Processes controlling arsenic enrichment along the eastern Arabian Sea surficial sediments

Abstract

The processes enriching redox-sensitive arsenic (As) was investigated in 111 surficial sediments (27–3679 m water depth) overlain by varying levels of dissolved oxygen along the eastern Arabian Sea. Under oxygenated conditions, diagenetic enrichment of As was noticed at deeper water depths (> 1200 m), while lattice held As dominant at few station from shallow depths (< 150 m). In sediments impinged by oxygen minimum zone (OMZ; 150–1200 m), As is released from organic matter during sub-oxic diagenesis. As seems to precipitate as As/iron sulfide mineral under intense OMZ based on a positive correlation between As and S and Cd in northeastern part of the study area, while As may diffuse to water column under less intense OMZ evidenced by lack of correlation between As and S and Cd in southeastern part. Several processes can enrich As. A careful approach is recommended for its usage in understanding anthropogenic sources, transport, and paleodepositional environment along eastern Arabian Sea.