A case study on small-size microplastics in water and snails in an urban river

Evaluating microplastic contamination in Omani mangrove habitats using large mud snails (Terebralia palustris)

This study investigated microplastic pollution in the large mud snail Terebralia palustris (Linnaeus, 1767) (Gastropoda: Potamididae) inhabiting the Avicennia marina mangrove ecosystems along the Sea of Oman. A modified digestion protocol, combining two methods, was employed to improve the detection of microplastics within the snail tissue. Results indicated that 50 % of the examined snails contained microplastics, with significant variability observed among different lagoons. Snails from the polluted Shinas lagoon exhibited higher levels of microplastics compared to those from the lowest polluted Al-Qurum Natural Reserve (MPA). The most prevalent type of microplastic in snail tissues was fibers, making up 75.7 % of the total. Fragments constituted about 24.2 %. Using portable Raman spectrometry, Polyurethane (PU) was identified as the predominant polymer, accounting for 50 % of the total. This was followed by Acrylic and Polyethylene, each representing 18.75 %, and Polyethylene Vynil Acetate (PEVA) at 12.50 %. Overall, it is clear that while snails do reflect the presence of microplastics (MPs) in their environment, their physical attributes do not strongly correlate with the levels or types of MPs they contain. Additionally, the significant difference between the abundance of MPs in sediment and in snails illustrates that, while snails may serve as general indicators of microplastic pollution, they may not be reliable as precise bioindicators or sentinel species for quantifying the extent of this pollution. Further studies are needed to explore other potential bioindicators in mangrove habitats.

The threat of microplastics and microbial degradation potential; a current perspective

Microplastics in marine environments come from various sources, and over the years, their buildup in marine environments suggests an inevitable need for the safe mitigation of plastic pollution. Microplastics are one of the chief and hazardous components of marine pollution, as they are transferred through the food chain to different trophic levels, affecting living organisms. They are also a source of transfer for pathogenic organisms. Upon transfer to humans, several toxic effects can occur. This review aims to assess the accumulation of microplastics in marine environments globally, the threat posed to humans, and the biodegradation potential of bacteria and fungi for future mitigation strategies. The versatility of bacteria and fungi in the biodegradation of different types of plastics has been discussed, with a focus on the microbial majority that has been cultivated in labs from the marine environment. We also propose that the exploration of yet-to-be-cultivated microbial majority can be a way forward for employing future strategies to mitigate microplastics.

Pollution characterization and multi-index ecological risk assessment of microplastics in urban rivers from a Chinese megacity

Currently, a comprehensive understanding of the pollution risks of microplastics (MPs) in urban river ecosystems is still lacking. This study investigated the spatial distribution and morphological characteristics of MPs in surface waters of major rivers in Shenzhen, a megacity in China, using laser direct infrared (LDIR) imaging. A promisingly comprehensive risk assessment method, MultiMP, was first proposed in this study, taking into account the multidimensional characteristics of MPs including abundance, size, shapes, and polymer types. The results showed that MPs were widespread and highly heterogeneous, and the abundance of MPs ranged from 38 to 18380 particles/L, with an average of 2305 particles/L. Morphologically, polyamide (PA) (average 53.7 %), 30-50 µm (73.8 %), and pellet (65.7 %) were the predominant MPs types. Driving factors analyses revealed geographical distance, salinity, water temperature, and total nitrogen had relatively higher impacts on the abundance and morphology of MPs. The MultiMP results indicated that most of the river sampling sites and five major basins in Shenzhen were at moderate to high-risk levels. Polymer type and abundance had a relatively high impact on the environmental risk of MPs in the region. These findings contribute to improving the insights and management of the MPs pollution risks in megacity water bodies.

