Mercury deposition in the Adirondacks: A comparison between precipitation and throughfall

The volume-weighted mean (VWM) Hg concentrations and the total cumulative fluxes in deciduous throughfall (6.6 ng L−1 and 12.0 μg m−2, respectively) were statistically higher than in precipitation (4.9 ng L−1 and 11.6 μg m−2, respectively) during 2 years of sampling at the Huntington Wildlife Forest in Newcomb, NY. Seasonally, the VWM Hg concentrations and the Hg fluxes in both precipitation and throughfall were lowest in winter and highest in summer. Due to the wash-off of dry deposition and foliar leaching, concentrations in throughfall were almost 50% higher than those in precipitation during the leaf-on period, while concentrations in throughfall were slightly higher than (or similar to) those in precipitation during the leaf-off period. During the 2 years of sampling, the total deposited cumulative flux in precipitation and deciduous throughfall were very similar (11.6 μg Hg m−2 and 12.0 μg Hg m−2, respectively), because the higher concentrations in throughfall were offset by smaller throughfall depths. Meteorological analysis indicated that the precipitation events resulting in the highest Hg fluxes were associated with trajectories that passed through regions of Midwest where major Hg sources including coal/oil-fired power plants and waste incinerators are located.