Dissecting the spatial scales of mercury accumulation in Ontario lake sediment |
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| Authors: | R. Brad Mills Andrew M. Paterson David R.S. Lean John P. Smol Greg Mierle Jules M. Blais |
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| Affiliation: | aUniversity of Ottawa, Department of Biology, Chemical and Environmental Toxicology, 20 Marie Currie Street, Ottawa, Ontario, Canada K1N 6N5;bOntario Ministry of the Environment, Dorset Environmental Science Centre, 1026 Bellwood Acres Road, P.O. Box 39, Dorset, Ontario, Canada;cPaleoecological Environmental Assessment and Research Laboratory, Department of Biology, Queen's University, Kingston, Ontario, Canada |
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| Abstract: | Total mercury concentration was analyzed in 171 lakes from pre-industrial (>30 cm depth; Hgpre-industrial) and present-day sediments (0.5–1 cm; Hgpresent-day). Numerous hot or cold spots of sediment mercury enrichment (Hg EF; Hgpre-industrial/Hgpresent-day) were evident as determined by local tests of autocorrelation, although in most cases, the maximum correlation among sites was not the nearest neighbor, indicating a strong influence of watershed characteristics. Hg EF was correlated with the area of open water (ha) (r = 0.91, p = 0.035), mine tailings (r = 0.94, p = 0.019), and organic deposits in surficial geology of the watershed (r = −0.91, p = 0.034). Through use of local rather than global regression coefficients, R2 increased from 0.20 (p = 0.005) to 0.60 (p = 0.013). A broad spatial pattern (>500 km) observed only in Hgpre-industrial was best explained by mean annual precipitation (shared variance = 3.5%), while finer spatial patterns only observed in Hgpresent-day and Hg EF were best explained by pH (average shared variance = 10.8%). |
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| Keywords: | Mercury enrichment Sediment Geographically weighted regression Spatial correlation Principal coordinates of neighbor matrices Watershed |
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