Upstream source control and Stormwater Treatment Areas (STAs) have reduced phosphorus (P) loads to Water Conservation Area 2A (WCA-2A), a northern Everglades wetland, by three quarters since year 2000. Nevertheless, large storages of P remain in enriched peat soils and it is unclear how legacy stores will impact spatial and temporal scales of recovery. We remeasured soil P enrichment along a well-studied eutrophication gradient in WCA-2A and applied a profile modeling approach with uncertainty analysis to assess changes in longitudinal soil P gradients 13 years after load reductions. We then analyzed existing internal water P data, using a novel data screening approach, for evidence of lowest possible water P concentrations independent from inflows. We interpret such water P limits as evidence of the strength of internal loading at a location. Results indicate that soil P enrichment persists in the 7.5 km long ''impacted'' zone, with no significant evidence of net advancement or recession, while a large pool of labile P in the flocculent layer consolidated and diminished. There is indeed evidence, both spatial and temporal, that this extensive zone of enriched soil P continues to elevate lowest achievable water P concentrations. The corresponding gradient of elevated water P limits is both receding and diminishing since load reductions, thus providing further evidence toward recovery. However, results also suggest that these ''transitory P limits'' due to internal loading are likely to persist for decades above water quality targets. These results advance our understanding of recovery in impacted wetlands and are relevant to Everglades restoration.
Natural systems use the natural processes of wetland ecosystems to both transform and hold on to many of the common pollutants that occur in household wastewater. This 8-page fact sheet briefly describes the principles and added benefits of natural systems. It then focuses on their use for treating small municipal wastewater flows from commercial and residential sites (i.e., septic systems or decentralized wastewater systems). Written by Kiara Winans, Shanin Speas-Frost, Mike Jerauld, Mark Clark, and Gurpal Toor, and published by the UF Department of Soil and Water Science, May 2012.
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