Potential effects of sediment dredging on internal phosphorus loading in a shallow, subtropical lake
Document Type
Article
Publication Date
1-1-2007
Abstract
Long-term phosphorus (P) loading to lakes has resulted in accumulation of P in sediments. Internal nutrient loading from sediments of shallow lakes such as Lake Okeechobee, Florida, has become a major concern in restoration programs. The objectives of this study were to determine (1) the potential impact of dredging on dissolved reactive P (DRP) flux out of sediments and (2) the equilibrium P concentration (EPCw) of post-dredge sediments. Intact sediment cores from one location representing P-laden mud sediments of the lake were obtained. Four simulated dredging treatments were implemented: control (no dredging-current conditions); top 30 cm; 45 cm; and 55 cm sediment removal. Phosphorus release/retention characteristics of sediments were determined at water-column DRP concentrations of 0, 0.016, 0.032, 0.064, and 0.128 mg/L. The water column in each core was replaced at approximately 60-day intervals, for a period of 1.2 years, with fresh lake water spiked with respective P concentrations. Significant decreases in water column DRP were observed only in sediment cores with 0–30 cm dredging. At ambient water column DRP levels, the P fluxes during the first 32 days were 0.4, 0.1, 0.4 and 0.2 mg P/m2/day for the 0, 30, 45, and 55 cm dredging treatments, respectively, and accounted for 11–38% of total P released during the 431 day study. At the end of the 1.2-year study, estimated EPCw were on the order of 0.033, 0.008, 0.022, and 0.037 mg P/L for 0, 30, 45 and 55 cm dredging treatments, respectively. Dredging the top 55 cm sediments would result in the removal of approximately 123 g P/m2, as compared to 80 and 108 g P/m2 for 30 and 45 cm dredging, respectively. Laboratory experiments suggest that dredging can reduce internal P loading. However, further evaluation is needed to determine the extent to which the controlled laboratory experiments can be used to predict fluxes in the lake under natural conditions, and the long-term sustainability of improving water quality by dredging. © 2007 Taylor & Francis Group, LLC.
Publication Source (Journal or Book title)
Lake and Reservoir Management
First Page
27
Last Page
38
Recommended Citation
Reddy, K., Fisher, M., Wang, Y., White, J., & James, R. (2007). Potential effects of sediment dredging on internal phosphorus loading in a shallow, subtropical lake. Lake and Reservoir Management, 23 (1), 27-38. https://doi.org/10.1080/07438140709353907