Summary of Abstract Submission

Abstract Submission No. IO50-03-0024PresentationOral

ORE MINERAL CONTAMINATION IN SEDIMENT CORES FROM THE MANDOVI ESTUARY, CENTRAL WEST COAST OF INDIA: AN ENVIRONMENTAL MAGNETIC APPROACH

A. Prajith*1, V. Purnachandra Rao1, Pratima M. Kessarkar1

1 CSIR - National Institute of Oceanography, India

ABSTRACT :

Ore mining for Fe and Mn is an important activity in the drainage basin of the Mandovi River. As ore material is loaded onto barges at shore stations and transported through the estuary to the port its contamination is expected in estuarine sediments. We investigate here the mineralogy and magnetic properties of four sediment cores along transect of the estuary. The ages of the sediments indicated modern age (1939 - 1955 AD) for those in the upper/middle estuary and relatively older age (1588 AD 539 AD) for those in the lower estuary/bay. The sediments of the upper/middle estuary are dominated by hematite and goethite, very high values of magnetic concentration parameters (lf, ARM and SIRM) and low S-ratios, where as those in lower estuary/bay are dominated by magnetite, low values of magnetic concentration parameters and high S-ratios. The fd% and ARM/SIRM indicated coarse, multi-domain/pseudo-single domain magnetic grains, resembling ore material in the upper/middle estuary. Magnetic grain size parameters indicated early diagenesis and removal of fine-grained magnetic minerals in organc-rich sediments of the middle estuary and, formation of magnetic minerals most probably, authigenic gregites in the lower estuary/bay. The enrichment factors and geo-accumulation index of Fe and Mn indicated significant to strong pollution of Mn and significant pollution for Fe in the upper/middle estuary. Our results indicate high sedimentation rates and strong ore material contamination in the upper/middle estuary and, low sedimentation rates and detrital dominated sediments in the lower estuary/bay.