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Title: XANES Demonstrates the Release of Calcium Phosphates from Alkaline Vertisols to Moderately Acidified Solution
Contributor(s): Andersson, Karl  (author); Tighe, Matthew  (author); Guppy, Christopher  (author)orcid ; Milham, Paul  (author); McLaren, Timothy (author); Schefe, Cassandra R (author); Lombi, Enzo (author)
Publication Date: 2016
Open Access: Yes
DOI: 10.1021/acs.est.5b04814
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Abstract: Calcium phosphate (CaP) minerals may comprise the main phosphorus (P) reserve in alkaline soils, with solubility dependent on pH and the concentration of Ca and/or P in solution. Combining several techniques in a novel way, we studied these phenomena by progressively depleting P from suspensions of two soils (low P) using an anion-exchange membrane (AEM) and from a third soil (high P) with AEM together with a cation-exchange membrane. Depletions commenced on untreated soil, then continued as pH was manipulated and maintained at three constant pH levels: the initial pH (pHi) and pH 6.5 and 5.5. Bulk P K-edge X-ray absorption near-edge structure (XANES) spectroscopy revealed that the main forms of inorganic P in each soil were apatite, a second more soluble CaP mineral, and smectite-sorbed P. With moderate depletion of P at pHi or pH 6.5, CaP minerals became more prominent in the spectra compared to sorbed species. The more soluble CaP minerals were depleted at pH 6.5, and all CaP minerals were exhausted at pH 5.5, showing that the CaP species present in these alkaline soils are soluble with decreases of pH in the range achievable by rhizosphere acidification.
Publication Type: Journal Article
Source of Publication: Environmental Science & Technology, 50(8), p. 4229-4237
Publisher: American Chemical Society
Place of Publication: Washington DC, United States of America
ISSN: 0013-936X
Field of Research (FOR): 050304 Soil Chemistry (excl. Carbon Sequestration Science)
Peer Reviewed: Yes
HERDC Category Description: C1 Refereed Article in a Scholarly Journal
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