【作者】 杨善谋；

【导师】 袁峰；

【作者基本信息】 合肥工业大学 ， 环境科学， 2010， 硕士

【摘要】 重金属元素污染已成为土壤环境的重要因素,并直接或间接的危害到人体健康。铜陵地区是世界上典型的矽卡岩铜金矿集区之一,是一个有三千多年开采历史的有色多金属矿区。随着矿业不断开采,有害重金属物质可以通过多种途径进入土壤,如大气沉降,工业废水和生活污水的排放,工业固废和城市垃圾以及农药化肥的施用,这些污染物主要集中在土壤表层或耕层,但随着时间的延长,污染物在土壤内部会迁移扩散和化学形态的相互转化。本文对铜陵矿区土壤重金属元素Cu、Cd全量及形态进行了全面系统的研究分析。铜陵地区表层土壤重金属形态含量和变异程度变化较大:Cu的总量均值为98.5(mg·kg-1),高于铜陵市土壤背景值(32.15 mg·kg-1),其化学形态以残渣态为主,有机结合态和铁锰氧化态次之。Cd的总量均值为3.45(mg·kg-1),远高于铜陵市土壤背景值(0.09 mg·kg-1),,最大值高达24.6(mg·kg-1),其化学形态中有机结合态最小(0.51 mg·kg-1)、离子交换态次之(0.77 mg·kg-1)。采用了地积累指数法、沉积物富集系数法、次生相富集系数法和次生相原生相分布比值法对研究区土壤重金属Cu、Cd进行了评价。结果表明:Cu、Cd的地积累指数主要为中强水平,个别处于极强水平;Cu的沉积富集系数为0～15之间,Cd的沉积富集系数为20～50之间,Cd的沉积作用大于Cu;Cu、Cd次生相富集系数法和次生相原生相分布比值法基本一致,Cu的次生相富集系数法和次生相原生相分布比值法结果大于Cd,但四种评价方法评价结果趋势基本一致。根据洁净区域和受污染区域沉积物中的“非稳态”重金属含量两者之间差值,估算土壤重金属的人为输入量。结果表明:Cu的输入量在0μg/g～458.03μg/g之间,平均值为54μg/g;Cd的输入量在0μg/g～21.70μg/g之间,平均值为1.63μg/g;运用剖面分析法分析了重金属Cu、Cd的形态迁移特征,结果表明:重金属Cu、Cd主要以离子交换态、碳酸盐结合态和有机质结合态迁移为主。根据缓变型地球化学灾害模型,研究了土壤中Cu、Cd的缓变型地球化学特征。结果表明TCASE+C与TRCPE+C+F+O之间、TCASE+C+F与TRCPE+C+F+O之间,符合缓变型地球化学灾害数学模型特征,土壤存在发生Cu、Cd缓变型地球化学灾害的可能性。对于Cu元素,在pH为5.0、5.0~2.0时,其缓变型地球化学灾害临界点分别为222.22、81.68 mg·kg-1,爆发点分别为438.75、384.99 mg·kg-1;对于Cd元素,在pH为5.0、5.0~2.0时,其缓变型地球化学灾害临界点分别为11.25、9.7 mg·kg-1,爆发点分别为14.61、24 mg·kg-1。随着酸性程度的增强,具有爆发Cu缓变型地球化学灾害可能的区域面积增大,临界点和爆发点均提前,研究区土壤中尚没有出现Cu、Cd缓变型地球化学灾害爆发的区域。土壤受到长期持续重金属输入积累以及土壤酸化、环境容量变小,是研究区土壤可能发生Cu、Cd重金属元素缓变型地球化学灾害的主要原因。更多还原

【Abstract】 Heavy metal pollution has become an important factor in the soil environment and directly or indirectly endanger human health. Tongling mine area is one of the typical skarn type Cu-Au Mining district in the World, which has been exploited for 3 -thousand-year. With the long-time exploitation of mineral, harmful heavy metals inter into the soil through a variety of ways, such as atmospheric deposition, industrial wastewater and domestic sewage discharge, industrial solid waste , municipal solid waste and pesticide chemical fertilizer, the most of these pollutants focus on the soil surface or topsoil, but with time, the contaminants in the soil will be moved widely and the chemical speciation transform into each other.In this article, we have researched total content and chemical fraction content of heavy metal Cu, Cd in study area. The content of heavy metals in surface soil changed greatly and the variation is also relatively large: the mean amount of Cu is 98.5 (mg kg-1), higher than the background value in study area (32.15 mg kg-1), The chemical fractions is mainly in residual fraction, organic fraction, and followed by Fe-Mn oxidation fraction, the mean amount of Cd is 3.45 (mg kg-1), far higher than the background value in study area (0.09 mg kg-1), maximum up to 24.6 (mg kg-1), organic bound fraction is the minimum (0.51 mg kg-1), followed by exchange fraction (0.77 mg kg-1).According to difference of labile fraction content of heavy metals between clean and contaminated areas, we have estimated anthropogenic input of heavy metals. The results showed that: the content of input of Cu is range from 0μg/g to 458.03μg/g, with average content of 54μg/g; the content of input of Cd is range from 0μg/g to 21.70μg/g, with average of content.63μg/g; and some time, using profile analysis method, we also have analyzed heavy metals Cu, Cd fraction migration characteristics, the results showed that: heavy metals Cu, Cd mainly in exchangeable fraction, carbonate fraction and organic matter fraction migrate.According to delayed geochemical hazards model, we have researched the soil Cu and Cd elements delayed geochemical characteristics in study area The results show that: the relationships between TCASE+C and TRCPE+C+F+O、TCASE+C+F and TRCPE+C+F+O fit mathematical model of delayed geochemical hazard better, there is the possibility of the outbreak of soil delayed geochemical hazard in study area. For the Cu element, in the pH of 5.0、5.0~2.0, burst critical point of delayed geochemical hazards is 222.22、81.68 mg·kg-1 respectively and burst point of delayed geochemical hazards is 438.75、384.99 mg·kg-1 respectively; at the same time, for the Cd element, in the pH of 5.0、5.0~2.0, burst critical point is 11.25、9.7 mg·kg-1 respectively and burst point is 14.61、24 mg·kg-1 respectively. As the acidity increasing, the size of the region with probability of the outbreak of Cu-based delayed geochemical hazards enlarged, burst critical point and burst point are ahead of schedule, while soil quality evaluation process in the lower soil Cu content also need to attract sufficient attention; the sensitivity of Cd on the acidity level less than Cu, with the degree of acidity to enhance its burst critical point is slightly ahead of schedule as well as burst point slight delay and the outbreak of Cd-based delayed geochemical hazards have relations with soil physical and chemical conditions、bio-availability etc. The outbreak of soil delayed geochemical hazard of Cu, Cd have not been yet in study area. The main reasons for possibility of the outbreak of Cu-based and Cd-based delayed geochemical hazards are the accumulation of long-term sustainability entry of soil heavy metals、soil acidification and diminishing environmental capacity in study area.更多还原