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

Abstract

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.

Microplastics in soil and groundwater of Korea: Occurrence, characteristics and risk assessment

“…The CF and PLI are used to evaluate the level of environmental pollution associated with a specific contaminant and to provide a comprehensive assessment of pollution levels for a given site. These indices are calculated as follows (Kabir et al, 2021;Amrutha et al, 2023):…”

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

“…The term “microplastics” (MPs) refers to these tiny fragments of plastic, which range in size from 1 µm to 5 mm. (Amrutha et al, 2023 ; Thompson et al, 2004 ). They can also be divided into primary and secondary MPs.…”

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

“…As such, the rivers flowing through these regions should be inspected for MP contamination, especially considering potential changes in consumption patterns and waste management practices during the pandemic. In addition, only a few studies have discussed the relationship between MP distribution and different environmental factors that govern their fate in these rivers ( Amrutha et al, 2023 ).…”

“…Currently, only one study has investigated the seasonal distribution of MPs in the riverine environments of Karnataka ( Amrutha et al, 2023 ), and there is a lack of information on the input of MPs from these rivers into the Arabian Sea, including any potential effects from the pandemic. The aim of this baseline paper is to conduct, for the first time, a temporal investigation of MPs along the Netravathi River Basin, which flows through the Western Ghats, rural and urban Dakshina Kannada, Karnataka, before emptying into the Ullal coastal area of the Arabian Sea, and to determine if COVID-19 influenced the presence and distribution of MPs.…”