The influence of water conservancy project on microplastics distribution in river ecosystem: A case study of Lhasa River Basin in Qinghai-Tibet Plateau

Water conservancy projects affect the migration, suspension, and deposition of microplastic (MP). However, its impact on MP pollution of river ecosystem remains elusive. Herein, we investigated the MP characteristics and the influence of water conservancy projects on MPs in the Lhasa River Basin of the Qinghai-Tibet Plateau, China. The results demonstrated that the MPs concentration in surface water decreased from upstream to downstream, as more MPs in surface water were settling down and stored in reservoir sediments in the midstream. It is postulated that reservoir sedimentation of MPs occurs at a greater rate due to the barrier effect of reservoirs, steady hydrodynamics, and weak salinity-induced buoyancy. To evaluate the ecological risk of the Lhasa River Basin, the pollution load index, the polymer hazard index, and the potential ecological risk index were analyzed. The upstream exhibits elevated polymer hazard index values (>100), and the potential ecological risk index values in the Lhasa River Basin showed ecological risk similar to those of pollution load index values. This research represents the initial exploration of MP distribution within the entire Lhasa River basin, providing a foundational framework for investigating the impact of water conservancy projects on MP migration.

Bioaccumulation and biochemical impact of polyethylene terephthalate microplastics in Cipangopaludina chinensis: Tissue-specific analysis and homeostasis disruption

Microplastics are a novel pollutant that adversely affect freshwater benthic organisms. However, few studies have investigated the mechanism underlying the bioaccumulation and the toxicity of microplastics. In this study, microplastics bioaccumulation of wild Cipangopaludina chinensis in the Songhua River were utilized, and a 28-day aquatic toxicity test was performed to determine the effects of exposure to polyethylene terephthalate (PET), the bioaccumulation of PET, and changes in multiple biomarkers in the muscle, gill, and kidney tissues. The concentration pattern of microplastics was as follows: kidney tissue > muscle tissue > gill tissue. Microplastic ingestion caused AChE inhibition led to significant increases in redox and energy metabolism indicators. Furthermore, the IBR analysis presented a "response-resistance-breakdown" process, indicating that Cipangopaludina chinensis possessed resistance with time (D14 and D21) and concentration (0.10 mg/L and 1.00 mg/L) thresholds. Tissue sensitivity to microplastics was ranked as gill > muscle > kidney, which was the opposite order of microplastic accumulation. These findings implied that less sensitive tissues stored a larger amount of pollutants, suggesting a reduction in tissue sensitivity to microplastics with higher microplastic occurrence rates. This study provides new insights into biological resistance to pollutant stress, warranting further investigation into the underlying mechanisms.

Determination of microplastics in sediment, water, and fish across the Orange-Senqu River basin

Microplastics are increasingly recognised as posing a significant environmental threat across systems. Their pervasive presence in freshwater poses a serious concern, given the heavy reliance of both humans and biodiversity on healthy, functioning freshwater ecosystems. Acknowledgment of the potential risks led the transboundary Orange-Senqu River Commission (ORASECOM) to include sampling for microlitter (primarily microplastics) in riverine sediment, surface water, and fishes, across Southern Africa as part of the third Joint Basin Survey (JBS3) in 2021. The aim was to establish a first, basin-wide estimate of microlitter contamination across compartments, setting a baseline for further monitoring. The survey showed that the abundance of microlitter in riverine sediment (0 - 4000 particles.kg-1 dry weight (dw)) and riverine water (1.00 ± 0.71 - 69.75 ± 68.55 SD items.L-1) varied considerably between sample sites, with no correlation between the two. The abundance of microlitter in fishes was low (average of 0.7 ± 0.4 items.individual-1). Course resolution analyses suggested that microlitter concentrations in riverine sediment and riverine water at each site did not correlate with land use directly upstream, though variation in microlitter abundance did isolate some hotspots of contamination. Discharge data collected from nine gauging stations near sampling sites confirmed that low flows prevailed in the system during the study, with high flows occurring approximately 5 months prior during the summer months. There is some variation in river flow across the catchment which is a likely driver of microlitter transport. This was evident in the polymer composition for sediment and water samples. Based on the average discharge at each gauging station and microlitter concentrations measured in riverine water, the estimated microlitter load ranged from ∼889 particles.s-1 to ∼17.9 million particles.s-1, with a substantial amount ending likely up in the mudbelt adjacent to the Orange River mouth. This assessment provides a first insight into the characterisation and distribution of microlitter in multiple compartments across the Orange-Senqu River basin. Overall, the findings highlight the need for continued monitoring across compartments at catchment scales to improve our understanding of microplastic pathways into and within riverine systems.

