Mercury（Hg） in the Arctic is a significant concern due to its bioaccumulative and neurotoxic properties, and the sensitivity of Arctic environments. Previous research has found high levels of Hg in snowpacks with hi...Mercury（Hg） in the Arctic is a significant concern due to its bioaccumulative and neurotoxic properties, and the sensitivity of Arctic environments. Previous research has found high levels of Hg in snowpacks with high chloride（Cl-） concentrations. We hypothesised that Cl- would increase Hg retention by decreasing Hg photoreduction to Hg（0） in melted Arctic snow. To test this, changes in Hg photoreduction kinetics in melted Alert, NU snow were quantified with changing Cl- concentration and UV intensity. Snow was collected and melted in Teflon bottles in May 2014, spiked with 0–10 μg/g Cl-, and irradiated with 3.52–5.78 W·m-2 UV（280–400 nm）radiation in a Luz Chem photoreactor. Photoreduction rate constants（k）（0.14–0.59 hr-1） had positive linear relationships with [Cl-], while photoreduced Hg amounts（Hg（Ⅱ）red） had negative linear relationships with [Cl-]（1287–64 pg in 200 g melted snow）. Varying UV and[Cl-] both altered Hg（Ⅱ）red amounts, with more efficient Hg stabilisation by Cl- at higher UV intensity, while k can be predicted by Cl- concentration and/or UV intensity, depending on experimental parameters. Overall, with future projections for greater snowpack Cl- loading,our experimental results suggest that more Hg could be delivered to Arctic aquatic ecosystems by melted snow（smaller Hg（Ⅱ）red expected）, but the Hg in the melted snow that is photoreduced may do so more quickly（larger k expected）.展开更多
基金provided by the NSERC Discovery grant # 341960-2013Canada Research Chairs Program to N.O. Scholarships to Erin Mann from NSERC CREATE and Memorial University of Newfoundland
文摘Mercury（Hg） in the Arctic is a significant concern due to its bioaccumulative and neurotoxic properties, and the sensitivity of Arctic environments. Previous research has found high levels of Hg in snowpacks with high chloride（Cl-） concentrations. We hypothesised that Cl- would increase Hg retention by decreasing Hg photoreduction to Hg（0） in melted Arctic snow. To test this, changes in Hg photoreduction kinetics in melted Alert, NU snow were quantified with changing Cl- concentration and UV intensity. Snow was collected and melted in Teflon bottles in May 2014, spiked with 0–10 μg/g Cl-, and irradiated with 3.52–5.78 W·m-2 UV（280–400 nm）radiation in a Luz Chem photoreactor. Photoreduction rate constants（k）（0.14–0.59 hr-1） had positive linear relationships with [Cl-], while photoreduced Hg amounts（Hg（Ⅱ）red） had negative linear relationships with [Cl-]（1287–64 pg in 200 g melted snow）. Varying UV and[Cl-] both altered Hg（Ⅱ）red amounts, with more efficient Hg stabilisation by Cl- at higher UV intensity, while k can be predicted by Cl- concentration and/or UV intensity, depending on experimental parameters. Overall, with future projections for greater snowpack Cl- loading,our experimental results suggest that more Hg could be delivered to Arctic aquatic ecosystems by melted snow（smaller Hg（Ⅱ）red expected）, but the Hg in the melted snow that is photoreduced may do so more quickly（larger k expected）.
