【作者】 刘晓文；

【导师】 南忠仁；

【作者基本信息】 兰州大学 ， 环境科学， 2009， 博士

【摘要】 土壤-植物系统重金属行为过程和风险的研究对于阻断重金属污染物进入食物链，防止对人体健康造成损害，促进土地资源的保护与可持续发展具有重要的意义；同时也为重金属污染土壤的修复和管理提供技术支撑。本文使用野外调查、野外淋滤试验、盆栽试验、室内淋滤试验、室内样品测试分析等方法以河西绿洲为例研究了干旱区典型土壤-植物系统中主要重金属行为过程及风险性，包括表层土壤重金属的空间变异规律、土壤重金属的纵向迁移机理、土壤重金属生物有效性以及潜在风险性。主要结论有：(1)金昌市表层土壤中Zn、Ni、Cu、Pb、Cd五种重金属元素的平均含量均超过了甘肃土壤背景值，其中Ni的平均含量还超过了国家土壤环境质量二级标准，Cu的平均含量甚至超过了国家土壤三级标准。不同土地类型下Zn含量的比较为林地＞农田＞居民区及公园＞公路绿化带＞戈壁；不同土地类型下Ni含量的比较为林地＞居民区及公园＞公路绿化带＞农田＞戈壁；不同土地类型下Pb含量的比较为农田＞居民区及公园＞公路绿化带＞林地＞戈壁；不同土地类型下Cu含量的比较为林地＞公路绿化带＞居民区及公园＞农田＞戈壁；不同土地类型下Cd含量的比较为林地＞居民区及公园＞公路绿化带＞农田＞戈壁。对于这五种元素来说，土地类型对土壤中重金属含量的影响程度为：Pb＞Zn＞Cd＞Cu＞Ni。(2)金昌市表层土壤中的Zn、Pb和Cd三种元的单因子污染均处于一级即清洁水平。相比之下，Ni和Cu的污染比较严重，其中，这五种土地类型土壤中的Ni均达到了四级即重度污染水平；公路绿化带、居民区及公园和林地土壤中的Cu均达到了四级即重度污染水平，戈壁和农田中的污染等级略低，均处于二级即轻度污染水平。五种土地类型下，Zn、Ni、Pb、Cu、Cd的内梅罗综合污染指数均为：Ni＞Cu＞Cd＞Zn＞Pb。地积累指数的结果表明，金昌市土壤中Zn和Pb的整体水平处于无污染程度，Cd处于轻度-中等污染程度，Ni处于中等污染程度，Cu的污染最为严重，处于中等-强污染程度。不同土地类型下土壤中重金属污染频率的结果显示，Pb不存在严重污染的情况，Zn和Cd严重污染的地区相对比较少，主要分布在农田和林地中；严重污染情况比较突出的Cu和Ni的不同土地类型比较为：Cu：公路绿化带＞居民区及公园＞林地＞农田＞戈壁；Ni：居民区及公园＞林地＞公路绿化带＞农田＞戈壁。地积累污染指数的空间分布结果跟各重金属污染浓度的分布结果一致。从分布范围上来看，Cu＞Ni＞Cd，Zn和Pb的污染范围均相对较小，并且Pb的污染水平也比较低。(3)金昌市农田土壤中重金属元素活化率中以Cu的活化率最高，虽然Cd的总量比较低，但其活化率却仅次于Cu，这两种元素的生物危害相性相对较大，研究区土壤中Zn、Pb的活化率相对较低，对作物的危害较小。Ni的活化率也不高，但由于其总量比较高，所以也存在一定程度的生物危害性。因子分析的结果为，研究区表层农田土壤中的Cu和Ni主要来源于工矿业活动；Zn、Cd、Pb则主要来源于农业生产活动。潜在生态风险评估则显示，接近一半的土壤样点的重金属潜在生态风险等级达到了中度及以上水平；从潜在生态危害单项系数来看，Cd＞Cu＞Ni＞Pb＞Zn，其中，Cu、Ni和Cd存在不同程度的潜在生态危害，Pb、Zn这两种元素的潜在生态风险则均处于低危害水平。有效态重金属Zn、Ni、Cu、Pb、Cd的含量均在白家咀和马家崖子附近存在高值区，并且Cu和Ni的EDTA提取态浓度值在东湾附近也比较高。此外，在中牌八队附近，EDTA提取态Cd的浓度值也偏高。寄予农产品质量安全的重要性，当地在进行粮食生产的同时，应增强农田土壤的安全性，严格控制土壤污染物，推行标准化农业生产。对于生态风险比较高的农田，应对其进行限制生产，并采取一定的措施进行修复。(4)野外淋滤试验和室内柱状实验中重金属的剖面分布特征相似，基本表现为外源重金属Cu、Zn、Pb、Cd进入土壤后，主要在表层10cm土层中富集，体现了重金属的表聚性；外源重金属进入土壤后，迁移距离短，试验时期内，迁移距离为15-20cm，自然剖面中迁移距离为45cm，外源重金属进入土壤后，虽然能在土壤中富集，但其土壤中富集的深度影响有限，目前未对地下水构成风险。野外调查所采集的耕作土壤剖面重金属变异规律研究中发现：Cu、Ni的表层富集现象明显，剖面各层Cu、Zn、Ni的总量分布差异较大。其中元素Cu和Ni分布规律相似，其浓度表现为表层至下先递减后稳定，同时这两中元素在各剖面中的迁移距离相当，基本在45cm附近，土壤剖面Zn的总量分布没有明显的规律性。受人类活动影响较大的五个剖面土壤的表层、亚表层中Cu含量和表层、亚表层以及心土层中的Ni含量基本超过中国环境质量二级标准，研究区域部分耕作土壤不再适合农作物生长，建议进行土壤修复。(5)外源重金属的加入，改变了重金属在土壤中的赋存形态，Cu、Zn、Pb主要表现为在表层0-10cm土层中碳酸盐态Cu，碳酸盐态Zn和铁锰氧化态Zn，碳酸盐态Pb所占比例较对照剖面明显增加。而元素Cd表现为剖面各土层中可交换态Cd含量均明显增加。虽然各元素含量分布特征受外源重金属的添加浓度和灌溉水pH影响不突出，但各元素的具体形态分布却在一定程度上受到影响。总体表现为Cd和Zn易受灌溉水pH值的影响，其中Cd影响最为明显。元素Cu和Pb易受外源添加量的影响。野外调查所采集的耕作土壤剖面中Cu主要以有机态和残渣态存在；Zn以参渣态为主要赋存形态；Ni主要以铁-锰氧化态和残渣态存在，三种元素的可交换态含量最少，不足1％。受外源Cu、Ni的影响，在土壤剖面中Cu和Ni有明显的形态变化层位，且该层位与它们在剖面中的迁移距离基本一致。0-45cm基本表现为有机态Cu＞残渣态Cu＞铁-锰氧化态Cu、碳酸盐态Cu＞可交换态Cu；Ni的铁-锰氧化态＞有机态、残渣态、碳酸盐态＞可交换态。45cm后的各层中Cu、Ni主要以残渣态存在。Zn在所有土层中均以残渣态为主要赋存形态。金昌城郊耕作土壤中Cu、Ni主要受人为活动影响，Zn主要来源于母岩成土过程。人为活动增加了土壤中Cu、Ni的含量，增大了Cu、Ni的潜在生物效应。(6)元素Cu、Ni易于在金昌市种植的小麦根部蓄积，元素Zn易于在小麦籽粒中积累。Cu、Ni、Zn三种元素在小麦体内的迁移能力为：Zn＞Cu＞Ni。金昌市野外调查的小麦籽粒中Cu的平均含量为9．37mg／kg，最大含量为11．64mg／kg，其中有部分样品超过国家食物卫生标准，超标率为18．18％；Zn在籽粒中的平均含量为31．39mg／kg，最大含量为43．