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Mercury photoreduction and photooxidation in lakes：Effects of filtration and dissolved organic carbon concentration

Journal of Environmental Sciences 2018年第6期30卷 151-159页

作者： Nelson J.O’Driscoll Emma Vost Erin Mann sara klapstein Robert Tordon Matthew Lukeman Department of Earth & Environmental Science Acadia University Wolfville B4P 2R6 Nova Scotia Canada Environment Canada Dartmouth Nova Scotia Canada Department of Chemistry Acadia University Wolfville B4P 2R6 Nova Scotia Canada

Mercury is a globally distributed, environmental contaminant. Quantifying the retention and loss of mercury is integral for predicting mercury-sensitive ecosystems. There is little information on how dissolved organic carbon（DOC） concentrations and particulates affect mercury photoreaction kinetics in freshwater lakes. To address this knowledge gap,samples were collected from ten lakes in Kejimkujik National Park, Nova Scotia（DOC： 2.6–15.4 mg/L）. Filtered（0.2 μm） and unfiltered samples were analysed for gross photoreduction, gross photooxidation, and net reduction rates of mercury using pseudo first-order curves. Unfiltered samples had higher concentrations（p = 0.04） of photoreducible divalent mercury（Hg（II）RED）（mean of 754 ± 253 pg/L） than filtered samples（mean of 482 ± 206 pg/L）;however, gross photoreduction and photooxidation rate constants were not significantly different in filtered or unfiltered samples in early summer. DOC was not significantly related to gross photoreduction rate constants in filtered（R2= 0.43; p = 0.08） and unfiltered（R2= 0.02; p = 0.71） samples; DOC was also not significantly related to gross photooxidation rate constants in filtered or unfiltered samples. However, DOC was significantly negatively related with Hg（Ⅱ）RED in unfiltered（R2= 0.53; p = 0.04）, but not in filtered samples（R2= 0.04;p = 0.60）. These trends indicate that DOC is a factor in determining dissolved mercury photoreduction rates and particles partially control available Hg（Ⅱ）RED in lake water. This research also demonstrates that within these lakes gross photoreduction and photooxidation processes are close to being in balance. Changes to catchment inputs of particulate matter and DOC may alter mercury retention in these lakes and could partially explain observed increases of mercury accumulation in biota.

关键词： Mercury Photoreduction Photooxidation Dissolved organic carbon(DOC) Particulates Kejimkujik National Park

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Assessing the utility of dissolved organic matter photoreactivity as a predictor of in situ methylmercury concentration

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Journal of Environmental Sciences 2018年第6期30卷 160-168页

作者： sara J.klapstein Susan E.Ziegler David A.Risk Nelson J.O'Driscoll Environmental Science Program Memorial University of Newfoundland Department of Earth Sciences St. Francis Xavier University Department of Earth and Environmental Science Acadia University

Methylmercury（MeHg） bioaccumulation is a growing concern in ecosystems worldwide. The absorption of solar radiation by dissolved organic matter（DOM） and other photoreactive ligands can convert MeHg into less toxic forms of mercury through photodemethylation. In this study, spectral changes and photoreactivity of DOM were measured to assess the potential to control photoreactions and predict in situ MeHg concentration. Water samples collected from a series of lakes in southwestern Nova Scotia in June, August, and September were exposed to controlled ultraviolet-A（UV-A） radiation for up to 24 hr. Dissolved organic matter photoreactivity, measured as the loss of absorbance at 350 nm at constant UV-A irradiation, was positively dependent on the initial DOM concentration in lake waters（r^2=0.94）. This relationship was consistent over time with both DOM concentration and photoreactivity increasing from summer into fall across lakes. Lake in situ MeHg concentration was positively correlated with DOM concentration and likely catchment transport in June（r = 0.77） but not the other sampling months. Despite a consistent seasonal variation in both DOM and Fe, and their respective correlations with MeHg, no discernable seasonal trend in MeHg was observed. However, a 3-year dataset from the 6 study lakes revealed a positive correlation between DOM concentration and both Fe（r = 0.91） and MeHg concentrations（r = 0.51） suggesting a more dominant landscape mobility control on *** DOM-MeHg relationships observed in these lakes highlights the need to examine DOM photoreactivity controls on MeHg transport and availability in natural waters particularly given future climate perturbations.

关键词： Methylmercury Dissolved organic carbon Photoreactions Kejimkujik National Park Freshwater lakes

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Corrigendum to Mercury photoreduction and photooxidation in lakes:effects of filtration and dissolved organic carbon *** of Environmental Sciences 68(2018)151-159

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Journal of Environmental Sciences 2021年第5期33卷 347-350页

作者： Nelson J.O'Driscol Emma Vost Erin Mann sara klapstein Robert Tordon Matthew Lukeman Department o f Earth&Environmental Science.Acadia University WolfuilleNova ScotiaCanada B4P 2R62 Environment Canada DartmouthNova Scotia Department of Chemistry Acadia UniversityWolfuilleNova ScotiaCanada B4P 2R6

"Filtered(0.2μm)and unfiltered samples were analyzed for gross photoreduction,gross photooxidation,and net reduction rates of mercury using pseudo first-order curves.

关键词： lakes Mercury dissolved

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