Atmospheric concentrations and wet/dry loadings of mercury at the remote Experimental Lakes Area, northwestern Ontario, Canada

Mercury (Hg) is a global pollutant released from both natural and human sources. Here we compared long-term records of wet deposition loadings of total Hg (THg) in the open to dry deposition loadings of THg in throughfall and litterfall under four boreal mixedwood canopy types at the remote Experimental Lakes Area (ELA) in northwestern Ontario, Canada. We also present long-term records of atmospheric concentrations of gaseous elemental (GEM), gaseous oxidized (GOM) and particle bound (PBM) Hg measured at the ELA. We show that dry THg loadings in throughfall and litterfall are 2.7 to 6.1 times greater than wet THg loadings in the open. GEM concentrations showed distinct monthly and daily patterns, correlating in spring and summer with rates of gross ecosystem productivity and respiration. GOM and PBM concentrations were less variable throughout the year, but were highest in winter when concentrations of anthropogenically sourced particles and gases were also high. Forest fires, Arctic airmasses and road sa...