Geochemical characterization of modern aeolian dust over the Northeastern Arabian Sea: Implication for dust transport in the Arabian Sea

摘要

The Arabian Sea, one of the most biologically productive oceanic regions, receive significant amount of nutrients through aeolian dust deposition which have potential to modulate surface water biogeochemical processes. Identification of dust sources is important to assess role of dust deposition to surface water biogeochemistry. Here we report geochemical characteristics (major elements and trace metals composition, clay mineralogy and radiogenic isotopes of Sr and Nd) of aeolian dust, derived from dust storms in Middle East and South West Asia, to decipher its sources and possible transport pathways over the Arabian Sea. Twelve bulk aerosol samples were collected, during dusty period, at a coastal station (Goa; 15.4° N, 73.8° E) located in the Northeastern Arabian Sea, spanning over three years in different seasons. A preliminary estimation of sources for dust storms was done using satellite imagery and air mass back trajectory analyses. Major element and trace metal compositions of storm derived dust samples indicate insignificant contribution from anthropogenic sources. Illite and chlorite are major clay minerals found in all dust samples, however, high palygorskite content were observed for dust sourced from the Arabian Peninsula. A more uniform Sr-Nd signature is found for those derived from Arabia, however, highly variable Sr-Nd isotope signatures were observed for those derived from the South West Asia (Iran and Makran coast). The reported comprehensive data set on geochemical characteristics of mineral dust, is the first attempt that provides important information to understand present and past dust emission and deposition over the Arabian Sea.