Distribution and Seasonal Variation of Trace metal concentration in Surface sediment of Dhamra Estuary. East coast of India

The Dhamra estuary is a major tropical estuary in the east coast of India which hydrographical characteristics are mostly governed by monsoon. A study was carried out to find out the trace metal concentration in the sediments of. Dhamra estuary. The concentration and distribution of selected trace metals in surface sediments of the Dhamra estuary were studied to determine the extent of anthropogenic inputs from mining activities and to estimate the effects of monsoon on geochemical processes in this tropical estuarine system. Analysis of bulk sediments from the Dhamra estuary shows that concentrations of Copper, Cobalt, iron, manganese, Cadmium, chromium, zinc and lead vary from 7.15–33.6 mg/kg,1.6–24.12 mg/kg, 0.88–6.333%, 0.024–0.165%, 0–1.2 mg/kg, 78–394.3 mg/kg,71.1–90.8 mg/kg and 0.8–18 mg/kg respectively. An important observation is that, in general, The lowest metal concentrations are found during the monsoon and the premonsoon compared to the postmonsoon. The enrichment of Cadmium, Chromium and Manganese reflects the intensity of corrosion resistance paints are used in ship and traller, which creates Cadmium contamination. For various metals the geoaccumulation index (Igeo) has been calculated to assess the degree of pollution in sediments. This shows that Cd, and Cr moderately contaminated the sediments. Igeo value of Cadmium, 2 mg/kg higher value in the post monsoon in the down stream region of estuary than in the monsoon and premonsoon seasons and of Chromium 1.47 mg/kg) was higher value in the premonsoon in the st-6 than in the monsoon and postmonsoon.