Cao Xinde, Ma Lena Q, Singh Satya P, Zhou Qixing
Soil and Water Science Department, University of Florida, 2169 McCarty Hall, Gainesville, FL 32611, USA.
Environ Pollut. 2008 Mar;152(1):184-92. doi: 10.1016/j.envpol.2007.05.008. Epub 2007 Jun 29.
This study investigated phosphate-induced lead immobilization from different Pb minerals in soils under varying pHs. Four soils were used, including one Pb-contaminated soil (NC-Soil) and three soils spiked with litharge (PbO), cerrusite (PbCO3), or anglesite (PbSO4), referred to as PbO-soil, PbCO3-soil, and PbSO4-soil, respectively. The soils were equilibrated with KCl and Ca(H2PO4)(2).H2O under pH of 3-7. At low pH (3 and 5), Pb solubility followed PbO-soil>PbCO3-soil>PbSO4-soil; while at pH=7, it was PbSO4-soil>PbO-soil>PbCO3-soil. Phosphate decreased Pb dissolution time from >180 to <60 min and reduced soluble Pb by 67-100%. This was mostly via transformation of Pb minerals into chloropyromorphite [Pb(5)(PO(4))(3)Cl]. Our results indicated that P addition can effectively transform various Pb minerals into insoluble chloropyromorphite in soils. This transformation was more significant at acidic condition (e.g., pH<or=5). Among the three Pb minerals tested, PbSO4 was the most effectively immobilized by P, followed by PbO and PbCO3. This study clearly demonstrated the importance of the form of Pb contamination and soil pH in determining the effectiveness of Pb immobilization in soils.
本研究调查了在不同pH值条件下，磷酸盐对土壤中不同铅矿物的铅固定作用。使用了四种土壤，包括一种铅污染土壤（NC - 土壤）和三种分别添加了密陀僧（PbO）、白铅矿（PbCO₃）或铅矾（PbSO₄）的土壤，分别称为PbO - 土壤、PbCO₃ - 土壤和PbSO₄ - 土壤。这些土壤用KCl和Ca(H₂PO₄)₂·H₂O在pH值为3 - 7的条件下进行平衡。在低pH值（3和5）时，铅的溶解度顺序为PbO - 土壤＞PbCO₃ - 土壤＞PbSO₄ - 土壤；而在pH = 7时，顺序为PbSO₄ - 土壤＞PbO - 土壤＞PbCO₃ - 土壤。磷酸盐将铅的溶解时间从＞180分钟减少到＜60分钟，并使可溶性铅减少了67 - 100%。这主要是通过将铅矿物转化为氯磷灰石[Pb₅(PO₄)₃Cl]实现的。我们的结果表明，添加磷可以有效地将土壤中的各种铅矿物转化为不溶性的氯磷灰石。这种转化在酸性条件下（例如，pH≤5）更为显著。在所测试的三种铅矿物中，PbSO₄被磷固定的效果最为显著，其次是PbO和PbCO₃。本研究清楚地证明了铅污染形态和土壤pH值在决定土壤中铅固定效果方面的重要性。
