[Effect of chlorine and phosphorus on water soluble and exchangeable lead in a soil contaminated by lead and zinc mining tailings].

Effect of chlorine on in situ lead immobilization using phosphorus in a soil contaminated by lead and zinc mining tailings was evaluated. The results showed that water soluble and exchangeable Pb were reduced by 92.0%-95.1% in the soil after P application. It was also suggested that application dosage of phosphorus at the P/Pb molar ratio of 0.6, was enough to remediate Pb toxicity in the soil. Compared to without Cl treatment at the level of molar ratio of 0.6 P/Ph, water soluble and exchangeable Pb in the soil treated with Cl was reduced markedly. It was concluded that the effects chlorine addition on in situ lead (Pb) immobilization using phosphate were improved. Visual MINTEQ model was employed to figure out Pb and P species distribution and saturation indices for minerals in the soils treated by P and Cl. The results showed that Pb activity was controlled by lead phosphate in the soil, especially pyromorphite [Pb5(PO4)3Cl], which would be the reason for Pb bioactivity reduction in the soil after application of Cl and P. The effective Pb bioactivity reduction indicated that addition of Cl was necessary to to improve in situ lead immobilization using phosphorous in the lead-contaminated soil.