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Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 383465
Title Phosphorus removal from soil using Fe oxide-impregnated paper: Processes and applications
Author(s) Los, A.M.D.; Temminghoff, E.J.M.; Schenkeveld, W.D.L.; Hiemstra, T.; Riemsdijk, W.H. van
Source Geoderma 151 (2009)3-4. - ISSN 0016-7061 - p. 282 - 289.
Department(s) Chair Soil Chemistry and Chemical Soil Quality
Publication type Refereed Article in a scientific journal
Publication year 2009
Keyword(s) p-i test - filter-paper - available phosphorus - ionic-strength - phosphate - adsorption - goethite - desorption - extraction - aluminum
Abstract Fe oxide-impregnated paper (Pi-paper) is used as an artificial Phosphorus (P) sink to study P availability in soils and runoff. Pi-papers were introduced as they would mimic P uptake by plant roots by decreasing the P concentration in solution to negligibly low levels and thus enhancing P desorption from the soils solid phase. The rate of transfer of P from soil to Pi-paper would thus be limited by the soil P desorption rate. The maximum desorption rate is indeed achieved when the original method is used in which (at least) four Pi-papers per gram soil are placed in a soil suspension (soil–solution ratio of 0.025 kg L- 1). In several studies this method has however been adapted depending on the research question of interest without investigating the effect of this adaptation to the processes involved in the transfer of P from soil to Pi-paper. The aim of this study is to improve our understanding of the processes that occur in the Pi-paper–solution–soil system and so to extend the theoretical basis of this method. Insight is gained in these processes by comparing the experimentally determined P transfer from soil to Pi-paper with P transfer that is modeled based on the measured P concentration in solution and the (kinetic) Langmuir equation of the Pi-paper. P adsorption by a Pi-paper from standard solutions is not instantaneous but can be described with a kinetic Langmuir equation that is a characteristic of the Pi-paper. Over time, the Pi-paper reaches equilibrium with the solution, and the kinetic Langmuir equation can be rewritten to a Langmuir equation. Regardless if there is equilibrium or not, P adsorption to the Pi-paper is a function of the P concentration in solution. By adding Pi-paper to a soil suspension, a re-distribution of P takes place between the reactive surface area of the soil and the new reactive surface area of the Pi-paper that initially contains no adsorbed phosphate. As opposed to the original method where the desorption rate was limiting the overall P transfer, the adsorption rate to the Pi-paper is limiting when one Pi-paper per gram soil is placed in a soil suspension (soil–solution ratio of 0.1 kg L- 1). In this situation, the P concentration in solution is found to be in equilibrium with the soil's solid phase. With increasing contact time (> ~ 24 h) the whole system approaches equilibrium. With each successive Pi-paper newly added, more P is removed from the soil system and the decrease of P in solution will be governed by the soil P desorption isotherm. Varying the number of Pi-papers and the soil to solution ratio thus has a large effect on the transfer rate between soil and Pi-paper and if either the soil desorption rate, the Pi-paper adsorption rate or a combination limits this transfer rate. With increased insight in the P transfer between soil and Pi-paper sink, it becomes possible to tailor the experimental design to help answer the research question one is interested in.
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