Phosphorus speciation and solubility in aeolian dust deposited in the interior American West

Aeoliandust is a significant source of phosphorus (P) to alpine oligotrophic lakes, but P speciation in dust and source sediments and its release kinetics to lake water remain unknown. Phosphorus K-edge XANESspectroscopy shows that calcium-bound P (Ca–P) is dominant in 10 of 12 dust samples (41–74%) deposited on snow in the central Rocky Mountains and all 42 source sediment samples (the fine fraction) (68–80%), with a lower proportion in dust probably because acidic snowmeltdissolves some Ca–P in dust before collection. Iron-bound P (Fe–P, ∼54%) dominates in the remaining two dust samples. Chemical extractions (SEDEX) on these samples provide inaccurate results because of unselective extraction of targeted species and artifacts introduced by the extractions. Dust releases increasingly more P in synthetic lake water within 6–72 h thanks to dissolution of Ca–P, but dust release of P declines afterward due to back adsorption of P onto Fe oxides present in the dust. The back sorption is stronger for the du...