Comparison of Phosphate Materials for Immobilizing Cadmium in Soil

• Published in: Archives of environmental contamination and toxicology Vol. 58; no. 2; pp. 268 - 274
• Main Authors: Hong, Chang Oh, Chung, Doug Young, Lee, Do Kyoung, Kim, Pil Joo
• Format: Journal Article
• Language: English
• Published: New York New York : Springer-Verlag 01-02-2010; Springer-Verlag; Springer; Springer Nature B.V
• Subjects: Analytical chemistry; Animal, plant and microbial ecology; Applied ecology; Bioavailability; Biological and medical sciences; Cadmium; Cadmium - analysis; Cadmium - chemistry; Charge; Charge materials; Diphosphates - chemistry; Earth and Environmental Science; Ecotoxicology; Ecotoxicology, biological effects of pollution; Environment; Environmental Chemistry; Environmental cleanup; Environmental Health; Environmental impact; Fertilizers; Filled plastics; Fundamental and applied biological sciences. Psychology; General aspects; Heavy metals; Materials selection; Monitoring/Environmental Analysis; Phosphates; Phosphates - chemistry; Plant extracts; Pollution; Potassium Compounds - chemistry; Science; Soil; Soil (material); Soil contaminants; Soil contamination; Soil pH; Soil Pollutants - analysis; Soil Pollutants - chemistry; Soil Science & Conservation; Studies; South Korea; Phosphate Material; CdCO3; Phosphate Adsorption; Phosphate Fertilizer; Visual MINTEQ; Phosphates; Cadmium; Pollutant; Soils; Pollution; Ecotoxicology; Toxicity; Environment; Heavy metal
• ISSN: 0090-4341; 1432-0703
• DOI: 10.1007/s00244-009-9363-2

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—Ca[H₂PO₄]₂·H₂O, [NH₄]₂HPO₄, KH₂PO₄, and K₂HPO₄) 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(H₂PO₄)₂ ∙ H₂O, KH₂PO₄, and K₂HPO₄ significantly decreased NH₄OAc-extractable Cd (plant-available form) concentrations with increasing application rates. Compared to other phosphate materials used, K₂HPO₄ 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 (NH₄)₂HPO₄ 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 CdHPO₄, Cd(OH)₂, and CdCO₃ analyzed by the MINTEQ program were significantly increased by K₂HPO₄ 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 K₂HPO₄ are effective for immobilizing soil Cd.