Contributions from typical sources to microplastics in surface water of a semiarid urban river

Urban regions are suggested to be the main source of microplastic pollution in rivers. Thus, we investigated the spatiotemporal distribution of microplastics in the surface water of the Lanzhou section of the Yellow River in a semiarid region and the contributions of typical sources. The average concentration of microplastics in the surface water of the river was 0.98 particles (p) L-1. The daily quantity flux and mass flux were 3.63 × 109 p d-1 and 95.38 kg d-1, respectively. Most of the microplastics in the river were fibers and fragments, composed of polyethylene terephthalate, polyamide, polypropylene and polyethylene. A large quantity and mass of microplastics were found in the high-flow period of the river. The hotspots of microplastic pollution were residential and tourist reaches. The spatial distribution of microplastics was influenced by anthropogenic factors. However, the main factor influencing the temporal distribution of microplastics was precipitation seasonality. Most of the microplastics in the surface water originated from drainage ditches. The direct contribution of microplastics from atmospheric deposition was also considerable. Our results suggest that the contribution of microplastics from atmospheric deposition to urban rivers is worthy of attention.

Exploring the trophic transfer and effects of microplastics in freshwater ecosystems: A focus on Bellamya aeruginosa to Mylopharyngodon piceus

Microplastics (MPs) can enter aquatic food webs through direct ingestion from the environment or indirectly via trophic transfer, but their fate and biological effects within local freshwater food chains remain largely unexplored. In this study, we conducted the first investigation on the trophic transfer and impacts of fluorescently labeled polystyrene microplastics (PS-MPs) (100-nm and 10-μm) in a model freshwater food chain consisting of the snail Bellamya aeruginosa and the commercially important fish Mylopharyngodon piceus, both prevalent in Chinese freshwater ecosystems. Quantitative analysis revealed substantial accumulation of MPs in B. aeruginosa, reaching an equilibrium state within 12 h of exposure. While steady-state was not observed, a pronounced time-dependent bioaccumulation of MPs was evident in M. piceus over a five-week period following dietary exposure through the consumption of contaminated B. aeruginosa. Notably, MPs of both sizes underwent translocation from the gastrointestinal tract to the muscle tissue in M. piceus. High-throughput sequencing of the gut microbiota revealed that exposure to 100-nm MPs significantly altered the microbial community composition in M. piceus, and both particle sizes led to increased relative abundance of potentially pathogenic bacterial genera. Our findings provide novel insights into the trophic transfer, tissue accumulation, and biological impacts of MPs in a model freshwater food chain, highlighting the need for further research to assess the ecological and food safety risks associated with microplastic pollution in freshwater environments.

Microplastics in water: Occurrence, fate and removal

A global study on tap water samples has found that up to 83% of these contained microplastic fibres. These findings raise concerns about their potential health risks. Ingested microplastic particles have already been associated with harmful effects in animals, which raise concerns about similar outcomes in humans. Microplastics are ubiquitous in the environment, commonly found disposed in landfills and waste sites. Within indoor environments, the common sources are synthetic textiles, plastic bottles, and packaging. From the various point sources, they are globally distributed through air and water and can enter humans through various pathways. The finding of microplastics in fresh snow in the Antarctic highlights just how widely they are dispersed. The behaviour and health risks from microplastic particles are strongly influenced by their physicochemical properties, which is why their surfaces are important. Surface interactions are also important in pollutant transport via adsorption onto the microplastic particles. Our review covers the latest findings in microplastics research including the latest statistics in their abundance, their occurrence and fate in the environment, the methods of reducing microplastics exposure and their removal. We conclude by proposing future research directions into more effective remediation methods including new technologies and sustainable green remediation methods that need to be explored to achieve success in microplastics removal from waters at large scale.

