Elevated Concentrations of Methyl Mercury in Streams after Forest Clear-Cut: A Consequence of Mobilization from Soil or New Methylation?
2009 (English)In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 43, no 22, 8535-8541 p.Article in journal (Refereed) Published
Concentrations of inorganic, mercuric mercury (Hg-II), methyl mercury (MeHg) and ancillary chemistry measured in first-order streams draining 0-4 (N = 20) and 4-10 (N = 27) year-old clear-cuts of former Norway Spruce Picea abies (Karst.) forest stands were compared with concentrations in streams draining 70 year-old Norway Spruce reference stands(N = 10). Concentrations of MeHg, and ratios of MeHg TOC-1 and Hg-II TOC-1, were significantly (p 0.01)elevated in 0-4 year-old clear-cuts, as compared to references. The only ancillary variable showing a significant elevation for 0-4 year-old clear-cuts was Mn (P 0.02). The 4-10 year-old clear-cuts showed intermediate concentrations with nonsignificant differences as compared to references, pH, nitrate, sulfate, Ca, Fe, TOC, TON, and the aromaticity of TOC (SUVA(254 nm)) showed nonsignificant differences between clear-cut age classes and references, Assuming that MeHg and Hg-II are mobilized from soil to stream to a similar relative extent as a consequence of clear-cutting, a calculation showed that 1/6 of the elevated MeHg concentration was due to enhanced mobilization from soil and 5/6 was due to new methylation of Hg-II 0-4 years after clear-cut New methylation after clear-cut is suggested to be stimulated by an increased availability of electron donors for methylating bacteria, as a consequence of degradation of logging residue ("slash") and soil organic matter. A subdivision of sites situated above and below the highest postglacial coastline (HC) revealed a significant elevation of MeHg, MeHg TOC-1 and Hg-II TOC-1 (p 0.05) beyond their references in 0-4 year-old clear-cuts above (but not below) the HC. This suggests that postglacial deposits of FeS(s) and FeS2(s) were not an important factor for elevation of MeHg after clear-cut.
Place, publisher, year, edition, pages
2009. Vol. 43, no 22, 8535-8541 p.
Earth and Related Environmental Sciences
IdentifiersURN: urn:nbn:se:su:diva-36962DOI: 10.1021/es900996zISI: 000271583400014OAI: oai:DiVA.org:su-36962DiVA: diva2:291442