Seasonal Variation in the Inputs and Fate of Mercury in a Northern Hardwood Forest

Abstract:

Northern forest ecosystems are sensitive to atmospheric mercury deposition. In this study, we examined the fate of mercury inputs to the Huntington Wildlife Forest (HWF) of the Adirondack region of New York State, USA, by conducting a mercury mass budget over the annual cycle. Mercury exchange processes analyzed included wet deposition, dry deposition, foliar accumulation, throughfall, litterfall, soil evasion, and vertical and horizontal soil drainage loss. The mercury transport processes were quantified by integrating data collected from different sources over recent years (2004-2011). Dry mercury deposition (16.3 µg m^-2 yr^-1) was more important than wet mercury deposition (6.3 µg m^-2 yr^-1) at the HWF; most of the atmospheric mercury deposition (> 60%) was retained in the forest soils where litterfall (17.2 µg m^-2 yr^-1) was the major input pathway. Soil evasion (6.5 µg m^-2 yr^-1) was the most important mercury export mechanism, exceeding mercury fluxes in lateral and vertical drainage from soil (2.8 µg m^-2 yr^-1). Our analysis showed marked seasonal variation in the transfers of mercury largely mediated by annual canopy development of the forest ecosystem. The upland hardwood forest ecosystem was a net sink for atmospheric mercury deposition.