【作者】 刘鹏；

【导师】 林玉锁； 宗良纲；

【作者基本信息】 南京农业大学 ， 环境科学， 2009， 硕士

【摘要】 本文对某铜冶炼厂周边废渣影响区土壤中重金属的分布特性,以及污灌区土壤中重金属的植物有效性做了研究。对废渣影响区土壤中重金属分布特性的研究结果显示,该调查区土壤中以铜和镉重金属污染为主。镉元素已经发生了较明显地向下迁移,污染浓度至0～40 cm,镉在土壤中分布特征与镉易于被水淋溶和在土壤中的形态以交换态为主有关。调查区土壤中的铜主要富集于表层土壤中(0-20 cm),这与土壤中的铜不易被水淋溶发生迁移和在土壤中形态主要以非交换态为主有关。由此可见,受重金属污染土壤中镉存在较大的环境风险。在对污灌区农田土壤中重金属的植物有效性的研究中,通过对单孝全提出的低分子量有机酸(LMWOAs)提取剂进行改进,形成新的提取剂(A-LMWOAs),来进行土壤重金属的植物有效性研究。实验结果表明,A-LMWOAs提取剂可以显著地提高土壤中铜和铅的提取量,但对化学性质活跃,较易被提取的锌和镉元素影响较小。并且A-LMWOAs提取剂对重金属的提取量与黑麦草盆栽试验确定的重金属生物有效性的相关性高于LMWOAs和氯化钙提取剂。证明A-LMWOAs能更好地模拟根际土壤环境,是一种评价土壤重金属植物有效性的优秀提取剂。本文对提取时间和提取液土比对重金属提取量的影响进行了深入研究。实验结果表明,A-LMWOAs重金属提取量随提取时间的增长呈指数函数式上升,随提取液土比的增大也呈指数函数式上升。A-LMWOAs提取剂提取土壤重金属,5小时是比较合适的震荡时间,30：1是比较合适的液土比。对A-LMWOAs提取剂的机理研究试验结果表明,对于铜和铅元素,先用LMWOAs提取,后用氯化钙提取剂顺序提取同一土壤样品,与先用氯化钙提取剂提取,后用LMWOAs提取相比,铜和铅的总提取量会更高；用LMWOAs提取过的土壤,再用氯化钙提取剂提取的铜和铅量,高于直接用氯化钙提取剂进行提取所提取的量；并且铜和铅的提取量会随着A-LMWOAs提取剂中LMWOAs成份浓度的增大而增大。证明A-LMWOAs中的LMWOAs成份会释放土壤中的铜和铅,使得氯化钙组分的离子交换作用能提取更多量的铜和铅。LMWOAs对土壤中锌和镉的释放作用不明显,因为锌和镉本身是化学性质活跃,易被提取的元素。多次提取实验研究表明,以液土比10：1的提取剂多次提取试验中前三次提取就可以完全提取易移动态的铜和镉,再次印证了选取的液土比30：1是合理的。并且重金属提取量随提取次数的增加呈指数衰减函数式下降,累积提取量随提取次数的增加呈指数衰减函数式上升。提取剂用量相同的情况下,多次提取相对于一步提取,可以提取土壤中更多量的铜,但对镉没有明显的作用。更多还原

【Abstract】 The heavy metal distribution characteristics in the soil of the waste residue influence area, and phyto-availability of the heavy metals in the soil of the wastewater irrigation area around a smelter were studied. The investigation of the heavy metal distribution characteristics in the waste influence area indicates that, Cu and Cd are main contaminants in this area. Cd has apparently migrated to subsurface (20-40cm and 40-60 cm) soil, probably because high percentages of Cd (50%-75%) in the soil are present as exchangeable species and it is easily to be eluviated by water. Cu is easy to accumulate in the surface (0-20 cm) soil because 30%-80%of Cu in the soil are present as organic matter bound species, and 1%-20%of Cu in the soil are present as exchangeale species, so Cu is not easy to be eluviated by water. In conclusion, Cd in this area could pose a potential leaching risk to the environment.In the study of the heavy metal phyto-availability in the sewage irrigation zone, the LMWOAs extractant proposed by Shan was adjusted and generated a new extractant called Adjusted-LMWOAs, and the A-LMWOAs was adopted in the study of the phyto-availability of the heavy metals in the soil. The result shows that, extractant A-LMWOAs can dramatically increase the extraction amount of Cu and Pb, but as for Zn and Cd, which were chemically active and easily to be extracted, no significant influense was observed. The A-LMWOAs extract amounts of the heavy metals were best correlated to the metal phyto-availability, so the adjust to the LMWOAs was succeed, and the A-LMWOAs is a good extractant in the evaluation of the phyto-availability of the heavy metals in the soil.The extract time and the ratio of the liquid/soil have big influences on the extraction amount of the heavy metals. The experiment results show that the extraction amount of heavy metals increased with the extract time and the ratio of solution to soil, and shows a exponential attenuation function.5 hours is the proper concussion time, and the proper ratio of solution to soil was 30:1, when adopting the extractant A-LMWOAs. The study of the mechanism of the A-LMWOAs indicates that, as for Cu and Pb, extract in sequence LMWOAs then 0.01mol/L CaCl2, would get bigger extraction amount than extract in sequence 0.01mol/L CaCl2 then LMWOAs; 0.01mol/L CaCl2 can extract more Cu and Pb from the soil which has been already extracted by LMWOAs, compare with the direct extraction with 0.01mol/L CaCl2; and also the extraction amount of Cu and Pb was observed increasing with the total concentrations of the LMWOAs. All above indicate that the LMWOAs as components in A-LMWOAs, can release the firmly bound Cu and Pb, and promote the ion exchange effect of the CaCl2. LMWOAs has no significant influence on the extraction of Zn and Cd in the soil, because they are chemically active and easily to be extracted.The result of the multi-extraction experiment shows that, the former three times extraction can completely extract the labile fraction of Cu and Cd, this is accord with the conclution that the ratio of the liquid to soil 30:1 is the best. The extract amount decreased with the extract frequency and shows a exponential attenuation function, the cumulative extract amount increased with the extract frequency and shows a decaying exponential function.更多还原