Abstract:

To assess the efficacy of five conditioning agents of lime powder (SCⅠ), dolomite powder (SCⅡ), oyster shell powder (SCⅢ), peat soil (SCⅣ) and silicate-calcium-magnesium-potassium fertilizer (SCⅤ) on passivation repair cadmium (Cd) pollution in paddy soils, this study conducted pot experiments using slightly acidic paddy soil with Cd pollution, and the effects of these conditioners on soil pH, the distribution characteristics of Cd speciation in the soil, and its bioavailability were monitored and analyzed. The results showed that after 60 days of each treatment, the soil pH increased by 1.81, 1.49, 1.17, 0.48 and 0.60 units, respectively. The distribution characteristics of water-soluble fraction, mild acido-soluble fraction, reducible fraction, oxidizable fraction and residue fraction Cd in the soil had changed in different degrees. Specifically, the distribution coefficient of water-soluble fraction Cd was reduced by 0.70%, 0.54%, 0.63%, 0.21%, and 0.24%, respectively; mild acido-soluble fraction Cd was reduced by 17.68%, 8.39%, 11.52%, 18.13%, and 15.95%; and the distribution coefficient of residual fraction Cd was increased by 14.27%, 5.33%, 11.54%, 17.70%, and 14.34% (P<0.05). This indicated that SCⅠ, SCⅡ, SCⅢ, SCⅣ and SCⅤ reduced the bioavailable Cd and increased the non-bioavailable Cd in the soil to varying degrees (P<0.05), and the passivation effects were 38.98%, 18.42%, 25.33%, 39.98% and 35.12% for Cd pollution in soils respectively. Therefore, all five conditioners demonstrated certain effectiveness in passivation repair Cd pollution in acidic paddy soils, warranting further test and verification demonstration application in safe utilization production technologies of Cd polluted acid paddy fields.

Key words: soil conditioner, paddy soil, cadmium, bioavailability, passivation effect, cadmium (Cd) pollution, soil repair