【作者】 焦伟；

【导师】 李光德； 卢少勇；

【作者基本信息】 山东农业大学 ， 环境工程， 2010， 硕士

【摘要】 湖泊重金属污染因其具有持久性、生物富集性和毒性而备受关注,一直是国际环境科学界的热点研究课题之一。本文依托于国家水体污染控制与治理科技重大专项(2008ZX07101),对太湖及滇池湖滨带表层底泥中几种主要重金属进行了调查研究,分析评价了重金属(Pb、Cd、Cu和Zn)污染程度、形态分布及其生态风险,并研究了不同环境因素对重金属释放的影响,旨在为合理预防和治理太湖、滇池重金属污染及湖滨带生态系统修复提供基础资料。获得的主要研究成果及认识如下:(1)与《全国土壤环境质量标准》(GB-15618-1995)比较,在研究的四种重金属中,太湖湖滨带表层沉积物中Cd污染严重,而滇池Cd和Cu污染严重,且滇池四种元素的平均含量均高于太湖,因此,就本次调查的四种重金属而言,其滇池重金属污染强度大于太湖。根据区域内各点位所处地理位置,太湖重金属污染强度总体上是北部区域>南部区域,而滇池则呈现出草海>外海北部>外海南部,但两湖总体均符合入湖口污染重于出湖口的规律。(2)由沉积物中各重金属及TOC含量相关分析可知:太湖湖滨带沉积物中各重金属之间并无显著相关性,各重金属与TOC之间相关性也不大;而滇池沉积物中Cu-Cd,Cu-Zn,Zn-Cd间均极显著相关,但各重金属与TOC之间相关性不大。(3)太湖和滇池湖滨带沉积物中四种重金属的生物有效性顺序分别为Zn>Cu>Cd>Pb和Zn>Cd>Pb>Cu,有明显差异。需要值得注意的是,太湖湖滨带沉积物中四种重金属的可提取态含量均超过60%,而滇池四种重金属中最高可提取态含量仅为53.06%,说明太湖湖滨带沉积物中四种重金属的活性较大,二次释放潜力高于滇池。(4)以单个重金属潜在生态危害系数评价,太湖湖滨带表层沉积物中主要生态风险因子是元素Cd,达到强生态危害,其余三种元素属轻微生态危害,各重金属对太湖湖滨带生态风险影响程度由高到低依次为:Cd>Cu>Pb>Zn。滇池湖滨带表层沉积物中主要生态风险因子同样是元素Cd,但其平均Eri值达到533.61,已具极强生态危害,远高于太湖,各重金属对滇池湖滨带生态风险影响程度与太湖一致,由高到低依次为:Cd>Cu>Pb>Zn。以多个重金属潜在生态危害指数评价,太湖湖滨带只是略微超过中等生态危害,而滇池湖滨带已具极强生态危害。(5)在6种pH条件下,底泥中四种重金属均随着pH值的增加,其释放率明显下降,在pH=2时,四种重金属的释放率最大。不同温度对不同重金属释放率的影响不同,但四种重金属的释放趋势基本相似,均是随着温度的升高,重金属的释放率增大。有机酸用量的增加,可明显促进四种重金属的释放,其中柠檬酸对Zn的释放能力最强,最大释放率可达77.53%;酒石酸对Zn的释放能力最强,最大释放率可达90.65%;草酸对Pb的释放能力最强,最大释放率可达43.16%。综合本次试验所用三种有机酸,其浸提能力大小顺序为酒石酸>柠檬酸>草酸。在相同有机酸用量不同pH条件下,底泥中四种重金属均随着pH值增加,释放作用逐渐减弱,但与无外加有机酸条件下相比,四种金属的释放率均有所增加。随着投加Nacl浓度的升高,四种金属的释放率均呈现增大趋势,在NaCl浓度<60 mmol/L时,四种重金属的释放率虽然随浓度的升高而增大,但变化幅度均不大,趋于平稳;当NaCl浓度>60 mmol/L时,各重金属的释放率随浓度的升高,变化幅度明显变大。更多还原

