污灌区盐渍化土壤重金属Cd的形态分析及其影响因素

以受盐渍化及重金属Cd污染的天津污灌区土壤作为研究对象,探讨盐渍化土壤重金属的形态分布及其影响因素。研究的盐分种类主要为NaCl和Na_2SO_4,盐度7个添加质量分数依次为0%(CK)、0.2%、0.4%、0.6%、1%、2%和5%],采用Tessier连续提取法测定土壤前3种重金属的形态(可交换态、碳酸盐结合态、铁锰氧化态),得出重金属的形态分布规律。结果表明:在添加NaCl盐度条件下,土壤中Cd碳酸盐结合态可交换态铁锰氧化态,可交换态含量与盐度、重金属总量、pH值和有机质均呈显著相关。在添加Na_2SO_4盐度条件下,土壤中Cd铁锰氧化态可交换态碳酸盐结合态,可交换态、碳酸盐结合态与pH值和有机质均呈极显著相关,铁锰氧化态与pH值呈显著负相关。盐度与Cd各形态也有不同程度的相关性。在添加NaCl盐度条件下,pH值对可交换态含量有重要影响;有机质对碳酸盐结合态含量有重要影响;Cd含量对铁锰氧化态含量有重要影响。在添加Na_2SO_4盐度条件下,有机质对可交换态含量有重要影响;pH值、有机质对碳酸盐结合态含量有重要影响;CEC对铁锰氧化态含量有重要影响。得出的Cd形态分布规律以及土壤各理化性质对Cd形态含量的影响分析对土壤重金属的污染防治和生态风险评价提供了基本的理论依据。

Soil Heavy Metal Cd in Sewage-irrigated Saline Soil: Chemical Forms and Influencing Factors

Cd polluted salinity soil in Tianjin sewage-irrigated area was used as the study object, chemical form distribution of Cd and its influencing factors were analyzed. The studied salt type was mainly NaCl and Na2SO4, 7 salinities were conducted, added mass fractions were 0% (CK), 0.2%, 0.4%, 0.6%, 1%, 2% and 5%, the first three kinds of Cd form (exchangeable, carbonate bound and Fe Mn the oxidation state) were studied by Tessier continuous extraction method, and the distribution law was obtained. The results showed that under the condition of adding NaCl, the carbonate bound state > exchangeable state > Fe Mn oxidation state, the exchangeable state content was significantly correlated with salinity, total heavy metal, pH value and organic matter. Under the condition of adding Na2SO4, the Fe Mn oxidation state > exchangeable state > carbonate bound state, the exchangeable state and carbonate bound were significantly correlated with pH value and organic matter, and the Fe Mn oxidation state was negatively correlated with pH value. There was also a correlation between salinity and Cd forms. Under the condition of adding NaCl, pH value had important effect on exchangeable Cd content; and organic matter had important influence on the carbonate bound state; the content of Cd had important influence on the Fe Mn oxidation state. Under the condition of adding Na2SO4, organic matter had important influence on exchangeable Cd content; pH value and organic matter had important effect on carbonate bound state; CEC had important influence on Fe Mn oxidation state. The distribution pattern of Cd and the effects of soil physical and chemical properties on Cd forms obtained by this study could provide a theoretical basis for the prevention and control of soil heavy metal pollution and for the ecological risk assessment.