Parameterizing Soil Emission and Atmospheric Oxidation-Reduction in a Model of the Global Biogeochemical Cycle of Mercury

• Published in: Environmental science & technology 2013-11, Vol.47 (21), p.12266-12274
• Main Authors: Kikuchi, Tetsuro, Ikemoto, Hisatoshi, Takahashi, Katsuyuki, Hasome, Hisashi, Ueda, Hiromasa
• Format: Article
• Language: English
• Subjects: Applied sciences; Arctic Regions; Atmosphere - chemistry; Atoms & subatomic particles; Biogeochemistry; Computer Simulation; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Global environmental pollution; Japan; Mercury; Mercury - analysis; Models, Theoretical; Oxidation; Oxidation-Reduction; Pollution; Pollution, environment geology; Radiation; Reproducibility; Reproducibility of Results; Seasonal variations; Seasons; Simulation; Soil - chemistry; Soil Pollutants - analysis; United States
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es401105h

Using the GEOS-Chem atmosphere–land–ocean coupled mercury model, we studied the significances of two processes, soil emission and atmospheric oxidation–reduction, in the global biogeochemical cycling of mercury and their parametrization to improve model performance. Implementing an empirical equation for soil emission flux (E soil) including soil mercury concentration, solar radiation, and surface air temperature as parameters enabled the model to reproduce the observed seasonal variations of E soil, whereas the default setting, which uses only the former two parameters, failed. The modified setting of E soil also increased the model-simulated atmospheric concentration in the summertime surface layer of the lower- and midlatitudes and improved the model reproducibility for the observations in Japan and U.S. in the same period. Implementing oxidation of atmospheric gaseous elemental mercury (Hg0) by ozone with an updated rate constant, as well as the oxidation by bromine atoms (Br) in the default setting, improved the model reproducibility for the dry deposition fluxes observed in Japan. This setting, however, failed to reproduce the observed seasonal variations of atmospheric concentrations in the Arctic sites due to the imbalance between oxidation and reduction, whereas the model with Br as the sole Hg0 oxidant in the polar atmosphere could capture the variations.