FRACTIONATION OF P SPECIES IN SUSPENDED SEDIMENTS OF IRONDEQUOIT CREEK, NY
In this study, we investigate the fractionation of P within suspended sediment, the primary mode of P transport through the system. Approximately 10 to 12 liters of water were collected at 4 locations within the watershed during stormflow events. Suspended sediment was collected by centrifugation. Stream bed sediments were collected from approximately the top 5 cm in a small core. Suspended sediment and stream bed sediment samples were fractionated following the Psenner method into exchangeable, Fe-association, Al-associated, organic matter (OM) associated and Ca-associated P. Suspended and stream bed samples have similar percentages of exchangeable and Al-associated P with approximately 4% exchangeable P, and 26 to 31% Al-associated P. Suspended sediment samples are, on average, significantly higher in Fe and OM associated P, and significantly lower in Ca-associated P. Ca-associated P, which represents the most stable and least bioavailable form of P, averages 21% of the P in suspended sediment but 48% in stream bed sediment. These results suggest that Ca-associated P increases with depth so that sediment from the surface, which may be remobilized during stormflow, has the lower concentrations in this fraction. Furthermore, with higher amounts of OM-associated P in suspended sediment, it suggests that P may be more bioavailable from this source.