Anthropogenic mercury migration from Asia to the open ocean

Abstract To evaluate the path of anthropogenic mercury (Hg) from Asia to the Pacific Ocean, we report mercury stable isotopes in zooplankton from the East China Sea to the Bay of Bengal, and in the Philippine Sea and the Central Pacific. Here, we find that zooplankton mercury concentration decreases and δ 202 Hg and Δ 199 Hg increase with distances away from Asia, depicting anthropogenic mercury dilution. Anomalies of even mass-number isotopes (Δ 200 Hg), used to decipher between near-surface and tropospheric oxidation, suggest that 40–48% of anthropogenic Hg(0) is initially oxidized at the marine boundary layer or via terrestrial vegetation, and >50% of anthropogenic Hg(0) is circulated to the upper atmosphere for oxidation and removal to the Pacific. The fact that both near-surface and atmospheric Hg(0) oxidation supplies bioavailable Hg(II) strengthens the case for mitigating Hg(0) emissions. Recently reported climate-projected increase in riverine mercury fluxes may also benefit by reducing anthropogenic Hg(0) available for vegetative uptake.