土壤pH、有机质和含水氧化物对镉、铅竞争吸附的影响  

Effects of pH, Organic Matter and Hydrous Oxides on Competitive Adsorption of Cd^(2+) and Pb^(2+) by Soil

作　　者：林大松[1] 徐应明[1] 孙国红[2] 戴晓华[1] 

机构地区：[1]农业部环境保护科研监测所,农业环境与农产品安全重点开放实验室,天津300191 [2]天津农学院基础科学系,天津300384

出　　处：《农业环境科学学报》2007年第2期510-515,共6页Journal of Agro-Environment Science

基　　金：国家重点基础研究发展规划课题(2002CB410806);国家自然科学基金(20077014);天津市科技创新能力与环境建设平台项目(05SYSYJC2500)

摘　　要：采用一次平衡法(振荡16h)研究了土壤pH值、有机质和含水氧化物(以晶质氧化铁和非晶质氧化铁为代表)对Cd2+、Pb2+在水稻土上竞争吸附的影响。结果表明,pH值是影响土壤吸附Cd2+、Pb2+的主要因素,土壤对金属离子Cd2+、Pb2+的吸附量随pH值的增大而增加。土壤pH值为5.0和6.5时,对Cd2+、Pb2+的吸附量分别达到最大。当土壤去除有机质后,土壤对Cd2+、Pb2+的吸附均降低,与对照相比,分配系数Kd,Cd、Kd,Pb分别下降54%￣64%和36%￣52%;土壤去除非晶质氧化铁后,Kd,Cd、Kd,Pb与对照相比分别下降32%￣45%和15%￣33%。有机质和非晶质氧化铁对Cd2+、Pb2+的选择性为:Pb2+>Cd2+。当土壤晶质氧化铁和非晶质氧化铁均去除后,土壤吸附Cd2+、Pb2+量不但未降低,反而有不同程度的增加,Kd,Cd、Kd,Pb明显高于对照。The preferential retention of heavy metals by soils is critical to their availability to plant and mobility through the soils down to the groundwater. We examined the competitive adsorption of Cd^2＋ and Pb^2＋ by a paddy soil as affected by pH, organic matter and hydrous oxides. Cadmium and lead adsorption from Cd-Pb binary solution produced two different adsorption isotherms. The adsorption isotherm of the metals showed that maximum adsorption occurred at pH 5.0 for Cd^2＋ and pH 6.5 for Pb^2＋, probably due to the difference in the first hydrolysis constants of the metals. The distribution coefficient Kd, which defines the affinity of the metals for the soil adsorbents, was much greater for Pb^2＋ than Cd^2＋. The removal of organic matter from the soil reduced 54%-64% for Kd,cd and 36%-52% for Kd,Pb as compared to the natural soil. Similarly, removing amorphous hydrous oxide by oxalate extraction prior to the introduction of Cd and Pb reduced Kd,Cd 32%--45% and Kd,Pb 15%-33% as compared to the natural soil, but when both amorphous and crystalline hydrous oxides were removed before Cd^2＋ and Pb^2＋ addition, the Ka, cd increased 100%, whereas Kd,Pb increased by more than twice as compared to the natural soil. It seemed that reactions with organic matter and amorphous oxides were the major influencing factors on Cd^2＋, whereas Pb^2＋ might be largely sorbed by cation exchange reaction when in competition with Cd^2＋ for binding sites in soils. The metal binding sites in the amorphous hydrous oxides and organic matter were more selective for Pb^2＋ than Cd^2＋.

关 键 词：土壤 镉 铅 竞争吸附 分配系数 含水氧化物 有机质 

分 类 号：S153[农业科学—土壤学]