The Arctic: a sink for mercury
Mercury is a persistent, toxic and bio-accumulative pollutant of global interest. Its main mass in the troposphere is in the form of elemental gas-phase mercury. Rapid, near-complete depletion of mercury has been observed during spring in the atmospheric boundary layer of frozen marine areas in Arctic, sub-Arctic and Antarctic locations. It is strongly correlated with ozone depletion. To date, evidence has indicated strongly that chemistry involving halogen gases from surface sea-salt is the mechanism of this destruction. Precisely which halogen gases are the main players has remained unresolved. Our novel kinetic data and multiscale modelling show that Br atoms and BrO radicals are the most effective halogens driving mercury oxidation. The reduction of oxidized mercury deposited in the snow pack back to Hg0 and subsequent diffusion to the atmosphere is observed. However, it cannot compensate for the total deposition, and a net accumulation occurs. We use a unique global atmospheric mercury model to estimate that halogen-driven mercury depletion events result in a 44% increase in the net deposition of mercury to the Arctic. Over a 1-yr cycle, we estimate an accumulation of 325 tons of mercury in the Arctic.
Document Type: Research Article
Affiliations: 1: Meteorological Service of Canada, Environment Canada, 2121 Route Transcanadienne, Dorval, QC, Canada 2: Département des sciences biologiques, Université de Montréal, 90 Vincent D'Indy, D-223, Montreal, PQ, Canada, H2V 2S9 3: Meteorological Service of Canada, Environment Canada, Toronto, Ontario, Canada, M3H 5T4 4: Environment Division, AREP, World Meteorological Organization, 7 bis, Avenue de la Paix, BP2300, 1211 Geneva 2, Switzerland 5: Departments of Atmospheric & Oceanic Sciences, and Chemistry McGill University, 801 Sherbrooke Street West, Montreal, PQ, Canada, H3A 2K6
Publication date: November 1, 2004