河谷型城市土壤有害金属有机酸与细菌淋溶特性

Leaching characteristic of toxic metals in urban soil from valley city by organic acid and soil bacterial

在野外调查与前期研究的基础上,根据一点多样混合采样法收集宝鸡河谷型城市污染土壤样品50个.通过等温振荡平衡法研究了人工合成的螯合剂EDTA、DTPA、低分子有机酸草酸(Oxalic acid)、丁二酸(Butanedioic acid)、柠檬酸(Citrate)和枯草芽孢杆菌对城市污染土壤有害金属As、Cr、Cu、Pb、Sb、V、Zn的淋溶解吸特性.研究结果表明,EDTA、DTPA对宝鸡城市污染土壤As、Cr、Cu、Pb、Sb、V、Zn的整体淋溶解吸效果要优于草酸、丁二酸和柠檬酸.有机酸对宝鸡城市土壤有害金属As、Cr、Cu、Pb、Sb、V、Zn淋洗速率顺序为:柠檬酸:Pb>Sb>Zn≈As>Cu>V>Cr;DTPA:Pb≥Cu≈Zn>Sb>As>V>Cr;EDTA:Pb≥Zn>Cu>Sb>As>V>Cr;草酸:Pb>Sb>As>V>Cu>Cr;丁二酸:Cr>Pb>Sb>As>V>Cu(丁二酸淋洗的Cr随时间缓慢增加).枯草芽孢杆菌对土壤有害金属淋溶具有pH和温度的依赖性,特别对Pb、Sb的淋溶解吸特为敏感,较高pH(pH=6)淋溶要大于低pH(pH=2).研究表明,枯草芽孢杆菌淋溶土壤有害金属是细菌本身、有机酸和淋溶液pH共同作用的过程.重金属Pb和Sb是宝鸡市环境污染与人群健康风险最主要的因子,因此,有机酸和细菌及其淋溶pH综合作用对西部河谷型城市土壤有害金属Pb、Sb复合污染的原位修复提供了新的思路.

A total of 50 samples were collected by classical cone and quarter technique from 0- 20 cm top soil in the valley city of Baoji. Leaching kinetics of toxic metal As,Cr,Cu,Pb,Sb,V and Zn in soil by EDTA,DTPA,oxalic acid,butanedioic acid,citrate and soil bacterial Bacillus subtilis washing were conducted with batch experiments. Results showed that the leaching capacity of aminopolycarboxylic acids including of EDTA and DTPA was better than that of low molecular weight organic acids such as oxalic acid,butanedioic acid and citrate acid. The order of leaching rate by five organic acids decreased as： Pb≥Zn Cu Sb As V Cr for EDTA,Pb≥Cu≈Zn Sb As V Cr for DTPA,Pb Sb As V Cu Cr for oxalic acid,Cr Pb Sb As V Cu for butanedioic acid（ Cr increases with butanedioic acid leaching）,and Pb Sb Zn≈As Cu V Cr for citrate. The leachate of toxic metals was dependence upon pH and temperature when used by soil bacterial Bacillus subtilis,especially for Pb and Sb. The toxic metal leachate in high pH（ pH = 6） was greater than that of the low pH（ pH = 2）. The leaching process was collectively affected by the pH,bacteria itself and organic acid in bacterial inner and outer interfaces. The results displayed that the toxic metal Pb and Sb are the main pollution and potential risk factorsin Baoji environment,and soil bacterial Bacillus subtilis is a novel plant growth promoting rhizobacteria（ PGPR） for improving in situ phytoremediation efficiency of Pb and Sb polluted soils and sites.