title: Temporal and spatial patterns of internal phosphorus recycling in a South Florida (USA) stormwater treatment area.
abstract: Large constructed wetlands, known as stormwater treatment areas (STAs), have been deployed to remove phosphorus (P) in drainage waters before discharge into the Everglades in South Florida, USA. Their P removal performance depends on internal P cycling under typically hydrated, but with occasionally desiccated, conditions. We examined the spatial and temporal P removal capacity under different hydrologic conditions along a STA flow path. While inflow soils are P enriched, the outflow region of the wetland contained P-unsaturated soils with minimal net recycling of bound soil P to the water column as plant-available P. The outflow-region soils were characterized by low porewater soluble reactive P (SRP) (≤40 μg L) and high total sulfide (TS) (2-9 mg L) concentrations, and total ammoniacal nitrogen (TAN) and SRP flux rates that averaged 1.51 and 0.002 mg m d, respectively. Pronounced increases in porewater and surface-water concentrations of SRP, dissolved organic P (DOP), and TAN were observed immediately after rehydration of the cell after an extended drought. Elevated total P concentrations persisted at the outfall of the cell for several months thereafter, resulting in an annual outflow total P concentration nearly threefold higher than the long-term mean. Relative to processes that can occur during extended periods of inundation, such as sulfate-enhanced P release from organic matter mineralization or iron sulfide formation, aerobic oxidation of organic matter during prolonged dryout periods is a more significant biogeochemical process in compromising soil P retention in STAs.
authors.affiliation: DB Environmental, Inc. Rockledge, FL, USA.
authors.forename: Forrest E
authors.initials: FE
authors.lastname: Dierberg
authors.forename: Thomas A
authors.initials: TA
authors.lastname: DeBusk
authors.forename: Jaimee L
authors.initials: JL
authors.lastname: Henry
authors.forename: Scott D
authors.initials: SD
authors.lastname: Jackson
authors.forename: Stacey
authors.initials: S
authors.lastname: Galloway
authors.forename: Mark C
authors.initials: MC
authors.lastname: Gabriel
mesh_terms: D005431:Florida; D010084:Oxidation-Reduction; D010758:Phosphorus / Q000302:isolation & purification*; D059027:Recycling; D012987:Soil / Q000032:analysis; D018508:Water Purification / Q000706:statistics & numerical data*; D060753:Water Quality; D053833:Wetlands
chemical_list: D012987:Soil; D010758:Phosphorus