Microplastic pollution in the Chapora River, Goa, Southwest India: spatial distribution and risk assessment

The amount of information available on the microplastic (MP) contamination in Goa's riverine water systems is currently limited. The abundance, size, colour, and polymer composition of microplastics in Chapora River surface water were investigated in this study. MPs in Chapora River surface water ranged from 0.1 particles/L (station 13) to 0.47 particles/L (station 5). The mean (± standard deviation) MP concentration was 0.25 (± 0.13) particles/L. Fibre was the dominant shape (77.15%), followed by fragments (12.36%), films (9.36%), and foam (1.12%). Most MPs were found in the 0.1-0.3 mm size range, then in the 0.3-1 mm and 1-5 mm. The dominant type of polymer studied was polyethylene terephthalate (PET; 46%), followed by high-density polyethylene (HDPE; 14%), polypropylene (PP; 5%), and polystyrene (PS; 1%). The risk assessment study indicated high risk with respect to PHI, while PLI shows low risk in the area. The source of MPs was mostly anthropogenic in nature in the region. When compared with other tropical rivers, MP pollution was relatively lower in the Chapora River. Nevertheless, the baseline data will help the local administration take mitigation measures to reduce the impact of MP pollution in the region.

Microplastics in Scylla Serrata: A baseline study from southwest India

Scylla serrata plays a crucial role in India's seafood exports yet there exists limited understanding on the occurrence of microplastics (MPs) in these crabs. In this baseline study, we examined the presence of microplastics in the digestive tracts of S. serrata collected from the Kota mangroves, southwestern coast of India. Our analysis revealed the presence of 264 MPs in all the samples with an average (± standard deviation) of 29.33 (±11.53) MPs/Individual. The most dominant categories were fibres (98.86 %) and fragments (1.14 %). Primarily 0.1-0.3 mm (50.90 %) and 0.3-1 mm (37.65 %) size range dominated. The predominant polymers were polypropylene (33.71 %), high-density polyethylene (31.44 %), and polyethylene terephthalate (17.80 %). Scanning electron microscopy revealed extensive weathering on the surface of the microplastics. Risk assessments indicated severe risks to S. serrata due to microplastic ingestion emphasizing the need to protect delicate ecosystems like mangroves and the biota within.

Integrated LIBS-Raman spectroscopy: A comprehensive approach to monitor microplastics and heavy metal contamination in water resources

The increased use of plastic products and global industrial conditions have contaminated natural resources, especially water, with pollutants such as microplastics and trace elements, including heavy metals. Hence, continuous monitoring of water samples is an urgent requirement. However, the existing microplastic-heavy metal monitoring methodologies require discrete and sophisticated sampling approaches. The article proposes a multi-modal LIBS-Raman spectroscopy system for detecting microplastics and heavy metals from water resources with unified sampling and pre-processing approaches. The accomplishment of the detection process is using a single instrument by exploiting the trace element affinity of microplastics, which operates in an integrated methodology to monitor water samples for microplastic-heavy metal contamination. The polypropylene (PP), polyethylene (PE), and polyethylene terephthalate (PET) plastic types dominate the identified microplastics from different sampling spots: in an estuary formed by the Swarna River near Kalmadi (Malpe) in Udupi district, and from River Netravathi in Mangalore, Dakshina Kannada District, Karnataka, India. The detected trace elements from microplastic surfaces include heavy metals such as Al, Zn, Cu, Ni, Mn, and Cr and other elements counting Na, Mg, Ca, and Li. The system could record concentrations of trace elements down to 10 ppm, and comparing results with the conventional technique of Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) confirms the ability of the system to detect trace elements from microplastic surfaces. In addition, comparing results with direct LIBS analysis of water from the sampling site shows better results in microplastic-based trace element detection.

