摘要:
为考察多种重金属同时存在的混合溶液对藻类的生物毒性，选择Cr(Ⅲ)、Pb(Ⅱ)、Hg(Ⅱ)、Cd(Ⅱ)、Mn(Ⅱ)5种重金属，以按照国家饮用水卫生标准限值浓度配制的单一重金属溶液和多种重金属混合溶液为受试样品，并利用本实验室开发的藻红外测试技术，评价了低浓度下单一重金属溶液和多种重金属共存溶液对藻的生物毒性。实验结果显示：按照饮用水标准限值配制的5种单一重金属溶液均未观察到对藻有生物毒性，但在多种重金属共存的27个不同组合的混合溶液中，有73.1%的样品表现出明显的生物毒性；藻响应出现率与混合溶液中重金属的总浓度呈正相关关系(r=0.8942)。当多种重金属以二元至五元混合时，藻响应出现率分别为50%、80%、100%、100%，表明随着重金属组分的增加，混合溶液的毒性作用越来越显著。当不同混合溶液的重金属总浓度大于0.11 mg·L-1时，平均累积藻响应占比显著上升到93%，表明重金属混合溶液中藻的毒性与总浓度之间存在剂量响应关系。采用平均藻响应出现率分析，结果显示混合溶液中不同重金属的相对影响顺序为：Cr(Ⅲ)87.5%＞Pb(Ⅱ)和Hg(Ⅱ)58.3%＞Cd(Ⅱ)和Mn(Ⅱ)54.3%，表明Cr(Ⅲ)表现出的藻毒性远高出其他重金属。现行的水质标准通常采用单一指标和限值，本研究结果表明采用单一指标不能有效规避多种污染物共存体系的环境风险。
Abstract:
To investigate the biotoxicity of mixed solution of a variety of heavy metals on algae, we selected five heavy metals including Cr(Ⅲ), Pb(Ⅱ), Hg(Ⅱ), Cd(Ⅱ), and Mn(Ⅱ) to prepare sample solutions with a single heavy metal and various mixed heavy metals, according to the limit concentrations of the National Hygiene Standard for Drinking Water, and evaluated the effect of these sample solutions on algae. The experimental results are as follows: No single heavy metal solution, which was prepared according to the limit standard value, was observed to show biotoxicity. On the contrary, 73.1% of the samples showed significant biotoxicity in 27 different mixtures of heavy metal coexistence. The total concentrations of heavy metals were positively correlated to the toxicity to the algae (r=0.8942). The ocurrence rates of positive algea response in mixtures of heavy metals from 2 kinds to 5 kinds were 50%, 80%, 100%, and 100%, respectively, indicating that the toxic effects of the mixed solutions were enhanced with the increasing heavy metal components. When the total concentrations of heavy metals in different mixed solutions were more than 0.11 mg·L-1, the average cumulative percentage of results with positive algea resonse increased significantly to 93%, indicating that a dose-response relationship existed between the toxicity and the total concentrations of mixed heavy metals. Besides, the results also showed that the order of relative influence of different heavy metals in the mixed solution was as follows: Cr(Ⅲ) was 87.5%; Pb(Ⅱ) and Hg(Ⅱ) were both 58.3%; Cd(Ⅱ) and Mn(Ⅱ) were both 54.3%. It is indicated that the toxicity of Cr(Ⅲ) was much higher than other heavy metals. The current water quality standards usually use a single indicator and limit value. However, according to the results of our study, it cannot effectively avoid the environmental risks of the coexistence of multiple heavy metals.
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