Investigation into Sources of High Nitrate Concentrations in Orange Trail Creek, State Botanical Garden of Georgia David Radcliffe 1 and Karin Lichtenstein 2 Abstract Sampling of the Orange Trail Creek at the State Botanical Gardens by the Upper Oconee Watershed Network in April of 2004 found relatively high concentrations of nitrate- nitrogen. The College of Agricultural and Environmental Sciences subsequently funded a study by UGA scientists to determine the source of nitrate. Seven groundwater monitoring wells were installed in the area surrounding the creek and sampled during the summer of 2005. Soil core samples were taken at each site where monitoring wells were installed and several additional areas where shallow rock prevented installing ground water wells. Additional stream samples were also taken. Nitrate-nitrogen concentrations in the monitoring wells ranged from 4.3 to 19.7 mg/L. It appears that there are three sources of nitrate in the local area. One apparent source is one or more of the four wastewater lagoons at the UGA Swine Farm. The lagoon(s) appear to have leaked wastewater into fractures beneath the lagoon(s) where groundwater moves rapidly to springs that are headwaters of the eastern branches of the Orange Trail Creek. A second apparent source is the spray field at the UGA Swine Farm where wastewater from the lagoons has been applied. Groundwater movement from this area is likely to be the source of high nitrate in the northeastern branch of Orange Trail Creek. A third source appears to be coming from the hill north of Orange Trail Creek where the Poultry Science Complex is located and causing high nitrate concentrations in the north west branch of Orange Trail Creek. The identity of this source is unknown, but it may be poultry litter that was stacked in this area in the past, or wastewater pumped from a lagoon farther north and applied to a spray field on the south face of the hill. The nitrate in the creek and local ground water does not impose a threat to human health in that no drinking wells are installed in this area. However, steps should be taken to reduce nitrate concentrations where Orange Trail Creek enters the Oconee River (a constructed wetland is suggested), to properly close down the lagoons on the Swine Farm, and to identify the exact source of nitrate at the Poultry Science Complex. Background In April of 2004, the Upper Oconee Watershed Network (UOWN) conducted their annual River Rendezvous event where community volunteers collected water samples from local streams. At this event, samples that were taken along the Orange Trail Creek at the State Botanical Gardens contained high levels of nitrate. These findings then sparked a further investigation in which UOWN found that during baseflow conditions two spring-fed locations along Orange Trail Creek had average nitrate levels of 27 mg/L. Nitrate levels 1 Professor, Crop and Soil Sciences Department, University of Georgia 2 Research Technician, Crop and Soil Sciences Department, University of Georgia 1
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Investigation into Sources of High Nitrate Concentrations in Orange Trail Creek, State Botanical Garden of Georgia
David Radcliffe1 and Karin Lichtenstein2
Abstract Sampling of the Orange Trail Creek at the State Botanical Gardens by the Upper Oconee Watershed Network in April of 2004 found relatively high concentrations of nitrate-nitrogen. The College of Agricultural and Environmental Sciences subsequently funded a study by UGA scientists to determine the source of nitrate. Seven groundwater monitoring wells were installed in the area surrounding the creek and sampled during the summer of 2005. Soil core samples were taken at each site where monitoring wells were installed and several additional areas where shallow rock prevented installing ground water wells. Additional stream samples were also taken. Nitrate-nitrogen concentrations in the monitoring wells ranged from 4.3 to 19.7 mg/L. It appears that there are three sources of nitrate in the local area. One apparent source is one or more of the four wastewater lagoons at the UGA Swine Farm. The lagoon(s) appear to have leaked wastewater into fractures beneath the lagoon(s) where groundwater moves rapidly to springs that are headwaters of the eastern branches of the Orange Trail Creek. A second apparent source is the spray field at the UGA Swine Farm where wastewater from the lagoons has been applied. Groundwater movement from this area is likely to be the