天然和热活化蛏子壳粉对污染土壤中Cd赋存形态的影响

摘要

To achieve effective remediation of Cd contaminated soil,an indoor incubation was conducted to explore the effects of razor calm shell powder (RASP) at different pre-treatment on cadmium speciation in external cadmium brown soil with time under the conditions of adding different ratios.The results showed that the soil pH increased by the increase of rates of passivators and gradually immobilized with the incubation time.However,the soil pH in treatments was always higher than that for control.All of the treatments during the culture time showed a downward trend in soil exchangeable Cd content except the treatments was gradually decreased and then slightly elevated in 5 d.After 60 days of culture,the decreasing rates of exchangeable cadmium were:calcined RASP at 800 ℃ ＞calcined RASP at 600 ℃ ＞natural RASP,and they had decreased the soil exchangeable Cd contents by 52.0％-67.1％,40.7％-45.7％ and 33.6％-43.6％,respectively.The correlation analysis indicated that the soil pH and exchangeable cadmium content were negatively correlated in 5 d.Nevertheless,the left period did show significantly and negatively correlate,while the three passivators could evidently decrease the concentration of exchangeable cadmium,and improved the contents of cadmium in carbonate bounded form,iron and manganese bounded form,organic matter bounded form and residual form at different levels.pH was the key factor to influence the adsorption,desorption,complexation and co-precipitation of heavy metal ions.The research highlighted that the razor calm shell powder had positive effects on the availability and speciation transformation of Cd in soil,and in the meanwhile provided a novel way to remediation and use of Cd contaminated soil.%为实现对Cd污染农田土壤的安全利用,通过室内培养试验,阐明天然蛏子壳粉、600℃热活化蛏子壳粉和800 ℃热活化蛏子壳粉在不同添加比例下对外源污染棕壤土中Cd赋存形态随时间变化的影响.结果表明,土壤pH随蛏子壳粉添加量的增加而增加,且不同蛏子壳粉在同一添加比例下随培养时间延长呈平稳下降趋势,但都明显高于对照.在整个培养期间,可交换态Cd呈现先升高后降低的趋势,同时各处理不同程度地提高了碳酸盐结合态、铁锰结合态、有机结合态和残渣态Cd的含量.培养60 d后,各处理组对Cd形态转化的贡献率为800℃热活化蛏子壳粉＞600℃热活化蛏子壳粉＞天然蛏子壳粉,且三者使土壤中可交换态Cd含量分别降低了52.0％ ～ 67.1％、40.7％ ～45.7％、33.6％ ～ 43.6％.由土壤pH与土壤可交换态Cd含量的相关性分析表明,在培养5d时,二者呈显著负相关关系,其余时期均呈极显著负相关关系.土壤pH是影响重金属离子发生吸附、解吸、络合和共沉淀的重要因素.研究显示,蛏子壳粉对污染土壤中Cd在有效性和形态转化方面起到一定的积极作用,从而为Cd污染土壤的修复利用提供了新的思路.