25mg／kg，所有样品均未超过国家食物卫生标准；小麦籽粒中Ni的平均含量为3．57mg／Kg，最大含量为5．5mg／kg，以人造奶油卫生标准的1．0mg／Kg作为参考值，研究中的所有小麦样品籽粒中Ni浓度均远高于该标准值，可见研究区域的小麦籽粒中Ni超标突出，造成通过饮食方式造成的健康风险较大，应对所研究的区域进行重金属污染的土壤进行修复或改变种植方式。(7)盆栽试验研究发现油菜的地上部、根部分别对Cd、Pb有较另外部分强的累积能力，油菜各部分对Zn的累积能力向差不多；芹菜的根部对Cd、Zn、Pb具有较地上部分更强的累积能力；胡萝卜地上部分对Cd的累积能力较根部略强，Zn、Pb均为低添加浓度下在胡萝卜地上部的累积能力较根部强，而在较高剂量的添加浓度下根部的累积能力略高于地上部分。从不同蔬菜相同部位的对比分析可知，三种蔬菜中胡萝卜对Cd、Zn、Pb的累积能力最差，芹菜的根部和油菜的地上部分累积能力相对比较强。种植三种蔬菜后土壤中Cd、Zn、Pb各形态的变化各不相同。油菜原状土壤中Cd主要以残渣态和碳酸盐结合态的形式存在，油菜试验土壤中的Cd则以碳酸盐结合态和铁锰氧化物结合态为主要的存在形式：芹菜原状土壤中Cd主要以铁锰氧化物结合态和碳酸盐结合态形式存在，芹菜试验土壤中的Cd则主要以碳酸盐结合态和可交换态的形式存在；胡萝卜原状土壤中Cd的主要存在形态为残渣态，在低Cd添加浓度下的胡萝卜试验土壤中，残渣态仍是主要的存在形态，但随着外源Cd添加量的增加，残渣态的比例大幅度降低，可交换态和碳酸盐结合态成为主要的存在形式。油菜原状土壤中Zn主要以残渣态的形式存在，油菜试验土壤中的Zn则以铁锰氧化物结合态和碳酸盐结合态为主要的存在形式；芹菜原状土壤中Zn主要以残渣态形式存在，芹菜试验土壤中的Zn则主要以铁锰氧化物结合态和碳酸盐结合态的形式存在；胡萝卜原状土壤中Zn的主要存在形态为残渣态，胡萝卜试验土壤中的Zn除铁锰氧化物结合态的含量比较高以外，残渣态的含量相对其他形态也比较高。油菜原状土壤中Pb主要以残渣态形式存在，油菜试验土壤中的Pb则以碳酸盐结合态和铁锰氧化物结合态为主要的存在形式；芹菜原状土壤中Pb主要以残渣态和铁锰氧化物结合态形式存在，芹菜试验土壤中的Pb主要以碳酸盐结合态和和铁锰氧化物结合态的形式存在；胡萝卜原状土壤中Pb的主要存在形态为残渣态，在胡萝卜试验土壤中以碳酸盐结合态和铁锰氧化物结合态为主要的存在形式。从生物有效性的角度出发，对土壤中各元素形态与蔬菜中重金属含量之间的相关分析可知，土壤中Cd的可交换态均为三种蔬菜的有效态，土壤中Zn的可交换态和碳酸盐结合态均为油菜和芹菜的有效态，Zn的碳酸盐结合态和铁锰氧化物结合态则为胡萝卜的有效态，对油菜吸收有效的Pb形态为土壤中的可交换态和碳酸盐结合态，对芹菜吸收有效的Pb有效态形式为土壤中的可交换态，对胡萝卜吸收Pb有效的形态则为碳酸盐结合态。Zn和Pb在三种蔬菜中的有效态形式存在一定的差异。对三种蔬菜富集系数的比较分析可知，芹菜对Cd、Zn、Pb的富集能力均为最强，胡萝卜对Cd和Zn的富集能力最弱，油菜对Pb的富集能力最弱：从转运系数的对比分析则可以看出，Cd、Zn、Pb在芹菜体内的迁移能力均是最弱的，在较低外源金属添加情况下，Cd和Zn均在胡萝卜中的迁移能力最强，随着添加浓度的增加，这两种元素在油菜中的迁移能力超过了在胡萝卜中的迁移能力，除对照点外，Pb在胡萝卜中的迁移能力一直为最强。更多还原

【Abstract】 Behavioural process and ecological risk of heavy metal in soil-plant system play a dominantrole in hindering heavy metals passing into food chain and threatening human health. The study willnot only accelerate the land protection and sustainable development but also will providetechnological support for soil management and remediation of soils contaminated by heavy metals.Field-survey method, Field-leaching experiments, pot-culture experiments, laboratory-leachingexperiments and laboratory analysis were carried to study the chemical behavior and ecological riskon soil-plant system for representative soils in the arid area, which was taking the oasis in the Hexicorridor for an example. The main results show as follows:(1) The average content of Zn, Ni, Cu, Pb, Cd in surface soils all surpassed background value insoil from GanSu province. Moreover the average content of Ni surpassed theⅡgrade standard of soilenvironmental quality and the average content of Cu surpassed theⅢgrade standard of soilenvironmental quality. Zn content between different land use was as follows:woodland＞farmland＞residential areas＞highway green belt＞desert; Ni content was as follows:woodland＞residential areas＞highway green belt＞farmland＞desert; Pb content was as follows:farmland＞residential areas＞highway green belt＞woodland＞desert; Cu content was as follows:woodland＞highway green belt＞farmland＞desert; Cd content was as follows: woodland＞residentialareas＞highway green belt＞farmland＞desert. Different land use had effect on heavy metal content insoils, and the degree was as follows: Pb＞Zn＞Cd＞Cu＞Ni.