Improved precision in As speciation analysis with HERFD-XANES at the As K-edge: the case of As speciation in mine waste

Abstract

High-energy-resolution fluorescence-detected (HERFD) X-ray absorption near-edge spectroscopy (XANES) is a spectroscopic method that allows for increased spectral feature resolution, and greater selectivity to decrease complex matrix effects compared with conventional XANES. XANES is an ideal tool for speciation of elements in solid-phase environmental samples. Accurate speciation of As in mine waste materials is important for understanding the mobility and toxicity of As in near-surface environments. In this study, linear combination fitting (LCF) was performed on synthetic spectra generated from mixtures of eight measured reference compounds for both HERFD-XANES and transmission-detected XANES to evaluate the improvement in quantitative speciation with HERFD-XANES spectra. The reference compounds arsenolite (As2O3), orpiment (As2S3), getchellite (AsSbS3), arsenopyrite (FeAsS), kaňkite (FeAsO4·3.5H2O), scorodite (FeAsO4·2H2O), sodium arsenate (Na3AsO4), and realgar (As4S4) were selected for their importance in mine waste systems. Statistical methods of principal component analysis and target transformation were employed to determine whether HERFD improves identification of the components in a dataset of mixtures of reference compounds. LCF was performed on HERFD- and total fluorescence yield (TFY)-XANES spectra collected from mine waste samples. Arsenopyrite, arsenolite, orpiment, and sodium arsenate were more accurately identified in the synthetic HERFD-XANES spectra compared with the transmission-XANES spectra. In mine waste samples containing arsenopyrite and either scorodite or kaňkite, LCF with HERFD-XANES measurements resulted in fits with smaller R-factors than concurrently collected TFY measurements. The improved accuracy of HERFD-XANES analysis may provide enhanced delineation of As phases controlling biogeochemical reactions in mine wastes, contaminated soils, and remediation systems.

Coupling High-Energy Resolution Fluorescence Detected X-ray Absorption Spectroscopy with Microfluidic Cells for in Situ Monitoring of Tungsten Nanoparticles Redox Transformation

“…This signal-to-noise ratio was estimated on the edge and postedge regions of experimental XANES spectra measured on environmental samples (sediments, living organisms) containing 2 to 135 mg W kg –1 (Figure ). This signal-to-noise ratio is close to the one used in Saurette et al and 10 times higher than the one used in Proux et al LCF was applied to fit the theoretically generated spectra with the reference compounds (W, WO 2 , and WO 3 ). For LCF, the uncertainty on the amount of each component was estimated to be approximately 10% of the total amount of the target element .…”

“…Quantitative Comparison of HERFD and Conventional XANES Spectroscopy. Following the approaches outlined by Proux et al and Saurette at al., 17,33 LCF analyses were carried out on the three sets of theoretically generated spectra acquired in conventional, HERFD L α1 and HERFD L β2 modes, respectively. Then, the standard errors between the theoretical percentage of compounds used and the percentages obtained by LCF were calculated (Figure 5 and Table 1).…”

“…Proux et al 17 observed an 8-fold improvement in precision when applying LCF to reconstruct 50 theoretical spectra, using HERFD-XANES spectra of four mercury reference compounds. Saurette et al 33 calculated the standard error of the LCF with eight As reference compounds (reconstruction of 3500 computer-generated arsenic mixtures) of the HERFD-XANES and compared to the LCF of the transmission-XANES spectra. The authors observed improvement in the precision of the LCF when using HERFD-XANES for four out of the eight As reference compounds investigated.…”

Improved precision in As speciation analysis with HERFD-XANES at the As K-edge: the case of As speciation in mine waste. Corrigendum

“…The name of an author in the article by Saurette et al (2022) [J. Synchrotron Rad. 29, 1198-1208 is corrected.…”

“…The name of the second author in the article by Saurette et al (2022) is incorrectly given as Y. Zou Frinfrock. The correct spelling is Y. Zou Finfrock, as given above.…”