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Research article - Peer-reviewed, 2020

Phosphorus in 2D: Spatially resolved P speciation in two Swedish forest soils as influenced by apatite weathering and podzolization

Adediran, Gbotemi A.; Tuyishime, J. R. Marius; Vantelon, Delphine; Klysubun, Wantana; Gustafsson, Jon Petter

Abstract

The cycling and long-term supply of phosphorus (P) in soils are of global environmental and agricultural concern. To advance the knowledge, a detailed understanding of both the vertical and lateral variation of P chemical speciation and retention mechanism(s) is required, a knowledge that is limited in postglacial forest soils. We combined the use of synchrotron X-ray fluorescence microscopy with multi-elemental co-localisation analysis and P K-edge XANES spectroscopy to reveal critical chemical and structural soil properties. We established a two-dimensional (2D) imagery of P retention and speciation at a microscale spatial resolution in two forest soil profiles formed in glaciofluvial and wave-washed sand. The abundance and speciation of P in the upper 40 cm was found to be influenced by soil weathering and podzolization, leading to spatial variability in P speciation on the microscale (< 200 pm) with P existing predominantly as organic P and as PO4 adsorbed to allophane and ferrihydrite, according to XANES spectroscopy. These species were mostly retained at sharp edges and in pore spaces within Al and Si-bearing particles. Despite the relatively young age ( < 15,000 years) of the soils, our results show primary mineral apatite to have weathered from the surface horizons. In the C horizon however, a large fraction of the P was in the form of apatite, which appeared as widely dispersed ( > 600 pm) hot spots of inclusions in aluminosilicates or as discrete micro-sized apatite grains. The subsoil apatite represents a pool of P that trees can potentially acquire and thus add to the biogeochemically active P pool in temperate forest soils.

Keywords

Phosphorus retention and speciation; Postglacial forest soils; Apatite weathering; Podzolization; X-ray fluorescence microscopy and spectroscopy

Published in

Geoderma
2020, volume: 376, article number: 114550
Publisher: ELSEVIER

Authors' information

Adediran, Gbotemi
Swedish University of Agricultural Sciences, Department of Soil and Environment
Swedish University of Agricultural Sciences, Department of Soil and Environment
Klysubun, Wantana
Synchrotron Light Res Inst
Swedish University of Agricultural Sciences, Department of Soil and Environment
Gustafsson, Jon Petter (Gustafsson, Jon-Petter)
Royal Institute of Technology (KTH)

UKÄ Subject classification

Soil Science

Publication Identifiers

DOI: https://doi.org/10.1016/j.geoderma.2020.114550

URI (permanent link to this page)

https://res.slu.se/id/publ/107328