Spatial Distribution of Phosphorus in the Kissimmee River Floodplain Soils and Sediments.

Construction of a canal in the 1960s through the Kissimmee River in south-central Florida led to severe degradation of the river-floodplain ecosystem.  Restoration of a portion of the river, consisting of filling in the canal with spoil left from dredging, thereby restoring flow to the original river channel and inundating the broad floodplain, commenced in 1999 and will be completed in 2014. This study was designed to provide a spatial catalogue of present soil conditions and a baseline assessment of phosphorus within the floodplain to detect changes to the landscape over time. The study area distinguished two degrees of restoration progress – Phase I, a partially restored area, and Phase II, an area which is currently un-restored. Surface soil samples (0-10 cm) were collected from 115 predetermined sites in each of Phase I and Phase II. Soil biogeochemical data obtained included: pH; water soluble P (WSP); total P (TP) and total metals, TFe, TAl, TCa and TMg. To compare soils from different landscape units, each Phase was grouped into six major classes. These classes included: i) Channels (active, passive, abandoned, and remnant river channels); ii) Backfill (backfilled C-38 canal areas); iii) Flood Plain Zone; iv) Spoil (spoil mounds, re-graded spoil); v) Upland Ecotone (upland ecotone zone, depression); and vi) Other (road ditch, farm ditch, tributary slough, pit, borrow area, etc.). Spoil areas along the canal and areas where the canal had been backfilled with spoil were significantly different from the other landscape units in that they had higher pH, high TP, TAl, and TFe, all indications of phosphate-rich geological deposits. Water-soluble P in these materials was low compared with values of WSP from manure-impacted soils with similar TP ranges within the same Basin. It is likely that apatite, which releases P in small amounts, is a component of the spoil material.