Atmospheric source of mercury to the ocean constrained by isotopic model
Zhengcheng Song, Shaojian Huang, Yujuan Wang, Peng Zhang, Tengfei Yuan, Kaihui Tang, Xuewu Fu, Yanxu Zhang
Abstract
Mercury is a potent neurotoxin that poses significant health risks to humans, primarily through seafood consumption. Atmospheric deposition is the largest source of oceanic mercury, in either oxidized (HgII) or elemental (Hg0) form. Understanding the relative contributions of atmospheric HgII and Hg0 to the ocean is essential for accurately assessing global mercury budgets. Earlier even mercury isotope (Δ200Hg) analyses suggested equivalent HgII/Hg0 contributions but neglected spatial variations in atmospheric Δ200Hg signatures. Here, we developed a 3D atmospheric model incorporating mercury chemistry and isotopic fractionation to address this limitation. Our simulations reveal distinct atmospheric Δ200Hg patterns and quantify their deposition to the ocean. Constrained by observed Δ200Hg data in the ocean, we propose an updated deposition ratio of atmospheric HgII to Hg0 to the ocean, which may exceed 2:1, higher than the previously reported 1:1. Our findings are crucial for assessing atmospheric mercury dispersal and predicting the recovery of marine ecosystems. Marine mercury, from atmospheric Hg0 /HgII deposition, threatens ecosystems. Isotope studies proposed 1:1 HgII/Hg0 ratios but ignored spatial variability. Here, a 3D isotope model reveals HgII deposition exceed Hg0 by >2:1, revising mercury budgets.