【作者】 严莎；

【导师】 周启星；

【作者基本信息】 南开大学 ， 环境科学， 2012， 博士

【摘要】 近年来，我国水环境中苯系物的污染问题日益严重，其含量逐年升高，对水生生态系统和人体健康产生了重大危害。本论文选择苯系物为研究对象，探讨了甲苯、乙苯和二甲苯污染物对典型水生生物的毒害效应，同时搜集苯、甲苯、乙苯和二甲苯相关的毒性数据，对我国水环境苯系物的水质基准展开了尝试性研究。研究选取泥鳅（Misgurnus anguillicaudatus）为受试鱼类，探讨了甲苯、乙苯和二甲苯三种污染物对典型鱼类的毒害效应。急性毒性试验研究发现，甲苯、乙苯和二甲苯对泥鳅具有明显的剂量-效应关系。甲苯、乙苯和二甲苯对泥鳅的96h-LC₅₀分别为149.7、92.7和88.9mg/L。本研究还研究了14天长期暴露对泥鳅脑部乙酰胆碱酯酶（AChE）、肝脏部位超氧化物岐化酶（SOD）、过氧化物酶（POD）、过氧化氢酶（CAT）、谷胱甘肽转移酶（GST）和脂质过氧化生理生化指标的变化情况。研究结果表明：6种生理指标对三种污染物的胁迫的灵敏度各不相同。总体上看，AChE对乙苯和二甲苯的污染指示能力要比甲苯好，而抗氧化酶对甲苯，乙苯的指示能力比较好，这其中GST和POD较适合指示甲苯和乙苯短时间的氧化胁迫，而GST对14天的二甲苯胁迫也有较好的敏感性，脂质过氧化对三种污染物的胁迫都比较敏感。综合考虑，基于甲苯、乙苯和二甲苯生态毒理指标的7天最低有影响浓度（Lowest-Observed-Effect Concentration，LOEC）分别为：5、10和20mg/L。化合物对水生植物的毒性试验在生态风险评价中长期处于次要地位，远远不及对鱼类和无脊椎动物的毒性研究，资料的积累极为欠缺，因此也极少应用于水质管理质量基准等保护政策的制定中。因此本文选取了黑藻（Hydrillaverticillata）、苦草（Vallisneria spiralis）、水芹（Oenanthe javanica （Blume） DC）、黄菖蒲（Iris pseudacorus）和千屈菜（Spiked Loosestrlfe）五种典型水生植物，研究了三种污染物对植物色素含量、超氧化物岐化酶（SOD）、过氧化物酶（POD）、过氧化氢酶（CAT）和脂质过氧化的影响情况。结果显示，不同的生理指标的灵敏程度各不相同。总体来说，本实验中所选取的生理标志物对短时间（7天）甲苯、乙苯和二甲苯的暴露有较好的指示作用，这可能是由于时间延长，生物体内已受到一定程度的破坏，生理指标的灵敏性已不如初期；也有可能是生物体在逐渐适应污染物胁迫的环境，因此生物体内机能有一定的恢复。其毒害机制还有待于在以后的工作中进一步的研究和探讨。另外根据结果可知，沉水植物更适合指示污染物的毒害效应，挺水植物对污染物的耐性更强。综合比较不同生物标志物对三种污染物不同的响应程度，得到甲苯对黑藻、苦草、水芹和千屈菜的7天LOEC分别为7.30、5.00、10.00和5.00mg/L；乙苯对黑藻、苦草、水芹和千屈菜的7天LOEC分别为1.15、5.00、5.00和5.00mg/L；二甲苯对黑藻、苦草、水芹和千屈菜的7天LOEC分别为2.36、5.00、5.00和5.00mg/L。为了制定符合我国水生态系统特征的水质基准，本研究还搜集了四种苯系物相关的毒理数据，采用国际上普遍使用的3种方法分别推导了我国苯、甲苯、乙苯和二甲苯的淡水水生生物基准。采用毒性百分数排序法得出四种污染物基准最大浓度分别为2.34、6.73、2.54和5.36mg/L，基准连续浓度（CCC）分别为NA、0.49、0.27和0.72mg/L；采用物种敏感度分布法得出的三种污染物的短期危险浓度分别为9.77、8.55、5.87和10.39mg/L，长期危险浓度分别为NA、0.62、0.63和1.42mg/L；采用评价因子法得出的我国四种污染物的淡水水生生物基准是单值，分别为0.54、0.46、0.11和0.15mg/L。比较3种方法得出的基准值认为，毒性百分数排序法较另2种方法更为恰当，得到的基准值可以保护更大范围的水生生物。根据以上结果，最终确定苯、甲苯、乙苯和二甲苯的基准最大浓度（CMC）分别为6.73、2.54和5.36mg/L；基准连续浓度（CCC）分别为NA、0.49、0.27和0.72mg/L。可以看出，由于苯缺少慢性毒性试验数据，因此无法推导其慢性基准值，有待于在以后的试验中进一步探讨和完善。该研究将为科学制订BTEX地表水环境质量标准以及排放标准提供重要的理论依据，也为我国今后系统开展水质基准的科学研究提供示范。更多还原

