外源DOM对湿地土壤吸附重金属Pb^(2+)、Cd^(2+)的影响

Effects of DOM on wetland soil adsorption of heavy metals Pb^(2+)and Cd^(2+)

为了解溶解性有机质(DOM)对湿地土壤重金属的吸附特征,采用批量平衡法,结合紫外-可见吸收光谱技术,探究了两种外源DOM(苔草DOM和腐殖酸HA)对湿地土壤吸附Pb^(2+)、Cd^(2+)的影响。结果表明:HA的紫外吸收强度明显大于苔草DOM,且HA分子量、腐殖化程度、芳香性、疏水性组分及芳环上含氧官能团含量均大于苔草DOM。在HA作用下湿地土壤对Pb^(2+)、Cd^(2+)均可在8h达到吸附动态平衡,但吸附过程存在差异。不同外源DOM对湿地土壤吸附重金属效果不同,苔草DOM浓度越高对湿地土壤吸附Pb^(2+)的促进作用越明显;HA对湿地土壤吸附高浓度Pb^(2+)(600 mg·L^(-1))总体表现为促进作用,当HA浓度增大到500 mg·L^(-1)时则与Pb^(2+)产生竞争,对低浓度Pb^(2+)(30 mg·L^(-1))表现为抑制作用。当苔草DOM添加浓度高于500 mg·L^(-1)时,对湿地土壤吸附Cd^(2+)表现出促进作用;HA对湿地土壤吸附Cd^(2+)表现为促进作用且在浓度为250 mg·L^(-1)时促进效果最佳。

In order to understand the characteristics of dissolved organic matter(DOM)adsorbing heavy metals in wetland soil,the effect of two exogenous DOM(Carex DOM and humic acid HA)on the adsorption of Pb^(2+)and Cd^(2+)in wetland soil was explored by using the batch balance method and by utilizing the technology of ultraviolet-visible absorption spectroscopy.The results showed that the UV absorption intensity of HA was significantly greater than that of Carex DOM,and the molecular weight,the degree of humification,the aromaticity,the hydrophobic components and the oxygen-containing functional groups on the aromatic ring of HA were greater than those of Carex DOM.Under the action of HA,both Pb^(2+)and Cd^(2+)can reach the dynamic equilibrium adsorption of wetland soil in 8h,but the adsorption process is different.Different exogenous DOM has different effects on the adsorption of heavy metals in wetland soil.The higher the concentration of Carex DOM,the more obvious the promotion of Pb^(2+)adsorption in wetland soil.HA promotes the adsorption of high concentrations of Pb^(2+)(600 mg·L^(-1))in wetland soils.When the concentration of HA increases to 500 mg·L^(-1),it competes with Pb^(2+),and shows an inhibitory effect on low concentrations of Pb^(2+)(30 mg·L^(-1)).When the concentration of Carex DOM is higher than 500 mg·L^(-1),it will promote the adsorption of Cd^(2+)in wetland soil.HA promoted the adsorption of Cd^(2+)in wetland soil,and the promotion effect was best when the concentration was 250 mg·L^(-1).