Distribution and transformation of cadmium formations amended with serpentine and lime in contaminated meadow soil
2015
Wang, Xue | Liang, Cheng-Hua | Yin, Yan
PURPOSE: Much farmland soil suffers severe cadmium (Cd) pollution. Many studies indicate that amended in-situ passivation economically, practically, and effectively repairs Cd-contaminated soil. However, few have researched the effect of a serpentine and lime combination on soil properties and the transformation of Cd formations. MATERIALS AND METHODS: We conducted a laboratory incubation experiment. First, the soil samples were mixed with a 10 mg/kg level of Cd and maintained at stable equilibrium for 1 week. Second, the soil was amended in different ways and cultivated for 60 days. Ten treatments were applied: different doses of serpentine (S1, S2, S3), lime (L1, L2, L3), serpentine combined with lime (L2S1, L2S2, L2S3), and control treatment (CK). Finally, the soil was sampled at various culture periods for test analysis. RESULTS AND DISCUSSION: The content of available Cd was significantly and negatively correlated with pH (r = −0.751**). The available Cd in the soils subject to S1–S3, L1–L3, and L2S1–L2S3 treatments were 13.85–25.84 %, 23.41–33.07 %, and 27.48–34.57 % lower, respectively, than those under the control treatment when cultured for 60 days. The content of exchangeable Cd generally decreased in all treatments. Opposite trends were observed in relation to Fe–Mn oxide, organic matter, and residual Cd amounts. The L2S3 treatment was optimal, with the highest decreasing amplitude (29.13 %) of exchangeable Cd content. CONCLUSIONS: Applying serpentine and lime can reduce available Cd and convert bioavailable Cd into the potential biological available state and biological non-availability state Cd. On the whole, the combination of serpentine and lime achieves the best effect.
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