(3) Single factor index showed that Ni in all sites was in heavy polluted; Cu in soil from highwaygreen belt, residential areas and woodland was in heavy polluted; while other heavy metals were notpolluted states. Nemerow multi-factors index of heavy metals was as follows: Ni＞Cu＞ed＞Zn＞Pb. Thegeoaccumulation index indicated Zn and Pb were in unpolluted states, Cd was in light-middle polluted,Ni was in middle polluted and Cu was in middle-heavy polluted. There was some sites from farmlandand woodland, the Zn and Cd content of which were in heavy polluted. The content of Cu followingan order were highway green belt＞residential aeras＞woodland＞farmland＞Desert. While the content ofNi was as follows: residential aeras＞woodland＞highway green belt＞farmland＞desert.(4) The activity index of Cu was higher than other heavy metals and the second of activityindex was Cd. These showed Cu and Cd had great potential harm to surroundings. While Zn activityindex and Pb activity index were relatively lower and they had less harm to surroundings. The totalcontent of Ni increased harm to biology although its activity index was lower. The results from factoranalysis suggested that Cu and Ni in top soil were mainly originated from industrial and miningactivities, while Zn, Pb and Cd were mainly originated from agricultural activities. The potentialecological risk assessment showed that the risk of about half sites were in middle-heavy level. Thesingle potential ecologicao risk index of heavy metal following an order was Cd＞Cu＞Ni＞Pb＞Zn.Moreover Cd, Cu, Ni existed different degrees of risk and the risk of Pb, Zn were in a low level. There were highest available concentrations of heavy metals neighbourhood BaiJiaZui and MaJiaYaZi.The Cu and Ni content extracted by EDTA was high neighbourhood DongWan. The Cdconcentrations extracted by EDTA was high neighbourhood ZhongPai.(5) Profile distribution of heavy metals are similar in soil through field-leaching experimentsand laboratory-leaching experiments. The result indicated that the maximum values of total Cu, Zn, Pband Cd were in the superficial horizons (0-10cm) in soil columns. The result indicated distance ofheavy metals downward movement were short in soil columns of leaching experiments during theperiod of test. Filed-survey result showed that action of distribution and transfer for total contents ofCu, Ni were similar in soil column from field-survey. Cu ,Ni were enriched in the upper layer andconcentrations decreased with increasing soil depth