Physical and chemical characterization of dissolved arsenic in the South China Sea

Abstract Arsenic in the marine environment is important because its biogeochemistry is closely linked to the phosphorus cycle. The chemical speciation approaches of dissolved arsenic can identify As(III), As(V), and methylated arsenic species, all of which collectively reveal the involvement of microbial processes in the arsenic cycle. The physical speciation methods, or molecular weight distribution approaches, of dissolved arsenic can disclose the reactivity of arsenic based on the size-reactivity continuum model. We applied a combined physical and chemical characterization method to the dissolved arsenic in seawater from the South China Sea (SCS) to understand arsenic reactivity in the marine biogeochemical cycle. The dissolved inorganic arsenic (DIAs) exhibited typical semi-conservative depth profiles, and the low-molecular-weight (LMW,