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  • 1
    ISSN: 1573-515X
    Keywords: mercury ; methylmercury ; partitioning ; rivers ; watersheds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Seven Wisconsin rivers with contrasting, relativelyhomogeneous watershed composition were selected toassess the factors controlling mercury transport.Together, these watersheds allow comparisons ofwetland, forest, urban and agricultural land-uses.Each site was sampled nine times between September1993 and September 1994 to establish seasonalsignatures and transport processes of total mercury(HgT) and methylmercury (MeHg). Our resultsclearly show that land use and land cover stronglyinfluence mercury transport processes. Under base-flowconditions, unfiltered MeHg yield varies by a factorof sixteen (12–195 mg km-2 d-1), andincreases with the fraction of wetland area in thewatershed. Elevated mercury yields during high floware particle-phase associated in agricultural sites,but filtered-phase associated in wetland sites.Methylmercury represented less than 5% of totalmercury mobilized during the spring thaw across allwatersheds. Autumn MeHg yield was generally 11–15%of HgT in wetland influenced watersheds, thougha maximum of 51% was observed. In some cases, singlehigh-flow events may dominate the annual export ofmercury from a watershed. For example, one high-flowevent on the agricultural Rattlesnake Creek had thelargest HgT and MeHg yield in the study (107 and2.32 mg km-2 d-1, respectively). The mass ofmercury transported downstream by this single eventwas an order of magnitude larger than the eight other(non-event) sampling dates combined. These resultsunderscore the importance of watershed characteristicsand seasonal events on the fate of mercury in freshwater rivers.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-2932
    Keywords: dissolved organic carbon ; partition coefficients ; rivers ; trace metals ; watersheds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Trace metal clean-techniques were applied in the determination of the levels and particle partitioning of Al, Cd, Cu, Pb, Zn in 14 rivers in Wisconsin. Nine headwater and five receiving water sites, representing both major river systems and diverse physiographic regions were sampled in the fall of 1991 and 1992, and spring of 1993. Mean filterable concentrations (range) of Cd 9.5 (4.6–26), Cu 620 (110–1800), Pb 76 (20–200), and Zn 460 (160–930) ng L-1 are comparable with recent data from oceanic, Great Lakes, and other river systems determined by researchers using modern ‘clean’ methods. Metal partition coefficients at each site generally followed the trend (pooled mean log Kd): Pb (5.84) 〉 Zn (5.54) 〉 Cd (4.92) 〉 Cu (4.94). Order-of-magnitude differences in Kds were observed between sites, however, a large fraction of this variance could be explained by dissolved organic carbon (DOC) levels and degree of anthropogenic perturbation. Watershed yields of Cd, Pb, and Zn, under baseflow conditions were a very small fraction, typically 1–2%, of atmospheric loading. Copper yields represented a much higher fraction, particularly during spring high flow conditions. Filterable levels and yields of Al, Pb, and Zn are significantly higher in non-calcareous systems than in calcareous ones, which correlates with the higher levels of DOC in non-calcareous, forested systems.
    Type of Medium: Electronic Resource
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