Plant Science Department, South Dakota State University, 1110 Rotunda Lane North, Brookings, SD 57007, USA.
Arch Environ Contam Toxicol. 2010 Feb;58(2):268-74. doi: 10.1007/s00244-009-9363-2. Epub 2009 Jul 26.
A study was conducted to compare the effects of phosphate (P) materials in reducing cadmium extractability. Seven P materials (commercial P fertilizers--fused phosphate (FP), 'fused and superphosphate' [FSP], and rock phosphate [RP]; P chemicals--CaH(2)PO(4).H(2)O, NH(4)HPO(4), KH(2)PO(4), and K(2)HPO(4)) were selected for the test. The selected P source was mixed with Cd-contaminated soil at the rate of 0, 200, 400, 800, and 1,600 mg P kg(-1) under controlled moisture conditions at 70% of water holding capacity, then incubated for 8 weeks. FP, Ca(H(2)PO(4))(2) H(2)O, KH(2)PO(4), and K(2)HPO(4) significantly decreased NH(4)OAc-extractable Cd (plant-available form) concentrations with increasing application rates. Compared to other phosphate materials used, K(2)HPO(4) was found to be the most effective in reducing the plant-available Cd concentration in soil, mainly due to the negative charge increase caused by soil pH and phosphate adsorption. Contrary to the general information, FSP and (NH(4))(2)HPO(4) increased Cd extractability at low levels of P application (<400 mg kg(-1)), and thereafter Cd extractability decreased significantly with increasing application rate. RP scarcely had an effect on reducing Cd extractability. Ion activity products of CdHPO(4), Cd(OH)(2), and CdCO(3) analyzed by the MINTEQ program were significantly increased by K(2)HPO(4) addition, but the effect of Cd-P compound formation on reducing Cd extractability was negligible. Conclusively, the P-induced alleviation of Cd extractability can be attributed primarily to Cd immobilization due to the increase in soil pH and negative charge rather than Cd-P precipitation, and therefore, alkaline P materials such as K(2)HPO(4) are effective for immobilizing soil Cd.
进行了一项研究，以比较不同磷酸盐（P）材料对降低镉提取率的影响。选择了 7 种 P 材料（商业 P 肥料——熔融磷（FP）、“熔融和过磷酸钙”[FSP]和磷矿粉[RP]；P 化学品——CaH(2)PO(4).H(2)O、NH(4)HPO(4)、KH(2)PO(4)和 K(2)HPO(4))进行测试。在 70%的持水能力条件下，将选定的 P 源与 Cd 污染土壤以 0、200、400、800 和 1600 mg P kg(-1)的比例混合，然后在 8 周内进行培养。FP、Ca(H(2)PO(4))(2) H(2)O、KH(2)PO(4)和 K(2)HPO(4)随着施用量的增加，显著降低了 NH(4)OAc 可提取 Cd（植物有效形态）浓度。与使用的其他磷酸盐材料相比，K(2)HPO(4)在降低土壤中植物有效 Cd 浓度方面最为有效，这主要是由于土壤 pH 值和磷酸盐吸附导致的负电荷增加所致。与一般信息相反，FSP 和（NH(4))(2)HPO(4)在低 P 施用量（<400 mg kg(-1))下增加了 Cd 的提取率，此后随着施用量的增加，Cd 的提取率显著降低。RP 对降低 Cd 提取率几乎没有影响。MINTEQ 程序分析的 CdHPO(4)、Cd(OH)(2)和 CdCO(3)的离子活度积显著增加，但 Cd-P 化合物形成对降低 Cd 提取率的影响可以忽略不计。综上所述，P 诱导的 Cd 提取率降低可归因于土壤 pH 值和负电荷增加导致的 Cd 固定，而不是 Cd-P 沉淀，因此，碱性 P 材料如 K(2)HPO(4)可有效固定土壤 Cd。