【Abstract】 Monocyclic aromatic hydrocarbons such as benzene, toluene, ethylbenzene andxylene （BTEX） are commonly used in the blending of petrol and also used as solventand raw material in chemical production such as paints, polymers andpharmaceuticals. As a consequence of their wide usage, they are common wastematerials. High levels of BTEX compounds in aquatic environment have often beendetected frequently, which led to serious effects to the aquatic systems and human. Inthis paper, toxicological effects of toluene, ethylbenzene and xylene on some typicalaquatic organisms were investigated, and we made an initial attempt to enact theWater Quality Criteria for BTEX （benzene, toluene, ethylbenzene and xylene）.Freshwater fish Misgurnus anguillicaudatus was adopted as experimental animalto study the acute and chronic toxic effects of toluene, ethylbenzene and xylene. Theacute toxicity test indicated that the96h-LC₅₀of three pollutants were149.7,92.7and88.9mg/L, respectively. Exposed to toluene, ethylene and xylene at low level for14days, acetylcholinesterase （AChE）, lipid peroxidation, antioxidant defenses systemincluding superoxide dismutase （SOD）, peroxidase （POD）, catalase （CAT） andglutathione-S-transferase （GST） were studied. The result showed that physiologicalindicators tested differed in their sensitivities to different pollutants. Overall, AChEwas better to be a good indicator of ethylbenzene and xylene; antioxidant enzymeswere more suitable to indicate the toxicity of toluene and ethylbenzene, which GSTand POD were more suited to be biomarkers of oxidative stress of toluene andethylbenzene for a short time; GST was also sensitivity to the xylene for14days;MDA was more sensitive to the three pollutants. According to the date, theLowest-Observed-Effect Concentrations （LOECs） of toluene, ethylbenzene andxylene on Misgurnus anguillicaudatus were5,10and20mg/L, respectively.Macrophytes are playing a vital role in material circulation and energy flow inaquatic environment, however, the data were relatively limited and have served arelatively minor role in regulatory decision. Therefore, five macrophytes that widely distributed in China were chosen as experiment plants to study the toxic effects oftoluene, ethylbenzene and xylene. Chlorophyll contents, malondialdehyde （MDA）,superoxide dismutase （SOD）, peroxidase （POD） and catalase （CAT） in plants wereinvestigated. The result showed that the different physiology indexes in differentplants had various sensitivities to the three pollutants. Conclusion in general,biomarkers chosen in our research have worked well as indicators of toxic effects oftoluene, ethylbenzene and xylene in a short exposing time. The reason may be that theplants had been damaged due to prolonged exposing time; physiological indexes wereless sensitive than that at early exposure time to the pollutants. Another explanationwas that the macrophytes have gradually adapted to the stresses of pollutants, andthey could restore the metabolism functions to a certain degree.The results also indicated that the emergent aquatic plants was more resistance totoluene, ethylbenzene and xylene, and the submerged plants were more suitable toindicate the toxic effects. Comparing all the data based on toxicity test onmacrophytes, the Lowest-Observed-Effect Concentrations （LOECs） of toluene onHydrilla verticillata, Vallisneria spiralis, Oenanthe javanica （Blume） DC and SpikedLoosestrlfe were7.30,5.00,10.00and5.00mg/L, respectively; LOECs ofethylbenzene on the four plants were1.15,5.00,5.00and5.00mg/L, respectively；LOECs of xylene on the four plants were2.36,5.00,5.00and5.00mg/L,respectively.In order to derive Water Quality Criteria that can protect the freshwaterecosystem and biota system, all available toxicity data of BETX to Chineserepresentative species in freshwater were collected. Three widely used criteriaderivation methods including the toxicity percentile rank method, species sensitivitydistribution and assessment factor method were used to derive aquatic life criteria forthe three substances. The results showed that for toxicity percentile rank method，thecriteria maximum concentrations of benzene, toluene, ethylbenzene and xylene were2.34,6.73,2.54and5.36mg/L respectively，the criteria continuous concentrationswere NA,0.49,0.27and0.72mg/L respectively; for species sensitivity distributionmethod，the criteria of short term hazardous concentrations of four substances were 9.77,8.55,5.87and10.39mg/L, the long term hazardous concentrations were NA,0.62,0.63and1.42mg/L，respectively; for the assessment factor method，the criteriaof freshwater benzene, toluene, ethylbenzene and xylene were expressed by one value，which were0.58,0.46,0.11and0.15mg/L for toluene, ethylbenzene and xylene.Meanwhile，the criteria values for freshwater were studied and compared among thethree methods. It showed that the toxicity percentile rank method was more suitablethan the other two methods to derive Water Quality Criteria in our study. The criteriavalues derived from the toxicity percentile rank method can protect a wider range ofaquatic organisms.Based on all the analysis, the final recommended Water Quality Criteria forBTEX （benzene, toluene, ethylbenzene and xylene） in freshwater were that thecriteria maximum concentrations of benzene, toluene, ethylbenzene and xylene were2.34,6.73,2.54and5.36mg/L respectively，the criteria continuous concentrationwere NA,0.49,0.27and0.72mg/L. We couldn’t derive the criteria of chronictoxicity for benzene for lack of the chronic toxicity values, so it remains to beimproved in future research.更多还原