Microplastics in the marine environment of St. Mary's Island: implications for human health and conservation

Microplastics have now been identified as a class of emerging pollutants and is considered as a threat to aquatic organisms. This baseline paper investigated the distribution, composition, and potential ecological risks of microplastic (MP) pollution on St. Mary's Island, revealing an average abundance of 0.218 particles/L in water samples. Blue fibres and white foams were the primary MPs identified, and fishing activities and packaging were the main sources of pollution. Six types of polymers were identified: low-density polyethylene (LDPE), polystyrene (PS), polyamide (PA), polypropylene (PP), polyethylene (PE), and high-density polyethylene (HDPE). The Polymer Hazard Index (PHI) and Potential Ecological Risk Index (PERI) indicated a medium environmental risk for the island. Additionally, it was discovered that MPs' surfaces contained dangerous substances that could endanger aquatic life. The research emphasizes the significance of implementing measures such as responsible disposal, management, elimination, regulatory policies, and local administration techniques to mitigate the impact of MP pollution on the island's shores and marine biota. This research provides a baseline for monitoring MP contamination and underscores the need for continuous investigation to assess their impacts on marine life.

Did the COVID-19 pandemic play a role in the spatial and temporal variations of microplastics? Evidence from a tropical river in southern India

Personal protective equipment (PPE) use has increased because of COVID-19, producing more microplastics (MPs). The pandemic's impact on MP pollution in Indian rivers is little understood. In this study, the Netravathi River in Karnataka was investigated for the spatiotemporal distribution of MPs. The MPs abundance, size, and categories varied seasonally, with a higher concentration during the monsoon seasons. The reduction in rainfall during MON20 and the COVID-19 lockdown can be the reasons for the significant decrease in the MP concentration when compared to MON19. Polyethylene and polyethylene terephthalate were the most abundant polymers, with a shift from polyethylene to the latter (74 %) during post-monsoon season post-lockdown. The situation of MP pollution in Western Ghats can be mitigated with the aid of appropriate waste management of plastic trash and greater public awareness about the disposal of single-use plastics, which has risen significantly during the COVID-19 pandemic.

Exploring the presence and distribution of microplastics in subterranean estuaries from southwest India

Rivers, surface runoff, and the wind all transport microplastics (MPs) to the ocean. There is a knowledge gap concerning the distribution of microplastics in transitional subterranean estuaries. Here, we report the presence of microplastics in the pore water, groundwater, and sea water from four locations in southwest India. Pore water, groundwater, and seawater had mean MP abundances (± standard deviations) of 0.75 (±0.66), 0.15 (±0.1), and 0.11 (±0.07) MPs/l, respectively. Fibres were the dominant category of MPs found. Fourier-transformed infrared spectroscopy revealed the presence of polymers like polyester, low-density polyethylene, and polystyrene. Possible sources of microplastic are fishing activities, tourism, and coastal residents. The microplastics-derived risk assessment scores indicate severe risk to the ecosystems. Fibrous microplastics in pore water indicate that these linear particles can migrate vertically through sandy sediments, reaching subterranean estuaries. We believe submarine groundwater discharge can act as a possible pathway for microplastics to enter the oceans.

A first report on the spatial and temporal variability of microplastics in coastal soils of an urban town in south-western India: Pre- and post-COVID scenario

We present a first study on the temporal changes (2019-2021) in the microplastic abundance in the coastal soils of an urban town in the south-western part of India. All sampling stations exhibited higher abundances of microplastics in soils collected during 2021 (959.7 ± 277.7 particles/kg) compared to those collected in 2019 (515.1 ± 182.7 particles/kg). Morphologically, flakes, fibres, and films are the most abundant types documented in the soil environment. The microplastics of 0.3-5 mm size are relatively more abundant (60.6 %) compared to those of 0.03-0.3 mm size (39.4 %) in 2021. The three main types of polymers (polypropylene and high- and low-density polyethylene) in the soil exhibited an increase in abundance during an interval of 15 months (October 2019 to March 2021). In addition to packaging materials, the enhanced use of surgical masks during the COVID-19 period might have acted as a source of microplastic contamination in the soils.

Time to kick the butt of the most common litter item in the world: Ban cigarette filters

Cigarette filters offer no public health benefits, are single-use plastics (cellulose acetate) and are routinely littered. Filters account for a significant proportion of plastic litter worldwide, requiring considerable public funds to remove, and are a source of microplastics. Used cigarette filters can leech toxic chemicals and pose an ecological risk to both terrestrial and aquatic ecosystems. Bottom-up measures, such as focusing on consumer behaviour, are ineffective and we need to impose top-down solutions (i.e., bans) if we are to reduce the prevalence of this number one litter item. Banning filters offers numerous ecological, socioeconomic, and public health benefits.

