Sorption and Desorption of Copper and Cadmium in a Contaminated Soil Affected by Soil Amendments

Sorption and desorption processes control the bioavailability of heavy metals in the environment. Soil incubation and batch experiments were conducted to evaluate the effects of soil amendments on sorption, and desorption of Cu2+ and Cd2+ in a contaminated acidic paddy soil. The study showed that limestone and silicon fertilizer increased Cu2+ and Cd2+ sorption 2.43‐ and 1.13‐fold, which was higher than calcium magnesium phosphate, Chinese milk vetch, pig manure, and peat. The Freundlich equation fitted sorption of Cu2+ and Cd2+ better than the Langmuir and Temkin equations. High desorption percentages of sorbed Cu2+ (mean of 67.1%) and Cd2+ (mean of 78.2%) were observed from the contaminated soil. Limestone and silicon fertilizer significantly decreased the desorption percentage of sorbed Cu2+ to 11.4 and 40.0%, respectively, and significantly decreased the desorption percentage of sorbed Cd2+ to 42.5 and 61.0%, respectively. However, the other four amendments did not show significant impact. Increasing soil pH significantly increased contents of sorbed Cu2+ and Cd2+, and negatively influenced desorption of sorbed Cu2+ and Cd2+. Application of amendments changed Cu and Cd fractions in soils, which might affect the sorption and desorption of Cu2+ and Cd2+. The effects of soil amendments on sorption and desorption of heavy metals may be useful for predication of their remedy efficiency to heavy metal contamination.