不同类型贝壳粉对土壤镉赋存形态的影响差异

通过室内培养探究不同类型贝壳粉对土壤中不同形态镉含量的影响,向培养完成的土壤中施用3种添加比例的天然扇贝壳粉与蛏子壳粉,分别在第1,5,15,30,50天测定土壤pH及镉的各赋存形态含量。结果表明,添加文石型与方解石贝壳粉对土壤pH升高均有一定程度的贡献,施用2种贝壳粉后,随贝壳粉添加比例的增多土壤pH升高。不同种类贝壳粉处理的土壤pH差异不大,在50天后2种贝壳粉不同添加比例间差异最明显。在整个培养过程中,随培养天数的增加,添加不同类型贝壳粉均能使镉污染土壤可交换态镉含量下降,碳酸盐结合态镉、铁锰氧化物结合态镉、有机结合态镉与残渣态镉含量整体逐渐升高。其中,使用文石型贝壳粉作钝化剂较方解石型效果更佳。随着贝壳粉添加比例变大,可交换态镉向镉的其他赋有形态转化的程度越大。培养50天后,添加不同种类贝壳粉处理的土壤有效态镉含量同CK相比均显著降低。当添加文石型贝壳粉的比例为5%时,生物可利用态镉占总镉比例最低。施用文石型贝壳粉能比方解石型贝壳粉更好地降低土壤有效态镉的活性。

Effects of Different Shell Powder Types on Soil Cadmium Speciation

The effects of different types of shell powder on different forms of cadmium in soil were investigated through indoor culture. Three proportions of natural scallop shell powder and ascarid shell powder were applied to the soil after the culture. The soil pH and cadmium forms were measured on the 1st, 5th, 15th, 30th and 50th days after the application of shell powder, respectively. The results showed that the addition of aragonite and calcite shell powder contributed to the increase of soil pH. After adding the two kinds of shell powder, the soil pH increased with the increasing of shell powder addition ratio. The pH value of soil treated with different kinds of shell powder was not different, and the difference in soil pH value was the most obvious among different addition ratios after 50 days. During the whole cultivation process, with the increasing of the culture days, shell powders could reduce the exchangeable cadmium content in the cadmium-contaminated soil, while the contents of carbonate-bound cadmium, iron-manganese oxides, organic-bound cadmium and residual cadmium increased gradually as a whole. Among them, the applying the aragonite shell powder as a passivating agent was more effective than the calcite type. As the proportion of shell powder increased, the exchangeable cadmium changed to other cadmium speciation was more. After 50 days of culture, the contents of available cadmium in soils treated with shell powder were significantly lower than that of CK. When the addition ratio of shell powder was 5%, the bioavailable cadmium accounted for the lowest proportion of total cadmium. The results showed that aragonite shell powder had better effect of reducing soil available cadmium activity than that of calcite shell powder.