Cadmium and Lead Speciation as Affected by Soil Amendments in Calcareous Soil

Abstract

Abstract

This study investigated impacts of different application rates of soil amendments on cadmium (Cd) and lead (Pb) speciation in calcareous soil and the contents in wheat grain in pot experiments. Results showed that soil amendments could significantly decrease soil pH, which altered Cd and Pb speciation. When applied potassium dihydrogen phosphate (KH₂PO₄) and chicken manure amendment at a rate of 24–48 g/kg, the Cd exchangeable and carbonate-bound forms decreased by 34–63% and 13–25%, respectively, whereas decreases for the two Pb forms were 17–19% and 42–53%, respectively. In contrast, in the treatment with KH₂PO₄ and chicken manure amendment, the Cd weak organic, Fe-Mn oxide-bound, strong organic-bound, and residual forms increased by 25–63%, 53–89%, 31–88%, and 4–41%, respectively; these four Pb forms increased by 14–25%, 35–40%, 3–30%, and 38–65%, respectively. In addition, applications of KH₂PO₄ and chicken manure amendment at 24–48 g/kg also significantly decreased Cd and Pb contents in wheat grain (8–32% for Cd and 19–53% for Pb), suggesting that KH₂PO₄ and chicken manure amendment facilitated conversion of phytoavailable to less phytoavailable Cd and Pb forms.