Assessment of P concentrations in different types of Florida surface soils

It is important to establish baseline concentrations of phosphorus (P) for Florida surface soils and to document systematic variations in P concentrat ion according to regional geography and soil classifications, in order to a ssist in assessment of eutrophication of lakes caused by P contamination. I n this study, concentrations of P in 448 geographically and pedogenically r epresentative Florida surface soils were determined using EPA Method 3052 ( HCl-HNO3-HF digestion) and ICP. Results showed that P concentrations follow ed a log-normal distribution and that the geometric mean (GM) and baseline concentration (defined as 95% of the expected range of background concentra tions) provided the most satisfactory statistical results. Based on the GM, P concentrations for Florida surface soils were much lower than the averag e for U.S. soils and generally followed the order: His tosols > Mollisols, Inceptisols P Ultisols greater than or equal to Alfisols, Entisols > Spodos ols. The lowest GM concentrations for P were found in Aquods and Orthods (S podosol suborders), followed by Psamments tan Entisol suborder) and Aqualfs tan Alfisol suborder). Geographical and taxonomic distributions of P sugge sted that soil properties were the primary controlling factors for P concen trations. Higher mean P concentrations in the northern and central regions of the peninsula may reflect the influence of local phosphatic clay deposit s.