Spatial, seasonal and ecological risk assessment of microplastics in sediment and surface water along the Thoothukudi, south Tamil Nadu, south east India

Evidence of microplastics in the polychaete worm (capitellids-Capitella capitata) (Fabricicus, 1780) along Thoothukudi region

Research on the occurrence of microplastics in invertebrates of the Thoothukudi region is limited. Capitellids are non-selective suspension feeders and are usually used as bioindicator of water pollution. Hence, an investigation was carried out to identify the microplastic occurrence in the capitellids (Capitella capitata) (Fabricius, 1780) collected from the Vellapatti and Spic Nagar sites of the Thoothukudi region. Result from this investigation showed the occurrence of 0.21 ± 0.17 items/indiv and a mean abundance of 13.33% in Thoothukudi coast. The mean microplastic abundance in the capitellids was significantly higher in the Spic Nagar (0.26 ± 0.19 MPs/indiv), probably due to the dumping of plastic waste, fishing and recreational activities. However, no significant difference was observed between seasons. Only fragments (Vellapatti 66.66% and Spic Nagar 33.33%) and fibre-shaped microplastics (Vellapatti 50% and Spic Nagar 50%) were identified. The size and colour of the microplastics dominant in both sites were 1-2 mm (Vellapatti 77.77% and Spic Nagar 75%) and blue (Vellapatti 88.88% and Spic Nagar 87.5%), respectively. The results of Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) analysis revealed the presence of polyethylene (PE) and polypropylene (PP) polymers in the capitellids. PE polymer is one of the most common sources of microplastics contamination globally and it is also frequently found in the coastal waters of Thoothukudi. This accounted for the high occurrence of PE polymers in the capitellids with the occurrence rate of 77% in Vellapatti and 58.52% in Spic Nagar. The present study provides baseline data on the occurrence, characterization (shapes, sizes and colours) and qualitative analysis of the microplastics in the capitellids, and their presence was influenced by their non-selective feeding habits. Further, future studies have to be conducted to identify the levels of microplastics in different polychaetes and other invertebrates to better understand the effects of microplastic pollution in invertebrate communities.

Deciphering the seasonal dynamics of microplastic morphotypes and associated co-contaminants along the northwest coast of India

In the present study, the northwest coast of India, bordering the Arabian Sea, was selected to evaluate the microplastic (MP) abundance. This is the first study to emphasize the effects of different seasons on MP distribution. The collected MPs were dried, segregated, and evaluated based on their morphotype, size, color, and polymer type. A total of 1756.6, 7326.6, and 202 particles/kg of sand were estimated in the pre-monsoon, monsoon and post-monsoon seasons, respectively, with a dominance of polypropylene (PP) type of plastic in the pre-monsoon and high-density polyethylene (HDPE) in monsoon and post-monsoon seasons. HDPE and PP collected MPs during the monsoon season were further characterized for associated contaminants. Metal absorbance was detected using SEM-EDX mapping and ICP-MS. The presence of organic compounds (OCs) was analyzed using GC-MS. MPs exhibit distinct associations with metals, among which the HDPE pellet morphotype exhibits a higher range of metal adsorption. Total 61 different OCs were associated with MPs. The HDPE pellets contained the highest amounts of hydrophobic organic compounds. PP pellets were found to contain triglycerides, fatty aldehydes, and alkaloids, along with HOCs. Among morphotypes, pellet forms of MPs were found to adsorb more contaminants. These co-contaminants infiltrate the study area through sewage runoff and shoreline debris deposition, subsequently interacting with MPs. Furthermore, the MP diversity was studied by employing the MP diversity integrated index, which suggests that most of the MP diversity was observed in the pre-monsoon period. The pollution load index employed an MP risk assessment, which presented a low degree of MP contamination. In contrast, the polymer hazard index was calculated as 21650.3 in post-monsoon, placing the area under the extreme danger category. It is evident from the data that the types of MP is more important than their number. Thus, MP morphotypes have importance in the adsorption of co-contaminants.

