Distribution coefficients of cadmium and zinc in different soils in mono‐metal and competitive sorption systems
2015
Shaheen, Sabry M. | Tsadilas, Christos D. | Rupp, Holger | Rinklebe, Jörg | Meissner, Ralph
We aimed to investigate the distribution coefficients (Kd) of Cd and Zn in different soils in mono‐metal (MS) and competitive sorption (CS) systems. Eleven surface soil samples varying widely in their origin and properties were collected in Egypt and Greece. Sorption isotherms were determined and Kd derived. Clayey Entisols showed a higher affinity for Zn, while a Histosol showed a higher affinity for Cd. In MS the Kd of Zn was higher than the Kd of Cd in the studied soils, except for an Aridisol and acidic Alfisols. In case of CS the Kd of Zn was higher than the Kd of Cd in the soils. The Kd of Cd decreased in CS compared to MS. The decreasing percentage of Kd‐Cd ranged from 6.5% in the Histosol to 81.8% in the sandy Entisols. Kd‐Zn in CS decreased in the Entisols, Alfisols, and Histosol, but increased in the Aridisol, Vertisol, and Mollisol compared to MS. This suggests that upon co‐addition of the two metals to the soil Zn became preferentially sorbed at the expense of Cd. Permanent charge clayey soils with relatively low Fe‐, Al‐ and Mn‐oxides content sorbed more Cd and Zn than the variable charge red soils with a higher content of these oxides. Cation exchange capacity (CEC), soil organic matter, Ald, Fed, Feₒ, Alₒ and total carbonates are important for the sorption of Cd, whereas clay, CEC, Sid, Siₒ and Alₒ content determine the sorption of Zn.
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