University of Northern British Columbia, Natural Resources and Environmental Studies, Prince George, BC, Canada V2N4Z9.
J Environ Manage. 2013 Feb 15;116:156-62. doi: 10.1016/j.jenvman.2012.11.037. Epub 2013 Jan 9.
Pyromorphite (PY) and some zinc phosphates (Zn-P) are very sparingly soluble minerals and hence can immobilize Pb and Zn in contaminated soils. However, mechanisms leading to the poor efficiency of PY and Zn-P formation in contaminated soils amended with P still remain unclear. We studied the influence of two low molecular weight organic acids (LMWOA) - oxalic acid and citric acid and diethylene triamine pentaacetic acid (DTPA) - in PY and Zn-P formation in a P-amended contaminated soil. Despite the high levels of metals (∼4% Pb and 21% Zn) in the study soil, the addition of up to 1% inorganic P transformed only up to 37% and 17% of the total Pb and Zn to PY and Zn-P, respectively. Semi-quantitative estimates from a linear combination fitting of X-ray absorption near edge spectra (LC-XANES fitting) showed that the formation of PY decreased from 37% to 3% of the total Pb in the presence of oxalic acid and the addition of 1% P. The reduced PY formation may be associated with the increase in organic-bound Pb from 9% to 54% and decrease in carbonate associated Pb from 42% to 12% with oxalic acid addition as indicated by a chemical sequential extraction (SE) technique. Citric acid seemed to have a less adverse effect in PY formation than oxalic acid. Our data also suggests both oxalic and citric acids have less adverse effects on the efficiency of Zn-P formation. From this study we conclude that the abundance of LMWOA in soil environments can be one factor contributing to the poor efficiency of P amendments practices to effectively immobilize Pb and Zn in metal contaminated soils.
磷氯铅矿 (PY) 和一些锌磷酸盐 (Zn-P) 的溶解度非常低，因此可以将 Pb 和 Zn 固定在污染土壤中。然而，在添加 P 的污染土壤中，导致 PY 和 Zn-P 形成效率低下的机制仍不清楚。我们研究了两种低分子量有机酸（LMWOA）-草酸和柠檬酸以及二乙烯三胺五乙酸（DTPA）在添加 P 的污染土壤中 PY 和 Zn-P 形成的影响。尽管研究土壤中的金属含量很高（约 4%的 Pb 和 21%的 Zn），但添加高达 1%的无机 P 仅将 37%和 17%的总 Pb 和 Zn 分别转化为 PY 和 Zn-P。来自 X 射线吸收近边光谱（LC-XANES 拟合）的线性组合拟合的半定量估计表明，在草酸存在的情况下，PY 的形成从总 Pb 的 37%减少到 3%，并且添加 1%的 P。LC-XANES 拟合的半定量估计表明，在草酸存在的情况下，PY 的形成从总 Pb 的 37%减少到 3%，并且添加 1%的 P。与草酸添加相关的有机结合态 Pb 从 9%增加到 54%，碳酸盐结合态 Pb 从 42%减少到 12%，这可能与 PY 形成减少有关，这表明化学顺序提取（SE）技术。柠檬酸似乎对 PY 形成的不利影响小于草酸。我们的数据还表明，草酸和柠檬酸对 Zn-P 形成效率的不利影响都较小。从这项研究中我们得出结论，土壤环境中 LMWOA 的丰度可能是导致 P 改良实践有效固定金属污染土壤中 Pb 和 Zn 的效率低下的因素之一。
