Particulate phosphorus removal via wetland filtration: An examination of potential for hypertrophic lake restoration |
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Authors: | Edgar F Lowe Lawrence E Battoe David L Stites Michael F Coveney |
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Institution: | (1) St. Johns River Water Management District, P.O. Box 1429, 32178-1429 Palatka, Florida, USA |
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Abstract: | Lake Apopka in Florida, USA, is a large (area=124 km2), hypertrophic (mean total phosphorus=0.220 g/m3; mean chlorophylla=60 mg/m3) lake, with a large sedimentary store of available P (1635 × 106 g P). Phosphorus loading from floodplain farms (132 × 106 g P/yr) has been the primary cause of eutrophication. Assuming elimination of farm P loading, the Vollenweider model predicts
a decline in equilibrium P concentration from 0.270 to 0.024 g/m3, if the P sedimentation coefficient (σ) remains constant. It is likely, however, that the value for σ will fall with the
elimination of farm loading due to unabated internal P loading from the sediments. Under a worst-case scenario (σ=0), the
model predicts that exportation of P from the lake via wetland filtration will greatly accelerate the lake's recovery. Recirculation
of lake water through a 21-km2, created wetland and elimination of farm P loading is projected to result in a negative P balance for the lake (−23 × 106 g P/yr) leading to depletion of P stores in the lake in about 60 yr. The estimated cost of the project, $20 million, is less
than 3% of the estimated cost of dredging. A 3.65-km2 demonstration project is underway to test and refine the wetland filtration technique. We believe the technique could be
cost-effective for other hypertrophic lakes. |
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Keywords: | Restoration Wetland Lake Eutrophication Florida Phosphorus Vollenweider |
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