Feasibility of phosphate fertilizer to immobilize cadmium in a field

• Published in: Chemosphere (Oxford) 2008-02, Vol.70 (11), p.2009-2015
• Main Authors: Hong, Chang Oh, Lee, Do Kyoung, Kim, Pil Joo
• Format: Article
• Language: English
• Subjects: Applied sciences; bioaccumulation; Biological and medical sciences; Cadmium; Cadmium - chemistry; Cadmium - metabolism; Decontamination. Miscellaneous; Diphosphates - chemistry; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; fertilizer application; Fertilizers; Fundamental and applied biological sciences. Psychology; Fused and superphosphate; Immobilization; Non agrochemicals pollutants; Phosphate; phosphates; phosphorus fertilizers; Phytopathology. Animal pests. Plant and forest protection; phytoremediation; Plant Roots - metabolism; Plant Shoots - metabolism; polluted soils; Pollution; Pollution effects and side effects of agrochemicals on crop plants and forest trees. Other anthropogenic factors; Pollution effects. Side effects of agrochemicals; Pollution, environment geology; Radish; radishes; Raphanus; Raphanus - metabolism; Raphanus sativus; Soil and sediments pollution; Soil Pollutants - chemistry; Soil Pollutants - metabolism; soil pollution; superphosphate
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2007.09.025

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 4OAc 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.