Analysing micro- and nanoplastics with cutting-edge infrared spectroscopy techniques: a critical review

The escalating prominence of micro- and nanoplastics (MNPs) as emerging anthropogenic pollutants has sparked widespread scientific and public interest. These minuscule particles pervade the global environment, permeating drinking water and food sources, prompting concerns regarding their environmental impacts and potential risks to human health. In recent years, the field of MNP research has witnessed the development and application of cutting-edge infrared (IR) spectroscopic instruments. This review focuses on the recent application of advanced IR spectroscopic techniques and relevant instrumentation to analyse MNPs. A comprehensive literature search was conducted, encompassing articles published within the past three years. The findings revealed that Fourier transform infrared (FTIR) spectroscopy stands as the most used technique, with focal plane array FTIR (FPA-FTIR) representing the cutting edge in FTIR spectroscopy. The second most popular technique is quantum cascade laser infrared (QCL-IR) spectroscopy, which has facilitated rapid analysis of plastic particles. Following closely is optical photothermal infrared (O-PTIR) spectroscopy, which can furnish submicron spatial resolution. Subsequently, there is atomic force microscopy-based infrared (AFM-IR) spectroscopy, which has made it feasible to analyse MNPs at the nanoscale level. The most advanced IR instruments identified in articles covered in this review were compared. Comparison metrics encompass substrates/filters, data quality, spatial resolution, data acquisition speed, data processing and cost. The limitations of these IR instruments were identified, and recommendations to address these limitations were proposed. The findings of this review offer valuable guidance to MNP researchers in selecting suitable instrumentation for their research experiments, thereby facilitating advancements in research aimed at enhancing our understanding of the environmental and human health risks associated with MNPs.

Intelligent classification and pollution characteristics analysis of microplastics in urban surface waters using YNet

Microplastics (MPs, ≤ 5 mm in size) are hazardous contaminants that pose threats to ecosystems and human health. YNet was developed to analyze MPs abundance and shape to gain insights into MPs pollution characteristics in urban surface waters. The study found that YNet achieved an accurate identification and intelligent classification performance, with a dice similarity coefficient (DSC) of 90.78%, precision of 94.17%, and recall of 89.14%. Analysis of initial MPs levels in wetlands and reservoirs revealed 127.3 items/L and 56.0 items/L. Additionally, the MPs in effluents were 27.0 items/L and 26.3 items/L, indicating the ability of wetlands and reservoirs to retain MPs. The concentration of MPs in the lower reaches of the river was higher (45.6 items/L) compared to the upper reaches (22.0 items/L). The majority of MPs detected in this study were fragments, accounting for 51.63%, 54.94%, and 74.74% in the river, wetland, and reservoir. Conversely, granules accounted for the smallest proportion of MPs in the river, wetland, and reservoir, representing only 11.43%, 10.38%, and 6.5%. The study proves that the trained YNet accurately identify and intelligently classify MPs. This tool is essential in comprehending the distribution of MPs in urban surface waters and researching their sources and fate.

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

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

Distribution and characteristics of microplastics in an urban river: The response to urban waste management

The rivers have been proven to be potential sources and the major transport pathways of microplastic (MP) in natural aquatic eco-systems, yet there is an absence of understanding the provenances and distribution dynamics of MP in fluvial water body of urban regions. The present investigation aimed to characterize the distribution and accumulation of MPs in both surface water and riverine bed sediments in a typical urban river (Nanming River, southwest China), during the dry and wet seasons of 2021. MP were detected throughout the entire sample set, with average surface water abundances of 750 ± 53 n/m3 and 693.3 ± 40 n/m3 in dry and wet seasons, respectively, and 2250 ± 496.7 n/kg (dw) in surface sediments. Furthermore, the composition of 25 polymer types MPs were analyzed. The sediment of the Nanming River is a sink for MPs, recording their long-term accumulation. Multivariate statistical analysis-based results indicated that urban littering and agricultural input were the major contributors of non-point MP in the Nanming River, while the discharged effluent was another factor influencing the distribution of MPs in urban fluvial system. The average abundance of MPs was negatively correlated with purchase power parity (PPP), demonstrating that the poorly waste management results in a higher abundance of MPs in municipal river systems. The present study systematically characterized the distribution of MPs in medium-sized urban rivers systems in Southwest China. These findings can inform policy and management decisions to reduce MPs pollution in urban rivers and protect aquatic ecosystems.

