RESUMEN
The increased load of plastic in waste streams after the COVID-19 pandemic outbreak has increased the possibility of microplastics (MPs) contamination channelling through the rivers and infiltrating the aquatic ecosystems. MPs in packaged water, community-stored water, groundwater, and surface water of Kaveri River (KR), Thamirabarani River (TR), Adyar River (AR), and Cooum River (CR) in Tamil Nadu were therefore investigated about 2 years after the COVID-19 pandemic outbreak. Using µFTIR and µRaman spectroscopy, polyamide, polypropylene, polyethylene, ethylene vinyl alcohol copolymer resin, and polyvinyl chloride were identified as the primary polymer types. The average number of MPs was 2.15 ± 1.9 MP/L, 1.1 ± 0.99 MP/L, 5.25 ± 1.15 MP/L, and 4 ± 2.65 MP/L in KR, TR, AR, and CR, respectively, and 1.75 ± 1.26 MP/L in groundwater, and 2.33 ± 1.52 MP/L in community stored water. Only LDPE was detected in recycled plastic-made drinking water bottles. More than 50% of MPs were found to be of size less than 1 mm, with fibrous MPs being the prevalent type, and a notable prevalence of blue-coloured microplastics in all the sample types. The Pollution Load Index (PLI) was >1 in all the rivers. Toxicity rating based on the polymer risk index (PORI) categorized AR and TR at medium risk (category II), compared to KR and CR at considerable risk (category III). Overall pollution risk index (PRI) followed a decreasing trend with CR > AR > KR > TR of considerable to low-risk category. Ecological risk assessment indicates a negligible risk to freshwater biota, except for four sites in the middle and lower stretches of Adyar River (AR - 2, AR - 4) and upper and lower stretches of Cooum River (CR - 1, CR - 3), located adjacent to direct sewer outlets, and one location in the lower stretch of Kaveri River (KR - 9), known for fishing and tourist activities.
