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Evolution of phosphorus speciation with depth in an agricultural soil profile
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2016 (English)In: Geoderma, ISSN 0016-7061, E-ISSN 1872-6259, Vol. 280, 29-37 p.Article in journal (Refereed) Published
Abstract [en]

With time, different soil-forming processes such as weathering, plant growth, accumulation of organic matter, and cultivation are likely to affect phosphorus (P) speciation. In this study, the depth distribution of P species was investigated for an agricultural clay soil, Lanna, Sweden. Small amounts of apatite-P was demonstrated in the topsoil whereas the speciation of Pat 70-100 cm depth consisted of approximately 86% apatite according to P K-edge XANES (X-ray absorption near-edge structure) spectroscopy. Because there were only minor differences in bulk mineralogy and texture, these variations in P speciation were interpreted as the result of apatite weathering of the topsoil. Speciation modeling on soil extracts supported this idea: hydroxyapatite was not thermodynamically stable in the top 50 cm of the soil. Apatite was enriched in the bulk soil relative to the clay fraction, as expected during apatite dissolution. Combined results from batch experiments, XANES spectroscopy and X-ray diffraction suggested chemical transformations of the topsoil as a result from accumulation of organic matter and airing from tillage followed by enhanced weathering of apatite, amphiboles, clay minerals, and iron oxides. This caused the formation of poorly crystalline secondary iron and aluminum (hydr)oxides in the topsoil, which retained part of the released P from apatite. Other P was incorporated into organic forms. Furthermore, the results also showed that short-term acidification below the current pH value (below 5.5 in the topsoil and 7.2 in the deeper subsoil) caused significant solubilization of P. This is attributed to two different mechanisms: the instability of Al-containing sorbents (e.g. Al hydroxides) at low pH (in the topsoil), and the acid-mediated dissolution of apatite (the subsoil).

Place, publisher, year, edition, pages
Elsevier, 2016. Vol. 280, 29-37 p.
Keyword [en]
Acidification, Apatite, Clay, Secondary iron and aluminum (hydr)oxides, X-ray adsorption spectroscopy
National Category
Soil Science
Research subject
Land and Water Resources Engineering
URN: urn:nbn:se:kth:diva-191735DOI: 10.1016/j.geoderma.2016.06.004ISI: 000380626700005ScopusID: 2-s2.0-84974653012OAI: diva2:957510
Swedish Research Council Formas, 2010-1677

QC 20160906

Available from: 2016-09-02 Created: 2016-09-02 Last updated: 2016-09-06Bibliographically approved

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Gustafsson, Jon Petter
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