Analysis of oxygen isotopes of inorganic phosphate (δ18Op) in freshwater: A detailed method description

Abstract

The ability to identify the origin of phosphorus is essential to effectively mitigate 14 eutrophication of freshwater ecosystems. The oxygen isotope composition of orthophosphate (δ 18 Op) 15 has been suggested to have a significant prospective as a tracer for P entering freshwater ecosystems. 16 The δ 18 Op tracing method is, however, still in its preliminary stages and has proven challenging to 17 implement for new practitioners. In order to achieve progress in developing the application of δ 18 Op 18 signatures as a tracing tool, there is a need to eliminate the methodological challenges involved in 19 accurately determining δ 18 Op. This technical note describes the various steps needed to concentrate 20 and isolate orthophosphate in freshwater samples into an adequately pure analyte (Ag3PO4), without 21 isotopic alteration during processing. The protocol compiles the disperse experiences from previous 22 studies, combined with our own experience. 23 24 25