firstly and reached a steady level. The transferdepth of Cu and Ni down profiles reached 45centimeters. Moreover Cu content in top layer, inferiorlayer and Ni content in top layer, inferior layer, subsoil layer all surpass theⅡgrade standard of soilenvironmental quality. The results showed that although additive heavy metals were enriched in soilcolumn, the horizon depth which additive heavy metals reached was limited, heavy metals did not acthigh pollution risk to shallow groundwater.(6) Cu and Ni were riched in the roots, while Zn was riched in the seeds. Thetransfer capacity of Cu, Zn, Ni was as follows:Zn＞Cu＞Ni. The average concentrations ofCu in seeds was 9.37mg/kg, and the max concentrations was 11.64mg/kg. Cu contentabout 18.18% of sites exceeded the national hygienic limits for food in China. The averageconcents of Zn in seeds was 31.39mg/kg ,the max concents was 43.25mg/kg. The Zn content of allsites were below the national hygienic limits for food in China. The average content of Ni in seedswas 3.57mg/kg, the max content was 3.57mg/kg. The Ni content of all sites exceeded the referencevalue.(7) The percent of Cu in carbonate fraction, Zn in carbonate fraction, Zn in Fe-Mn oxidefraction, Pb in carbonate fraction in soil horizon (0-10cm) of leaching experiments column werehigher than they in original soil column, while percent of Cd in exchange fraction in all layer werehigher . Although total content distribution of heavy metals in soil column were not impactedseriously by additive heavy metals content and the pH of irrigation water, distribution of forms forheavy metals were impacted. Distribution of forms for Cd and Zn were influenced by the pH ofirrigation water, while Cu and Ni were influenced by additive heavy metals content. Field-surveyresult showed that Copper was distributed mainly in the organic fraction and the residual fraction, Zndistributed mainly in the residual fraction, Ni was distributed mainly in the Fe-Mn oxide fraction andthe residual fraction. The percent of Cu, Zn, Ni in the exchange fraction waslower than one percent..From 0 to 45 centimeters, Cu was distributed as follow: organic fraction＞residual fraction＞Fe-Mnoxide fraction、carbonate fraction＞exchangeable fraction, The content of Ni was Fe-Mn oxidefraction＞organic fraction、residual fraction、carbonate fraction＞exchangeable fraction., while Cu andNi were mainly in the residual fraction after 45 centimeter horizon. Zn was distributed in the residual fraction in all layer. Cd,Pb content in shoot and root of rape were more than other organs. Zn contentin organs of rape was not very different. Cd,Zn,Pb content in shoot of Celery was more. Cd contentin shoot of carrot was more than that of in the root slightly. The distribution of Zn, Pbin shoot and in