Inter riverine variability in microplastic distribution among two tropical rivers - Chalakudy and Periyar, Southwest India

The study intends to bridge the lack of baseline information on microplastic (MPs) contamination in two river systems (Periyar: the longest river, lifeline of the Kerala State and Chalakudy: the fifth longest river) and hence is highly relevant. Sampling was carried out twice during December 2020 and January 2021. Elevated level of contamination was recorded at midstream sites in Chalakudy and downstream sites at Periyar. Small-sized particles (<100 <mu>m) constituted the majority (>45%) in both river systems resulting from the disintegration of larger particles or direct release of primary MPs. Prevalence of fragment shape, accounting for approximate to 48-71% across all sites in both rivers, resulted from the disintegration of meso or macro plastics. Preponderance of blue-coloured particles (approximate to 33-67%) inferred potential risk to aquatic organisms. Low-density polyethylene emerged as the dominant polymer group, originated from packaging materials and bottles. Overall abundance and recovery rate in both rivers indicate that MPs occur at all sites, irrespective of land use patterns, sourced to the degradation of abandoned fishing gears, shipping, tourism activities, and untreated waste disposal. The high risk of microplastic pollution in the study area was endorsed by polymer hazard index and coefficient of microplastic impact index.