Lead and Arsenic X-ray absorption spectral models fit as linear combination of known standards

In this study, smelter contaminated soil was treated with various soil amendments (ferric sulphate [Fe2(SO4)3], triple superphosphate [TSP] and biochar) to determine their efficacy in immobilizing soil lead (Pb) and arsenic (As). XAS were collected on soils and mine waste materials at the Materials Research Collaborative Access Team 10-BM for As and 10-ID for Pb, Advanced Photon Source at Argonne National Laboratory. Arsenic XAS data collection at 10-BM was measured at the As K edge (11867 eV) using a 4-element Vortex fluorescence detector. Four layers of aluminum foil to filter out background fluorescence from iron and other elements in the samples. Three to five step scans were collected in fluorescence by Vortex detector at 45° incident to sample and down beam transmission on energy calibration standard. Energy was calibrated to set at the 1st derivative inflection point zero of sodium arsenate standard to 11874 eV. Data were then background subtracted and converted to k space for EXAFS region analysis. Data processed for EXAFS analysis were k3-weighted and all e0 set to 11870 eV for uniform k range start energy. Spline range was 0.5-12 k. Lead XAS data collection at 10-ID utilized a Si(111) mono to tune energy to the Pb L3-edge (13035 eV). Samples were measured in fluorescence using a Mirion-Canberra 7-element Ge detector at 45° incident to the sample. For each sample, three to five scans were collected in both transmission and fluorescence mode with a Pb foil for reference sample. Calibration was performed by assigning the first derivative inflection point of Pb foil scan to 13035 eV. Analysis of Pb spectra utilized LCF of the 1st derivative norm(E) from -20 to 80 eV from e0, constraints of all weights between 0 and 1 and sum of weights normalized to 1. Standards were sequentially removed based on statistical improvement of fit. Components contributing less than ten percent were removed, followed by refitting with remaining components. The combination of standards resulting in the lowest R-factor results for each sample was reported. Arsenic spectra were analyzed LCF utilizing the EXAFS range of spectra. Preliminary data checking indicated As oxidation states of all samples contained only AsV as confirmed by matching edge position with the sodium arsenate pellet used for energy calibration. As EXAFS range were utilized for quantitative speciation from a k-range of 3-10 Å-1. This dataset is associated with the following publication: Alankarage, D., A. Betts, K.G. Scheckel, C. Herde, M. Cavallaro, and A.L. Juhasz. Remediation options to reduce bioaccessible and bioavailable lead and arsenic at a smelter impacted site - consideration of treatment efficacy. ENVIRONMENTAL POLLUTION. Elsevier Science Ltd, New York, NY, USA, 341: 122881, (2024).

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[
  "https://doi.org/10.1016/j.envpol.2023.122881"
]