Summary of Abstract Submission

Abstract Submission No. IO50-03-0026PresentationOral

SIGNIFICANCE OF ATMOSPHERIC INPUT OF CHEMICAL CONSTITUENTS TO NORTH INDIAN OCEAN

M.M. Sarin*1, Bikkina Srinivas1

1 Physical Research Laboratory, Ahmedabad 380 009, INDIA

ABSTRACT :

Air-sea deposition of chemical constituents to the Arabian Sea (ARS) and Bay of Bengal (BoB), two important limbs of the Indian Ocean, is influenced by natural and anthropogenic sources during the late NE-monsoon. Our recent studies have focused on air-sea deposition of mineral dust, nutrients (N, P and Fe) and toxic trace metals to the Indian Ocean. The chemical processing of mineral dust during atmospheric transport and enhanced solubility of Fe has implications to further increase in the deposition of this micro-nutrient to BoB. The mass ratio of nutrients (NInorg/NTot, Norg/NTot and PInorg/nss-Ca2+) also suggests further increase in their air-sea deposition to the surface BoB. Based on atmospheric deposition of P and Fe, C-fixation in BoB (1.1 Pg yr-1) is dominated by anthropogenic sources and that in ARS (0.3 Pg yr-1) is limited by P and Fe. This is attributed to poor fractional solubility (~1%) of mineral dust over the Arabian Sea. However, N-fixation by diazotrophs in the two oceanic regions is somewhat similar (0.03 Pg yr-1). Our estimate of N-deposition (0.2 Tg yr-1) to the northern Indian Ocean is significantly lower than model results. The increase in aerosol toxicity is also evident from high enrichment factors of anthropogenic trace metal (Pb, Cd, Cr, Cu and Mn). The enhanced solubility of anthropogenic fractions of trace metals, relative to their dust derived component, is an important issue for assessing factors that influence the marine ecosystem in the Indian Ocean.