The Immobilization Of Lead And Cadmium In Soil By Chalcogenide

Heavy metals exit in soil with many fractions, and the hazardous of them depend more on metal’s bioavailability and migratory. Therefore, it’s an effective method that adopt chemical stabilization to reduce bioavailability and migratory for its investment and quick results. The choice of stabilizer is a critical factor in a successful chemical stabilization program. The paper chose sodium sulfide as stabilizer, determined the ability of sulfide and influencing factors, meanwhile, the paper investigated the influence of lead and cadmium on rape growth.In this paper, through more than two months of rape cultivation, we found that lead and cadmium inhibited rape’s growth, the effect would be more obvious at high concentration or lead-cadmium combination contamination. We also found that there was an obvious linear relationship between the enrichment concentration of lead/cadmium in rape and exchangeable fraction amount in soil through comparing these two data, which means that the concentration of exchangeable fraction is an appropriate parameter to measure the bioavailability of HMs. In order to study the feasibility of sodium sulfide that used to immobilize lead and cadmium, some parameters such as sodium sulfide dosage, soil pH, organic matter content in the immobilization process and fraction distribution of lead and cadmium in soil were investigated in artificial contaminated soil. The results show that the addition of sulfide can change the fraction distributions of lead and cadmium in the soil, reduce exchangeable fraction of them significantly. When conditions appropriate, the decrease values of exchangeable fraction about lead and cadmium are97.4%and73%, respectively. In the immobilization process, the changes of soil pH, organic matter content have great influence on the process of lead immobilization. The results show that there are high immobilize efficiencies in acid soil or low organic matter content soil. Compared to the lead, organic matter content and soil pH have little impact on cadmium-immobilize efficiency. When environment temperature or change pH value of extracting agent changed, leaching concentration remains generally stable. It suggests that immobilization efficiency of sulfide will not be affected by temperature changes or acid rain in a certain time.