Mukul Sharma Current Research Interests in Isotope Geochemistry

• Near surface geochemistry of osmium
• Generation of oceanic lithosphere: the role of mantle heterogeneities
• Magma Differentiation and Source Characteristics of Continental Flood Basalts
• Early evolution of the earth: the terrestrial record of 146Sm
• Study on continental weathering using osmium isotopes
• Variations in Solar Magnetic Activity and the Sun-Climate Connection
• Tracing the source of groundwater arsenic in Bangladesh Delta
• Geochemical and isotopic studies of cosmic dust
• Near surface geochemistry of osmium
• Osmium and Iridium Transport through Estuarine Environments

Osmium and Iridium Transport through Estuarine Environment

The Os/Ir ratios of meteorites and all major terrestrial reservoirs are close to 1.0. In contrast, enormous fractionation between Os and Ir is observed in the deep oceans (Os/Ir = 65). The Ir data from the Baltic Sea in combination with those of the rivers and the deep oceans appear to suggest substantial scavenging of Ir in the estuary. On the other hand, the concentration of Os in the rivers is quite similar to that of the deep oceans (= 55 femtomol kg-1). It follows that the high Os/Ir ratio of the deep oceans is a direct consequence of the different rain out mechanisms of these elements in the estuaries or in the oceans. During transport through estuaries, Ir is quantitatively scavenged by Fe-oxyhydroxides and Os removal is closely associated with that of Al and organic matter. If true, it would suggest that the process of fractionation of Os and Ir through the estuarine filter plays a dominant role in influencing the Os/Ir ratio of deep oceans. We are investigating the Os and Ir removal in estuaries along salinity gradients in order to establish the behavior of these elements as the river plume mixes with seawater.