How relevant is the deposition of mercury onto snowpacks? – Part 2: A modeling study

• Published in: Atmospheric Chemistry and Physics
• Main Authors: D. Durnford, A. Dastoor, A. Ryzhkov, L. Poissant, M. Pilote, D. Figueras-Nieto
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2012
• Subjects: Physics; QC1-999; Chemistry; QD1-999; Arctic; Arctic Ocean; Hudson Bay; Canada; Hudson; Kuujjuarapik; Sea ice; Subarctic
• Online Access: https://doi.org/10.5194/acp-12-9251-2012; https://doaj.org/article/7af3436d586f41a4a6c6be5a35d34e46

An unknown fraction of mercury that is deposited onto snowpacks is revolatilized to the atmosphere. Determining the revolatilized fraction is important since mercury that enters the snowpack meltwater may be converted to highly toxic bioaccumulating methylmercury. In this study, we present a new dynamic physically-based snowpack/meltwater model for mercury that is suitable for large-scale atmospheric models for mercury. It represents the primary physical and chemical processes that determine the fate of mercury deposited onto snowpacks. The snowpack/meltwater model was implemented in Environment Canada's atmospheric mercury model GRAHM. For the first time, observed snowpack-related mercury concentrations are used to evaluate and constrain an atmospheric mercury model. We find that simulated concentrations of mercury in both snowpacks and the atmosphere's surface layer agree closely with observations. The simulated concentration of mercury in both in the top 30 cm and the top 150 cm of the snowpack, averaged over 2005–2009, is predominantly below 6 ng L −1 over land south of 66.5° N but exceeds 18 ng L −1 over sea ice in extensive areas of the Arctic Ocean and Hudson Bay. The average simulated concentration of mercury in snowpack meltwater runoff tends to be higher on the Russian/European side (>20 ng L −1 ) of the Arctic Ocean than on the Canadian side (<10 ng L −1 ). The correlation coefficient between observed and simulated monthly mean atmospheric surface-level gaseous elemental mercury (GEM) concentrations increased significantly with the inclusion of the new snowpack/meltwater model at two of the three stations (midlatitude, subarctic) studied and remained constant at the third (arctic). Oceanic emissions are postulated to produce the observed summertime maximum in concentrations of surface-level atmospheric GEM at Alert in the Canadian Arctic and to generate the summertime volatility observed in these concentrations at both Alert and Kuujjuarapik on subarctic Hudson Bay, Canada. We find that the ...