含方解石物质对土壤镉赋存形态的影响

Effects of Substances Containing Calcite on Cadmium Speciation in Contaminated Soil

通过室内培养试验,探究赤泥粉、海泡石粉、方解石粉在不同添加剂量情况下随时间变化对外源污染草甸土土壤镉赋存形态的影响。结果表明,土壤pH值随着钝化剂用量的增加而增加,且均明显高于对照。添加赤泥与其他2种钝化剂处理对pH值影响有所不同,随时间的延长分别呈现先降低后升高最后趋于平稳和缓慢降低的趋势。培养50d后,添加5%赤泥对土壤pH值影响最大,相较对照提高了4.09个单位。土壤可交换态镉的含量随钝化剂用量的增加而降低,培养50d后,当钝化剂添加量为1%,3%时,可交换态镉降低率分别为方解石>海泡石>赤泥、方解石>赤泥>海泡石;钝化剂添加量为5%时,降低率为赤泥>方解石>海泡石。pH值与交换态镉相关性分析表明:添加赤泥处理极显著负相关;添加海泡石处理相关性不显著;添加方解石处理无相关关系。各处理均能显著降低可交换态镉的含量,同时不同程度提高了碳酸盐结合态、铁锰氧化物结合态、有机质结合态、残渣态镉含量,其中碳酸盐结合态最为明显。

An indoor cultivation experiment was conducted to explore the effects of red mud powder,sepiolite powder and calcite powder on cadmium speciation in external cadmium contaminated meadow soil with time under the conditions of different adding doses.The results indicated that the soil pH increased with the increasing amount of passivators,and was significantly higher than that in control treatment.Red mud showed different effect on soil pH,compared with the other 2kinds of passivators,which decreased at first,then increased and finally tended to be stable with the extension of time,or slowly lowered during all the culture period.After 50 day cultivation,adding 5%red mud had the greatest influence on soil pH,which increased by 4.09 units compared with control treatment.The concentration of exchangeable cadmium of soil decreased with the increasing passivator amount.After the 50 th day of cultivation,when the adding amounts of passivators were 1% and 3%,the decreasing rates of exchangeable cadmium were：Calcitesepiolitered mud,and calcitered mudsepiolite,respectively.When the adding amount of passivators was 5%,the decreasing rate of exchangeable cadmium was：Red mudsepiolitecalcite.The correlation analysis showed that soil pH and exchangeable cadmium content were negatively correlated in red mud treatment,and did not significantly correlate in sepiolite treatment,while showed no correlation in calcite treatment.The 3 kinds of passivators could significantly decrease the concentration of exchangeable cadmium,and at the same time,and improved the contents of cadmium in carbonate bounded form,Fe-Mn oxide bounded form,organic matter bounded form and residual form,and the improvement was the most obvious for carbonate bounded cadmium.