Concentrations and distributions of mercury species in surface water and porewater of Lake Caohai, Guizhou Province

Abstract

运用金汞齐-冷原子荧光光谱法(CVAFS)和气相色谱技术(GC),对贵州省草海不同水文季节(枯水期和丰水期)表层水中汞的各种赋存形态,包括总汞(HgT)、溶解态汞(HgD)、活性汞(HgR)、颗粒态汞(HgP)、总甲基汞(MeHgT)、溶解态甲基汞(MeHgD)和颗粒态甲基汞(MeHgP)以及沉积物间隙水剖面中的溶解态总汞和甲基汞含量进行了测定.结果显示:草海表层水体总汞浓度为1.7-9.0ng/L,活性汞浓度为0.06-1.4ng/L,总甲基汞浓度为0.11-0.67ng/L.沉积物间隙水中溶解态汞浓度为8.6-39.6ng/L,溶解态甲基汞浓度为0.11-4.9ng/L.实验数据表明,草海湖水以溶解态汞为主,其占总汞的比例为枯水期87%,丰水期51%,溶解态汞与总汞呈显著相关(丰水期<0.01;枯水期<0.05),颗粒态汞与总汞也呈显著相关(丰水期<0.01;枯水期<0.05).溶解态甲基汞与总甲基汞呈显著相关(丰水期<0.01;枯水期<0.05),表明溶解态甲基汞控制总甲基汞的分布.沉积物间隙水溶解态汞与溶解态甲基汞浓度明显高于上覆水体,表明沉积物为草海湖水中汞的一个重要来源.;Concentrations and distributions of various mercury (Hg) species, including total Hg (HgT), dissolved Hg (HgD), reactive Hg (HgR), particulate Hg (HgP), total methylmercury (MeHgT), dissolved methylmercury (MeHgD), and particulate methylmercury (MeHgP) in surface water and porewater of the sediment collected from Lake Caohai during the flood and dry seasons were analyzed by using CVAFS and GC techniques. The concentrations of HgT ranged from 1.7 to 9.0ng/L, HgR from 0.06 to 1.4ng/L, and MeHgT from 0.11 to 0.67ng/L in surface water, respectively. In the sediment porewater, the concentrations of HgD varied from 8.6 to 39.6ng/L, and MeHgD ranged from 0.11 to 4.9ng/L. The Hg species in surface water was mostly dominated with dissolved forms with an average of 87% of HgT in dry flow period and 51% of HgT in flood flow period, respectively. The HgD and HgP forms were significantly correlated with HgT. The MeHgD were positively correlated to MeHgT, showing that distributions of MeHgT were controlled by MeHgD. Concentrations of HgD and MeHgD in porewater were higher than that obtained in the underlying water, which suggestted that the sediment was a dominant Hg source to the lake.