δO as a tracer of PO losses from agricultural landscapes.

Accurately tracing the sources and fate of excess PO in waterways is necessary for sustainable catchment management. The natural abundance isotopic composition of O in PO (δO) is a promising tracer of point source pollution, but its ability to track diffuse agricultural pollution is unclear. We tested the hypothesis that δO could distinguish between agricultural PO sources by measuring the integrated δO composition and P speciation of contrasting inorganic fertilisers (compound vs rock) and soil textures (sand, loam, clay) in southwestern Australia.