Assessment, characterization, and quantification of microplastics from river sediments

Detection of microplastics based on splicing grating spatial heterodyne Raman spectroscopy

As a new type of persistent pollutant, microplastics pose a serious threat to the earth's ecological environment and human health. Efficient and reliable microplastic detection technology is of great significance in the management of microplastic pollution. Aiming at the problems of low signal-to-noise ratio (SNR), narrow spectral range and low spectral resolution in traditional microplastic detection technology, a splicing grating spatial heterodyne Raman spectroscopy (SG-SHRS) is proposed in this paper. The splicing grating is composed of four sub-gratings with groove densities of 320, 298, 276 and 254 gr / mm, respectively. Each sub-grating has an independent sub-filter to improve the SNR of the system. The system is simulated, built and calibrated. The actual resolution of the SG-SHRS system is 0.7 cm-1, and the spectral detection range of a single sub-grating is 2947.2 cm-1. Four kinds of microplastics, polyamide (PA), polystyrene (PS), polycarbonate (PC), and polyphenylene sulfide (PPS), were detected by the SG-SHRS system. The complete Raman spectral information of microplastics was obtained, and the peak assignment of Raman characteristic peaks of the four kinds of microplastics was analyzed. By comparing the test results with a commercial dispersion spectrometer, it has been proven that the SG-SHRS system has the advantages of high spectral resolution, wide spectral range, and high SNR, and has good application prospects in the field of microplastic detection.

Effects of microplastics on sedimentary geochemical properties and microbial ecosystems combined with hydraulic disturbance

Microplastics (MPs) pollution is widely investigated owing to its potential threats to river ecosystems. However, it remains unclear whether hydraulic disturbance deepens or mitigates the effects of MPs-contaminated sediments on the river environment. Herein, we studied the impact of sediment aggregates, organic matter, and enzyme activity, with emphasis on microbial community structure and function in sediments exposed to MPs (1 %, 5 %, and 10 % w/w) in conjunction with hydraulic disturbance. The experimental results showed that the influence of MPs on the sediment under hydraulic disturbance is more significant than that of static culture, especially for various environmental factors (MWD, MBC, and sucrase activity etc.). The proportions of the >0.05 mm-fraction aggregates increased from 74-76 % to 82-88 % in the sediment throughout the entire disturbance process. It has been found that the disturbance generally promotes the interaction between MPs and sediments. FAPROTAX analysis demonstrated that the disturbance reduced the difference in effects on microbial functional genes between the control group and the MPs-added groups by up to 10 times, suggesting that the effects of disturbance on MPs-contaminated sediments are relatively complex. This work provides new insights into the effects of hydraulic disturbance on physicochemical properties and microbial communities of MPs-contaminated sediment.

Microplastics and associated polycyclic aromatic hydrocarbons in surface water and sediment of the Bay of Bengal coastal area, India: sources, pathway and ecological risk

In the aquatic environment around the world, microplastic contamination has been a common and ongoing issue. Particularly, the ability of microplastics to absorb persistent organic pollutants (POPs) and then transmit these POPs to aquatic creatures has attracted a lot of interest. A stereomicroscope was used to detect the size, shape, and color of the microplastics (MPs), and Fourier Transform Infrared (FTIR) spectroscopy was used to identify the polymer composition of the MPs. To address MP transit, destiny, and mitigation, a study of MP pollution coastal areas is required. In the current study, MP pollution in the collected sample from upper layer of water and sediment of the Digha and Puri beaches along the coast of BOB was evaluated. The average concentration with SD of MPs observed in water was 5.3 ± 1.8 items/L whereas, in sediments, it was 173.4 ± 40.1 items/kg at Digha beach. The mean MPs abundance in the Puri beach was 6.4 ± 1.7 items/L in the water and 190.4 ± 28.0 items/kg in the sediments. The investigated total 16-PAHs concentrations were 164.7 ng/g, 121.9 ng/g, 73.6 ng/g, and 101.3 ng/g on the MPs surface of foam, fragment, fibers, and film respectively in the studied MPs sample. Smaller than 1000 µm size of MPs are distributed in the largest concentration. Fibers, films, fragments, and foam were the most common shapes of MPs. The molecular structure of MPs in water and sediment samples was analysed i.e., polyesters (PEs), polypropylene (PP), polyethylene (PE), polymethyl methacrylate (PMMA), polystyrene (PS), polyamide (PA), polycarbonates (PC), and polyurethane (PU). The obtained result offers an accurate assessment of the PLI, and the investigated polymer facilitates determining the polymer hazard levels, which emphasizes the risk associated with it.

