Department of Earth & Environmental Science, Acadia University, Wolfville, NS, Canada.
Chemosphere. 2012 Aug;88(10):1220-6. doi: 10.1016/j.chemosphere.2012.03.073. Epub 2012 Apr 21.
Uncertainties in projected ultraviolet (UV) radiation may lead to future increases in UV irradiation of freshwater lakes. Because dissolved organic carbon (DOC) is the main binding phase for mercury (Hg) in freshwater lakes, an increase in DOC photo-oxidation may affect Hg speciation and bioavailability. We quantified the effect of DOC concentration on the rate of abiotic DOC photo-oxidation for five lakes (DOC=3.27-12.3 mg L(-1)) in Kejimkujik National Park, Canada. Samples were irradiated with UV-A or UV-B radiation over a 72-h period. UV-B radiation was found to be 2.36 times more efficient at photo-oxidizing DOC than UV-A, with energy-normalized rates of dissolved inorganic carbon (DIC) production ranging from 3.8×10(-5) to 1.1×10(-4) mg L(-1)J(-1) for UV-A, and from 6.0×10(-5) to 3.1×10(-4) mg L(-1)J(-1) for UV-B. Energy normalized rates of DIC production were positively correlated with DOC concentrations. Diffuse integrated attenuation coefficients were quantified in situ (UV-A K(d)=0.056-0.180 J cm(-1); UV-B K(d)=0.015-0.165 J cm(-1)) and a quantitative depth-integrated model for yearly DIC photo-production in each lake was developed. The model predicts that, UV-A produces between 3.2 and 100 times more DIC (1521-2851 mg m(-2) year(-1)) than UV-B radiation (29.17-746.7 mg m(-2) year(-1)). Future increases in UV radiation may increase DIC production and increase Hg bioavailability in low DOC lakes to a greater extent than in high DOC lakes.
紫外线（UV）辐射预测的不确定性可能导致未来淡水湖中 UV 辐射的增加。由于溶解有机碳（DOC）是淡水湖中汞（Hg）的主要结合相，DOC 光氧化的增加可能会影响 Hg 的形态和生物利用度。我们量化了五个湖泊（DOC=3.27-12.3mgL(-1))中 DOC 浓度对非生物 DOC 光氧化速率的影响，这些湖泊位于加拿大基吉柯吉克国家公园。在 72 小时内，用 UV-A 或 UV-B 辐射照射样品。结果表明，UV-B 辐射比 UV-A 更有效地光氧化 DOC，UV-A 产生的溶解无机碳（DIC）的能量归一化速率范围为 3.8×10(-5)至 1.1×10(-4)mgL(-1)J(-1)，UV-B 的速率范围为 6.0×10(-5)至 3.1×10(-4)mgL(-1)J(-1)。DIC 产量的能量归一化速率与 DOC 浓度呈正相关。在现场量化了漫射积分衰减系数（UV-A K(d)=0.056-0.180Jcm(-1)；UV-B K(d)=0.015-0.165Jcm(-1))，并为每个湖泊开发了一个定量的深度积分模型来预测每年 DIC 的光产量。该模型预测，UV-A 产生的 DIC（1521-2851mgm(-2)year(-1))比 UV-B 辐射（29.17-746.7mgm(-2)year(-1))多 3.2 到 100 倍。未来 UV 辐射的增加可能会增加 DIC 的产量，并使低 DOC 湖泊中的 Hg 生物利用度增加的幅度大于高 DOC 湖泊。
