Preliminary investigation on the occurrence and associated risks of Microplastics, Polyaromatic Hydrocarbons in the Ansupa Wetland: A Ramsar site in Odisha, India

Microplastics (MPs) and polycyclic aromatic hydrocarbons (PAHs) pollution together pose significantly higher ecological and health risks in freshwater ecosystems than either pollutant alone. However, studies on the distribution and associated risks of MPs and PAHs pollution in relation to hydrological parameters are limited. The present study investigates the occurrence, spatial distribution, interrelationship of MPs, PAHs, and hydrological parameters, and their ecological risks in Ansupa Lake. Surface water samples were collected from 8 different locations and analysed using standardized physico-chemical, spectroscopic, microscopic, and chromatographic methods. The average abundance of MPs and PAHs was found to be 15.5±17.3 mg/L and 0.13±0.16 mg/L, respectively. MPs were extracted and characterized using a microscope and Fourier-Transformed Infrared Spectroscopy (FTIR), whereas PAHs were characterized in High Performance Liquid Chromatography (HPLC). The results revealed 10 different polymers such as Polyurethane (PU), Polyvinyl chloride (PVC), Polyethylene terephthalate (PET), Polystyrene (PS), Acrylonitrile butadiene styrene (ABS), Polypropylene (PP), Low density polyethylene (LDPE), High density polyethylene (HDPE), Polyethylene (PE), and Polyamide (PA) with highest occurrence of PET, PE, HDPE, and LDPE (100%) followed by PVC, PS, and ABS (87.5%). Twelve different types of PAHs were found among which benzo [b] fluoranthene (87.5%) showed highest % occurrence. PAHs containing 2 or 3 rings (Low molecular weight (LMW) PAHs were detected in higher concentration as compared to PAHs containing 4, 5, and 6 rings (high molecular weight (HMW) PAHs. Source diagnostic ratio showed both petrogenic and pyrolytic origin of PAHs, with predominance of petrogenic PAHs. The principal component analysis (PCA) was carried out, and the results shown strong correlation between MPs with transparency, dissolved oxygen (DO), alkalinity, conductivity, and total dissolved solids (TDS), and PAHs with air temperature, whereas no significant relation was observed between MPs and PAHs. The pollution load index (PLI) and polymer hazard index (PHI) of MPs ranged between 1-4.35 and 25- 437587.5, respectively, depicting a low level of PLI with the presence of high-extremely hazardous polymer types. Whereas, the ecological risk assessment (ERA) of PAHs was found to be at high risk.