a positive moderate correlation with percent sand (r = 0.40) and clay (r = 0.42), and a negative high correlation with percent silt (r=-0.80). For microplastics and heavy metals, a positive moderate correlation was observed for iron (r = 0.52) and zinc (r = 0.58), while a negative weak correlation was present for lead (r=-0.06). Microplastics and flow velocity showed weak correlations demonstrating that the accumulation in the bottom river sediment may be based on the proximity of the plastic source rather than on the flowing water with plastic sources. Results reflect the diverse influences on the Pasig River which is surrounded by informal settlements, manufacturing industries, urban offices, and residential areas. More plastic management initiatives and better implementation of existing laws should be done by the government.