Comparing Total Reflection X-Ray Fluorescence and Atomic Absorption Spectrometry for Trace Element Analyses In Mining Areas.

Soil contamination in mining areas generally occurs due to the presence of many elements. Under such a situation, total reflection X-ray fluorescence spectrometry (TXRF) has being considered as an advantageous technique because of simultaneous elemental determination in shorter analysis time (200-1000s), minimal samples amounts (10 µL), minimization of reagents consumption, and analysis of trace concentrations (sub ppm). This work aimed to evaluate the concentrations of trace elements by TXRF comparing it with atomic absorption spectrometry (AAS) in Pb- and As-contaminated soil/sediment samples from mining areas. Soil/sediment sample as well as standard reference materials (SRMs NIST 2710 and BCR 143R) were digested in a microwave oven, using HNO₃ according to the USEPA 3051A method. TXRF analyses were carried out in digestion extracts by adding Ga as an internal standard. Spectra were analyzed with standard methods using a specific software. Extract replicates were also analyzed by AAS for comparison. High As (from 37 up to 2964 mg kg^-1) and Pb (from 19 up to 7319 mg kg^‑1) semitotal concentrations were found in the soil/sediment samples from the studied mining areas. Correlation coefficients between TXRF and AAS analyses were 0.992 for As and 0.999 for Pb. Lead and As recovery in the NIST 2710 was 118 and 107% by TXRF and 83 and 90% by AAS, respectively. For BCR 143R, Pb recovery was 103% by TXRF and 77% by AAS. The TXRF technique had the additional advantage of determining also Cu, Cr, Fe, Mn, and Zn in mining samples. The results show that this technique is a suitable and an accurate tool for the chemical characterization of trace elements in soil. Sponsored by CNPq, CAPES and FAPEMIG.