【作者】 李淑；

【导师】 顾泳洁；

【作者基本信息】 华东师范大学 ， 生态学， 2007， 硕士

【摘要】 苏州河是上海的母亲河，不仅是主要的城市水道，也是上海主要历史人文景观。随着上海经济的发展，苏州河接纳了大量来自沿岸的工业和生活污水，水质恶化，大量污染物累积于底泥中。近年来苏州河重金属污染也受到越来越多的关注，苏州河底泥是重金属的蓄积库，随着环境因子的变化，底泥中的重金属可能再次释放进入水体，造成二次污染。本文采用苏州河底泥为实验材料，在实验室条件下模拟环境因子——pH值的变化，研究苏州河底泥重金属铅的释放情况，同时采用逐级分离方法提取底泥各形态铅，研究pH值变化对底泥铅迁移、转化的影响。结果表明：pH值的变化对苏州河底泥铅的释放速率有显著的影响。水体pH值发生变化，在短期内就能引起底泥中铅的快速释放，但随着时间的延长，底泥铅的释放速率减慢。底泥铅释放量随时间不断累积，并且从pH7.0—pH5.5随着酸度增强铅的释放量逐渐增加，在pH5.5左右可能存在一个铅释放的转折点，中性到碱性区域（pH7.0—pH8.0）在释放初期随着pH值的升高铅释放量有所降低，时间延长至第7d时该区的铅释放量也呈现逐渐上升的趋势。pH值变化对底泥各形态铅百分含量有显著影响，各处理组底泥形态铅以残渣态，铁、锰氧化物结合态为主。pH7.0—pH4.5碳酸盐结合态含量随酸性增强而下降。pH7.5—pH8.0组有机质、硫化物结合态百分含量逐渐降低，碱性的增强使腐殖酸等腐殖质分解，与之相结合的铅得到释放从而引起了底泥铅的大量释放。近年来对苏州河重金属污染的研究大多限于对河水、底泥的理化分析，对其污染的生物监测甚少报道，理化指标的分析虽可直接反映污染现状，但却不足以反映重金属对整个水体生态系统的潜在危害，因此本论文的第二部分内容通过实验室条件下红鲫鱼Pb²⁺曝露实验来探讨红鲫鱼脾脏抗氧化系统的SOD、CAT、GP_x、GSTs等抗氧化酶以及GPT、AKP、Na⁺K⁺—ATPase等代谢酶作为水体重金属污染监测生物标志物的可行性。实验结果显示：在整个曝露过程中SOD、CAT活力均被诱导，短期曝露（3d）对SOD、CAT活力无显著影响，各处理SOD活力在曝露6d时普遍被诱导，其中2.0 mg／L组活力被显著诱导（P＜0.05），达到2.53U／mgprot，1.0、2.0 mg／L组CAT活力在6d时均被显著诱导，并且高浓度组（1.0、2.0 mg／L）CAT的活力与低浓度组（0.1、0.2 mg／L）差异显著（P＜0.05），9d时2.0 mg／L组SOD活力仍继续被诱导，0.5、1.0 mg／L组SOD活力也呈现显著诱导趋势（P＜0.05），分别提高约77％、128％，0.5 mg／L组CAT活力达到5.00U／mgprot，显著高出对照组约55％（P＜0.05）。前6d的低浓度曝露使GP_x活性被诱导，酶活力随Pb²⁺浓度提高而增强，3d时0.5、1.0 mg／L组活性均极显著高于对照组（P＜0.05），9d时1.0 mg／L组GP_x活性被显著抑制（P＜0.05），2.0 mg／L组酶活性进一步被抑制，差异达到极显著水平（P＜0.01）。轻度的胁迫诱导了GSTs活力的上升，曝露时间的延长和曝露浓度的提高导致胁迫程度的加剧，GSTs活力受抑制，高浓度组（1.0、2.0 mg／L）GSTs活力在3d时已被显著诱导（P＜0.05），并显著高于0.1、0.2、0.5 mg／L等低浓度组，6d时细胞内Pb²⁺和过氧化产物的累积使得0.1、0.2、0.5 mg／L等低浓度组的GSTs活力逐步被诱导，但1.0、2.0 mg／L组GSTs活力呈现被抑制趋势，9d时抑制趋势更为明显0.5、1.0、2.0 mg／L组的活力均极显著低于对照组（P＜0.01）。Pb²⁺曝露对GPT、AKP、Na⁺K⁺—ATPase活力的影响表现为：高浓度处理（1.0、2.0mg／L）GPT活力在曝露初期即呈现被诱导趋势，随着曝露时间的延长至9d，低浓度组（0.2、0.1mg／L）GPT活性也被诱导。AKP活性在3d时被诱导，6d时1.0、2.0mg／L等高浓度组活力被进一步诱导，但随着Pb²⁺的过量累积，9d时各处理组的活性均被抑制。Na⁺K⁺—ATPase活性也呈现明显的时间、剂量效应关系，曝露前期Pb²⁺的轻微胁迫诱导了脾脏Na⁺K⁺—ATPase活性，2.0 mg／L组Na⁺K⁺—ATPase活力被显著诱导（P＜0.05），曝露时间延长至9d时，各处理Na⁺K⁺—AWPase活力出现不同程度的抑制，0.5、2.0mg／L组Na⁺K⁺—ATPase活力仅为对照的45％、64％，差异达到极显著水平（P＜0.01）。7种酶对重金属铅曝露的敏感程度为：GSTs＞AKP＞Na⁺K⁺—ATPase＞GP_x＞SOD／CAT／GPT。经过30d的净水恢复后，鱼体GPT、Na⁺K⁺—ATPase活力均有所恢复，但高浓度处理组的Na⁺K⁺—ATPase活力仍被抑制。本论文的结果说明苏州河底泥重金属铅在环境PH值发生变化时存在再次释放，造成二次污染的危险。适当的清淤、控制生活生产污染的输入、保持水体PH值等环境因子的稳定，可降低重金属二次污染的可能。水体中的重金属对红鲫鱼产生氧化损伤效应，对消化、吸收、转运、生长等过程产生影响，因此抗氧化防御系统成分和代谢酶类活性的变化在一定程度上反映了重金属对生物体的损伤，因此红鲫鱼脾脏SOD、CAT、GP_x、GSTs等抗氧化酶以及GPT、Na⁺K⁺—ATPase等代谢酶活力变化可作为生物标志物来监测苏州河重金属铅污染状况。更多还原

