Influence of 2015 flood on the distribution and occurrence of microplastic pellets along the Chennai coast, India

•Seasonal variation of microplastic pellets along the Chennai coast was quantified.•White colour PE and PP pellets were the dominant in all sampling locations.•Threefold increase in pellets was observed after the 2015 Chennai flood.•Sources of pellets on beaches of Chennai coast are both land and ocean-based.

The sources, distribution, surface features, polymer composition and age of microplastic pellets (MPPs) in surface sediments along the Chennai coast during March 2015 (pre-Chennai flood) and November 2015 (post-Chennai flood) were characterised using a Stereoscopic microscope and FTIR-ATR spectroscopy. White MPPs were the most abundant, and specifically polyethylene (PE) and polypropylene (PP) were the dominant polymer types of MPPs found on the coast during both the times. The abundance of MPPs in November 2015 was three-fold higher than those found in March 2015, confirming that huge quantity of fresh MPPs washed through Cooum and Adyar rivers from land during the flood. The winds and surface currents during November were the driving forces for the transportation and deposition of MPPs from the sea to beaches. The results of this study will be useful to formulate beach MPPs litter management policies to effectively create long-term solutions.