Release of Cadmium From a Triple Superphosphate and a Phosphate Rock in Soil

Abstract

Although phosphorous fertilizers containing elevated amount of cadmium (Cd) could affect Cd accumulation in soils and crops, the extent of the effect may depend on the amount of Cd added and the rate of Cd release from those fertilizers. This study examined Cd forms of a triple superphosphate (TSP) and a western phosphate rock (PR) by sequential extractions and the rate of Cd release from the fertilizers by incubation in a silt loam and subsequent extraction with diethylenetriaminepentaacetic acid (DTPA). The lability of TSP Cd was high, as evidenced by its high solubility in water (36.0%) and 1 M HCl (57.8%). The lability of PR Cd, in contrast, was very low, with 0.1% soluble in water, 29.9% soluble in 1 M HCl, and 70.1% in the residual form. Although soil DTPA-Cd was substantially higher when the soil was treated with the TSP than with the PR at the same Cd rate, the difference narrowed as more PR Cd became extractable by DTPA with time, which reflected increased lability of PR Cd after incorporation into the soil. However, substantial amounts of the added TSP Cd (50%) and PR Cd (77.3%) remained not extractable by DTPA after 210 days of incubation. High correlation of DTPA-Cd with DTPA-zinc (Zn) in the TSP-or PR-treated soils suggested concurrent release of Zn with Cd from both P fertilizers. This should be beneficial, considering Zn can compete with Cd during bioaccumulation processes. (Soil Science 2007;172:257-265)

Soil-diffusive gradient in thin films partition coefficients estimate metal bioavailability to crops at fertilized field sites

“…Phosphate fertilizer is water soluble and contains predominantly metal salts and crushed phosphate rock. Release of Cd from parent rock is time dependent; as the phosphate rock ages, more Cd is released [30]. Competition for available binding sites on soil solids has been shown to suppress sorption for both Cd and Ni [28,29] and may have increased metal lability.…”

Status of Sustainable Balance Regulation of Heavy Metals in Agricultural Soils in China: A Comprehensive Review and Meta-Analysis

“…In most cases, phosphorus (P) fertilizers and compound fertilizers contain significantly higher concentrations of heavy metals than nitrogen (N) and potassium (K) fertilizers [31]. Phosphorous rock, as a raw material of P fertilizers contains a certain concentration of Cd [71]. Compound fertilizers include organic fertilizers such as manure, crop residues like rice and wheat straw, sewage sludge, and solid wastes [72], which include a higher content of heavy metals than P fertilizers.…”

Efectos del cadmio sobre la germinación y crecimiento inicial de cinco variedades de Oryza sativa L. cultivadas en Ecuador

“…En los suelos agrícolas, el Cd puede alcanzar un nivel alto debido a la aplicación de fertilizantes, abonos y lodos de depuradoras, riego con aguas residuales industriales y deposición atmosféricas por actividades industriales y urbanas (Liu et al, 2007). Sin embargo, la acumulación de Cd en los suelos agrícolas se ha atribuido principalmente a la fertilización por períodos prolongados con fertilizantes fosfatados, mismos que pueden contener altas concentraciones de Cd, dependiendo del origen de la roca fosfática utilizada para su fabricación (Kuo et al, 2007;Ramírez et al, 2016).…”