Preliminary Assessment of Sediment Phosphorus Flux at Beaver Lake, Arkansas

1. Preliminary Assessment of Sediment Phosphorus Flux at Beaver Lake, Arkansas S. Sen1, B.E. Haggard2, I. Chaubey1, M. D. Matlock1, T. A. Costello1, and K. R. Brye3 Ecological Engineering Group 1 Biological & Agricultural Engineering Department, University of Arkansas, Fayetteville, AR, USA. 2 USDA-ARS, Poultry Production & Safety Research Unit, Fayetteville, AR, USA. 3 Crop, Soil & Environmental Sciences Department, University of Arkansas, Fayetteville, AR, USA. Results Anaerobic Aerobic Objectives (b) (a) The overall goal of this study was to measure internal sediment phosphorus flux in Beaver Lake. Specifically, our objectives were to (a) evaluate sediment P flux under aerobic and anaerobic conditions, (b) evaluate temporal and spatial variability of sediment P flux, (c) estimate the effect of alum treatment on sediment P flux. Figure 1. Location of the Beaver Lake watershed, (a) major sub-watersheds, (b) sampling sites, and the land use categories within the watershed Figure 5.Soluble reactive phosphorus concentrations under aerobic and anaerobic conditions with incubation time in the overlying water of the intact sediment cores from three sites in Beaver Lake for summer, 2003. Introduction Beaver Lake is a multi-purpose reservoir constructed in 1963 on the White River in northwestern Arkansas (Figure 1). This impoundment is operated by the U.S. Army Corps of Engineers for the purposes of hydroelectric power, flood control, and recreation. The reservoir is the main drinking water supply for 250,000 people in the northwestern Arkansas. The primary inflows to Beaver Lake include the White River, Richland Creek, Brush Creek, and War Eagle; several other smaller tributaries also are inflows. The average total phosphorus (TP) load into Beaver Lake is 75 Mg yr-1, and the White River contributes ~62% of the overall load (Haggard et al., 2003) (Table 1). Approximately, 65% of the TP entering the reservoir is in the soluble form (Haggard et al., 2003), which is considered to be available for algae growth. Aerobic Methods Anaerobic • Six intact sediment cores (generally < 50-cm in length) were collected at each site using acrylic Plexiglas tube (6.35 cm x 100 cm long) by skilled scuba divers (Figure 2) . • Upon return to the lab, the volume of overlying water was adjusted to one liter in the intact sediment water column and cores were wrapped with aluminum (Al) foil to avoid exposure of light (Figure 3). • The overlying water was aerated with aquarium pumps via Tygon tubing under aerobic condition (air) and anaerobic condition (N2 gas with 330 ppm CO2) (Figure 3). • A 60-mL aliquot was removed from each core for five consecutive days, and then for every other day for two weeks, and 20-mL was filtered using 0.45 micron filter, acidified to pH 2 with HCl and analyzed for soluble reactive phosphorus (SRP). • The amount of water removed for these samples was replaced by filtered lake water of known dissolved P composition to maintain a constant volume (1 L) of overlying water. • Sediment P flux (mg m-2 d-1) was calculated based on the change of SRP concentration (corrected for replacement of lake water) in the overlying water column divided by the surface area of the sediment core incubation system (0.0032 m2) and the number of incubation days (~ 21 days). • All cores from fall sampling were treated with alum (Al2(SO4)3. 14H2O) dose estimated based on the internal P flux from sediment (James, and Barko, 1999) (Site 1: 0.05g; Site 2: 0.25 g; Site 3: 0.10 g alum) and incubated again for 21 d under aerobic or anaerobic conditions (Figure 4). Figure 6.Soluble reactive phosphorus concentrations under aerobic and anaerobic conditions with incubation time in the overlying water of the intact sediment cores from three sites in Beaver Lake for fall, 2003 (before alum treatment). Table 1. Estimated Soluble Reactive Phosphorus and Total Phosphorus loading from four sub-watersheds in the Beaver Lake watershed for 1993-1995 (Haggard et al., 2003). Anaerobic Aerobic Recently, the Beaver Water District has become concerned with episodic taste and odor problems in the drinking water produced from Beaver Lake. These concerns and other scientific interests prompted several investigations into Beaver Lake. The purpose of this study was to evaluate the ability of bottom sediments in Beaver Lake to release P. Specifically, we quantified sediment P flux under aerobic and anaerobic conditions at three sites at Beaver Lake; these sampling locations were located in the lacustrine (Site 1), transitional (Site 2) and riverine zones (Site 3) of the reservoir (Figure 1). One sediment station was selected in each zone of the reservoir because a pronounced trophic gradient exists in Beaver Lake from the headwaters to the reservoir (Haggard et al., 1999). Several studies have shown that internal P loads are a significant P source (Table 2) and have maintained eutrophic conditions in some lakes and reservoirs even after external sources have been reduced (Van der Molen and Boers, 1994). The typical range for sediment P flux is 0.03 – 5.71 mg m-2 d-1 under anaerobic condition and 2.78 – 32.00 mg m-2 d-1 under aerobic condition (Table 2). Figure 7.Soluble reactive phosphorus concentrations under aerobic and anaerobic