Transporte de contaminantes em solo e rejeito de mineração por teste em coluna comparado com modelagem hidrogeoquímica

Abstract

The mining activity undoubtedly has its importance for the country's economy, but this activity also causes different environmental impacts. The soil of these regions is composed of different elements, some of them with toxic characteristics. Mineral exploration can increase the concentration of these unwanted elements or even make it easier for them to reach water resources and living beings. The mobility of these elements in the soil can help in understanding the environmental impact caused by this activity. Currently, there are simulation programs that are capable of predicting the behavior of metals and other substances in complex systems such as soil, facilitating the study of this mobility of elements. This study aimed to evaluate the transport of potentially toxic metals in soil and mining waste samples through a column test and compare the results with simulations performed using the PHREEQC software. Soil and waste samples were collected from a gold mining company located in Conceição do Pará, in Minas Gerais. The samples were characterized by different techniques to determine their composition. Vertical columns were filled with samples and a solution containing Ag+, Ba2+, Cu2+, As3+, Zn2+, Pb2+, Cd2+ and Ni2+ was passed through the columns and the effluent collected on days 01, 04, 10 and 15 after the beginning of the experiment. The effluent from the column and the solubilization, leaching and digestion tests of the sample were determined by ICP OES to determine the concentration of the cations of interest in solution. The characterization information was used as input in the PHREEQC software to simulate the column test and the results were compared. Except for arsenic and silver, the other determined elements showed a good correlation between simulated and experimental data. The soil, within the analyzed time, was able to adsorb a large part of the material inserted in the column, reaching a saturation close to the tenth day for the determined elements. In some cases, such as nickel and lead, there was a decay in the graph, indicating a possible desorption process on the fifteenth day. The waste did not adsorb significant amounts of elements, indicating that the mineral beneficiation process substantially altered the adsorption sites previously present in the soil. The PHREEQC software demonstrated good predictive capacity in the simulations when compared to the spine test.