Lixiviação de cobre e zinco em solo corrigido com resíduo de gesso da construção civil e sob aplicação de água residuária da suinocultura

Abstract

The presence of important nutrients for crops in swine wastewater (SW) causes it be used as a soil fertilizer. Among the nutrients that are present in the SW, there are Copper and Zinc; even though they are essential to the plants, they can contaminate the plant, the soil and the groundwater through leaching processes, if applied in excess. Besides the addition of fertilizers, it is necessary to correct soil pH in order to eliminate elements that are toxic to the crops; for this reason, liming technique, the addition of limestone, is performed. Along with the limestone, farmers have been also applying calcium sulfate (CaSO4), which penetrates to the soil more easily. Although it does not correct the soil’s pH, it eliminates the toxic elements. For its characteristics, the calcium sulfate might increase the leaching process for Cu and Zn. Thus, the objective of this paper is to evaluate the Cu and Zn leaching processes from the application of SW, along with the addition of limestone and plaster from civil construction for liming of soil and its minimization in subsuperficial layers. For this reason, columns of soil were filled with samples of Haplorthox respecting the following treatments: T1 (Soil + SW), T2 (Soil + limestone + SW) and T3 (Soil + limestone + plaster + SW). The quantity of SW applied was equivalent to the doses of nitrogen recommended for corn crop; also, the same method was used to estimate the need of limestone and plaster. The leachate material was collected and send for Cu and Zn concentration analysis, by atomic absorption spectrophotometry. The result was compared by statistical lines comparison test, with 5% of significance. The results showed that limestone retained zinc to the soil and plaster from civil construction promoted the metal’s leaching, if compared to the use of only limestone. However, with the right management of SW and plaster, it was shown to be benefic to crops while not offering the risk of groundwater contamination, once the leaching processes was higher in the treatment T1 than in treatments T2 and T3. Copper leaching only occurred in the soil corrected with limestone. Because zinc leaching did not occur excessively, the possibility of using plaster from civil construction is indicated, along with limestone in crop soils.