SORPTION AND LEACHING OF METALS IN THE SOIL DUE TO APPLICATION OF DISSOLVED ORGANIC MATTER

Abstract

Agriculture is one of the most important nonpoint sources of soil contamination by heavy metals, and the presence of dissolved organic matter (DOM) in soil can influence the movement of metals. The objective of this research was to evaluate the effect of DOM on the sorption and leaching of copper (Cu) and zinc (Zn) in the soil. Clay soil samples collected at a 0-30 cm depth were used to conduct the experiments, and DOM was extracted from dairy cow manure. Soil tests to evaluaye sorption were carried out in the batch method, two treatments being considered: without the presence of DOM (control) and with the presence of DOM, in different concentrations of Cu and Zn. Experimental results were adjusted to models of the of Langmuir and Freundlich isotherms. In the leaching experiment, columns were filled with soil previously contaminated with Cu and Zn and the distilled water was passed through them; afterwards, the leachate was collected. The sorption of copper and zinc in the soil was greater in the presence of DOM, possibly by the availability of sorption sites and interactions of metals with the DOM structure. The leaching of copper in soil was facilitated by the application of DOM, which can enable large-scale contamination of groundwater. No differences were found in zinc leaching considering water or DOM, however this metal has high mobility in the soil under study.