Characterization of phosphorus species in sediments from the Arabian Sea oxygen minimum zone: Combining sequential extractions and X-ray spectroscopy
Kraal, P.; Bostick, B.C.; Behrends, T.; Reichart, G.J.; Slomp, C.P. (2015). Characterization of phosphorus species in sediments from the Arabian Sea oxygen minimum zone: Combining sequential extractions and X-ray spectroscopy. Mar. Chem. 168: 1-8. dx.doi.org/10.1016/j.marchem.2014.10.009
In: Marine Chemistry. Elsevier: Amsterdam. ISSN 0304-4203; e-ISSN 1872-7581, more
The bulk phosphorus (P) distribution in sediment samples from the oxygen minimum zone of the northern Arabian Sea was determined using two methods: sequential chemical extraction (the ‘SEDEX’ procedure) and X-ray absorption near-edge structure (XANES) spectroscopy of the phosphorus K-edge. Our results show good agreement between iron (Fe-)associated P and calcium phosphate minerals (Ca-P) determined by both methods. Furthermore, we find that SEDEX exchangeable P likely represents loosely Fe-bound P, and that the SEDEX detrital fraction may consist partly of polyphosphate, i.e. microbially synthesized intracellular phosphate. Below productive waters with relatively high sedimentary organic matter and P contents, polyphosphates may represent an important P sink that is not easily identified by chemical sequential extraction. This study highlights the value of SEDEX as a generally accurate and fast P speciation technique (especially for Fe- and Ca-P) and, for the first time, demonstrates the possibilities of P K-edge XANES as a bulk P speciation tool for marine sediments.
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