New Insights on Ecosystem Mercury Cycling Revealed by Stable Isotopes of Mercury in Water Flowing from a Headwater Peatland Catchment

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
Martin Tsz-Ki Tsui, Assistant Professor (Creator)
The University of North Carolina at Greensboro (UNCG )
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Abstract: Stable isotope compositions of mercury (Hg) were measured in the outlet stream and in soil cores at different landscape positions in a 9.7-ha boreal upland-peatland catchment. An acidic permanganate/persulfate digestion procedure was validated for water samples with high dissolved organic matter (DOM) concentrations through Hg spike addition analysis. We report a relatively large variation in mass-dependent fractionation (d202Hg; from -2.12 to -1.32‰) and a smaller, but significant, variation of mass-independent fractionation (?199Hg; from -0.35 to -0.12‰) during two years of sampling with streamflow varying from 0.003 to 7.8 L s–1. Large variations in d202Hg occurred only during low streamflow (<0.6 L s–1), which suggest that under high streamflow conditions a peatland lagg zone between the bog (3.0 ha) and uplands (6.7 ha) becomes the dominant source of Hg in downstream waters. Further, a binary mixing model showed that except for the spring snowmelt period, Hg in streamwater from the catchment was mainly derived from dry deposition of gaseous elemental Hg (73–95%). This study demonstrates the usefulness of Hg isotopes for tracing sources of Hg deposition, which can lead to a better understanding of the biogeochemical cycling and hydrological transport of Hg in headwater catchments.

Additional Information

Environmental Science and Technology. v52 n4 (Feb 20, 2018) 1854-1861
Language: English
Date: 2018
Soils, Dissolved organic matter, Deposition, Mercury, Isotopes

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