root was different with additive heavy metals content increasing.Comparative analysis revealed that the accumulation level of Cd, Zn, Pb by carrot wasthe worst, while the accumulation level of Cd, Zn, Pb by the root of Celery and the shootof rape were the most. Distribution of forms for heavy metals were different. Cd was mainlydistributed in the residual fraction and carbonate fraction in original soil planted rape, while Cd wasmainly distributed in the Fe-Mn oxide fraction in polluted soil. Cd distributed mainly in Fe-Mn oxidefraction and carbonate fraction in original soil while Cd distributed mainly in the carbonate fractionand exchange fraction in polluted soil with planting Celery. For carrot, Cd was mainly distributed inthe residual fraction in original soil, while distribution of Cd in polluted was different with additiveheavy metal content increasing. Zn was mainly distributed in the residual fraction in original soilplanted rape, while Zn was mainly distributed in the Fe-Mn oxide fraction and carbonate fraction inpolluted soil. Zn distributed mainly in the residual fraction in original soil while Zn distributed mainlyin the Fe-Mn oxide fraction and carbonate fraction in polluted soil with planting Celery. For carrot, Znwas mainly distributed in the residual fraction in original soil. while distribution of Zn in polluted soilwas mainly in the Fe-Mn oxide fraction and residual fraction.Pb was mainly distributed in the residualfraction in original soil planted rape, while Pb was mainly distributed in the Fe-Mn oxide fraction andcarbonate fraction in polluted soil. Pb distributed mainly in the residual fraction and Fe-Mn oxidefraction in original soil while Pb distributed mainly in the Fe-Mn oxide fraction and carbonate fractionin polluted soil with planting Celery. For carrot, Pb was mainly distributed in the residual fraction inoriginal soil. while distribution of Pb in polluted soil was mainly in the Fe-Mn oxide fraction andcarbonate fraction.Correlation analysis showed that Cd in the exchange fraction was more available to rape, celeryand carrot. Zn in the exchange fraction and carbonate fraction was more available to rape, celery;while Zn in the carbonate fraction and Fe-Mn oxide fraction was more available to carrot. Pb in theexchange fraction and carbonate fraction was was more available to rape. Pb in the exchange fractionwas more available to celery. Pb in the carbonate fraction was more available to carrot.The BCF of celery for Cd, Zn, Pb was highest while BCF of carrot for Cd, Zn was lowest. ForPb, the accumulation level of carrot was worst. The transfer level of celery for Cd, Zn, Pb was worst.Under different content, transfer level of carrot and rape for Cd, Zn were different. The TF of carrotfor Pb was highest.更多还原