PHOSPHORUS SORPTION CHARACTERISTICS OF EVERGLADES SOILS ALONG A EUTROPHICATION GRADIENT

We examined the P sorption characteristics of northern Everglades peat soils along a eutrophication gradient to understand the P retention e fficiency of the soils. The amount of phosphate adsorbed on the soils ce, and the zero equilibrium phosphate concentration supported by the soils (EPCo) exhibited a linear decrease with distance from the inflow structures supplying agricultural drainage (r(2) = 0.74 and 0.71, res pectively; P < 0.05; n = 18). Values of Q and EPCo for the enriched so ils are an order of magnitude higher than for unenriched soils, Estima ted Q values of the soils compare well with the exchangeable P fractio n determined by KCl and HCO3 extraction. Comparison of soil EPCo and p ore water PO4-P values with the surface water PO4-P concentrations sug gests that soils may serve as an additional internal source of P to th e overlying water column in nutrient-enriched areas. Linear phosphate adsorption coefficient (K) of the alkaline Everglades soils is higher than that of acidic pocosin bog peat soils of North Carolina but lower than wetland soils and sediments with a high mineral content. Phospho rus sorption characteristics of the Everglade soils are most likely re gulated by CaCO3.