Elemental Distribution in Innershelf Sediments off Coondapur, West Coast of India

The innershelf sediments of Coondapur were studied for Cu, Pb, Zn, Ni, Co, V, Mn, Cr, Fe, Ti, Al, Ca, organic matter composition and magnetic susceptibility to understand their distribution, enrichment and element burial phases in the sediments. Along most of the transects, the sediments of 30m depth have shown more concentrations of Cu, Zn, Ni, Co, Mn, Fe, Ca and organic matter than those of 20 and 10m depth. The comparisons with sediments of uncontaminated natural formations, innershelf sediments of other unpolluted regions and world averages in different geological formations shows that the study area is unpolluted and the data can be used as a base line for future pollution studies. The sequential leaching of elements shows that they are mainly (∼60-80% of the total content) associated in detrital clay and heavy minerals followed by (∼20-30% of the total) in sulphide phase. The concentrations of all the element (except Mn) in other phases (exchangeable ions, loosely sorbed ions, carbonate constituents and interstitial water) were negligible. Nearly 40% of the total Mn is present in the leachates of EDT A and acetic acid soluble fractions. Mn concentration is almost negligible (6-11 % of the total) in acetic acid-hydroxylamine hydrochloride leachate (oxide phase) and its concentration is considerable (10-30% of the total) in H₂O₂-ammonium acetate leachate (sulphide phase). These observations suggest that reducing conditions may be prevailing in the innershelf off Coondapur.