Metal Mobilization Factor Modeling

Published: 22-07-2018| Version 1 | DOI: 10.17632/kmpv8s7nbk.1
Contributors:
Taufik Abrao,
maria santos

Description

EDXRF analysis is useful to describe the extension of the sorbate mobilization to the liquid phase and the mobilization degree can be explained from different ways. Considering that fluorescence yield is proportional to the peak area, it can be suggested a sorption-desorption behavior. Metal ion mobilization can be observed from the difference in the integration of the sorption and desorption fluorescence peaks. Once desorption integrated area was lower than sorption, the metal ion mobility to the liquid phase was actual for both soil and sediment, to a higher extent for sediment (SD-0), with 34% Hg2+ desorption and almost total desorption for Cd2+ and Pb2+. For the other samples desorption ranged from 15 to 19%. However, a simple desorption is not enough to describe mobilization processes in a river basin. In this way, an innovative mobilization factor (MF) representing the desorption rate from the integration of the normalized difference of the sorption-desorption peaks was determined and is represented in Figures provided by the MatLab script (see SD0_data.m and SD700_data.m files for sediment and SL0_data.m and SL700_data.m files for soil). The response area selected for the elements was considered for the two higher peak areas within their energy (10.55 and 12.62 keV for Pb; 9.98 and 11.82 for Hg) and at 23.11 keV for Cd \cite{serradilla_2007}. The other peaks correspond to lower-energy transitions of the target analytes and these were not considered for the MF. Mobilization factors ranged from 0.063 to 0.103 (L$\alpha$) to mercury, 0.420 to 0.930 (L$\alpha$) to lead and 0.106 to 0.322 to cadmium (K$\alpha$). The MF was approximately 9.0 and 6.4 times higher for lead than for mercury and cadmium in SD-0, respectively. Despite Hg and Pb have shown two most intense peaks (L$\alpha$ and L$\beta$), respectively, the calculated MF from the shoulder (max and min) on the integral of each peak (red line) was similar for both peaks of mercury and of lead, demonstrating the robustness of the technique and of the MF proposed. In this way, it is enough to calculate only for a shoulder to get the MF.

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