source of high nitrate in the northeastern branch of Orange Trail Creek. A third source appears to be coming from the hill north of Orange Trail Creek where the Poultry Science Complex is located and causing high nitrate concentrations in the north west branch of Orange Trail Creek. The identity of this source is unknown, but it may be poultry litter that was stacked in this area in the past, or wastewater pumped from a lagoon farther north and applied to a spray field on the south face of the hill. The nitrate in the creek and local ground water does not impose a threat to human health in that no drinking wells are installed in this area. However, steps should be taken to reduce nitrate concentrations where Orange Trail Creek enters the Oconee River (a constructed wetland is suggested), to properly close down the lagoons on the Swine Farm, and to identify the exact source of nitrate at the Poultry Science Complex. Background In April of 2004, the Upper Oconee Watershed Network (UOWN) conducted their annual River Rendezvous event where community volunteers collected water samples from local streams. At this event, samples that were taken along the Orange Trail Creek at the State Botanical Gardens contained high levels of nitrate. These findings then sparked a further investigation in which UOWN found that during baseflow conditions two spring-fed locations along Orange Trail Creek had average nitrate levels of 27 mg/L. Nitrate levels
1 Professor, Crop and Soil Sciences Department, University of Georgia 2 Research Technician, Crop and Soil Sciences Department, University of Georgia
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at the confluence of the Orange Trail Creek and the Oconee River were an average of 7.5 mg/L, far above the average of 1.5 mg/L for streams in the Athens Clarke County region. These preliminary findings along the Orange Trail Creek indicated that possible sources of contamination might be the University of Georgia Swine Farm, the University of Georgia Poultry Farm, and/or an unknown source related to the Botanical Gardens. Thus, further research was needed to identify the exact origin(s) of these contaminants. The College of Agricultural and Environmental Sciences funded an investigation by a group of UGA scientists (see Appendix A) led by Dr. Radcliffe in December, 2004 and work began soon after to determine the locations of the sources of high nitrates. Objectives The primary objectives of this study were to determine and identify the sources of high nitrate concentrations in the Orange Trail Creek in the State Botanical Gardens of Georgia. The long term goal is to prevent the flow of these contaminants into the Oconee River. Methodology The project began, as stated, with the initial sampling by UOWN in April of 2004. Final approval and funding for further investigation was granted for a collaborative effort between the Department of Crop and Soil Sciences, Department of Geology, the Atlanta-based environmental consulting firm Brown and Caldwell, and the State Botanical Gardens of Georgia in December of 2004. A preliminary reconnaissance plan for the field work to determine the sources of nitrate contaminants was completed in April of 2005 with all parties involved. This preliminary plan called for the installation of one-inch diameter temporary monitoring wells at 11 locations throughout the small watershed. GPS points of the location of each site were taken. On May 4 and 5, 2005, temporary wells were installed throughout the watershed and were specifically located downslope from the lagoons at the UGA Swine Farm, in the application fields of the Swine Farm, near the UGA Poultry Complex, near the headwaters of the Orange Trail Creek tributary along the Botanical Gardens Road, and along the western edge of the Creek near the Botanical Garden main buildings (Figure 1). The one-inch diameter monitoring wells were installed using a Geoprobe direct-push rig and provided a range of depths from 1.2 m to 14 m. The wells were sand-packed and sealed with bentonite above the sand pack. In all, three dry wells (where no water was produced) and seven developed wells (where water was produced) were installed. As the wells were installed, soil cores were extracted to the maximum depth of the wells and bagged, labeled and stored for further lab analysis. Initial water samples were retrieved and analyzed for specific conductivity, nitrate-nitrogen, ammonium-nitrogen, and phosphate using an 890 Hach colorimeter with AccuVac ampules.