Assessment of pollution and risks associated with microplastics in the riverine sediments of the Western Ghats: a heritage site in southern India

There is very little knowledge on microplastic pollution in the Western Ghats (WG), a heritage site in southwest India. To address this, we have studied the spatiotemporal variations of sedimentary microplastics (MPs) from the River Sharavathi, a pristine river in the Western Ghats (WG), southern India. The rich biodiversity in the region makes it relevant to analyse the distribution of this emerging pollutant that is causing harm to the biota and the ecosystem. We analysed the sedimentological and carbon content (organic and inorganic) of these sediments and explored their relationship with MPs. Finally, risk assessment indices such as the Pollution Load Index (PLI), the Polymer Hazard Index (PHI), and the Potential Ecological Risk Index (PERI) were calculated to detect the levels of plastic pollution. The concentration of MPs ranged from 2.5 to 57.5 pieces/kg and 0 to 15 pieces/kg during the pre-monsoon and post-monsoon seasons, respectively. The dip in the MPs' abundance during the post-monsoon season was due to the extremely high rainfall in the river basin during July-August 2019, which would have entrained the sedimentary MPs and transported them to the coast/Arabian Sea. Smaller MPs (0.3-1 mm) were more abundant than the larger MPs (1-5 mm), mainly due to the breakdown of sedimentary plastics by physical processes. Fragments, films, foams, and fibres were the main categories of MPs, and the main polymers were polyethylene, polyethylene terephthalate, and polypropylene. No significant relationship was observed between the sedimentological properties and microplastics, which may be due to the different physical properties of sediments and microplastics. The PLI, PHI, and PERI indices suggest different contamination levels in the river basin. Based on the PLI scores, all the samples belong to the hazardous level I suggesting minor risk category, and the risk of microplastic pollution falls under the high to hazardous risk category based on the PHI values. The PERI value ranged from 160 to 440 and 40 to 2240 during the pre-monsoon and post-monsoon seasons, respectively. The risk assessment in a region known for its rich biodiversity is crucial, as the data can be used by the district administration to mitigate plastic pollution.

A baseline study of microplastic pollution in a Southern Indian Estuary

Knowledge on the processes controlling the vertical distribution of microplastics (MPs) in estuaries is less. This research was carried out to determine the MP distribution in the surface, middle, and bottom layers of the Udyavara River Estuary in southwest India. The mean (± standard deviation) concentrations were 320.83 (± 98.30), 514.55 (± 352.16), and 755.03 (± 400.96) particles/m³, respectively. Fibres, films, and fragments dominated, and 57 % of the MPs had a size range of 0.3-1 mm, while 43 % had a size of 1-5 mm. The main polymers were high-density polyethylene and polyethylene terephthalate. A positive correlation (r = 0.421, p = 0.0205, n = 30) exists between the MPs and salinity, suggesting that the MPs are held by dense saline waters. The mean pollution load index value was 2.25 indicating severe pollution. Microplastic pollution is due to harbour, fishing, industrial activities, the effects of southwest monsoon rain, and tidal currents.

Hidden problems in geological heritage sites: The microplastic issue on Saint Mary's Island, India, Southeast Arabian Sea

Microplastics (MPs) have become a dominant constituent of several oceanic islands. This study focuses on the occurrence and distribution of MPs present in the beach sediments of Saint Mary's Island (SMI), a geological heritage site located in the south-eastern part of the Arabian Sea. The average (standard deviation) abundance of MPs on this island was 97.18 (80.49) particles/kg. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy revealed that MPs are composed of high-density polyethylene (HDPE), low-density polyethylene (LDPE), polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyamide (PA). Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS) highlighted the presence of Cr, As, Pb, and Cd (harmful pollutants) on MP surfaces. The MPs in the SMI are largely contributed by the nearby fishing harbour, touristic beaches and estuaries. The results of this study, act as a starting point for continuous environmental monitoring in this unique region of the world.