Microplastics in the Volta Lake: Occurrence, distribution, and human health implications

Pollution of plastic waste in aquatic ecosystems in Ghana is of significant concern with potential adverse effects on food safety and ecosystem function. This study examined the abundance and distribution of microplastics (MPs) in freshwater biota samples namely: the African river prawn (Macrobrachium vollenhovenii), the Volta clam (Galatea paradoxa), Nile tilapia (Oreochromis niloticus), and sediment from the Volta Lake. Both biota and sediment samples were subjected to microscopic identification and FTIR analysis. In biota samples, the highest mean microplastic abundance of 4.7 ± 2.1 items per individual was found in the prawn, while the Nile tilapia recorded the least (2.8 ± 0.6 items per individual). A total of 398 microplastic particles were observed in sediment samples from the Volta Lake. Microfibers were the major plastic shapes identified in biota and sediment samples. We examined the relationship between microplastic abundance, biota size, and sediment properties. Despite the lack of statistical significance, microplastic shape, size, and polymer composition in assessed organisms mirrored those in the benthic sediment. Polyethylene, polypropylene, polyester, and polystyrene were the four dominant polymer types identified in the organisms and sediments. Although the estimated human exposure was relatively low compared with studies from other regions of the world, the presence of microplastics raises concern for the safety of fisheries products consumed by the general populace in the country. This research is essential for developing effective mitigation measures and tackling the wider effects of microplastic contamination on Ghana's freshwater ecosystems, particularly the Volta Lake.

Recycling and Degradation of Polyamides

As one of the five major engineering plastics, polyamide brings many benefits to humans in the fields of transportation, clothing, entertainment, health, and more. However, as the production of polyamide increases year by year, the pollution problems it causes are becoming increasingly severe. This article reviews the current recycling and treatment processes of polyamide, such as chemical, mechanical, and energy recovery, and degradation methods such as thermal oxidation, photooxidation, enzyme degradation, etc. Starting from the synthesis mechanism of polyamide, it discusses the advantages and disadvantages of different treatment methods of polyamide to obtain more environmentally friendly and economical treatment schemes. Finding enzymes that can degrade high-molecular-weight polyamides, exploring the recovery of polyamides under mild conditions, synthesizing environmentally degradable polyamides through copolymerization or molecular design, and finally preparing degradable bio-based polyamides may be the destination of polyamide.

Biodegradation of low-density polyethylene film by Bacillus gaemokensis strain SSR01 isolated from the guts of earthworm

In recent years, low-density polyethylene (LDPE) has emerged as an essential component of the routine tasks that people engage in on a daily basis. However, over use of it resulted in environmental buildup that contaminated aquatic habitats and human health. Biodegradation is the most effective way for controlling pollution caused by synthetic plastic waste in a sustainable manner. In the present study, the LDPE degrading bacterial strain was screened from gut of Earthworms collected from plastic waste dumped area Mettur dam, Salem district, Tamil Nadu, India. The LDPE degrading bacterial strain was screened and identified genotypically. The LDPE degrading Bacillus gaemokensis strain SSR01 was submitted in NCBI. The B. gaemokensis strain SSR01 bacterial isolate degraded LDPE film after 14 days of incubation and demonstrated maximum weight loss of up to 4.98%. The study of deteriorated film using attenuated total reflection-Fourier transform infrared revealed the presence of a degraded product. The degradation of LDPE film by B. gaemokensis strain SSR01 was characterized by field-emission scanning electron microscopy analysis for surface alterations. The energy dispersive X-ray spectroscopy test confirmed that the broken-down LDPE film had basic carbon reduction. The present study of LDPE flim biodegradation by B. gaemokensis strain SSR01 has acted as a suitable candidate and will help in decreasing plastic waste.

Microplastics, their abundance, and distribution in water and sediments in North Chennai, India: An assessment of pollution risk and human health impacts

