Composite Calcareous Conditioners Remediate the Alkaline Paddy Soil Contaminated by Cadmium
Calcareous materials(quicklime and limestone powder)were mixed with seed meal and sepiolite at different ratios to prepare composite calcareous conditioners,which were then used to remediate the alkaline paddy soil contaminated by cadmium.Field plot experiments were conducted to study the effects of the composite calcareous conditioners on soil pH,available cadmium content in soil,and cadmium content in brown rice.Furthermore,the cost and benefit of cadmium reduction were analyzed.The results showed that composite calcareous conditioners reduced the content of available cadmium in soil by increasing soil pH,thus reducing the absorption and accumulation of cadmium in rice.The calcareous materials(quicklime:limestone powder=1∶2)applied at 3 600 kg/hm2 with seed meal and sepiolite increased the soil pH by 0.47-0.67,reduced the soil available cadmium by 34.71%-44.94%,and decreased the cadmium content in brown rice by 39.60%-53.47%.Moreover,the effects enhanced with the increase in the application rate.Furthermore,the composite calcareous conditioners increased the rice yield by 1.75%-10.59%,and the yield-increasing effect was affected by the amount of seed meal.The results of cost-benefit analysis showed that the cost for 1%reduction of cadmium in brown rice first decreased and then increased with the increase of the cadmium reduction rate in brown rice.The benefit decreased as the cadmium reduction rate in brown rice and the remediation cost increased.Considering the effect and cost of cadmium reduction in brown rice,the optimal formula of the composite calcareous conditioner was recommended as quicklime(1 200 kg/hm2)+limestone powder(2 400 kg/hm2)+sepiolite(1 500 kg/hm2).
calcareous materialseed mealsepiolitecomposite conditionercadmiumheavy metal
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