Influence of Sample Pretreatment on P Speciation in Sediments Evaluated with Sequential Fractionation and P K-edge XANES Spectroscopy

Abstract

ABSTRACT Sequential phosphorus (P) fractionation procedures are one of the most widely used wet chemical methods for characterizing P pools in soils and sediments, but have also been criticized repeatedly for their lack of accuracy to measure chemically specified phosphate fractions. In the recent investigation, sediments from two different sample locations with the same pretreatments were analyzed with sequential P fractionation. To verify traditional assignments of P fractionation results, P K-edge X-ray absorption near edge structure (XANES) spectroscopy was applied on the sediments and especially on the residues after the sequential extraction steps. Results of both methods indicated that the influence of sample pretreatment on the distribution of P pools was much lower compared to the effects of different sample origins. Kettle hole sediments were dominated by moderately labile iron (Fe) and aluminum (Al) associated P species, whereas Bodden sediments contained more stable calcium (Ca)–P species. Sample pretreatment of sediments can be similar to traditional soil sample pretreatment without causing fundamental changes in P speciation. The P K-edge XANES spectroscopy confirmed most assumptions of sequential P fractionation.