Plastic particles, measuring <5 mm in size, mainly originate from larger plastic debris undergoing degradation, fragmenting into even smaller fragments. The goal was to analyze the spatial diversity and polymer composition of microplastics (MPs) in North Chennai, South India, aiming to evaluate their prevalence and features like composition, dimensions, color, and shape. In 60 sediment samples, a combined count of 1589 particles were detected, averaging 26 particles per 5 g-1 of dry sediment. The water samples from the North Chennai vicinity encompassed a sum of 1588 particles across 71 samples, with an average of 22 items/L. The majority of MPs ranged in size from 1 mm to 500 μm. The ATR-FTIR results identified the predominant types of MPs as polystyrene, polyvinyl chloride, polyethylene, polyethylene terephthalate, and polypropylene in sediment and water. The spatial variation analysis revealed high MPs concentration in landfill sites, areas with dense populations, and popular tourist destinations. The pollution load index in water demonstrated that MPs had contaminated all stations. Upon evaluating the polymeric and pollution risks, it was evident that they ranged from 5.13 to 430.15 and 2.83 to 15,963.2, which is relatively low to exceedingly high levels. As the quantity of MPs and hazardous polymers increased, the level of pollution and corresponding risks also escalated significantly. The existence of MPs in lake water, as opposed to open well water, could potentially pose a cancer risk for both children and adults who consume it. Detecting MPs in water samples highlights the significance of implementing precautionary actions to alleviate the potential health hazards they create.

Polyurethane degradation by extracellular urethanase producing bacterial isolate Moraxella catarrhalis strain BMPPS3

Plastic waste has become a global issue and a threat to the ecosystem. The present study isolated polyurethane (PU) degrading bacterial species from soil dumped with plastic wastes. Four bacterial isolates, RS1, RS6, RS9 and RS13 were obtained and their ability to degrade PU in a synthetic medium with PU as a sole source of carbon was assessed individually. After thirty days of incubation, the highest PU weight loss of 67.36 ± 0.32% was recorded in the medium containing RS13 isolate. The results of FTIR revealed the occurrence of carbonyl peaks. The putative isolate RS13 confirmed with the genus Moraxella according to 16S rRNA gene sequencing and the isolate was specified as Moraxella catarrhalis strain BMPPS3. The restriction analysis of Moraxella catarrhalis strain BMPPS3 revealed that the GCAT content to 51% and 49% correspondingly. Moraxella catarrhalis strain BMPPS3 was able to colonize on PU surface and form a biofilm as revealed by SEM investigation. Fatty acids and alkanes were found to be the degradation products by GC-MS analysis. The presence of these metabolites facilitated the growth of strain RS13 and suggested that ester hydrolysis products had been mineralized into CO2 and H2O. Extracellular biosurfactant synthesis has also been found in Moraxella catarrhalis strain BMPPS13 inoculated with synthetic media and mineral salt media containing PU and glucose as carbon sources, respectively with a significant level of cell-surface hydrophobicity (32%). The production and activity of extracellular esterase showed consistent increase from day 1-15 which peaked (1.029 mM/min/mg) on day 24 significantly at P < 0.001. Crude biosurfactants were lipopeptide-based, according to the characteristic investigation. According to this study findings, Moraxella catarrhalis produces biosurfactants of the esterase, urethanase and lipase (lipopeptide) types when carbon source PU is present.

Polystyrene microplastics induced disturbances in neuronal arborization and dendritic spine density in mice prefrontal cortex

An increasing use of plastics in daily life leads to the accumulation of microplastics (MPs) in the environment, posing a serious threat to the ecosystem, including humans. It has been reported that MPs cause neurotoxicity, but the deleterious effect of polystyrene (PS) MPs on neuronal cytoarchitectural morphology in the prefrontal cortex (PFC) region of mice brain remains to be established. In the present study, Swiss albino male mice were orally exposed to 0.1, 1, and 10 ppm PS-MPs for 28 days. After exposure, we found a significant accumulation of PS-MPs with a decreased number of Nissl bodies in the PFC region of the entire treated group compared to the control. Morphometric analysis in the PFC neurons using Golgi-Cox staining accompanied by Sholl analysis showed a significant reduction in basal dendritic length, dendritic intersections, nodes, and number of intersections at seventh branch order in PFC neurons of 1 ppm treated PS-MPs. In neurons of 0.1 ppm treated mice, we found only decrease in the number of intersections at the seventh branch order. While 10 ppm treated neurons decreased in basal dendritic length, dendritic intersections, followed by the number of intersections at the third and seventh branch order were observed. As well, spine density on the apical secondary branches along with mRNA level of BDNF was significantly reduced in all the PS-MPs treated PFC neurons, mainly at 1 ppm versus control. These results suggest that PS-MPs exposure affects overall basal neuronal arborization, with the highest levels at 1 and 10 ppm, followed by 0.1 ppm treated neurons, which may be related to the down-regulation of BDNF expression in PFC.

