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 Cu 2+ and Cd 2+ in a contaminated acidic paddy soil. The study showed that limestone and silicon fertilizer increased Cu 2+ and Cd 2+ 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 Cu 2+ and Cd 2+ better than the Langmuir and Temkin equations. High desorption percentages of sorbed Cu 2+ (mean of 67.1%) and Cd 2+ (mean of 78.2%) were observed from the contaminated soil. Limestone and silicon fertilizer significantly decreased the desorption percentage of sorbed Cu 2+ to 11.4 and 40.0%, respectively, and significantly decreased the desorption percentage of sorbed Cd 2+ 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 Cu 2+ and Cd 2+ , and negatively influenced desorption of sorbed Cu 2+ and Cd 2+ . Application of amendments changed Cu and Cd fractions in soils, which might affect the sorption and desorption of Cu 2+ and Cd 2+ . 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.