Multi-element effects on arsenate accumulation in a geochemical matrix determined using µ -XRF, µ -XANES and spatial statistics

The objective of this work was to develop approaches for assessing effects of co-localized geochemical matrix elements on the accumulation and chemical speciation of arsenate applied to a soil matrix. Synchrotron X-ray fluorescence microprobe ( µ -XRF) images collected across 100   µ m × 100   µ m and 10   µ m × 10   µ m regions of a naturally weathered soil sand-grain coating before and after treatment with As(V) solution showed strong positive partial correlations (r ′ = 0.77 and 0.64, respectively) between accumulated As and soil Fe, with weaker partial correlations (r ′> 0.1) between As and Ca, and As and Zn in the larger image. Spatial and non-spatial regression models revealed a dominant contribution of Fe and minor contributions of Ca and Ti in predicting accumulated As, depending on the size of the sample area analyzed. Time-of-flight secondary ion mass spectrometry analysis of an area of the sand grain showed a significant correlation (r = 0.51) between Fe and Al, so effects of Fe versus Al (hydr)oxides on accumulated As could not be separated. Fitting results from 25   As   K-edge microscale X-ray absorption near-edge structure ( µ -XANES) spectra collected across a separate 10   µ m × 10   µ m region showed ∼ 60% variation in proportions of Fe(III) and Al(III)-bound As(V) standards, and fits to µ -XANES spectra collected across the 100   µ m × 100   µ m region were more variable. Consistent with insights from studies on mode...
Source: Journal of Synchrotron Radiation - Category: Physics Authors: Tags: reactive microsites multi-component complexity arsenic partial correlation spatial regression research papers Source Type: research