James A. Montgomery, Department of Environmental Science and Studies, DePaul University, Chicago, IL and J. Marshall Eames, Department of Biology, Armstrong State University, Savannah, GA
This poster presents a cautionary tale of what can happen when past land use history and assessment of soil quality are not incorporated into wetland restoration protocols. Since 1998 we have monitored water quality at Prairie Wolf Slough Wetland Demonstration Project (PWS), a restored farmed wetland located adjacent to the Chicago River in north suburban Chicago. PWS receives stormwater runoff directly from residential and commercial land uses, and it discharges into the Chicago River. The original objectives of this study were to assess spatial and temporal variations in water flow and compute a mass balance for nutrients and solids. Water samples were collected at inlet and outlet discharge points. Within a year after the restoration we found that concentrations and loadings of total (TP) and soluble reactive phosphorus (SRP) were both higher at the outlet than at the inlet, indicating that PWS is a point source to the river. Post-restoration P loss from farmed fields has been well documented in the literature. We then changed the objective of our study to focus solely on identifying and quantifying sources of P input into and out of the wetland. Since 1998, long-term TP and SRP concentrations and loadings have increased by as much as 279% from the inlet to the outlet. P sources include atmospheric deposition and release of legacy fertilizer P from wetland sediment as well as mineralization of organic matter. Twenty years after the restoration, PWS continues to export phosphorus to the river, indicating that long time periods at least on the scale of decades may be required for wetland ecosystems to reach equilibrium between P inputs and outputs. Our study clearly demonstrate the need for researching land use history and including soil quality assessment into wetland restoration planning, design and monitoring protocols.