School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China.
Environ Sci Pollut Res Int. 2013 Sep;20(9):5913-21. doi: 10.1007/s11356-012-1349-3. Epub 2012 Dec 22.
Phosphorus-bearing materials have been widely applied in immobilization of heavy metals in contaminated soils. However, the study on the stability of the initially P-induced immobilized metals in the contaminated soils is far limited. This work was conducted to evaluate the mobility of Pb, Cu, and Zn in two contrasting contaminated soils amended with phosphate rock tailing (PR) and triple superphosphate fertilizer (TSP), and their combination (P + T) under simulated landfill and rainfall conditions. The main objective was to determine the stability of heavy metals in the P-treated contaminated soils in response to the changing environment conditions. The soils were amended with the P-bearing materials at a 2:1 molar ratio of P to metals. After equilibrated for 2 weeks, the soils were evaluated with the leaching procedures. The batch-based toxicity characteristic leaching procedure (TCLP) was conducted to determine the leachability of heavy metals from both untreated and P-treated soils under simulated landfill condition. The column-based synthetic precipitation leaching procedure (SPLP) were undertaken to measure the downward migration of metals from untreated and P-treated soils under simulated rainfall condition. Leachability of Pb, Cu, and Zn in the TCLP extract followed the order of Zn > Cu > Pb in both soils, with the organic-C- and clay-poor soil showing higher metal leachability than the organic-C- and clay-rich soil. All three P treatments reduced leachability of Pb, Cu, and Zn by up to 89.2, 24.4, and 34.3 %, respectively, compared to the untreated soil, and TSP revealed more effectiveness followed by P + T and then PR. The column experiments showed that Zn had the highest downward migration upon 10 pore volumes of SPLP leaching, followed by Pb and then Cu in both soils. However, migration of Pb and Zn to subsoil and leachate were inhibited in the P-treated soil, while Cu in the leachate was enhanced by P treatment in the organic-C-rich soil. More than 73 % P in the amendments remained in the upper 0-10 cm soil layers. However, leaching of P from soluble TSP was significant with 24.3 % of P migrated in the leachate in the organic-C-poor soil. The mobility of heavy metals in the P-treated soil varies with nature of P sources, heavy metals, and soils. Caution should be taken on the multi-metal stabilization since the P amendment may immobilize some metals while promoting others' mobility. Also, attention should be paid to the high leaching of P from soluble P amendments since it may pose the risk of excessive P-induced eutrophication.
含磷材料已广泛应用于受污染土壤中重金属的固定。然而，对于最初 P 诱导的固定在受污染土壤中的金属的稳定性的研究还远远不够。本工作旨在评估在模拟垃圾填埋场和降雨条件下，用磷矿尾矿（PR）和过磷酸钙肥料（TSP）以及它们的组合（P+T）处理两种不同污染土壤中 Pb、Cu 和 Zn 的迁移性，以确定 P 处理污染土壤中重金属在响应变化环境条件下的稳定性。土壤中 P 与金属的摩尔比为 2:1。在平衡 2 周后，通过淋滤程序对土壤进行评估。采用批式毒性特征浸出程序（TCLP）测定模拟垃圾填埋条件下未经处理和经 P 处理的土壤中重金属的浸出率。采用柱式人工模拟降雨淋滤程序（SPLP）测定模拟降雨条件下未经处理和经 P 处理的土壤中金属的向下迁移率。在两种土壤中，TCLP 提取物中 Pb、Cu 和 Zn 的浸出率顺序为 Zn>Cu>Pb，有机碳和粘土贫土的金属浸出率高于有机碳和粘土丰富土。与未处理土壤相比，所有三种 P 处理均使 Pb、Cu 和 Zn 的浸出率降低了 89.2%、24.4%和 34.3%，TSP 处理的效果最为显著，其次是 P+T 处理，然后是 PR 处理。柱实验表明，在 10 个 SPLP 淋滤体积后，Zn 的向下迁移率最高，其次是 Pb 和 Cu，在两种土壤中都是如此。然而，在 P 处理土壤中，Pb 和 Zn 向底土和淋出液中的迁移受到抑制，而在有机碳丰富土壤中，Cu 则因 P 处理而增强。在添加物中超过 73%的 P 仍留在 0-10cm 的上层土壤中。然而，可溶 TSP 中的 P 淋失量很大，在有机碳贫土中，24.3%的 P 进入淋出液。在 P 处理土壤中，重金属的迁移性随磷源、重金属和土壤的性质而变化。由于 P 改良剂可能固定一些金属，同时促进其他金属的迁移，因此应对多金属稳定化保持警惕。此外，应注意可溶性 P 改良剂中 P 的高淋失量，因为这可能会带来过度的 P 诱导富营养化风险。