Polyethylene Microplastics Affected Survival Rate, Food Intake and Altered Oxidative Stress Parameters in Freshwater Snail Indoplanorbis exustus

Microplastics have a negative impact on aquatic ecosystems. Gastropod mollusks serve as bioindicators and are good model systems for ecotoxicological studies. To assess oxidative damage, we exposed the ram's horn snail, Indoplanorbis exustus, to various concentrations of low-density polyethylene microplastics (size range 8-100 µm). The main objectives were microplastics preparation, characterization, and examination of their effect on the essential organs of I. exustus. Scanning electron microscopy, fourier transform infrared spectroscopy and x-ray diffraction techniques confirmed the polymer type of laboratory prepared polyethylene microplastics. The LC50 value of microplastics for snails was calculated to be 872 mg/L after 96 h of exposure. We observed a significant elevation in superoxide dismutase, catalase and lipid peroxidation levels with increasing concentrations of microplastics. Microplastics exposure also affected protein content, total food intake and total weights. Moreover, snails failed to recover post-treatment. Snails collected from contaminated source of microplastics served as positive control for the study. Hence, we can conclude that microplastics cause overall impairment in the physiological parameters and show adverse effects on the freshwater snail, I. exustus.

Microplastic pollution in organic farming development cannot be ignored in China: Perspective of commercial organic fertilizer

Commercial organic fertilizer, an essential fertilizer for developing organic farming in China, has been identified as a potentially important source of microplastics (MPs) on farmland. However, little is known about the occurrence of MPs in commercial organic fertilizers and their potential ecological risks nationwide. Here, stereoscopy and laser-infrared imaging spectrometry were used to comprehensively investigate the abundance, size, type and morphology of MPs in commercial organic fertilizers collected from mainland China, assess the ecological risks, and predict MP contamination. Commercial organic fertilizers contained many MPs (8.88 ×103 to 2.88 ×105 items/kg), especially rich in small-size MPs (<100 µm), accounting for 76.53%. The highest MP pollution load value was observed in fertilizers collected from East China. Chlorinated polyethylene, polyurethane, polyethylene and polypropylene were the dominant MPs with the shape of film and fragment, concentrated in small sizes (<100 µm). The risk index (H-index) of the MPs was used to quantify the ecological risk of the MPs in the different samples, and most of the fertilizers were at level Ⅲ with high risk. Predictably, 2.32 × 1013 - 2.81 × 1016 MPs will accumulate in orchard soils after five years of fertilization, especially in South, Southwest and East China. This study provides primary scientific data on MP pollution in commercial fertilizer and the health development of organic farming.

Interventions of river network structures on urban aquatic microplastic footprint from a connectivity perspective

Microplastic footprint in urban river networks can be disturbed by multiple urbanization features, and regional river structures are generally overlooked. In this research, we analyzed the distribution of microplastics and potential impact pattern of river structures on it in a typical urban river network in Nanjing, China. Surface waters of the river network were jointly detected by multiple methods, and the Renkonen similarity index was used to study spatial variabilities of microplastics characteristics. Microplastics were ubiquitous and abundant, showing five (>50 μm) and six (20∼50 μm) hotspots, and heterogeneities in the shape and type of microplastics larger than 100 μm were prominent, presumably influenced by river network scale and connectivity. River structure parameters associated with network connectivity were obtained by combining graph theory and an entropy-based set-pair analysis model. Aiming at the action pathway of river structures, by using correlation and partial least squares regression analysis, we found that river node (confluences and sluices) ratio, river frequency, river network density, and water system circularity were significantly positively correlated with microplastic abundance, and confluences with poor connectivity had a greater indirect intervention intensity on the microplastic distribution. The land use characteristics dominated the fitting of microplastic abundance, which was about 1.2 times better than river structures, and the comprehensive land use intensity and river network connectivity were the critical factors, respectively. Potential ecological risks of microplastics were evaluated, resulting in relatively severe levels. This study proposed targeted measures to control urban microplastic pollution by combining the perspective of river network characteristics. To summarize, our exploration of microplastic footprint based on urban river network structures from the perspective of river network connectivity provides new insights into microplastic management.

