Photochemical Oxidation of Dissolved Elemental Mercury by Carbonate Radicals in Water
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- 作者：Feng He ; Weirong Zhao ; Liyuan Liang ; Baohua Gu
- 刊名：Environmental Science & Technology Letters
- 出版年：2014
- 出版时间：December 9, 2014
- 年：2014
- 卷：1
- 期：12
- 页码：499-503
- 全文大小：268K
文摘
Photochemical oxidation of dissolved elemental mercury, Hg(0), affects mercury chemical speciation and its transfer at the water鈥揳ir interface in the aquatic environment. The mechanisms and factors that control Hg(0) photooxidation, however, are not completely understood, especially concerning the role of dissolved organic matter (DOM) and carbonate (CO32鈥?/sup>) in natural freshwaters. Here, we evaluate Hg(0) photooxidation rates affected by reactive ionic species (e.g., DOM, CO32鈥?/sup>, and NO3鈥?/sup>) and free radicals in creek water and a phosphate buffer solution (pH 8) under simulated solar irradiation. The Hg(0) photooxidation rate (k = 1.44 h鈥?) is much higher in the presence of both CO32鈥?/sup> and NO3鈥?/sup> than in the presence of CO32鈥?/sup>, NO3鈥?/sup>, or DOM alone (k = 0.1鈥?.17 h鈥?). Using scavengers and enhancers for singlet oxygen (1O2) and hydroxyl (HO鈥?/sup>) radicals, as well as electron paramagnetic resonance spectroscopy, we found that carbonate radicals (CO3鈥⑩€?/sup>) primarily drive Hg(0) photooxidation. The addition of DOM to the solution of CO32鈥?/sup> and NO3鈥?/sup> decreased the oxidation rate by half. This study identifies an unrecognized pathway of Hg(0) photooxidation by CO3鈥⑩€?/sup> radicals and the inhibitory effect of DOM, which could be important in assessing Hg transformation and the fate of Hg in water containing carbonate such as hard water and seawater.