Análise multielementar por EDXRF em amostras de solo de região agrícola de Duas Barras

Abstract

Contamination of soils by heavy metals can occur through anthropogenic factors such as the accumulation of solid waste. At Duas Barras, for more than twenty years, the same area is used for the management of garbage, either by sorting, discarding or just transhipping, a process in which the material discarded from a transport to another. In this work, the technique of Energy Dispersive X-Ray Fluorescence (EDXRF) was used in order to identify the multielementar composition of six soil samples collected in this area, to establish the concentration of elements and to verify if there is contamination by heavy metals. Samples were collected superficially at a maximum depth of 5 cm. Thereafter, they were ground manually and fully sieved in order to achieve particle size homogeneity at 75 μm. Then, they were conditioned in an oven at 60ºC until reaching a constant mass. The system used in the analysis was developed in the Laboratory of Electronic Instrumentation and Analytical Techniques (LIETA) of the Institute of Physics Armando Dias Tavares - University of the State of Rio de Janeiro (UERJ) and consists of a portable XRF system formed by a mini tube of low power X-ray with silver anode (Ag) operating at 15 - 35 keV / 100 μA and a silicon detector (Si). In the process, 500 mg of compound composed of 300 mg portions of sample and 200 mg of boric acid (H3BO3) were pressed at approximately 2x102 MPa for about 15 minutes in order to obtain fine pellets with a diameter of 2.54 cm and surface density of 100 mg / cm2. Seventeen elements were detected: Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Ga, Br, Rb, Sr, Zr, Nb and Pb. Concentration was calculated using Radiation Intensity, Sample Absorption, System Sensitivity, and other parameters. The analysis of the results was done using the ANOVA and Tukey tests, while the element concentration was compared to reference values and it was concluded that copper (Cu), potassium (K) and calcium (Ca) accumulation occurs above the mean values. Thus, the study of the level of soil pollution accumulation through the EDXRF technique has proved to be a low-cost and efficient technique in determining the elemental concentration of the components.