【Abstract】 Because of the persistence, bio-accumulation and toxicity, heavy metal pollution of lake has been one hot research topic in the international environment community. This study relied on the National Water Pollution Control and Management (2008ZX07101), investigated the surface sediments from lakeside belt of Lake Taihu and Lake Dianchi, analyzed species distribution and ecological risk of heavy metal pollution, and studied the release mechanism of heavy metals(Pb, Cd, Cu, Zn) in the different environmental factors. Aim of this study is to control heavy metal pollution in Lake Taihu and Lake Dianchi, and provide the basic information of ecosystem recovery of lakeside belt. The main research results obtained are listed below:(1)The surface sediment from lakeside belt of Lake Taihu was mainly polluted by Cd compared with the《Environmental quality standard for soils》(GB-15618-1995), while Lake Dianchi was mainly polluted by Cd and Cu, and the Lake Dianchi pollution was stronger than Lake Taihu, with the four heavy metals in Lake Dianchi having a higher concentration. The overall intensity of heavy metal pollution of Lake Taihu was northern estuaries>southern estuaries, outflow estuaries>inflow estuaries, and of Lake Dianch was Lake Caohai>northern Lake Waihai>southern Lake Waihai.(2)According to the correlation analysis of various heavy metals and TOC, there was no positive correlation between these heavy metals and TOC in Lake Taihu, there was a remarkable correlation between Cu and Cd, Cu and Zn, Zn and Cd in Lake Dianchi, but the correlation of heavy metals with TOC was weak.(3)The bioavailability of four heavy metals in Lake Taihu varied in the descending order of Zn, Cu, Cd and Pb, while the bioavailability of heavy metals in Lake Dianchi varied in descending order of Zn, Cd, Pb and Cu. Need to be noted that the extractable concentrations of four heavy metals in Lake Taihu all exceeded 60%, which indicated the heavy metals in Lake Taihu had a higher second release potential and a reactivity than Lake Dianchi.(4)Based on the potential ecological risk assessment results, Cd was the main ecological risk factor in Lake Taihu, reaching a strong ecological risk, the ecological risk of other three heavy metals was low, and order of ecological risk of heavy metals in lakeside belt of Lake Taihu in the descending order was Cd, Cu, Pb and Zn. Cd was also the main ecological risk factor in Lake Dianchi, but the average Eri reached 533.61, with a much higher ecological risk than Lake Taihu, the order of ecological risk of heavy metals in lakeside belt of Lake Dianchi was same with Lake Dianchi. Lake Taihu only slightly exceeded medium ecological risk, while Lake Dianchi reached a very strong ecological risk.(5)The pH values had significant effect on the release of all four heavy metals in sediments. In the condition of six pH values, the higher pH values, the release amount was more. When pH value reached to 2, the release amount of four heavy metals reached the most. When pH value was in alkaline region, the release amount almost did not change. Temperature also had effect on the release of heavy metals from the sediments. The higher temperature, the release amount was more. When the temperature reached to 35℃, the four heavy metals release amount also reached the most. Organic acids tend strongly to combine with heavy metals and had an effect on the release of heavy metals from the sediments, of which the effect of citric acid on the release of Zn was the strongest, and the highest release rate reached to 77.53%, the effect of tartaric acid on the release of Zn was the strongest, and the highest release rate reached to 90.65%, and the effect of oxalate acid on the release of Pb was the strongest, the highest release rate reached to 43.16%. The order of extraction capacity of this three organic acids was tartaric acid>citric acid>oxalate acid. In the condition of same amount of organic acids and different pH values, the release amount of all four heavy metals in sediment decreased with the pH values increased. But compared with the condition of no additional organic acids, the release rate of the four heavy metals increased, and the release rate all exceeded 70% at pH=2. The higher concentration of NaCl, the release amount was more. When the concentration was below 60mmol/L, the change range was small, but when the concentration exceeded 60mmol/L, the change range was very obvious.更多还原