Assessment of Physico-Chemical Parameters and Heavy Metal Concentrations in Three Estuarine Waters Along the Ratnagiri Coast, Maharashtra, India

Abstract

As critical transitional zones between terrestrial and marine environments, estuarine ecosystems provide unique biodiversity and indispensable ecosystem services. These sensitive habitats are constantly threatened by human activities such as pollution and land-use change. This study was carried out to investigate the variations in some physicochemical parameters and heavy metal concentration levels in three coastal estuaries along the Ratnagiri coast. Water samples were collected from Bhatye, Kalbadevi and Sakhartar estuaries during monsoon (2022), winter (2022), and summer (2023). Air temperature ranged from 24.8°C to 33.5°C, water temperature varied between 24.2°C and 31.1°C - both showing distinct seasonal patterns. The pH values were in the range of 7.0 to 8.3 and the salinity values between 12.8-33.2 ppt, which reflected the freshwater-marine gradient influenced by monsoonal dynamics. The dissolved oxygen content of water was in the range 4.5 to 7.4 mg/L with higher values during monsoon due to increased turbulence and freshwater inflow. The heavy metals in water were Lead (1.39-3.90 μg/L), Cadmium (0.110-0.341 μg/L), Chromium (2.56-7.98 μg/L), Nickel (1.92-5.10 μg/L) and Zinc (6.21-15.36 μg/L), all within WHO permissible limits but with areas of localized increase at Kalbadevi estuary near industrial discharge points. In space, the pattern of pollutions is reflected with Sakhartar estuary still enjoying almost pristine conditions; Bhatye shows some (but not serious) contamination; while Kalbadevi estuary clearly suffered from man's activities. These results furnish baseline data essential for long-term observation and sustainable development of the marine environment in Ratnagiri region.