Microplastics Distribution in Sediments Collected from Myanmar

Microplastics (MPs) distributions have been increasingly reported in the terrestrial areas worldwide, but little information is available for ASEAN regions. In this study, 68 sediment samples of drainage channels, lakes, rivers and beaches from Myanmar were collected between 2014 and 2018, and analyzed to investigate the status of MPs concentration and prevalence. The high concentrations of MPs in sediments were found in urban cities called Yangon (13,855 pieces/kg dry weight), Mandalay (11,946 pieces/kg), and Pathein (12,583 pieces/kg), which were two orders of magnitude greater than the MPs concentrations in sediments collected in rural towns called Wundwin. These results suggested that the difference in high population densities and high municipal solid waste generation rates are related to the MPs contamination in sediments. Polyethylene, polypropylene and polyethylene terephthalate with fragments, lines/fibers and films/sheets were major polymers and shape in the sediment samples analyzed from Myanmar. To our knowledge, this is the first study to report the distribution of MPs in sediments from Myanmar.

Microplastic contamination in water and sediments of Mahanadi River, India: An assessment of ecological risk along rural-urban area

Worldwide, environmental concerns about MPs pollution have increased. Microplastic contamination that pollutes the ocean is mostly caused by terrestrial transfer from close proximity locations. A study of MPs pollution near coastal locations becomes necessary to address the MPs transit, fate, and mitigation. In the current study MPs pollution in the surface water and sediment of the Mahanadi River estuary was assessed during Pre-MS and MS. The size, shape, and colour of the MPs were determined using a stereomicroscope, and the MPs polymer composition was identified by Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) spectroscopy. The mean concentration of MPs that were potentially discovered in water was 16.6 ± 5.2 and sediments 197.3 ± 5.4 during Pre-MS. In the MS observed mean abundance of MPs was 15.1 ± 5.4 in water and 164.6 ± 76.9 in sediments. The highest abundant size was smaller than 1 mm; the most prevalent shape were fibers followed by film and fragments; black and white was a prominent colour in water and sediments respectively. Polyesters (PEs), polyethylene (PE), polyvinyl chloride (PVC), polypropylene (PP), polyamide (PA), Polystyrene (PS), and Polycarbonates (PC) were found in the analysis of the chemical composition of MPs in water and sediments samples. The calculated PLI value shows pollution load at category I, with polymer hazard levels at categories III, IV, and V, indicating very high risk. The current research results show that river inflows and fishing-related actions are probably the main causes of MPs pollution.

A critical review on remediation of microplastics using microalgae from aqueous system

Microplastics (MPs) are deemed to be a global concern due to their harmful negative effects on the aquatic environment and human beings. MPs have a significant impact on both fresh and marine water ecosystems. In many countries, there is concern about the deleterious consequences of MPs on human health due to the presence of MPs in aquatic life for higher intake of marine food (fish and shellfish). Exposure to MPs causes fish to suffer from growth retardation, neurotoxicity, and behavioural abnormalities and it affects human as well. It causes oxidative stress, neurotoxicity, cytotoxicity, and immune system disruption after being ingested to these contaminated fish in human body. Due to these reasons, it has become imperative to find ways to resolve this problem. This review paper represents a pioneering endeavor by consolidating comprehensive information on microplastic-polluted Indian riverine ecosystems and effective MPs removal methods into a single, cohesive document. It meticulously evaluates the principles, removal efficiency, benefits, and drawbacks of various techniques, aiming to identify the most optimal solution. Furthermore, this paper provides a comprehensive exploration of the interesting interactions between MPs and microalgae, delving into the intricate processes of hetero-aggregation. Additionally, it shines a spotlight on the latest advancements in understanding the efficacy of microalgae in removing MPs, showcasing recent breakthroughs in this field of research. Moreover, the work goes beyond conventional assessments by elucidating the characteristics of MPs and exploring diverse influencing parameters that impact MPs removal by microalgae and also addresses the potential future aspects. This thorough investigation uncovers important factors that could significantly contribute to the development of more efficient and sustainable remediation strategies.

Carbon nanoparticles fabricated microfilm: A potent filter for microplastics debased water

Microplastics were found to be the major pollutant across the globe. Plastic microbeads, like 0.5 mm, are very small and mainly used for exfoliation. The marine species cannot distinguish between their usual food and these microbeads. Microbeads have the potential to transfer up the food chain, which may lead to consumption by humans in the end. Activated carbon from inexpensive sources has greatly interested separation systems, especially in water treatment. In that view, carbon nanoparticles were produced, combined with polyvinylidene fluoride (PVDF) polymer, and used as a membrane to trap the microplastic particles. UV-Vis, FTIR, TEM, and powder X-ray diffraction (XRD) analysis confirmed the produced carbon nanoparticles. FT-RAMAN Spectroscopy studies, microbial viable cell count, and turbidity analysis followed the membrane preparation and post-treatment. The carbon nanoparticle fabricated nanofilm effectively eliminates the microbial count and microplastics and reduces the turbidity (0.13 NTU). This study confirms that the membrane effectively filters microplastics and other contaminants. Nowadays, nanofiltration technologies have been considered beneficial for eliminating microplastics to an efficiency of 95%. Further research is needed to determine a feasible low-cost, ecologically suitable, and effective solution to remove the microplastics in water.

