不同钝化剂对碱性镉污染土壤钝化效果研究

Study on the Passivation Effect of Different Passivators on Alkaline Cadmium Contaminated Soil

该研究以河南栾川石宝沟典型铅锌矿区镉污染农田土壤作为供试土壤,采用室内培养试验法,分别添加熟石灰、方解石、白云石、沸石、蒙脱石、生物炭等6种钝化材料,采用Tessier修正顺序七步提取法进行镉形态含量分析,研究不同钝化剂在1%、3%、5%添加量条件下对典型北方碱性土壤镉的钝化效果。结果显示,试验选用的6种钝化材料在不同程度上提升了土壤pH值,对pH值提升效果排序为熟石灰>蒙脱石>沸石>白云石>生物炭>方解石。不同钝化剂对离子交换态Cd的钝化作用具有一定的差异性,钝化效果排序为熟石灰>方解石>生物炭>沸石>白云石>蒙脱石,其中碱性物质熟石灰对离子交换态Cd的降低效果显著,同为碳酸盐矿物的方解石明显优于白云石,同为黏土矿物的沸石优于蒙脱石,生物炭钝化效果居中。其中5%添加量熟石灰、3%添加量方解石、1%添加量沸石、1%添加量生物炭钝化效果最为明显,对土壤离子交换态Cd含量分别降低了61.11%、25.32%、14.84%、24.76%。6种钝化剂的添加在不同程度上改变了Cd在土壤中的形态含量比例,总体来看,离子交换态镉含量显著降低,碳酸盐结合态、腐殖酸结合态、铁锰氧化物结合态镉含量明显增加,硅酸盐残余态镉含量小幅上升,强有机结合态略微下降。

Cadmium-contaminated farmland soil in a typical lead-zinc mining area in Shibaogou,Luanchuan,Henan Prov⁃ince was used as the test soil.The indoor culture test was done by adding 6 passivation materials including hydrated lime,calcite,dolomite,zeolite,montmorillonite,biochar.The Tessier modified sequence seven-step extraction method was used to analyze the cadmium form content to study the passivation effects of different passivators on the typical northern alkaline soil cadmium under the conditions of 1%,3%,and 5%.The results showed that the six passivation materials selected in the experi⁃ment increased the pH value of the soil to varying degrees,with the order of the effect of increasing the pH value as hydrated lime>montmorillonite>zeolite>dolomite>biochar>calcite.The passivation effect of different passivators on ion-exchanged Cd has certain differences,with the passivation effect in the order of hydrated lime>calcite>biochar>zeolite>dolomite>montmorillonite.Among them,the alkaline substance slaked lime is for ion-exchanged Cd.The reduction effect of calcite,which is also carbonate mineral,is significantly better than dolomite,zeolite,which is also clay mineral,is better than montmo⁃rillonite,and the passivation effect of biochar is in the middle.Among them,5%hydrated lime,3%calcite,1%zeolite,and 1%biochar have the most obvious passivation effects,The content of ion exchanged Cd in the soil was reduced by 61.11%,25.32%,14.84%,and 24.76%respectively.The addition of 6 kinds of passivators changed the proportion of Cd form content in the soil to varying degrees.In general,the content of ion-exchanged cadmium was significantly reduced,carbonate-bound state,humic acid-bound state,iron manganese oxide bound cadmium content increased significantly,the residual cadmium content of silicate increased slightly,and the strong organic bound state decreased slightly.