Determinação e Quantificação de Cádmio, Chumbo e Cobre por Análise Eletroquímica em Água Subterrânea da Região Oeste Paulista

There has been a considerable increase in the demand for water supply and distribution due to the industrialization process and the growth of population. Groundwater reserves were used to meet this need. However, the irregular disposal of domestic sewage and the existence of poorly constructed and poorly inspected landfills and other waste sites 1 make the municipal groundwater which has been used susceptible to contamination. In addition, the insertion of metals into aquifers is also naturally noted by hydrogeochemical interactions, such as the hydrological cycle that makes up the rainwater that percolates and leaches the soil by mixing existing water reserves. The objective of this study is to identify and quantify the concentrations of cadmium (Cd), lead (Pb) and copper (Cu) in three underground wells of the Campus of Presidente Prudente - SP of the FCT-UNESP, due to changes in depth and pH. The water samples were collected every two weeks from August/2015 to April/2016. The concentrations of Cd2+, Pb2+ and Cu2+ in water were determined employing differential pulse voltammetry with anodic stripping. Table 1 shows the concentrations in μg/L of Cd, Pb and Cu measured in the three well samples of FCT-UNESP and Table 2 presents the respective depths and pH values. According to the results, it is noted that the values of Cd2+ and Pb2+ are above the values acceptable by the CETESB (5 μg/L and 10 μg/L, respectively) while Cu2+ values are within acceptable standards (2000 μg/L). For the points P1 and P3, which presented more alkaline values, it is possible to verify the similar relation with the depth increase, justified by the type of soil found in the region. Principal component analysis (PCA) were also performed, indicating similarity in the concomitant behavior of increasing and decreasing Cd and Pb concentrations, in addition to Cu independent behavior. According to the data obtained with the measurements of pH and depth of the wells, the metals were generally found to tend to precipitate at more alkaline pH (P1 and P3), in the forms of carbonates, sulphates and hydroxides, while in slightly acidic pH the metals are arranged in the ionic form due to their mobility.