Trace Metal and Cation Transport in a Sandy Soil with Various Amendments
- B. Zhu and
- A. K. Alva
Cation interactions are important in retention and transport of trace metals and major cations in soils. This study was conducted to determine the effects of either gypsum, MgSO4, or K2SO4 on transport of Cu, Zn, Ca, and Mg from a slightly alkaline sandy soil (top 15-cm layer) using leaching columns. Concentrations of the above elements were measured in seven leachate fractions, each representing 0.64 pore volume. The concentrations of Cu and Zn in the leachate were greater in the K2SO4- amended than the unamended soil. Gypsum or MgSO4 amendments significantly decreased the recovery of Cu and Zn in the leachate, compared with that from the unamended soil; however, transport of Mg was increased in the gypsum-amended soil as a result of cation exchange. The concentration of dissolved organic carbon (DOC) was highest in the K2SO4-amended soil followed by the unamended soil and the MgSO4- and gypsum-amended soils. A positive correlation (r2 = 0.77) was found between the concentrations of Cu or Zn in the leachate fractions and that of DOC. Since Cu and Zn form complexes with organic ligands in soil solution, a decrease in transport of DOC from gypsum-amended soil appears to be responsible for the decreased transport of trace metals.
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