Impact of anthropogenic activities on the abundance of microplastics in copepods sampled from the southeast coast of India

In recent year, the use of plastics has become inevitable due to its unique properties that allow for the production of durable and non-durable goods. Post use, plastics enter the waste stream and now can be found in all compartments of the biosphere as microplastics (MPs). This study presents the abundance of MPs in surface water and within copepods in the southwestern Bay of Bengal during dry (June 2022) and wet season (November 2022). The MPs in the surface water were found in all three regions [Chennai, Tuticorin and Nagapattinam (four locations in each region)] and maximum in wet season (53 particles/m3). Moreover, during dry season the mean ingestion of MPs by copepods in Chennai (0.103 ± 0.04 particles/individual), Tuticorin (0.11 ± 0.07 particles/individual) and Nagapattinam (0.036 ± 0.01 particles/individual) is high compared to the wet season. The maximum level of MPs found in both surface water and ingestion by copepods in Tuticorin and Chennai is subjective to the high maritime activities than Nagapattinam region. Whatever, the anthropogenic activities in the study region increase the bioavailability of MPs pollutant in the copepods and transported to higher trophic levels, endangering marine life and human health. Hence, further studies are needed to determine their potential impact on marine food chain in this alarming situation.

Distribution of microplastics in seafloor sediments and their differential assimilation in nearshore benthic molluscs along the south-west coast of India

Spatial and temporal distribution of microplastics (MPs) in the nearshore seafloor sediments along the Southwest coast of India and their patterns of accumulation in selected infaunal and epibenthic molluscs with diverse feeding strategies were investigated. Along the 300-km coastal stretch, which is one of the most productive and biodiversity rich regions of the eastern Arabian Sea, notable levels of MP contamination in both sediment (617.7 items/kg dry weight) and molluscs (5.39 items/g) was recorded. The concentration of MPs in sediments also varied seasonally, with a higher prevalence during the post-monsoon season. Among the four molluscan groups studied, the highest MP abundance was recorded among scavenging gastropod Pseudominolia biangulosa (9.13 items/g), followed by microcarnivore scaphopod Tesseracme quadrapicalis (5.96 items/g). In comparison, the suspension feeding bivalve, Anadara hankeyana and deposit feeding clam Jitlada philippinarum had lesser accumulation of MPs (2.98 items/g and 3.50 items/g respectively). The majority of MPs in sediments and within molluscs were less than 250 μm in size (89.14%) and were predominantly fibres and fragments. Chemical characterisation of MPs revealed eleven types of polymers dominated by polyethylene (PE) and polypropylene (PP). Present study identified positive correlations between ingested MP polymers and the feeding strategies of molluscs. Higher values for the ecological risk assessment indices (PHI, PLI and PERI) in most of the stations indicated the severity of plastic pollution in the region. Molluscs being a major contributor to the benthic food web is also a connecting link to higher trophic levels. Hence understanding the specificity in the MPs accumulation pattern within this group has far reaching significance in utilizing them as potential bioindicators for pollution studies in marine ecosystems.

Spatial distribution and vertical characteristics of microplastics in the urban river: The case of Qinhuai River in Nanjing, China

Microplastics (MPs) are emerging as global environmental pollutants, significantly influencing the safety of city rivers. This study investigated six sampling sites in the Qinhuai River of Nanjing, which explored the distribution and characteristics of MPs and the microbial structure in 2023. The studied river contained various levels of MPs with average concentrations of 667.68 items/L, whose abundance firstly decreased midstream and then increased downstream. The MPs abundance upstream was higher in surface water column, microplastics midstream and downstream accumulated more in deep water column. Black and blue are prevalent in the color distribution, while the polymers of PC, PP and PS changed with increasing depth, with a proportion of 74 % ∼ 97 % in the dominant shapes of granules. Furthermore, the water with higher MPs may stimulate the growth of MPs-related bacteria in sediments, including the genus of Pseudoxanthomonas and Dechloromonas. Our research will provide constructive support for enhancing urban river management strategies.