Microplastics in Freshwater Ecosystems of India: Current Trends and Future Perspectives

Microplastics (MPs)-i.e., plastic particles less than 5 mm in length-are becoming a growing environmental concern due to their potential ecotoxicological impacts on aquatic ecosystems. In India, MPs contamination is a significantly growing problem due to increased plastic production as well as its low rate of recycling. As a result, MPs research work in India has gained considerable attention in the last two decades. The objective of this study is to conduct a comprehensive review of the existing scientific literature on MPs in freshwater ecosystems (e.g., lakes and rivers) of India. A bibliographical search was used to conduct the literature review across a number of databases including ScienceDirect, Google Scholar, and ResearchGate. We found that in comparison to the marine ecosystem the source, transport, and fate of MPs in freshwater ecosystems of India are still underexplored, and we found only 18 relevant papers. This review work reveals that there is no standard procedure for separating MPs from water and sediment samples, and as a result, comparing the results was a challenging task. The larger MPs (>500 μm) in water and sediments were identified most commonly using the attenuated total reflection (ATR) Fourier Transform Infrared (FTIR) spectroscopy technique (ATR-FTIR), whereas smaller-sized MPs (<500 μm) were identified using FTIR fitted with a confocal microscope, also known as μ-FTIR imaging or chemical imaging. We found that white-colored fibers and fragments of polypropylene (PP), polyethylene terephthalate (PET), and polyethylene (PE) were the most common polymer types in the freshwater ecosystems of India. Although research on MPs in freshwater ecosystems of India has gained momentum over the past decade, the literature review reveals a limited understanding of the impact of MPs' weathering patterns, the role of biofouling, and the role of water hyacinths on freshwater ecosystem services in India. Furthermore, the fluxes of MPs to the Indian oceans are not constrained, and atmospheric transport in high-altitude mountains, which have already been made fragile by climate change, has not been fully investigated. This study, therefore, calls for additional assessments of MPs in freshwater ecosystems-particularly in the central parts of India.

Seasonal influence on microplastics in the sediments of a non-perennial river - Noyyal, Tamil Nadu, India

Microplastic (MP) is a contaminant presently causing a significant environmental risk. The present study aims to extract, measure, and classify MP in sediment samples from two seasons (monsoon and summer) in Noyyal River, South India. Microplastic was separated from sediments using the Sediment Microplastic Isolation technique. Microplastics were detected in four forms: foams, films, fragments, and fibres. Dominant polymer types during monsoon are Polystyrene (29%), Polycarbonate (13%), Nylon (13%), and Ethylene Vinyl Acetate (13%). Throughout summer, Polystyrene (17%) was the prevalent polymer type, followed by Nylon (14%), Polycarbonate (11%), and Polyvinyl Chloride (9%). Scanning Electron Microscope (SEM) demonstrated that MPs exhibit diverse surface morphologies, including foamy, fibrous, and granular nature. It also shows tearing and fracturing of MPs and aging, indicating substantial summer degradation. Using Polymer Hazard Index (PHI) and Pollution Load Index (PLI), MP vulnerability in sediments indicates that despite lesser PLI, the MPs pose an extreme danger threat to the environment during the summer season compared to the monsoon. The study thus provides insight into the seasonal variation of MPs and their threat in Noyyal River sediments, which will aid in formulating guidelines for the minimization of MPs in river systems.

Multigenerational effects of co-exposure to dimethylarsinic acid and polystyrene microplastics on the nematode Caenorhabditis elegans

In the current study, we assessed the impact of DMA (dimethylarsinic acid) and MPs (microplastics) interactions in C. elegans over the course of five generations. We found that the redox state of the organisms changed over generations as a result of exposure to both pollutants. From the third generation onward, exposure to MPs reduced GST activity, indicating reduced detoxifying abilities of these organisms. Additionally, dimethylarsinic exposure decreased the growth of organisms in the second, fourth, and fifth generations. In comparison to isolated pollutants, the cumulative effects of co-exposure to DMA and MPs seem to have been more harmful to the organisms, as demonstrated by correlation analysis. These findings demonstrate that DMA, despite being considered less hazardous than its inorganic equivalents, can still have toxic effects on species at low concentrations and the presence of MPs, can worsen these effects.

