Hong Chang Oh, Lee Do Kyoung, Kim Pil Joo
Division of Applied Life Science (BK21), Graduate School, Gyeongsang National University, 900, Kaswa-dong, Jinju 660-701, South Korea.
Chemosphere. 2008 Feb;70(11):2009-15. doi: 10.1016/j.chemosphere.2007.09.025. Epub 2007 Oct 30.
To reduce effectively cadmium (Cd) phytoextractability by phosphate fertilizer in Cd contaminated soil, fused and superphosphate (FSP) was applied at the rate of 0, 33.5 (recommendation level), 167.5, and 335 kg P ha(-1) for radish (Raphanus sativa L.). Unlike from what we expected, soil Cd extractability and Cd concentration in radish increased with increasing FSP application in the field. To determine the effect of FSP on Cd immobilization, FSP was mixed with the selected soil at the rate of 0, 200, 400, 800, and 1600 mg P kg(-1) and then incubated for 8 weeks. As observed in the field study, NH(4)OAc extractable Cd concentration increased slightly with FSP addition up to 400 mg P kg(-1) and thereafter dramatically decreased upon increasing its application rate. Soil pH and negative charge were decreased at low level of FSP application up to 400 mg P kg(-1), but thereafter continually increased with increasing application level. This could be indirect evidence that net soil negative charge was increased by the specific adsorption of phosphate at the high rate of FSP application over 400 mg P kg(-1). The labile Cd fraction (water soluble and exchangeable+acidic fraction) increased with increasing FSP application by 400 mg P kg(-1) and thereafter gradually decreased with corresponding increase in unlabile fraction (oxidizable and residual fraction). Based on these results, FSP might be applied with a very high rate over 800 mg P kg(-1) to decrease Cd extractability in the selected field. However, this level is equivalent to 1440 kg P ha(-1), which is about 43 times higher than the recommendation levels for radish production and resulted in a significant increase in water soluble P concentration creating a new environmental problem. Therefore, the feasibility of FSP to reduce Cd extractability in the field is very low.
为有效降低镉（Cd）污染土壤中磷肥对镉的植物提取率，在种植萝卜（Raphanus sativa L.）的土壤中分别以0、33.5（推荐水平）、167.5和335 kg P ha⁻¹的用量施用钙镁磷肥（FSP）。与预期不同的是，田间土壤中镉的提取率和萝卜中的镉含量随FSP施用量的增加而增加。为确定FSP对镉固定的影响，将FSP以0、200、400、800和1600 mg P kg⁻¹的用量与选定土壤混合，然后培养8周。正如田间研究中所观察到的，添加FSP至400 mg P kg⁻¹时，醋酸铵可提取镉浓度略有增加，此后随着施用量的增加急剧下降。在FSP施用量低至400 mg P kg⁻¹时，土壤pH值和负电荷降低，但此后随着施用量的增加持续升高。这可能间接证明，在FSP施用量超过400 mg P kg⁻¹时，由于磷酸盐的特异性吸附，土壤净负电荷增加。随着FSP施用量增加至400 mg P kg⁻¹，不稳定镉组分（水溶性和可交换性+酸性组分）增加，此后随着非不稳定组分（可氧化和残留组分）相应增加而逐渐降低。基于这些结果，在选定田间，可能需要以超过800 mg P kg⁻¹的非常高用量施用FSP以降低镉的提取率。然而，这个用量相当于1440 kg P ha⁻¹，约为萝卜生产推荐用量的43倍，导致水溶性磷浓度显著增加，产生了新的环境问题。因此，FSP在田间降低镉提取率的可行性非常低。
