![]() ![]() Trends in RGM and TPM 2.5 were less clear due to shorter measurement periods and low concentrations, however, in spring at the high Arctic site (Alert) when RGM and TPM 2.5 concentrations were high, concentrations of both increased by 7%–10% per year. Concentrations of total Hg in precipitation declined up to 3.7% yr −1. Concentrations of GEM decreased at rates ranging from −0.9% to −3.3% per year at all sites where measurements began in the 1990s. Diel and seasonal patterns in atmospheric GEM, RGM and TPM 2.5 concentrations reflected differences in patterns of anthropogenic emissions, photo-induced surface emissions, chemistry, deposition and mixing. A spatial analysis across Canada revealed higher air concentrations and wet deposition of Hg in the vicinity of local and regional emission sources, and lower air concentrations of Hg at mid-latitude maritime sites compared to continental sites. Here we update long-term trends of Hg in air and precipitation, and present more extensive measurements on patterns and trends in speciated Hg species (gaseous elemental mercury-GEM, reactive gaseous mercury-RGM, and total particulate mercury on particles <2.5 μm-TPM 2.5) at several sites. ![]() Atmospheric mercury (Hg) measurements from across Canada were compiled and analysed as part of a national Hg science assessment. ![]()
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