title: Atmospheric mercury in the Canadian Arctic. Part I: a review of recent field measurements.
abstract: Long-range atmospheric transport and deposition are important sources of mercury (Hg) to Arctic aquatic and terrestrial ecosystems. We review here recent progress made in the study of the transport, transformation, deposition and reemission of atmospheric Hg in the Canadian Arctic, focusing on field measurements (see Dastoor et al., this issue for a review of modeling studies on the same topics). Redox processes control the speciation of atmospheric Hg, and thus impart an important influence on Hg deposition, particularly during atmospheric mercury depletion events (AMDEs). Bromine radicals were identified as the primary oxidant of atmospheric Hg during AMDEs. Since the start of monitoring at Alert (NU) in 1995, the timing of peak AMDE occurrence has shifted to earlier times in the spring (from May to April) in recent years, and while AMDE frequency and GEM concentrations are correlated with local meteorological conditions, the reasons for this timing-shift are not understood. Mercury is subject to various post-depositional processes in snowpacks and a large portion of deposited oxidized Hg can be reemitted following photoreduction; how much Hg is deposited and reemitted depends on geographical location, meteorological, vegetative and sea-ice conditions, as well as snow chemistry. Halide anions in the snow can stabilize Hg, therefore it is expected that a smaller fraction of deposited Hg will be reemitted from coastal snowpacks. Atmospheric gaseous Hg concentrations have decreased in some parts of the Arctic (e.g., Alert) from 2000 to 2009 but at a rate that was less than that at lower latitudes. Despite numerous recent advances, a number of knowledge gaps remain, including uncertainties in the identification of oxidized Hg species in the air (and how this relates to dry vs. wet deposition), physical-chemical processes in air, snow and water-especially over sea ice-and the relationship between these processes and climate change.
authors.affiliation: Environment Canada, Air Quality Processes Research, Toronto M3H 5T4, Ontario, Canada. Electronic address: Alexandra.Steffen@ec.gc.ca.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Steffen
authors.affiliation: University of Waterloo, Department of Earth and Environmental Sciences, Waterloo N2L 3G1, Ontario, Canada.
authors.forename: Igor
authors.initials: I
authors.lastname: Lehnherr
authors.affiliation: Environment Canada, Air Quality Processes Research, Toronto M3H 5T4, Ontario, Canada.
authors.forename: Amanda
authors.initials: A
authors.lastname: Cole
authors.affiliation: McGill University, Department of Chemistry, 801 Sherbrooke St. W., Montreal H3A 2K6, Quebec, Canada; McGill University, Department of Atmospheric and Oceanic Sciences, 801 Sherbrooke St. W., Montreal H3A 2K6, Quebec, Canada.
authors.forename: Parisa
authors.initials: P
authors.lastname: Ariya
authors.affiliation: Environment Canada, National Prediction Development Division, Dorval H9P 1J3, Quebec, Canada.
authors.forename: Ashu
authors.initials: A
authors.lastname: Dastoor
authors.affiliation: Environment Canada, National Prediction Development Division, Dorval H9P 1J3, Quebec, Canada.
authors.forename: Dorothy
authors.initials: D
authors.lastname: Durnford
authors.affiliation: Environment Canada, Aquatic Contaminants Research Division, Burlington L7R 4A6, Ontario, Canada.
authors.forename: Jane
authors.initials: J
authors.lastname: Kirk
authors.affiliation: Environment Canada, Aquatic Contaminants Research Division, Montreal H2Y 2E7, Quebec, Canada.
authors.forename: Martin
authors.initials: M
authors.lastname: Pilote
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D001110:Arctic Regions; D001272:Atmosphere / Q000737:chemistry; D002170:Canada; D004784:Environmental Monitoring; D008628:Mercury / Q000032:analysis*
chemical_list: D000393:Air Pollutants; D008628:Mercury
keywords: Arctic; Atmosphere; Mercury; Redox; Snow; Temporal trends