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

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

Temporal and spatial variation of microplastics in Baotou section of Yellow River, China

Freshwater rivers play the key role in providing drinking water sources and building the bridge of oceans and lands. Hence, environmental pollutants can be transferred into drinking water through a water treatment process and transported land-based microplastics into the ocean. Microplastics are considered a new pollutant that is becoming a threat to freshwater ecosystems. The present study investigated the temporal and spatial variation of microplastics abundance and their characteristics of occurrence in surface water, sediment and soil samples of Baotou section of Yellow River in China in March 2021 and September 2021. According to the LDIR analysis, the average abundances of microplastics in wet season (surface water 2510.83 ± 2971.27n/L, sediment 6166.67 ± 2914.56n/kg) were higher than that in dry season（surface water 432.5 ± 240.54n/L, sediment 3766.67 ± 1625.63n/kg), particularly being significant difference in the dry and wet seasons of surface water. The predominant polymer types in surface water (PBS and PET during the dry season, PP during the wet season) demonstrated that the temporal variation of microplastics abundance in surface water could be attributed to the combined effect of the regional precipitation, fishing activities and improper disposal of plastic waste. And the results of spatial abundances of microplastics showed that the microplastics abundance of soil and sediment was higher than that in river water and microplastics abundance in the river of the south side was the higher than other water sampling sites, revealing the differences of microplastics burden at the different sampling sites. Moreover, it is worth noting that a large amount of PAM was detected in sediments and soil, but not in water, and the biodegradable plastics PBS and PLA were also detected in the Yellow River. It was a very useful information for evaluating environmental impacts and ecological effects of degradable plastics compared to the traditional plastics after the implementation of a new environmental policy in the future. Thus, this study provided insights into the temporal-spatial characteristics of microplastics in an urban river and raised environmental management awareness of the long-term threat to drinking water safety by microplastics.

Spatio-temporal evaluation and risk assessment of microplastics in nearshore surface waters post-2018 Kerala deluge along the southwest coast of India

Spatial and temporal distribution of microplastics along the nearshore surface waters of Kerala after the floods of 2018 was studied. Results indicated a seven-fold increase in its mean concentration (7.14 ± 3.03 items/m³) post deluge. The average abundance was highest during pre-monsoon (8.27 ± 3.09 items/m³). Fibres were the dominant group, with blue and black being the most prevalent colours. Polyethylene and polypropylene were the most commonly found polymers, possibly gaining entry through sewage waste or land-based plastic litter. Highest abundance of microplastic was recorded off Kochi categorising it at Hazard Level I under Pollution Load Index assessment. Similarly high levels of Pollution Hazard Index and Potential Ecological Risk Index were also reported due to the presence of hazardous polymers PVC and PU that can cause concern to marine life. The differential weathering pattern and surface morphology analysis suggested microplastics to be relatively old that had undergone substantial mechanical and oxidative weathering.

New insights into the distribution, potential source and risk of microplastics in Qinghai-Tibet Plateau

Microplastics (MPs) as emerging contaminants have become a major global concern, however, the distribution and origin of MPs in Qinghai-Tibet Plateau (QTP) and their impacts on ecosystem are poorly known. Hence, we systematically evaluated the profile of MPs on the representative metropolitan locations of Lhasa and Huangshui Rivers and the scenic sites of Namco and Qinghai Lake. The average abundance of MPs in the water samples was 7020 items/m³, which was 34 and 52 times higher than those for the sediment (206.7 items/m³) and soil samples (134.7 items/m³), respectively. Huangshui River had the highest levels, followed by Qinghai Lake, Lhasa River and Namco. Human activities rather than altitude and salinity impacted the distribution of MPs in those areas. Besides the consumption of plastic products by locals and tourists, laundry wastewater and exogenous tributary inputs, the unique prayer flag culture also contributed to the MPs emission in QTP. Notably, the stability and fragment of MPs were crucial for their fate. Multiple assessment models were employed to evaluate the risk of MPs. PERI model took MP concentration, background value and toxicity into account, comprehensively describing the risk differences of each site. The large PVC proportion in Qinghai Lake posed the highest risk. Furthermore, concerns should be raised about PVC, PE and PET in Lhasa and Huangshui Rivers, and PC in Namco Lake. Risk quotient suggested that aged MPs in sediments slowly released biotoxic DEHP and should be cleaned up promptly. The findings offer baseline data of MPs in QTP and ecological risks, providing important support for the prioritization of future control measures.

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.