Behaviour and Distribution Patterns of Particulate Metals in Estuarine and Coastal Surface Waters near Mangalore, Southwest Coast of India

Physico-chemical properties of water (pH, dissolved oxygen, salinity and suspended matter concentrations) and geochemistry (Cu, Pb, Zn, Ni, Co, Mn, Fe, Al, Ca and loss-on-ignition) of suspended particulates have been measured for the first time in the Netravati-Gurpur estuary and the adjacent coastal environment, southwestern India. The main objective was to understand the influence of physico-chemical properties of estuarine and coastal waters on the behaviour, association and dispersal patterns of particulate metals.

Suspended particulate matter (SPM) from the estuarine and coastal environments have higher Cu, Pb and Zn (by factors of 1.5-2.7) than the Netravati-Gurpur riverine SPM, indicating enrichment of these metals with increasing salinity. In contrast, Al, Fe, Mn, Co and Ni contents and the corresponding metaltal ratios are marginally lower (by factors of 1.1 - 1.5) than those for riverine SPM, suggesting not only a decrease of terrigenous influx seaward, but also removal of trace metals from the particulate phase. R-mode factor analysis of the data has shown that detrital particles (with Fe oxide coating), clays and Mn-oxide are the major factors that control particulate metal association. Factor score distribution patterns suggest that detrital particles coated with Fe oxide are deposited in the estuary and nearshore region, whereas clays and Mn-oxide seem to be transported further into the coastal sea. Copper, Pb and Zn show an anomalous behaviour and are negatively loaded on all the three major factors.