乌梁素海水体重金属元素赋存形态模拟分析

摘要

To analyze the contents and speciation of heavy metals copper (Cu), chromium (Cr) and cadmium (Cd) in the water of Wuliangsuhai Lake, the water samples from lake were collected to discuss the impact of temperature, redox and pH on the speciation of heavy metals by simulation with the PHREEQC. The results showed that the contents of Cr and Cd did not go beyond the surface water standards and national fisheries standards, but part of the samplings of Cu went beyond. The mainly chemical species of Cu in water solution were CuCl2- and Cu(OH)2, Cr was Cr (OH)3, and Cd were CdCl+, Cd2+and CdCl2. Their speciation was less influenced by temperature and more influenced by pH. While the water pH was low, the counter hydrolysis reaction of heavy metals was dominant, the content of Cl-, SO42- and other anionic ligands in the lake had obvious effects on their speciation and the speciation of heavy metals were CuCl2-, Cr(OH)2+, CdCl+, CdSO4. With pH increase, the reaction of heavy metals was transformed into the hydrolysis reaction and the main speciation in lake was Cu(OH)2,Cr(OH)3, CrO2-, CdOHCl and Cd(OH)2. Different redox condition in the lake had different effects on different heavy metals. In the reduction condition, CuCl2was dominant specie. In the oxidation condition, Cu(OH)2was dominant specie. Under the alkaline-neutral condition, there were less influenced for the form of Cr and Cd by changing of redox potential.%为探讨重金属元素在湖泊水体中的赋存形态及影响因素,采集乌梁素海水样,对湖水中重金属元素铜(Cu)、铬(Cr)、镉(Cd)含量与赋存形态进行分析,利用 PHREEQC 软件模拟分析水体温度、氧化还原性、酸碱性的变化对 Cu、Cr、Cd赋存形态的影响.结果显示,乌梁素海湖水中Cr、Cd含量都未超出地表水标准和国家渔业用水标准,但部分监测点Cu超标.湖水中Cu主要存在形态为CuCl2-、Cu(OH)2;Cr主要存在形态为Cr(OH)3;Cd主要存在形态为CdCl+、Cd2+、CdCl2.水体中Cu、Cr、Cd赋存形态受水温影响较小,受pH影响较大.水体pH较低时,重金属以配合反应为主,此时水体中Cl-、SO42-等阴离子配位体含量对其影响较为明显,主要赋存形态为CuCl2-、Cr(OH)2+、CdCl+、CdSO4;随着pH的升高,重金属逐渐发生水解反应,主要赋存形态为Cu(OH)2、Cr(OH)3、CrO2-、CdOHCl、Cd(OH)2等氢氧化物.水体的氧化还原性对不同重金属有不同影响.当水体处于还原状态时,Cu 以 CuCl2-含量为最大,处于氧化状态时,Cu(OH)2含量最大.在水体处于中性-弱碱性状态下,水体的氧化还原性对重金属Cr、Cd影响较小.