石油类污染物淡水短期水质基准研究及其对我国标准修订的意义

环境管理、应急处置和水质标准修订工作亟需石油类污染物淡水水质基准研究作为支撑. 本文筛选整理了大量本土物种毒性数据，利用SSD (物种敏感度分布法)和TPR (毒性百分数排序法)分析了5种典型石油类污染物(原油、苯、甲苯、乙苯和二甲苯)的淡水水生生物急性毒理数据，获得了保护我国淡水水生生物的短期水质基准值. 通过综合对比分析，认为利用SSD获得的基准值可作为石油类污染物的短期水质基准推荐阈值，原油和BTEX(苯系物，包括苯、甲苯、乙苯、二甲苯)的短期水质基准值分别为0.065、2.000、2.340、1.295和1.595 mg/L. 结果表明:①原油的毒性远大于BTEX，这可能是由于毒性的联合作用使得石油的毒性变强. ② 绿水螅对原油最敏感，原因可能是水螅更容易通过摄食或直接摄取获得原油WAF(水溶性组分)的有毒成分；鱼类相较于其他物种对苯更为敏感，而对其他BTEX而言，最敏感物种为节肢动物，原因可能是鱼类和节肢动物器官分化程度以及试验时的龄期选择存在差异，鱼类更易在短时间内将苯代谢为有毒的代谢产物. ③ 不同BTEX的敏感物种虽存在一定差异，但基准值未有数量级的差异. 研究显示，我国现行地表水环境质量标准中石油类标准未单独针对保护水生生物制定，BTEX标准的保护目标是基于人体健康而非水生生物，研究结果对我国石油类污染物环境管理、突发油类污染物对水生生物的危害及风险评估以及淡水水生生物特别是本土物种保护的水质标准制修订工作具有重要的借鉴作用. 

Short-Term Water Quality Criteria of Petroleum-Polluted Freshwater and Its Significance to Revision of China's National Standards

In recent years, sudden oil spill incidents have occurred frequently in China. Therefore, freshwater quality criteria for petroleum contaminated water are urgently needed for environmental management, emergency disposal, and the revision of water quality standards. Here, the acute toxicity data of five typical petroleum contaminants (crude oil, benzene, toluene, ethylbenzene and xylene) to freshwater aquatic organisms were analyzed using the species sensitivity distribution (SSD) method and the toxicity percentage ranking (TPR) method. Short-term water quality criteria values of petroleum contaminants for the protection of freshwater aquatic organisms in China were obtained based on a systematic review of the toxicity data of native species. Comparative analyses suggested that the criteria values obtained by the SSD method could be used as recommended thresholds for short-term water quality criteria of petroleum-contaminated freshwater. The obtained short-term water quality criteria values for crude oil and BTEX (benzene series, including benzene, toluene, ethylbenzene and xylene) contaminated freshwater were 0.065, 2.000, 2.340, 1.295 and 1.595 mg/L, respectively. The acute toxicity of crude oil was much greater than that of BTEX, which may be due to the synergistic effects between various toxic compounds. Hydra viridis was the most sensitive species towards crude oil because it obtained toxic components from the crude oil-water accommodated fraction (WAF) most efficiently through uptake or direct ingestion. Fishes were more sensitive to benzene than other species. For other BTEX, the most sensitive species were arthropods. This phenomenon may be due to differences in organ differentiation and age selection between fishes and arthropods. As a result, fishes are more likely to metabolize benzene into toxic compounds in a short time. Although there were differences in the sensitivity of species towards various BTEX compounds, the difference in the criteria values was in the same order of magnitude. The standards of petroleum contaminated water in China's current surface water environmental quality standards are not formulated separately for different aquatic organisms, and BTEX-related standards aim to protect human health rather than aquatic organisms. Therefore, the results of this study are significant to China's environmental management of petroleum contaminated water, as well as the hazard and risk assessment of sudden oil spill incidents to aquatic organisms. The results of this study may contribute to the formulation and revision of water quality standards to protect native species, especially freshwater aquatic organisms.