Microplastic pollution in riverine ecosystems: threats posed on macroinvertebrates

Microplastics (MPs) are pollutants of emerging concern that have been reported in terrestrial and aquatic ecosystems as well as in food items. The increasing production and use of plastic materials have led to a rise in MP pollution in aquatic ecosystems. This review aimed at providing an overview of the abundance and distribution of MPs in riverine ecosystems and the potential effects posed on macroinvertebrates. Microplastics in riverine ecosystems are reported in all regions, with less research in Africa, South America, and Oceania. The abundance and distribution of MPs in riverine ecosystems are mainly affected by population density, economic activities, seasons, and hydraulic regimes. Ingestion of MPs has also been reported in riverine macroinvertebrates and has been incorporated in caddisflies cases. Further, bivalves and chironomids have been reported as potential indicators of MPs in aquatic ecosystems due to their ability to ingest MPs relative to environmental concentration. Fiber and fragments are the most common types reported. Meanwhile, polyethylene, polypropylene, polystyrene, polyethylene terephthalate (polyester), polyamide, and polyvinyl chloride are the most common polymers. These MPs are from materials/polymers commonly used for packaging, shopping/carrier bags, fabrics/textiles, and construction. Ingestion of MPs by macroinvertebrates can physically harm and inhibit growth, reproduction, feeding, and moulting, thus threatening their survival. In addition, MP ingestion can trigger enzymatic changes and cause oxidative stress in the organisms. There is a need to regulate the production and use of plastic materials, as well as disposal of the wastes to reduce MP pollution in riverine ecosystems.

Microplastic pollution in the Himalayas: Occurrence, distribution, accumulation and environmental impacts

Microplastics have been reported from various ecosystems including lakes, ponds, wetlands, mountains, and forests globally. Recent research works showed microplastic deposition and accumulation in the Himalayan mountains and adjoining ecosystems, rivers and streams. Fine particles of microplastic originating from different anthropogenic sources can travel long distances, even upwards (altitudinally) through atmospheric transport and can pollute remote and pristine locations situated in the Himalayas. Precipitation also plays a vital role in influencing deposition and fallout of microplastics in the Himalayas. Microplastics can be trapped in the snow in glaciers for a long time and can be released into freshwater rivers by snow melting. Microplastic pollution in Himalayan rivers such as the Ganga, Indus, Brahmaputra, Alaknanda, and Kosi has been researched on both the upper and lower catchments. Additionally, Himalayan region draws many domestic and international tourists throughout the year, resulting in generation of massive and unmanageable volume of plastics wastes and finally ending up in the open landscapes covering forests, river streams and valley. Fragmentation of these plastic wastes can lead to microplastic formation and accumulation in the Himalayas. This paper discusses and explains occurrence and distribution of microplastics in the Himalayan landscapes, possible adverse effects of microplastic on local ecosystems and human population and policy intervention needed to mitigate microplastic pollution in the Himalayas. A knowledge gap was noticed regarding the fate of microplastics in the freshwater ecosystems and their control mechanisms in the Indian Himalayas. Regulatory approaches for microplastics management in the Himalayas sit within the broader plastics/solid waste management and can be implemented effectively by following integrated approaches.

Recent trends on microplastics abundance and risk assessment in coastal Antarctica: Regional meta-analysis

We investigated sources, abundance and risk of microplastics (MPs) in water, sediments and biota around Antarctica. The concentration of MPs in Southern Ocean (SO) ranged from 0 to 0.56 items/m³ (mean = 0.01 items/m³) and 0-1.96 items/m³ (mean = 0.13 items/m³) in surface and sub-surface water. The distribution of fibers in water was 50%, sediments were 61%, and biota had 43%, which were followed by fragments in the water (42%), sediments (26%), and biota (28%). Shapes of film had lowest concentrations in water (2%), sediments 13%), and biota (3%). Ship traffic, drift of MPs by currents, and untreated waste water discharge contributed to the variety of MPs. The degree of pollution in all matrices was evaluated using the pollution load index (PLI), polymer hazard index (PHI), and potential ecological risk index (PERI). PLI at about 90.3% of locations were at category I followed by 5.9% at category II, 1.6% at category III, and 2.2% at category IV. Average PLI for water (3.14), sediments (6.6), and biota (2.72) had low pollution load (<10). Mean PHI for water, sediments, and biota showed hazards level V with a higher percentage of 84.6% (>1000) and 63.9% (PHI:0-1) in sediments and water, respectively. PERI for water showed 63.9% minor risk, and 36.1% extreme risk. Around 84.6% of sediments were at extreme risk, 7.7% faced minor risk, and 7.7% were at high risk. While 20% of marine organisms living in cold environments experienced minor risk, 20% were in high risk, and 60% were in extreme risk. Highest PERI was found in the water, sediments, and biota in Ross Sea, due to high hazardous polymer composition of polyvinylchloride (PVC) in the water and sediments due to human activity, particularly use of personnel care products and waste water discharge from research stations.

