矿物对轻度重金属污染水稻田土壤镉的钝化效果

Study on the Passivation Effect of Minerals on Cd in Farmland Soil with Light Heavy Metal Pollution

针对日益严重的土壤镉(Cd)污染情况,综合国内外重金属污染土壤修复方法,改良剂原位修复技术是运用最为广泛的方法之一。分别以海泡石(BM2)、蒙脱石(BM3)、凹凸棒石(BM4)、沸石(BM5)、羟基磷灰石(BM6)和生石灰(BM7)不同种类矿物作为修复材料,并将其与生物炭(BM1)和对照(BM0)进行对比,在浙江省某一轻度Cd污染地区的农田土壤中进行2年4季的田间钝化修复试验。结果表明,生物炭、海泡石、凹凸棒石、羟基磷灰石和生石灰都能略微增加水稻产量,但统计上并没有显著性差异。所有钝化处理都能降低土壤有效Cd含量和水稻籽粒Cd含量。各处理降低籽粒Cd含量的效果由大到小依次为生物炭、生石灰、沸石、蒙脱石、羟基磷灰石、凹凸棒石、海泡石和对照。其中,经生石灰处理后土壤有效Cd含量和水稻籽粒Cd含量分别为0.214和0.169 mg·kg^(-1),与BM0相比分别降低25.17%和41.26%。此外,与对照相比,生石灰处理可交换态Cd在全Cd中的质量占比降低10个百分点,但铁锰氧化物结合态和有机态Cd含量增加,其他矿物处理Cd形态变化趋势相同,说明矿物修复Cd污染土壤主要通过将可交换态Cd转化为铁锰氧化物结合态Cd和有机态Cd,而碳酸盐结合态Cd和残渣态Cd几乎不参与该过程的转化。

In view of the increasingly serious soil cadmium(Cd) pollution,the improper in-situ remediation technology is one of the most widely used methods based on the domestic and foreign heavy metal remediation methods.In this study,different minerals,i.e.,sepiolite(BM2),montmorillonite(BM3),attapulgite(BM4),zeolite(BM5),hydroxyapatite(BM6) and quicklime(BM7),and biochar(BM1) were used as restoration materials compared with control(BM0).A two-year remediation experiment was carried out on low Cd contaminated farmland soil in Zhejiang Province.The results show that biochar,sepiolite,attapulgite,hydroxyapatite,and quicklime slightly enhanced rice yield but with no statistically significant difference.All the passivation treatments reduced soil available Cd and rice grain Cd contents.The reduction of grain Cd contents was in an order of biochar > quicklime > zeolite > montmorillonite > hydroxyapatite > attapulgite > sepiolite > control.Besides,the soil available Cd and grain Cd after quicklime addition were 0.214 and 0.169 mg·kg^(-1),respectively,which were decreased by 25.17% and 41.26%,respectively compared with BM0.In addition,the proportion of exchangeable Cd to the total Cd reduced by 10 percentage point after quicklime treatment addition,but the contents of Fe-Mn oxide binding and organic Cd increased.The trends of changes of Cd forms in the other mineral treatments were the same,indicating that the minerals remediate Cd-contaminated soil mainly by the conversion of exchangeable Cd into Fe-Mn oxide binding and organic Cd.Carbonate binding and residue Cd almost did not participate in the process of transformation.