Speciation of Phosphate in Iron Rich Mineral Deposit in a High Mountain Lake Environment, a Study at the Micron Scale at the LUCIA Beamline

In a high mountain lake and catchment area, a natural process of phosphorus enrichment is observed, induced by the iron-cycle. Investigations focus on the speciation of P and Fe in iron and manganese rich oxidic mineral crusts formed at the surface of rock pebbles. Iron and phosphorus are spatially associated although they are not forming iron phosphate minerals. While Fe and P K edge XAS spectra suggest that phosphates are inner-sphere adsorbed by ferrihydrite-type minerals, slight variations in pre-edge and edge features and in EXAFS spectra suggest that the structure of the natural Fe-P mineral associations are more complex.