Atmospheric dry and wet deposition of mercury in Toronto

Atmospheric mercury (Hg) speciation and deposition are critical in understanding the cycling of mercury in the environment. To estimate the dry and wet deposition of mercury in an urban environment, concentrations of gaseous elemental mercury (GEM), gaseous oxidized inorganic mercury (GOIM), mercury associated with particles having size less than 2.5 μm (Hg(p) < 2.5) (December 2003–November 2004) and total particulate mercury (THg(p)) (June 2004–December 2004) in the atmosphere, as well as the concentrations of methyl mercury (MeHg) and total mercury (THg) in atmospheric precipitation samples (June 2005–January 2006 and September 2007–March 2008), were measured in downtown Toronto, Canada. y deposition rates of GOIM, Hg(p) < 2.5 μm and THg(p) estimated between December 2003 and December 2004 were 0.17–2.33 μg m−2 month−1, 0.04–0.32 μg m−2 month−1 and 0.17–1.11 μg m−2 month−1, respectively, while the wet deposition rates of methyl mercury and total mercury between June 2005–January 2006 and September 2007–March 2008 were 0.01–0.08 μg m−2 month−1 and 0.32–8.48 μg m−2 month−1, respectively. The total dry deposition (7.66–26.06 μg m−2 a−1, calculated as the sum of GOIM and THg(p) deposition) and the total wet deposition (= the wet deposition of total mercury = 18.60 μg m−2 a−1) contributed proportionally to the total atmospheric Hg deposition in Toronto.