Evaluation of the availability of heavy metals in lake sediments using SR-TXRF

Abstract

The analytical technique Synchrotron Radiation Total Reflection X-ray Fluorescence (SR-TXRF) was used to evaluate the contamination and bioavailability of heavy metals in samples of sediment collected at different depths. The samples were collected in one of the lakes located next to ceramic industries in Santa Gertrudes, São Paulo state in the southwest region of Brazil during the rainy season. In order to determine the concentration of bioavailable metals (mobile fraction) and metals that are representative of the geological matrix (residual fraction) in sediment samples, procedures of acid extraction were implemented. All measurements were carried out in the Synchrotron Light Source Laboratory (LNLS), located in Campinas, São Paulo state. For sample excitation, a polychromatic beam of approximately 2 mm (width) and 0.3 mm (height) was used, and for the detection of the characteristic X-rays produced, a Si(Li) detector was employed. The net areas of the X-ray peaks were obtained from the program (Quantitative X-ray Analysis System; QXAS). The elements V, Cr, Co, Cu, Zn and Pb, which are considered to cause higher environmental damage, showed high availability. The concentrations of these elements are above the reference values which correspond to soil protection and underground water quality of São Paulo state. The concentrations obtained indicate that the area in study is contaminated.