Abstract

Chen C Y, Huang J H, Li K, Osterwalder S, Yang C M, Waldner P, Zhang H, Fu X W, Feng X B (2023) Isotopic characterization of mercury atmosphere-foliage and atmosphere-soil exchange in a Swiss subalpine coniferous forest. Environmental Science & Technology, 57 (42): 15892-15903. [10.1021/acs.est.3c03576]

Keywords

atmospheric Hg-0;atmosphere-foliage/soil exchange;stable Hg isotopes;deposition;re-emission;gaseous elemental mercury;air-surface exchange;fractionation;deposition;emissions;vegetation;fluxes;hg(ii);quantification;precipitation;Engineering;Environmental Sciences & Ecology

Abstract

To understand the role of vegetation and soil in regulating atmospheric Hg0, exchange fluxes and isotope signatures of Hg were characterized using a dynamic flux bag/chamber at the atmosphere-foliage/soil interfaces at the Davos-Seehornwald forest, Switzerland. The foliage was a net Hg-0 sink and took up preferentially the light Hg isotopes, consequently resulting in large shifts (-3.27 parts per thousand ) in delta Hg-202 values. The soil served mostly as net sources of atmospheric Hg0 with higher Hg0 emission from the moss-covered soils than from bare soils. The negative shift of delta Hg-202 and Delta Hg-199 values of the efflux air relative to ambient air and the Delta Hg-199/Delta Hg-201 ratio among ambient air, efflux air, and soil pore gas highlight that Hg-0 re-emission was strongly constrained by soil pore gas evasion together with microbial reduction. The isotopic mass balance model indicates 8.4 times higher Hg-0 emission caused by pore gas evasion than surface soil photoreduction. Deposition of atmospheric Hg-0 to soil was noticeably 3.2 times higher than that to foliage, reflecting the high significance of the soil to influence atmospheric Hg-0 isotope signatures. This study improves our understanding of Hg atmosphere-foliage/soil exchange in subalpine coniferous forests, which is indispensable in the model assessment of forest Hg biogeochemical cycling.

LWF Classification

Network: LWF;mercury, Sites: Davos, Category: ISI,