Spatio-temporal distribution of microplastics in water and sediment samples of the Plankenburg river, Western Cape, South Africa

Microplastic (MPs) pollution has become a subject of environmental concern due to its wide ubiquity in the environment. Microplastics are possible sources of other hazardous chemicals to aquatic organisms due to their composition and sorption properties. In this study, MPs occurrence in water and sediment samples of the Plankenburg River, Western Cape, South Africa was investigated. The physicochemical characterization of the river water was done onsite. 30 L water samples were collected and filtered in 10 L triplicates through a 250 μm mesh onsite using a metal bucket. An additional 12 L sample was collected and filtered in 4 L triplicates through 20 μm mesh in the laboratory. The extraction of MPs from water in the laboratory was by density separation. Sediment samples were also collected at the selected sites, oven-dried and microplastics in the laboratory. Sampling was conducted over four seasons - spring, summer, autumn, and winter. Microplastics were classified by visual observation and Fourier Transform Infrared Spectroscopy (FTIR-ATR). The seasonal distribution of MPs in the surface water samples varied across all sites. However, spring samples had the highest MPs occurrence (5.13 ± 6.62 MP/L) and the least, in autumn (1.52 ± 2.54 MP/L). The MPs in sediment samples were observed in spring (1587.50 ± 599.32 MP/kg). Fibres were the most dominant microplastic particle type (shape), with a size range of 500-1000 μm at the different sites. The infrared spectroscopic analysis confirmed the dominant polymer type to be polyethylene. This study provides an understanding of the microplastic occurrence in the Plankenburg River system and gives a baseline for future monitoring and assessment of water and sediment in the South African freshwater systems.

Impact of microplastics on lead-contaminated riverine sediments: Based on the enzyme activities, DOM fractions, and bacterial community structure

Microplastics (MPs) are able to interact with diverse contaminants in sediments. However, the impacts of MPs on sediment properties and bacterial community structure in heavy metal-contaminated sediments remain unclear. In this study, we investigated the adsorption of Pb(II) by sediment-MPs mixtures and the effects of different concentration MPs on sediment enzyme activities, DOM fractions, and Pb bioavailability in riverine sediments, and further explored the response of sediment microbial community to Pb in the presence of MPs. The results indicated that the addition of MPs significantly decreased the adsorption amount of Pb(II) by sediments, especially decreased by 12.6% at 10% MPs treatment. Besides, the changes in enzyme activities, DOM fractions exhibited dose-dependent effects of MPs. The higher level of MPs (5% and 10%) tends to transform Pb into more bioavailable fractions in sediments. Also, MPs amendment was observed to alter sediment bacterial community structures, and community differences were evident in the uncontaminated and lead-contaminated sediments. Therein, significant increase of Bacteroidota, Proteobacteria and decrease of Firmicutes abundance in Pb-contaminated sediment at the phylum level were observed. These findings are expected to provide comprehensive information for assessing the combined ecological risks of heavy metals and MPs in riverine sediments.

Environmental and land use controls of microplastic pollution along the gravel-bed Ain River (France) and its "Plastic Valley"

Understanding microplastic particles (MPs) accumulation and transport along rivers represents a major task due to the complexity and heterogeneity of rivers, and their interactions with their wider corridor. The identification of MPs hotspots and their potential sources is especially challenging in coarse-bed rivers transporting a wide range of particle sizes with a high degree of variability in time and space. This research focuses on the gravel-bed Ain River (Rhône River tributary, France) which is managed by means of various dams and also hosts one of the major plastic production centres in Europe (Oyonnax and Bienne Plastic Valleys). In this research, (i) Geographical Information Systems (GIS) were used to locate plastic factories and to characterise the land use of the Ain River watershed. (ii) On the field, sediment samples were extracted from the hyporheic zone (HZ) of mobile gravel bar heads, while hydro-sedimentary settings were measured in order to describe site conditions. Sampling sites were especially established in downwelling areas (i.e. where the surface water entered the hyporheic zone), upstream and downstream of dams and plastic factories. (iii) After density separation and organic matter digestion of sediment, MPs were characterised with a µFTIR device followed by data processing via the siMPle software. This work highlighted the trapping efficiency of alluvial bars for MPs. The highest MPs concentrations were found along the Plastic Valleys (up to 4400 MPs/kg), while the lower river was less contaminated by MPs. After grain-size correction, a significant breakpoint was identified in the area of the main dams, revealing their major influence on MPs distribution. The variability in MPs concentrations and types suggested a local origin for most of MPs. A particular feature was the dominance of polypropylene (PP) which appears as a critical industrial heritage as the studied region is specialised in the manufacturing of hard plastics. Indeed, multivariate analyses also revealed that MPs concentrations and types were mostly driven by the vicinity of plastic factories and urban areas. This relationship between the land use, the presence of dams and MPs characteristics provides key results for the MPs assessment and the improvement of management issues along coarse-bed rivers.

