Abstract: The concentrations and chemical forms of copper (Gu) and zinc (Zn)
in surface soils directly influence the movement of Cu and Zn. In this study,
thirteen sandy soil samples with a wide range of total Cu and Zn concentrations
were collected for evaluating the relationships between Cu and Zn release and
extraction time, ratio of soil to water, pH and electrolyte types. The results
indicated that Cu released in batch extraction that represents long-term
leaching was mainly from exchangeable, and carbonate bound Cu fractions, and Zn
released in the batch extraction was mainly from its carbonate bound fraction.
However, the Cu and Zn leached from the soils using the column leaching that
represents short-term leaching were mainly from their exchangeable fractions.
Soil column leaching at different pH values indicated that the amounts of
leached Zn and Cu were greatly affected by pH. The Cu and Zn release
experiments with varying extraction times and ratio of soil to water suggest
that long-term water-logging in the soils after rain may increase contact time
of the soils with water and the release of Cu and Zn to water from the soils,
and total amounts of Cu or Zn released from the soils increase, but the Cu or
Zn concentration in the surface runoff decrease with increasing rainfall
intensity. The increased Ca concentration in soil solution increased stability
of organic matter-mineral complexes and might decrease the dissolution of
organic matter, and thus decreased the release of Cu-binding component of
organic matter. However, high concentration of Na in the soil solution
increased the dispersion of the organic matter-mineral complexes and increased
dissolution of organic matter and the release of Cu from the soils.