Elucidation of soil phosphorus speciation in mid‐Atlantic soils using synchrotron‐based microspectroscopic techniques. Issue 1 (11th February 2020)

• Record Type: Journal Article
• Authors: Gamble, Audrey V.; Northrup, Paul A.; Sparks, Donald L.
• Is Part Of: Journal of Environmental Quality. Volume 49:Issue 1(2020)
• Page Start: 184
• Page End: 193
• Publication Date: 2020-02-11
• Subjects: Agricultural ecology -- Periodicals; Environmental engineering -- Periodicals; Pollution -- Periodicals; 630
• DOI: 10.1002/jeq2.20027
• Languages: English
• ISSNs: 0047-2425

Abstract

Abstract: Phosphorus deficiency and excess are concomitant problems in agricultural soils of the mid‐Atlantic region. A fundamental understanding of soil P speciation is essential to assess P fate and transport in these soils. Current methods for soil P speciation often rely on sequential chemical extractions, which can introduce artifacts during analysis. To overcome limitations of current methods, this study evaluated synchrotron‐based micro‐focused X‐ray fluorescence (µ‐XRF) and X‐ray absorption near‐edge spectroscopy (µ‐XANES) techniques to assess soil P speciation in agricultural soils collected from the mid‐Atlantic region of the United States. Three soils with varying chemical and physical properties were analyzed with µ‐XRF maps collected at high (12, 000 eV) and tender (2240 eV) energies to evaluate colocation of P with Fe, Al, Ca, and Si in soil samples, and µ‐XANES spectra were collected at the P K‐edge for P hotspots. Combined µ‐XRF and µ‐XANES analysis was useful for identifying Ca phosphate, Fe phosphate, Al‐sorbed P, and Fe‐sorbed P species in heterogeneous soil samples. X‐ray fluorescence maps were valuable to distinguish Al‐oxide sorbed P from Fe‐oxide sorbed P species. A low signal‐to‐noise ratio often limited µ‐XANES data collection in regions with diffuse, low concentrations of P. Therefore, some P species may not have been detected during analysis. Even with varying degrees of self‐absorption and signal‐to‐noise ratios in µ‐XANES spectra, important inferences regarding P speciation in mid‐Atlantic soils were made. This study highlights the potential of µ‐XANES analysis for use in environmental and agricultural sciences to provide insights into P fate and transport in soils.