Surface-air mercury fluxes and a watershed mass balance in forested and harvested catchments

Chris S. Eckley; Collin A. Eagles-Smith; Michael T. Tate; David P. Krabbenhoft

doi:10.1016/j.envpol.2021.116869

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Surface-air mercury fluxes and a watershed mass balance in forested and harvested catchments

Chris S. Eckley·Collin A. Eagles-Smith·Michael T. Tate·David P. Krabbenhoft

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Abstract

Forest soils are among the world’s largest repositories for long-term accumulation of atmospherically deposited mercury (Hg), and understanding the potential for remobilization through gaseous emissions, aqueous dissolution and runoff, or erosive particulate transport to down-gradient aquatic ecosystems is critically important for projecting ecosystem recovery. Forestry operations, especially clear-cut logging where most of the vegetaiton is removed, can influence Hg mobility/fluxes, foodweb dynamics, and bioaccumulation processes. This paper measured surface-air Hg fluxes from catchments in the Pacific Northwest, USA, to determine if there is a difference between forested and logged catchments. These measurements were conducted as part of a larger project on the impact of forestry operations on Hg cycling which include measurements of water fluxes as well as impacts on biota. Surface-air Hg fluxes were measured using a commonly applied dynamic flux chamber (DFC) method that incorporated diel and seasonal variability in elemental Hg (Hg 0 ) fluxes at multiple forested and harvested catchments. The results showed that the forested ecosystem had depositional Hg 0 fluxes throughout most of the year (annual mean: −0.26 ng/m 2 /h). In contrast, the harvested catchments showed mostly emission of Hg 0 (annual mean: 0.63 ng/m 2 /h). Differences in solar radiation reaching the soil was the primary driver resulting in a shift from net deposition to emission in harvested catchments. The surface-air Hg fluxes were larger than the fluxes to water as runoff and accounted for 97% of the differences in Hg sequestered in forested versus harvested catchments.

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Environmental Pollution Article

Source-reported bounding extent: 45.606352077118316° to 46.069419674968515° latitude; -123.92028808593749° to -123.1842041015625° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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Chris S. Eckley, Collin A. Eagles-Smith, Michael T. Tate, David P. Krabbenhoft. 2021. Surface-air mercury fluxes and a watershed mass balance in forested and harvested catchments. https://doi.org/10.1016/j.envpol.2021.116869

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