复合改良剂对Cd污染稻田早晚稻产地修复效果

选取湖南省长沙市北山镇某中重度Cd污染稻田,连续种植早晚两季水稻,研究复合改良剂(石灰石+硅藻土+硫酸铁)对稻田土壤重金属Cd的生物有效性和水稻各部位累积Cd的影响.结果表明,施用复合改良剂提高了早、晚稻土壤pH值、CEC值,降低了早稻土壤中有机质含量(OM值).Cd的TCLP提取态与交换态Cd含量分别降低了18.0%~33.0%、5.4%~57.9%,但对晚稻土壤中Cd的2种提取态含量与OM值影响不显著.施用复合改良剂显著降低早稻糙米、谷壳、茎叶、根系中的Cd含量,分别降低了29.6%~56.1%、52.1%~54.0%、18.1%~80.7%、24.4%~41.6%.早稻与晚稻之间对Cd的转运能力呈现明显差异,Cd在晚稻植株体内的转运过程更为通畅.晚稻除谷壳中的Cd含量在2 g·kg~(-1)的添加量下有所上升外,复合改良剂对水稻各部位Cd含量影响不显著(P0.05).糙米中Cd含量与土壤中TCLP可提取态含量和Cd的交换态含量存在显著正相关关系.复合改良剂有效地抑制了早稻植株对土壤中Cd的吸收,糙米中的Cd含量显著降低;晚稻期间复合改良剂随水分流失,不能持续地固化土壤中的Cd,建议在各季稻之间补加一次.

Remedying Effects of a Combined Amendment for Paddy Soil Polluted with Cd for Spring and Autumn Rice

An in-situ paddy experiment was conducted to study the remedying effects of a combined amendment(calcium carbonate+diatomite+ferric sulfate) on Cd bioavailability in soil and Cd accumulation in rice for spring and autumn rice planted in a certain Cd contaminated paddy soil in Beishan Town, Changsha, Hunan Province. The results showed that:Application of the combined amendment significantly increased soil pH and CEC values in both cultivated seasons, but decreased soil OM contents for the spring rice. During the experiment, the contents of TCLP-extractable Cd and CaCl₂-extractable Cd in soil were reduced by 18.0%-33.0% and 5.4%-57.9%, respectively. The Cd contents in brown rice, husk, leave and root for the spring rice decreased by 29.6%-56.1%, 52.1%-54.0%, 18.1%-80.7% and 24.4%-41.6%, respectively, due to application of the combined amendment. There were significant differences in Cd transport capacity between spring rice and autumn rice, and the transportation of soil Cd in autumn rice was smoother than that in spring rice. For the autumn rice, the effects of the combined amendment were not significant(P>0.05), except that the Cd content in husk increased a little after applying 2 g·kg^-1 of the combined amendment. Significant positive correlations were found between the Cd contents in brown rice and the contents of TCLP-extractable Cd or CaCl₂-extractable Cd in soil. Application of the combined amendment effectively inhibited Cd uptake by rice root and reduced Cd content in brown rice for the spring rice; however, these remedying effects were significantly weakened for the autumn rice due to loss of the combined amendment with the movement of irrigation water in the spring season. Therefore, we suggest that supplement of the combined amendment is necessary between two rice cultivated seasons.