New insight into the effect of microplastics on antibiotic resistance and bacterial community of biofilm

Microplastics (MPs) could serve as substrates for microbial colonization and biofilm formation. However, research on the effects of different types of microplastics and natural substrates on biofilm formation and community structure in the presence of antibiotic-resistant bacteria (ARB) is limited. In this study, we employed by means of microcosm experiments to analyze the situation of biofilms conditions, bacterial resistance patterns, antibiotic resistance genes (ARGs) distribution, and bacterial community on different substrates using microbial cultivation, high throughtput sequencing and PCR. The result showed that biofilms on different substrates markedly increased with time, with MPs surfaces formed more biofilm than stone. Analyses of antibiotic resistant showed negligible differences in the resistance rate to the same antibiotic at 30 d, but tetB would be selectively enriched on PP and PET. The microbial communities associated with biofilms on MPs and stones exhibited variations during different stages of formation. Notably, phylum WPS-2 and Epsilonbacteraeota were identified as the dominant microbiomes of biofilms on MPs and stones at 30 d, respectively. Correlation analysis suggested that WPS-2 could potentially be a tetracycline-resistant bacterium, while Epsilonbacteraeota did not correlate with any detected ARB. Our results emphasized the potential threat posed by MPs as attachment carriers for bacteria, particularly ARB, in aquatic environments.

Occurrence of microplastics in commercially sold bottled water

Microplastics are ubiquitous in all environmental compartments, including food and water. A growing body of evidence suggests the potential health impacts of continuous microplastic ingestion on humans. However, a lack of information on microplastic exposure to humans through drinking water and the high heterogeneity of available data limits advancements in health risk assessments. In the present study, laser direct infrared spectroscopy (LD-IR) was used to determine the occurrence of microplastics in bottled water sold in China. Then, the ingestion level of microplastics through drinking water was estimated. The results showed that the average microplastic abundance in bottled water was 72.32 ± 44.64 items/L, which was higher than that detected in tap water (49.67 ± 17.49 items/L). Overall, the microplastic structures were dominated by films and mainly consisted of cellulose and PVC. Their sizes were concentrated in the range of 10-50 μm, accounting for 67.85 ± 8.40 % of the total microplastics in bottled water and 75.50 % in tap water. The estimated daily intake of microplastics (EDI) by infants through bottled water and tap water was almost twice as high as that by adults, although adults ingested more microplastics. The present results provide valuable data for further assessing human health risks associated with exposure to microplastics.

Identification of microplastics in human placenta using laser direct infrared spectroscopy

Microplastics are ubiquitous in the environment, including in food and drinking water. Consequently, there is growing concern about the human health risks associated with microplastic exposure through diet. However, the occurrence of microplastics in the human body, particularly in mothers and fetuses, is incompletely understood because of the limited amount of data on their presence in the body and the human placenta. This study evaluated the presence and characteristics of microplastics in 17 placentas using laser direct infrared (LD-IR) spectroscopy. Microplastics were detected in all placenta samples, with an average abundance of 2.70 ± 2.65 particles/g and a range of 0.28 to 9.55 particles/g. Among these microplastics, 11 polymer types were identified. The microplastics were mainly composed of polyvinyl chloride (PVC, 43.27 %), polypropylene (PP, 14.55 %), and polybutylene succinate (PBS, 10.90 %). The sizes of these microplastics ranged from 20.34 to 307.29 μm, and most (80.29 %) were smaller than 100 μm. Most of the smaller microplastics were fragments, but fibers dominated the larger microplastics (200-307.29 μm). Interestingly, the majority of PVC and PP were smaller than 200 μm. This study provides a clearer understanding of the shape, size, and nature of microplastics in the human placenta. Importantly, these data also provide crucial information for performing risk assessments of the exposure of fetuses to microplastics in the future.