Watershed influences on mercury in tributaries to Lake Ontario
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Watershed influences on mercury in tributaries to Lake Ontario Joseph S. Denkenberger1 Habibollah Fakhraei1 Brian Branfireun2 Mario Montesdeoca1 Charles T. Driscoll ●
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Accepted: 22 December 2019 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Mercury (Hg) concentrations and speciation were measured in nine tributaries to Lake Ontario as part of two independent field-sampling programs. Among the study tributaries, mean total Hg (THg) concentrations ranged from 0.9 to 2.6 ng/L; mean dissolved Hg (THgD) ranged from 0.5 to 1.5 ng/L; mean particulate Hg (THgP) ranged from 0.3 to 2.0 ng/L; and mean methylmercury (MeHg) ranged from 0.06 to 0.14 ng/L. Watershed land cover, total suspended solids (TSS), and dissolved organic carbon (DOC) were evaluated as potential controls of tributary Hg. Significant relationships between THgD and DOC were limited, whereas significant relationships between THgP and TSS were common across watersheds. Total suspended solids was strongly correlated with the percentage of agricultural land in watersheds. Particle enrichment of Hg (mass Hg/mass TSS) was highly variable, but distinctly higher in US tributaries likely due to higher TSS in Canadian tributaries associated with higher urban and agricultural land cover. MeHg was largely associated with the aqueous phase, and MeHg as a fraction of THg was positively correlated to percent open water coverage in the watershed. Wetland cover was positively correlated to THg and MeHg concentrations, while urban land cover was only related to higher THgP. Keywords Lake Ontario Mercury Land cover Watershed ●
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Introduction As one of the world’s largest bodies of water, the Laurentian Great Lakes provide drinking water, food, recreation, employment, and transportation for many stakeholders (Evers et al. 2011). The Great Lakes region is characterized by elevated emissions and deposition of mercury (Hg) (Pirrone et al. 1998; Miller et al. 2005; USEPA 2005; NESCAUM 2005; Choi et al. 2008; Denkenberger et al. 2012). Although efforts have been made to assess the environmental and ecological impacts of Hg on some of the Great Lakes (e.g., Back et al. 2003; Evers et al. 2011;
Supplementary information The online version of this article (https:// doi.org/10.1007/s10646-019-02157-4) contains supplementary material, which is available to authorized users. * Charles T. Driscoll [email protected] 1
Department of Civil and Environmental Engineering, 151 Link Hall, Syracuse University, Syracuse, NY 13244, USA
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Department of Biology and Centre for Environment and Sustainability, University of Western Ontario, London, ON N6A 5B7, Canada
Hurley et al. 2003, 1998a, 1998b; Mason and Sullivan 1997; Rolfhus et al. 2003, Zhou et al. 2017), limited information is available on the inputs of Hg to Lake Ontario. Lai et al. (2007) estimated net atmospheric deposition of Hg to Lake Ontario, including wet deposition, net exchange of elemental Hg with the atmosphere, and dry deposition of reactive gaseous
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