Wednesday, June 6, 2007 - 10:30 AM
219

Soil Phosphorus Accrual in Everglades Stormwater Treatment Areas

Forrest E. Dierberg, Ph.D, Kevin A. Grace, and Michelle Kharbanda. DB Environmental, Inc., 365 Gus Hipp Blvd., Rockledge, FL 32955

Large (352-6695 ha) Stormwater Treatment Areas (STAs) have been constructed in south Florida for reducing phosphorus (P) loadings from agricultural sources prior to discharge to the Everglades. We conducted a multi-year study to assess sediment P accrual in Cell 4 of STA-1W. For the initial 8.5 years of operation, sediment and P accrual rates followed an expected spatial pattern, with sediment accrual rates ranging from 1.2-1.6 cm/yr and 0.5 cm/yr for the front- and back-end of the wetland, respectively. The corresponding sediment P accrual rates were 1.2-1.5 g P/m2-yr and 0.55 g P/m2-yr. High hydraulic (> 20 cm/day) and mass P loadings (>10 g P/m2-yr) to the wetland beginning June 2002 resulted in an increased sediment P deposition rate at the front- and back-ends that were four and six times greater, respectively, than those during the lower HLR period (1993-2002). These data demonstrate that prolonged high P loads can accelerate sediment P deposition in STAs. In addition, data from STAs demonstrate natural perturbations such as hurricanes and floating tussock island formation can redistribute STA sediments, complicating the evaluation of long-term trends in sediment accrual.

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