Key Laboratory of Eco-environments in Three Gorges Reservoir Region, Ministry of Education, College of Resources and Environment, Southwest University, Chongqing 400715, China.
Chemosphere. 2012 Apr;87(2):171-6. doi: 10.1016/j.chemosphere.2011.11.077. Epub 2011 Dec 29.
Photoreduction is of immense importance to mercury transfer from water to atmosphere. In this investigation, the reduction of HgCl(2) and Hg(NO(3))(2) under dark, natural light and ultraviolet radiation (UV) was estimated using series of laboratory experiments. The result showed that the role of light irradiation in HgCl(2) reduction was entirely different from that in Hg(NO(3))(2). The rate of HgCl(2) reduction was in the order of UV>natural light>dark, compared with dark>natural light>UV of Hg(NO(3))(2). The experiments of mercury reduction treated by KNO(3) and CH(3)OH, which was used as a NO(3)(-) provider and a ⁱOH scavenger respectively, indicated that ⁱOH which was produced via direct photolysis of NO(3)(-) in water should be responsible for the unexpected inhibition of UV to Hg(NO(3))(2) reduction. The reduction of Hg(NO(3))(2) under different radiation intensity each of UVA, UVB and UVC was investigated. The result showed that UVB induced the highest mercury reduction while mercury reduction increased with light intensity. In addition, the kinetic study of mercury reduction under natural light was conducted through both concentration gradient method and trial method. The pseudo first rate constant was estimated to be 7×10(-4) min(-1).
光还原对于汞从水体向大气中的迁移具有重要意义。本研究采用一系列实验室实验，估算了黑暗、自然光和紫外辐射（UV）条件下 HgCl2 和 Hg(NO3)2 的还原情况。结果表明，光照在 HgCl2 还原中的作用与在 Hg(NO3)2 中的作用完全不同。HgCl2 还原的速率顺序为 UV>自然光>黑暗，而 Hg(NO3)2 的速率顺序为黑暗>自然光>UV。用 KNO3 和 CH3OH 处理汞还原实验，分别作为 NO3-的供应源和 ⁱOH 清除剂，表明水中 NO3-的直接光解产生的 ⁱOH 可能是导致 UV 对 Hg(NO3)2 还原抑制的原因。研究了不同辐射强度（UVA、UVB 和 UVC）下 Hg(NO3)2 的还原情况。结果表明，UVB 诱导的汞还原最高，而汞还原随光强度增加而增加。此外，还通过浓度梯度法和试验法进行了自然光下汞还原的动力学研究。估算出的拟一级反应速率常数为 7×10(-4) min(-1)。
