陕西省采矿业污染农田土壤中Cd、Pb的释放特征

Release characteristics of Cd and Pb from mining contaminated farmland soil in Shaanxi

【目的】研究陕西省采矿业污染农田土壤中Cd、Pb的分布及其释放特征。【方法】以采自陕西凤县、潼关、洛南某铅锌矿区污染农田土壤（FX、TG、LN）为研究对象，测定不同粒径土壤中Cd、Pb的总量和有效态量，并对不同农田土壤中Cd、Pb的化学形态进行了探讨，采用批处理法对FX、TG、LN土壤中Cd和Pb的释放动力学特征进行了分析。【结果】3个矿区污染农田土壤Cd总量均严重超标，TG和LN土壤Pb总量也达超标水平，FX、TG和LN土壤中Cd、Pb总量分别达到了107．84，218．62，179．29mg／kg及208．93，2216．61，1046．24mg／kg。3种土壤不同粒径土样中Cd、Pb总量均随着土壤粒径减小而增加，3种土壤Cd、Pb有效态量从大到小依次为TG〉LN〉FX。FX、TG、LN土壤中Cd有效态量分别为11．59～16．73，21．10～23．07，16．01～16．73mg／kg；Pb有效态量分别为18．30～25．05，140．22～210．59，25．81～44．06mg／kg。化学形态分析表明，在3种土壤中Cd、Pb均以碳酸盐结合态和硫化物态为主，水溶态所占比例较小；在FX土壤中未检测到水溶态Cd和Pb，在LN土壤中未检测到水溶态Pb。在污染土壤中水溶态cd、Pb的释放基本在12h以后达到平衡，其释放过程分为快速释放、慢速释放和动态平衡3个阶段，其释放规律符合准二级动力学过程。【结论】陕西省采矿业已经造成严重的农田土壤重金属污染，FX、TG和LN3种污染土壤中Cd、Pb的释放与土壤粒径以及重金属污染物的来源密切相关，水溶态Cd、Pb的释放过程是复杂的非均相扩散过程。

[Objective] This study investigated contents and release behaviors of Cd and Pb in soil pol- luted by mining industry in Shaanxi. [Method] Soils were collected from fields near mining sites in Fengxian （FX） ,Tongguan （TG） and Luonan （LN）. The total and available contents and speciation of Cd and Pb were tested accordi batch experiments. ng to particle size. Besides, the release behaviors of Cd and Pb were investigated using [Result] Soil was seriously polluted in these areas. More specifically, the total contents of Cd and Pb in 3 soil samples were 107.84,218.62,179.29 mg/kg and 208.93,2216.61,1 046.24 mg/kg, respectively. The total contents of Cd and Pb increased with the decrease of particle size, and the availability was in a decreasing order of TG〉LN〉FX for both Cd and Pb. The available contents of Cd ranged 11.59--16.73 mg/kg, 21.10- 23. 07 mg/kg,and 16.01-16.73 mg/kg for FX,TG and LN,respectively. The available contents of Pb ranged 18. 30--25. 05 mg/kg, 140. 22--210. 59 mg/kg, and 25.81--44.06 mg/kg for FX,TG and LN, respectively. Cd and Pb were mainly dominated by carbonate bounded species and sulfide species, while the water-soluble fraction was small. The release of Cd and Pb was complete within 12 h before reaching the equilibrium. The release process can be divided into 3 steps.quickrelease, slow-release and dynamic equilibrium, belonging to pseudo second order kinetics. [Conclusion] Soil was polluted seriously by the mining industry in all the three sites,and the release of Cd and Pb was strongly influenced by soil particle size and source of pollutants. In addition,the release of water soluble Cd and Pb was a complex heterogeneous diffusion process,