conditions with incubation time in the overlying water of the intact sediment cores from three sites in Beaver Lake for summer, 2003 (after alum treatment). Table 3. Spatial and temporal variability in sediment average P flux (mg m-2 d-1) at three different zones of Beaver Lake under aerobic and anaerobic conditions. Summary • SRP concentration in the overlying water showed no consistent trend during • aerobic conditions, but generally increased with time under anaerobic • conditions (Figure 5-7) • Sediment P flux was greater under anaerobic conditions compared to aerobic conditions (Table 3) • - 8 times greater than under anaerobic conditions during summer • - 3 times greater than under anaerobic conditions during fall • Results from intact sediment-water columns at Beaver Lake were similar to • those reported in other lakes and reservoirs (Table 2&3) • Spatial variability in sediment P flux existed in this preliminary study (Table 3) • - variability was greatest under anaerobic conditions • - P release was greatest at the transitional zone • Alum treatment was an effective control over sediment P flux (Figure 5-7) • - despite initial increase in SRP concentration of the overlying water, final SRP concentrations after 21 d of incubation were similar to initial conditions • - sediments and alum flocculate actually adsorb P from the overlying water in the intact sediment-water columns after alum treatment Table 2. Phosphorus release rate estimates under aerobic and anaerobic conditions (mg m-2 d-1) at different lakes as collected from literature around the North America and different parts of the World. Negative sign indicates adsorption of P by the sediments. Figure 2.Intact sediment cores collection by the Scuba divers at Beaver Lake, spring 2004. Figure 3. Intact sediment cores wrapped with Al foil under aerobic and anaerobic conditions at USDA-ARS laboratory at University of Arkansas. References Bannerman, R. T., D. E. Armstrong, G. C. Holdren, R. F. Harris. 1974. Phosphorus mobility in Lake Ontario sediments. Proc. 17th Conf. Great Lakes Reservoirs. p. 158-178. Burns, N. M., and C. Ross. 1972. Project Hypo. CCIW paper 6, and U. S. EPA Tech. Report TS-05071-208-24. Cooke, G. D., M. R. McComas, D. W. Waller, and R. H. Kennedy. 1977. The occurrence of internal phosphorus loading in two small eutrophic glacial lakes in northeastern Ohio. Hydrobiologia 56: 129-135. Diederik T. van der Molen, and Paul C. M. Boers. 1994. Influence of internal loading on phosphorus concentration in shallow lakes before and after reduction of the external loading. Hydrobiologia 275/276: 379-389. Dillon, P. J. 1975. The phosphorus budget of Cameron Lake, Ontario: The importance of flushing rate to the degree of eutrophy of lakes. Limnology Oceanography 20: 28-39. Haggard, B. E., P. A. Moore Jr., and P. B. Delaune. 2004. Phosphorus flux from reservoir bottom sediments in Lake Eucha, Okalahoma. Haggard, B. E., P. A. Moore, I. Chaubey, and E. H. Stanley. 2003. Nitrogen and phosphorus concentrations export from an Ozark Plateau catchment in the United States. Biosystems Engineering 86 (1): 75-85. Haggard, B.E., Jr., P.A. Moore, T.C. Daniel, and D.R. Edwards. 1999. Trophic Conditions and Gradients in the Headwater reaches of Beaver Lake, Arkansas: Proceedings of the Okalahoma Academy of Sciences 79: 73-84. Holdren, G. C., and D. E. Armstrong. 1980. Factors affecting phosphorus release from intact lake sediment cores. J. Environmental Quality 14: 79-87. James, William F., and John W. Barko. 2003. ERDC WQTN-PD-13. Online [http://libweb.wes.army.mil/uhtbin/hyperion/WOTN-PD-13.pd] August 2003. James, W. F., J. W. Barko, and H. L. Eakin. 1995. Internal phosphorus loading in Lake Pepsin, Upper Mississippi River. Freshwater Ecology, 10 (3): 269-276. Kim, L. H., E. Choi, and M. K. Stenstrom. 2003. Sediment characteristics, phosphorus types and phosphorus release rates between river and lake sediments. Chemosphere 50: 53-61. Lennox, L. J. 1984. Lough Ennel: Laboratory studies on sediment phosphorus release under varying mixing, aerobic and anaerobic conditions. Freshwater Biol. 14: 183-187. Moore, P.A. Jr., and K.R. Reddy. 1994. Role of Eh and pH on phosphorus geochemistry on sediments of Lake Okeechobee, Florida. J. Environmental Quality 23:955-964. Moore, P.A. Jr., K.R. Reddy, and D.A. Graetz. 1991. Phosphorus geochemistry in the sediment – water column of a hypereutrophic lake. J. Environmental Quality 20:869-875. Reckhow, K. H. 1977. Phosphorus models of lake management . Ph. D. thesis, Harvard Univ. 304 p. Sonzogni, W. C. 1974. Effect of nutrient input reduction on the eutrophication of the Madison lakes. Ph.D. thesis, Univ. Wisconsin. 342 p. Theis, T. L., and P. J. McCabe. 1978. Retardation of sediment phosphorus release by fly ash application. J. Water Pollut. Contr. Fed. 50: 2666-2676. Acknowledgement • This research in part is funded by the Arkansas Soil and Water Conservation Commission, the U. S. Environmental Protection Agency and the U.S. Department of Agriculture. • We highly appreciate the valuable help in field sampling and lab work by Stephanie • Williamson, Ray Avery and Anna Erickson at the USDA-ARS Poultry Waste and Water Quality Laboratory, Fayetteville, Arkansas. Figure 4. Alum treated intact sediment core collected by the Scuba divers at Beaver Lake, Fall 2003.