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Channelization of the Kissimmee River in south-central Florida in the 1960’s led to the degradation of the ecosystem in the river basin. Since the 1990’s attempts were made to restore portions of the Kissimmee River and floodplain to its original state. Environmental risk of P loss from sediment/soils can be evaluated using phosphorus saturation ratio (PSR; molar ratio of P to [Al+Fe]) and soil phosphorus storage capacity (SPSC) concepts. The change point (zero SPSC) amounts to a threshold PSR value above which P release from the soil increases. Positive SPSC indicates a soil is a P sink, while a negative value indicates that the soil is a P source. The objective of this study was to evaluate the P retention and release using the SPSC concept for the areas that have been already restored (Phase I) and the areas to be restored (Phase II-III). Surface soil samples (0-10 cm and 10-20 cm) from 115 predetermined sites from both Phase I and Phase II-III were collected resulting a total of 460 samples (2 depth * 2 phases * 115 sites). Soils were analyzed for P, Fe, Al, Ca and Mg in a Mehlich 1 solution at a 1:4 soil:solution ratio. Water soluble P (WSP) was analyzed in a 1:10 soil:water extract. Total P (TP) and total metals, TFe, TAl, TCa and TMg, were determined for all samples. While the TP for some samples were high (up to ~4000 mg kg-1), WSP was minimal indicating low P release risk. The relationship of SPSC and WSP for the floodplain soils and sediments was different compared to that from fertilizer-impacted soils suggesting that non-anthropogenic sources were involved in regulating P release at this river basin.
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