Influences of geochemical features of the watershed on methylmercury export in streams: Spatial and temporal trends

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Title: Influences of geochemical features of the watershed on methylmercury export in streams: Spatial and temporal trends
Authors: Sosso-Kolle, Kethy
Date: 2008
Abstract: Methylmercury (MeHg), the organic form of mercury (Hg), is a neurotoxin that bioaccumulates and magnifies through trophic transfer up the aquatic food chain, moving from the primary producers to the top predators and causing health problems in humans. The purpose of this study was to identify biogeochemical features of the watershed that lead to elevated levels of methyl mercury concentrations in the water in 10 stream sub-catchments. The % wetland, proximity of wetland to the stream and the slope of the sub-catchment, dissolved organic carbon, watercolor, conductivity, pH, sulfate and iron were shown to influence methyl mercury concentrations. Duplicate water samples (1L) were taken on a weekly basis between March 2005 and May 2007 and analyzed for MeHg using the GC-AFS for species detection. Many of these variables are covariables, where the slope of the river drainage basin is of critical importance. Shallow slopes are characterized by wetlands and waterlogged soils that result in watersheds with high DOC concentration, low pH and high iron concentration. In these soils, oxygen is low and iron is reduced to the more soluble form and binds to DOC, giving rise to color. MeHg production in these regions is also favored and MeHg binds to DOC and, thus, export from the watershed into the stream, especially during precipitation events.
URL: http://hdl.handle.net/10393/27732
http://dx.doi.org/10.20381/ruor-12225
CollectionTh├Ęses, 1910 - 2010 // Theses, 1910 - 2010
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