Heavy Metal accumulation in Estuarine Waters and Sediments: Role of Hydrographic Parameters along the Ratnagiri Coast, Maharashtra, India

Estuarine ecosystems plays crucial role in regulating the biogeochemical cycling of trace metals, serving as transitional zones between land and sea. Increasing anthropogenic pressures and pronounced seasonal fluctuations in river discharge often enhance the mobility, bioavailability, and ecological risks of heavy metals. Focusing on the Bhatye, Kalbadevi, and Sakhartar estuaries, this study investigates the influence of hydrographic parameters on the seasonal distribution, accumulation, and ecological risk of heavy metals in estuarine waters and sediments along the Ratnagiri coast, Maharashtra, India. Seasonal sampling was conducted during pre-monsoon, monsoon, and post-monsoon periods during the year 2022-2023. Concentrations of Cd, Cu, Zn, Cr, Ni, and Pb in surface waters and sediments were measured alongside key hydrographic parameters, including pH, salinity, turbidity, dissolved oxygen (DO), water temperature, and air temperature. Results indicated pronounced seasonal variations, with monsoon conditions characterised by elevated turbidity, decreased pH and salinity, and higher metal concentrations in both water and sediments. Strong correlations between hydrographic parameters and metal levels suggest that monsoon-driven freshwater influx and sediment resuspension are major factors influencing metal bioavailability. Sediment ecological risk assessment indicated moderate to high ecological risks during the monsoon, particularly for Pb and Cd. The findings underscore the importance of comprehensive water-sediment monitoring and seasonal assessment for the sustainable management of tropical estuaries.