Effects comparison between the secondary nanoplastics released from biodegradable and conventional plastics on the transfer of antibiotic resistance genes between bacteria

Antibiotic resistance genes (ARGs) have caused widespread concern because of their potential harm to environmental safety and human health. As substitutes for conventional plastics, the toxic effects of short-term degradation products of biodegradable plastics (polylactic acid (PLA) and polyhydroxyalkanoates (PHA)) on bacteria and their impact on ARGs transfer were the focus of this study. After 60 days of degradation, more secondary nanoplastics were released from the biodegradable plastics PLA and PHA than that from the conventional plastics polystyrene (PS). All kinds of nanoplastics, no matter released from biodegradable plastics or conventional plastics, had no significant toxicity to bacteria. Nanoplastic particles from biodegradable plastics could significantly increase the transfer efficiency of ARGs. Although the amount of secondary nanoplastics produced by PHA microplastics was much higher than that of PLA, the transfer frequency after exposure to PLA was much higher, which may be due to the agglomeration of PHA nanoplastics caused by plastic instability in solution. After exposure to the 60 d PLA nanoplastics, the transfer frequency was the highest, which was approximately 28 times higher than that of control. The biodegradable nanoplastics significantly enhanced the expression of the outer membrane pore protein genes ompA and ompC, which could increase cell membrane permeability. The expression levels of trfAp and trbBp were increased by repressed major global regulatory genes korA, korB, and trbA, which eventually led to an increase in conjugative transfer frequency. This study provides important insights into the evaluation of the environmental and health risks caused by secondary nanoplastics released from biodegradable plastics.

Investigation of microplastic pollution in Torghabeh River sediments, northeast of Iran

Rivers are the route of transfer of microplastics from upstream to downstream areas and seas. Microplastic tracing in river sediments can provide a better reflection of long-term microplastic pollution. This study aimed to investigate the occurrence and distribution of microplastic contamination in the Torghabeh River sediments in Khorasan Razavi (Iran). Sediment samples were collected from four sites along the river. Microplastic particles were classified according to type, shape, and color. The average microplastic concentration was 8 ± 2.82 particles per 100 g of dry sediments. Most of the microplastics detected in river sediments were in the form of filaments and fragments. A total of 32 polymers were identified and isolated from sediments. According to Raman spectroscopy results, polystyrene had the highest abundance compared to polyester, polyethylene, and other polymers. The predominant shape of the microplastics in the river sediment was filament and fragmented. It can be concluded that the areas that were exposed to human activity contained more microplastic contamination. The present investigation can also provide baseline information for the study of riverine ecosystems.

Improved photodegradation of antibiotics pollutants in wastewaters by advanced oxidation process based on Ni-doped TiO2

The number of antibiotic compounds in wastewaters has been growing globally due to the covid-19 problem. Using antibiotics to treat the patients would produce larger amounts of these compounds into the environment with negative impacts. Hence, finding out the method for the elimination of toxic organic pollutants as well as antibiotics in water is urgent (In this study, the treatment of antibiotic pollutants including cefalexin (CF) and tetracycline (TC) was investigated by applying the advanced oxidation process based on Ni-doped TiO₂ (Ni-TiO₂). The characterizations technologies such as XRD, XPS, UV-vis, PL, and PC indicated that Ni doping would improve the photocatalytic performance of TiO₂. In the photodegradation experiments, the Ni-TiO₂ possessed high photocatalytic degradation efficiencies with 93.6% for CF and 82.5% for TC. Besides, the removal rates of antibiotics after five cycles are higher than 75%, implying excellent stability of Ni-TiO₂ photocatalyst. The result from the treatment of wastewater samples revealed that the Ni-TiO₂ photocatalytic had good performance for removal of CF and TC at a high level of 88.6 and 80.2%, respectively.