海泡石对镉污染稻田钝化修复效果的稳定性

Remediation and persistent stability effects of sepiolite on cadmium-contaminated paddy soil

为探究海泡石对镉污染稻田土壤的钝化修复效果及其稳定性影响,通过开展连续两年4季的大田试验,分析成熟期稻米镉含量和土壤有效态镉含量,研究海泡石在异地对镉污染水稻土壤修复的适应性以及其修复效果的持久性效应,并通过分析稻米品质以及土壤酶活性,考察海泡石钝化修复对稻米品质和土壤环境的影响。结果表明:一次性施用不同剂量海泡石后,海泡石对镉污染稻田具有持续的钝化效果,能够显著降低糙米镉含量,但是其钝化作用随着时间延长有减弱趋势。海泡石钝化处理使第一年早稻和晚稻糙米镉含量分别比对照降低了21.0%~79.0%和63.8%~88.0%,其中当海泡石的添加量达到1.00 kg·m^(-2)时,可以使第一年早稻糙米镉含量降到我国食品中污染物限量标准(GB 2762—2017)中规定的限值(0.20 mg·kg^(-1))以下,但只有海泡石的添加量达到最大2.00 kg·m^(-2)时,才能使第一年晚稻糙米镉含量降到该标准限值以下;第二年,海泡石钝化处理使早稻和晚稻糙米镉含量分别比对照降低了4.0%~73.5%和21.4%~81.0%,但是只有海泡石施用剂量达到最大2.00 kg·m^(-2)时,才能使第二年早稻糙米镉含量降到标准限值0.20 mg·kg^(-1)以下,达到安全生产的目的,而其余处理的早稻和晚稻糙米镉含量均高于限量标准。研究表明,海泡石对镉污染稻田土壤镉具有较好的钝化修复效果,可以保障水稻的安全生产,但是在田间修复过程中,需要跟踪监测海泡石的钝化效果,必要情况下需要复施以确保其修复效果的持久稳定性。

In the present study,a 2-year field experiment was conducted to investigate the immobilization efficiency and remediation stability effects of sepiolite on Cd-contaminated paddy soil.Concentration of Cd in rice grain and available Cd in soil were determined along rice grain quality,soil Cd fractions,and soil enzyme activity.The results showed that sepiolite effectively and persistently immobilized Cd in paddy soils.However,the immobilization efficiency weakened over time.In the first year,sepiolite application significantly reduced the content of Cd in brown grain of early and late rice by approximately 21.0%~79.0%and 63.8%~88.0%,respectively,when compared with the control treatment.In addition,the content of Cd in brown grain of early rice was below the recommended tolerable level(0.20 mg·kg^(-1))at sepiolite application rates up to 1.00 kg·m^(-2).The content of Cd in brown grain of late rice was below the recommended tolerable level only when sepiolite application rate was the highest(i.e.,2.00 kg·m^(-2)).In the second year,sepiolite application significantly reduced the Cd content in brown grain of early and late rice by approximately 4.0%~73.5%and 21.4%~81.0%,respectively.Moreover,the Cd content in brown grain of early rice was below 0.20 mg·kg^(-1) only with the highest sepiolite application rate.Therefore,the results of the 2-year field experiment show the continuous effects of sepiolite on immobilization remediation of Cd-contaminated paddy soil;this could guarantee the safety of produced rice.Nonetheless,the remediation efficiency of sepiolite on Cd contaminated paddy soil needs to be tracked and monitored during the field remediation process;sepiolite should be reapplied,if necessary,to ensure the persistence of the remediation effect.