石灰海泡石钝化后两种轮作模式对重度镉污染农田土壤的利用及修复

Utilization and Remediation of Heavily Cadmium-Contaminated Agricultural Soils by Two Crop Rotation Patterns After Lime and Sepiolite Passivation

为安全利用并修复矿区重度镉污染农田,使作物达到饲料安全标准,以不同配比的石灰海泡石作为钝化剂,钝化后试验两种轮作模式(玉米-紫花苜蓿和玉米-黑麦草),综合分析比较,筛选出最佳的钝化剂配比及配套的轮作模式.进行大田试验,测定土壤理化性质、重金属Cd有效态含量及作物中Cd含量、生物量,并采用BCR形态分级试验研究土壤钝化前后重金属形态的变化,综合分析评价其修复效果.结果表明:①通过石灰海泡石的施加,能不同程度地提高土壤pH值、有机质和CEC.②推荐施加量为LS1(石灰6.6 t·hm^(-2)+海泡石9.9 t·hm^(-2)),相比CK可显著降低玉米根、茎、叶和籽粒中重金属Cd的含量,分别降低了70.27%、61.54%、46.51%和44.23%.紫花苜蓿地上部Cd显著下降了78.47%,而黑麦草地上部Cd显著下降了65.79%.玉米季、紫花苜蓿种植区和黑麦草种植区土壤有效态Cd钝化率分别为51.37%、69.58%和77.83%,土壤中重金属由活性高的弱酸提取态向活性低的残渣态进行转化.③推荐在施加量为LS1下,配合玉米-紫花苜蓿的轮作模式,相比CK,在略微提高玉米产量的同时可显著提高紫花苜蓿产量,且可饲用部分均能达到饲料标准[GB 13078-2017,ω(Cd)≤1 mg·kg^(-1)],实现安全种植的同时修复成本最低.

In order to safely utilize and remediate the heavily cadmium-contaminated farmland in a mining area and ensure that the crops meet the feed safety standards,two rotation patterns(maize-alfalfa and maize-ryegrass)were tested after passivation with different ratios of lime and sepiolite as passivating agents,and the best ratio of passivating agent and matching crop rotation patterns were selected through comprehensive analysis and comparison.The field test was conducted to determine the physical and chemical properties of the soil,the content of the effective state of the heavy metal Cd,and the content and biomass of Cd in crops.We also studied the changes in heavy metal morphology before and after soil passivation using the BCR morphology classification test and comprehensively analyzed and evaluated its remediation effect.①The results showed that the soil pH,organic matter,and CEC could be increased to different degrees by the application of lime and sepiolite.②The recommended application amount of LS1(lime 6.6 t·hm^(-2)+sepiolite 9.9 t·hm^(-2))significantly reduced the content of heavy metal Cd in maize roots,stems,leaves,and seeds by 70.27%,61.54%,46.51%,and 44.23%,respectively,compared with those of CK.The Cd above ground in alfalfa was significantly reduced by 78.47%,whereas the Cd above ground in ryegrass was significantly reduced by 65.79%.The effective state Cd passivation rate of the soil was 51.37%,69.58%,and 77.83%in the corn season,alfalfa growing area,and ryegrass growing area,respectively.The heavy metals in the soil were converted from the weak acid extracted state with high activity to the residual state with low activity.③The recommended crop rotation pattern of supporting maize-alfalfa under the applied amount of LS1 can significantly increase alfalfa yield while slightly increasing maize yield compared with those of CK,and the forageable parts can meet the feed standard[GB 13078-2017,ω(Cd)≤1 mg·kg^(-1)],achieving safe cultivation with the lowest restoration cost.