【作者】 王成慧；

【导师】 周涛发；

【作者基本信息】 合肥工业大学 ， 环境科学， 2010， 硕士

【摘要】 安徽省铜陵市位于长江中下游铁铜成矿带,区内富集大量铁、铜、硫、金矿产。长期的矿山采、选活动积累了大量的尾矿渣,对该区土壤环境造成了严重的重金属污染。而环境重金属的生物毒性不仅和它的总量有关,更大程度上取决于其形态分布,不同的形态产生不同的环境效应,从而影响重金属的毒性、迁移及其在自然界的循环。其中可交换态和碳酸盐结合态金属对人类和环境危害较大;铁锰氧化物结合态和有机结合态较为稳定,但在外界条件变化时也可释放出来;残渣态一般称为非有效态,不易释放出来。目前,根据重金属的形态毒性特征,修复重金属污染土壤的途径主要有两大类:(1)改变重金属在土壤中的存在形态,使其固定,从而降低其在环境中的迁移性和生物可利用性;(2)活化土壤中重金属,使其被植物体吸收从而转移出土壤。鉴于重金属形态在土壤重金属污染治理中的重要性,本文对铜陵市新桥矿区菜园表层土中重金属铜、镉形态进行了测定,同时研究了不同pH条件、不同柠檬酸浓度、不同针铁矿浓度及柠檬酸与针铁矿交互作用下土壤中铜、镉元素各形态变化规律,以期为土壤重金属污染治理提供一定的科学依据。得出的主要结论如下:(1)原土中铜、镉含量均远远超过当地土壤背景值,铜主要以残渣态为主,性质较稳定;镉以可交换态为主,易对生物体和环境产生毒害作用。(2)无机酸主要通过酸溶解作用改变重金属形态,在无机酸作用下铜和镉的碳酸盐结合态和有机结合态均与pH呈正相关。(3)添加不同浓度柠檬酸后土壤中Cu各态含量变化并不大,在3mmol/kg柠檬酸时土壤残渣态Cu含量最高,显示对土壤铜的钝化作用。而Cd各态含量变化均比较明显,总体上是使得有机结合态和残渣态向其它三态转化。(4)添加无机酸和柠檬酸作用时土壤中重金属铜、镉各态变化主要受pH影响,而柠檬酸通过络合作用减弱了这种变化。(5)针铁矿的添加使得土壤中生物可利用态铜含量减少,残渣态铜含量增加,对土壤铜体现了钝化作用。同时降低了镉的可交换态和有机结合态,而碳酸盐结合态镉和铁锰氧化物结合态镉百分比均高于原土,残渣态镉含量比原土中都有所降低。(6)柠檬酸与针铁矿交互作用时会形成针铁矿-柠檬酸的复合胶体,增强对重金属活性离子的吸附,降低重金属毒性。更多还原

【Abstract】 Tongling located at middle and lower reaches of the Yangtze River where there is an iron and copper metallogenic belt, and the area is rich in iron, copper, sulfur and gold mine. As a mining area, long time of mining related activities left large amounts of tailings, which have brought serious environmental problems of heavy metals.While the biotoxicity of heavy metal not only relates to the concentration but also to the morphological in further. Different morphological can cause different environmental effects, affect the toxicity, migration and the circulation in nature of heavy metals. Exchangeable fractions and carbonate bound bring more harmful to humans and the environment; Fe-Mn oxides bound and organic are more stable, but can release when external conditions changed; Residual is known as unavailable state, which is not easily released.Nowadays, according to the and biotoxicity of, there are two way to remand the soils contaminated caused by heavy metals: (1) To change the speciation of, made they fix up to soil so as to reduce the mobility and bioavailability;(2) To increase the activity of heavy metals to made they easily absorbed by plants, then heavy metals can be move out.Due to the importance of the morphological in the heavy metals pollution of soil, we have investigating the state of the copper and cadmium of the garden soil form Xinqiao in Tongling and the change of the state which in different environment include that the different PH, content of the citric acid and the goethite, and the interaction of the citric acid and the goethite. We can conclude that:1.The content of the copper and cadmium in the soil are far more than background values, in which, the copper is dominated by the residue form and the cadmium is by the exchange form. Both of which are more harmful to the organism and environment.2.The organically combined form and the carbonate form content of the copper and cadmium are positively correlated with the PH.3. Every state of copper in the soil content is almost constant in the different citric acid content and which is the highest in the 3 mol/kg. we can conclude that the role of copper is passivation; every state of cadmium changes are obvious, and in which the organic combination state and the residue state convention to the other three states.4.Every state of the copper and the cadmium in the soil are influenced by the PH when added the acid, however the varies will be slacked down because of the complexation of the citric acid.5. For copper, the goethite showed the passivation effects which made the content of the bioavialiable state decreased and the residual state increased; while for cadmium the of the exchange state and the organic combination state are decreased, both of the content of the carbonate and the iron manganese oxide state are higher than normal and the residue is lower than normal.6. The adsorption will be enhanced by the goethite-citric acid compound colloid which from the citric acid and goethite interaction.更多还原