石灰对稻米吸收Cd的影响及施用风险的区域调查与田间实验

Effects and application risk of liming on cadmium uptake by rice

通过区域调查与田间实验相结合的方法探讨施用石灰对土壤-水稻系统镉(Cd)污染的控制效果和潜在风险。区域调查结果显示,研究区稻米Cd超标率高达72.6%;石灰处理可降低21.1%的土壤Cd活性和9.7%的稻米Cd超标率,并小幅提升土壤pH,但存在不确定性。田间实验结果显示,经石灰处理后,稻米Cd含量从0.26 mg·kg^(-1)降为0.11 mg·kg^(-1),以高积累品种(VU8)Cd含量下降(降低0.19 mg·kg^(-1))最为明显。当石灰施用量从1.20 t·hm^(-2)提升到2.25 t·hm^(-2)时,稻米Cd含量不降反升。高Cd累积品种对于石灰使用量变化较为敏感。除土壤pH外,土壤锰(Mn)是稻米Cd累积的主要影响因子之一,而石灰施用造成了14.9%的土壤Mn流失,这可能是导致石灰效果不稳定的原因之一。调整石灰用量和配施Mn肥是解决稻米Cd污染的有效途径。

The control effect and potential risk of lime application on soil-rice system cadmium(Cd) pollution were investigated based a method combining the regional investigation and the field experiment. Regional investigation showed that the over-limit ratio of Cd concentration in rice in the study area was as high as 72.6%,the use of lime could reduce the soil Cd activity by 21.1% and the rice Cd exceeding rate by 9.7%, and increase the soil pH slightly, but there was uncertainty. Field experiment showed that the concentration of Cd in rice with lime treatment decreased from 0.26 mg·kg^(-1) to 0.11 mg·kg^(-1), and the high accumulation variety(VU8) showed more sensitivity(decrease by 0.19 mg·kg^(-1)). When the lime application rate increased from 1.20 t·hm^(-2) to2.25 t·hm^(-2), the Cd content of rice did not decrease but increase. Varieties with high Cd accumulation are more sensitive to changes in lime usage. In addition to soil pH, soil Mn is the major influencing factor of Cd accumulation in rice, and the lime use lead a loss of soil Mn by 14.9%, which may be one of the reasons for the unstable effect of lime use. The effective way to solve the Cd pollution of rice is to adjust the amount of lime dosage and apply Mn fertilizer.