【Abstract】 Suzhou greek is the mother river of Shanghai, and it’s sediment is the main storage of heavy metals .With the development of economy , a large number of contaminations input to the river which lead to the deterioration of water quality . Now the heavy metal pollution of Suzhou greek becomes the hot issue of many studies . Within these studies the results showed environmental condition changes could result a dramatic release of heavy metal from the sediment. We desired to find out the effect of variation of pH to the sediment of Suzhou greek throw our studies , including the release concentration of Pb²⁺ and the transformations of different chemical states . Our Results showed that variation of pH could cause significant release of Lead . The releasing speed of Lead was higher in the beginning , but it dropped after 3 days . Lead that released from the sediment was accumulated during the period of study .With the dropping of pH from 7.0 to 5.5 , the capacity of released Lead increased . There would be a turning point of release around pH 5.5 , below pH5.5 would cause a dramatic decrease of Lead release . From pH7.0 to 8.0 the concentration of Lead decreased with the increase of pH in the earlier period of study , after 5 days the total concentration of Lead increased in samples of pH7.5 and 8.0 . The sequential extraction results showed that the predominant chemical states of Lead in the sediment were FeMnOX and RES after 7 days of release . Lead which combined with carbonates would released from the sediment with the dropping of pH from 7.0 to 4.5 , because of the decomposition of carbonates . When PH increased from 7.0 to 8.0 the Lead which exist in SD/OM would easily released according to the decomposition of humus.Recently , researches which dealt with the heavy metal pollution of Suzhou greek were mainly carried out in the physical and chemical ways. Although it could reflect the recent condition of pollution , it could not preview the potential damage to the hole aquatic system . With our effort we wanted to determine some feasible biomarkers to monitor the Lead pollution in Suzhou greek. The results showed that the accumulation of Pb²⁺ in spleen of Carassius auratu would cause the oxidant damage to the tissue and stimulate the increase of SOD and CAT activities in the range of our study . Activity of GPx significantly increased （P<0.05） within conducts of 0.5 mg/L and 1.0 mg/L after 3 days of exposure . GPx of 0.1mg/L 0.5 mg/L and 1.0 mg/L significantly rised （P<0.05） after 6 days of exposure . But after 9 days the GPx of 1.0 mg/L dropped prominently （P<0.05） , only accounted for 75% of CK and the GPx activity of 2.0 mg/L reduced to 9.33U/mgprot （P<0.01） . During 9 days of exposure GSTs presented a similar tendency with GPx , in the earlier 3 days the GSTs of 1.0 mg/L and 2.0 mg/L were significantly induced by the accumulation of Pb²⁺ . After 6 days GSTs activities of lower concentrations were also highly induced . But it decreased dramatically （P<0.05） after 9 days . GPT tend to be induced within 9 days , lower concentrations of Pb²⁺ also caused the increase of activity after 9 days . AKP were induced within 6 days but it was restrained after 9 days . Na⁺K⁺—ATPase showed a obvious connection with concentrations of Pb²⁺ and time last of exposure . In the earlier 3 days Na⁺K⁺—ATPase of 2.0 mg/L reached 7.59U/mgprot （P<0.05） , but after 9 days Na⁺K⁺—ATPase of differet conducts in our research showed a tendency of decrease . All above showed these enzymes could be biomarkers of Lead pollution of. Suzhou greek . The sequence of the sensitivities of these enzymes could be: GSTs >AKP >Na⁺K⁺—ATPase> GPX > SOD/CAT/GPT.All above conclude that there would be a risk of Lead release from the sediment of Suzhou greek with the variation of pH and we can use enzymes such as SOD、 CAT、 GPx、 GSTs and GPT ,AKP ,Na⁺K⁺—ATPase as the biomarkers to monitor the pollution condition of heavy metal Lead in Suzhou greek .更多还原