Seasonal variations in the abundance and distribution of microplastic particles in the surface waters of a Southern Indian Lake

Hazardous anthropogenic particles, such as microplastics (MPs) in the lake ecosystems, are a serious concern. In this work, we have investigated the seasonal occurrence and distribution of microplastics in the surface water samples of Lake Manipal in southwest India. The concentration of MPs was found to be higher during the monsoon season (0.423 particles/L) in comparison with the post-monsoon (0.117 particles/L) period. The higher abundance is attributed to the input of storm-water sewers connected to the lake as well as surface runoff during periods of high rainfall. The concentrations of small-sized (0.3-1 mm) microplastics were greater in both seasons. Approximately 96% of the microplastics were fibres, followed by smaller amounts of fragments, pellets, films, and foams. Polyethylene terephthalate (PET) was the principal polymer composition of the microplastics, followed by cellulose. The PET and cellulose fibres were mainly derived from the laundering of clothes in the residential colonies and hostels situated close to the lake. The storm-water sewers were the likely conduit for these PET fibres into the lake. The Pollution Load Index (PLI) data reveals that pollution due to microplastics in Lake Manipal falls within the Level I risk category. The PLI was higher during the monsoon season due to an increased flux of these particles from the nearby region. During the post-monsoon period, the PLI values decreased, suggesting that MPs in the water column may have settled and mixed with the sediments. The baseline data generated in this study is important as different types of birds, amphibians, and other microorganisms are present in the environment of Lake Manipal. We also propose certain policy measures that can be adopted by the regional population to mitigate microplastic pollution in the lake and its vicinity.

Study of trace metal contamination and ecological risk assessment in the sediments of a tropical river estuary, Southwestern India

The present study aims to assess the extent of trace metal pollution in the sediments of Sita-Swarna estuary, west coast of India, and investigate their possible ecological risk on the aquatic environment. The sediment cores were analyzed for sand, silt, clay, organic carbon, and trace metals (Al, Fe, Mn, As, Cd, Co, Zn, Pb, Ni, Cr, and Cu) at 2-cm intervals. The study revealed that sediments have deposited in relatively violent to very violent hydrodynamic energy conditions. Factor analysis indicated that the metal distribution is mainly controlled by Fe-Mn oxyhydroxides and organic carbon. Further, the geochemical approach, pollution indices, and statistical evaluation revealed moderate pollution in the catchment. From an ecotoxicological perspective, the estimated risk index (RI) value was found to less than 150, indicating low risk for aquatic life. Thus, this baseline study would help to adopt strategies in pollution control and protect the fragile marine environment.

The first report on the source-to-sink characterization of microplastic pollution from a riverine environment in tropical India

Microplastics are plastic pieces <5 mm in size that are more harmful than large plastic debris. The world's oceans contain large amounts of these particles, and their presence is severely affecting the marine organisms. Smaller aquatic organisms ingesting microplastics, mistaking them for food, and their subsequent entry into the food chain is of significant concern. Rivers are major carriers of these materials from the terrestrial environment to the oceans. In this study, for the first time, we have done the source-to-sink characterization of microplastics (5 mm-0.3 mm) for a tropical Indian river, namely the Netravathi River, which debouches into the Arabian Sea. Here, we present a detailed investigation made on water, sediments and soil samples collected from the river catchment. All the samples showed the presence of microplastics with a mean numerical abundance of 288 pieces/m³ (water), 96 pieces/kg (sediment) and 84.45 pieces/kg (soil). Fibres, films and fragments are the main categories obtained from the catchment. The microplastics present in the samples were mostly transparent and white coloured which are due to the decay of plastic carry bags, packing materials and fishing lines. Different coloured microplastics were also present in lesser numbers. Polyethylene (PE) and polyethylene terephthalate (PET) are the most abundant polymers present in the samples. Fragmentation of larger plastic materials which is due to mismanaged solid waste and garment washing are the primary sources of these materials in the river catchment. Moreover, the sampling sites near to important pilgrim centres like Dharmasthala and Subrahmanya, register higher concentration of fibres released due to washing of clothes. The study concludes that the Netravathi River is contaminated with microplastics from its origin to the sink. However, the spatial distribution and abundance of microplastic particles demonstrate the influence of population distribution, land use and good household practices of waste management in some areas.