Copper and zinc transfer limits to soil solution of mixtures containing different clay and organic matter contents

Abstract Establishing Cu and Zn transport limits to soil solution, may be a parameter to regulate maximum allowable concentrations of these heavy metals in soils. The study aimed to estimate Cu and Zn contents in soil mixtures with varying clay and soil organic matter (SOM) contents, from which the two heavy metals are transported to the soil solution. Samples of the Bw horizon of a Oxisol and of the A horizon of a Inceptisol were used to make soil mixtures with clay contents ranging from 170 to 700 g kg− 1 and SOM ranging from 18 to 95 g kg− 1. Cu and Zn adsorption curves were obtained to determine the maximum adsorption capacities (MAC) using the Langmuir model. Cu transport limits ranged from 118 to 187 mg kg− 1 the lowest values were found in soil mixtures containing lower clay contents in combination with higher SOM contents. Zn transport limits ranged from 61 to 116 mg kg− 1 the highest values were found in soil mixtures containing lower clay contents combined with higher SOM contents. Cu and Zn transport limits can be used as safe limits for supervisory bodies, technical assistance institutions and farmers to monitor the potential for environmental contamination.