Toxicologia Ambiental e Analítica

Assessing the Extraction Efficiency of CaCl2 and Rhizon Extraction Methods after the Application of Organic Matter and CaCl2 as Soil Amendments to Enhance the Mobility of Cd and Zn

Abstract

Amoakwah E, Van Slycken S, Tack F.M.G and Essumang D

A pot experiment was conducted to study the extractability of cadmium and zinc by CaCl2 and rhizon extraction methods after the application of organic matter and chloride as soil amendments. Two methods, Rhizon and CaCl2 extraction methods were concurrently employed to study the effects of the various amendments on the mobility of Cd and Zn. Both CaCl2 and Rhizon extraction methods generally extracted appreciable amounts of the heavy metals after the application of the amendments. However, the results from the experiment shows that the Rhizon samplers extracted higher concentrations of both Cd and Zn as compared to the CaCl2 extraction method. The use of Rhizon soil moisture sampler is also non destructive to the soil and makes it possible to ascertain levels of heavy metals at equilibrium in the soil solution without changing the compisition of the soil solution in the process of extracting it. Assessment of the soil pH in the soil samples and the Rhizon extracts after the application of the amendments showed no significant difference with the control. Comparatively, application of CaCl2 had a significant mobilizing effect on the mobility of both Cd and Zn as a result of the combined effect of complexation of Cd and Zn by the chloride anion, and by the fact that Cd and Zn are preferentially absorbed in cation exchange positions. Therefore the Ca2+ ion can displace these metals into the soil solution.