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On May 18, 2005, six wells were developed (8a, 8b, 5, 6, 1, 2) using 1 meter disposable pvc bailers (Figure 1) and water samples were collected in sterile 500mL bottles. On June 29, 2005, the seventh well (Well 3) was developed and a water sample was collected in a sterile 500mL bottle. On August 26, 2005, six stream samples were taken from the Orange Trail Creek. These were located at the headwater spring, the second bridge along the Orange Trail, at the top of the wetland, at the bottom of the wetland, along a “background” stream that enters the wetland, and along the stream that drains from the UGA Swine Farm (Figure 1). The soil samples that were retrieved from the well installation, along with the water samples, were sent to the UGA Soil, Plant and Water Laboratory (2400 College Station Road, Athens, GA). The soils were analyzed with a KCl extraction in a Perstorp EnviroFlow 3000 Auto Analyzer and a Thermo Jarell-Ash model ICP, for aluminum (Al), boron (B), calcium (Ca), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), molybdenum (Mo), sodium (Na), ammonium-nitrogen (NH4-N), nickel (Ni), nitrate-nitrogen (NO3-N), elemental phosphorus (P), lead (Pb), sulfur (S), and zinc (Zn) in mg/L. The water samples were also analyzed for alkalinity, Al, NH4-N, B, Cd, Ca, carbon dioxide (CO2), chloride (Cl), Cr, specific conductivity, copper (Cu), fluoride (F), Fe, Mg, Mn, Mo, Ni, NO3-N, phosphate (PO4), P, potassium (K), silica (SiO2), sodium (Na), and sulfate (SO4) (mg/L). These analyses were completed using ion chromatography and a colorimetric method on a Dionex DX-100 Ion Chromatograph, the Orion model 162 A Conductance-Resistance Meter, and the Perstorp EnviroFlow 3000 AutoAnalyzer that is equipped with a NH4-N cartridge.
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Figure 1 Map of Well Locations
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Figure 2 Map of Nitrate Concentration
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Results Nitrate-N concentrations from the wells sampled on May 18 (wells 1, 2, 5, 6, 8a, and 8b) and on June 29 (well 3) and from the stream on August 26 are shown in Figure 2 and 3. The well nitrate concentrations range from 4.29 mg/L (well 3) to 19.69 mg/L (well 8a). Background concentrations for nitrate-N are generally considered to be 3 mg/L or less, so only well 3 might be considered background.1 The highest concentration was measured in well 8a (19.69 mg/L), which is located directly downslope from the second lagoon from the north on the UGA Swine Farm. The wells located in and near the application field of the Swine Farm (wells 5, 6) also yielded high nitrate concentrations (8.65 mg/L and 11.93 mg/L). In addition, the wells directly south of the UGA Poultry Farm (wells 1, 2) along the Botanical Gardens Road, yielded high values of nitrate (14.50 mg/L and 10.53 mg/L). The six stream samples also provided a wide range of nitrate values ranging from negligible concentrations to 17.1 mg/L (at the headwaters of the Orange Trail Creek) (Figure 2).
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Figure 3 Nitrate-Nitrogen (mg/L) concentrations in Orange Trail Creek watershed Ammonium concentrations from the well water samples were highest in the wells downslope from the lagoons at the UGA Swine Farm (wells 8a and 8b in Figure 4). In
1 Madison, R.J., and J.O. Brunett. 1985. Overview of the occurrence of nitrate in ground water of the United States. U.S. Geol. Surv. Water Supply Pap. 2275.
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these wells, ammonium concentrations were 4.93 mg/L and 7.29 mg/L, respectively. Ammonium concentrations at the remaining wells were all below 0.50 mg/L.
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Figure 4 Ammonia-Nitrogen (mg/L) concentrations in Orange Trail Creek watershed The soil core data showed a similar pattern to the well water data (Figure 5). The lowest concentrations of nitrate-N were seen in well 3 located downslope of the Botanical Garden buildings. Concentrations in soil cores from this well were generally less 2 mg/L, which can be considered background levels. The soils from the one of the wells downslope from the lagoons at the Swine Farm (well 8a) yielded higher nitrate concentrations, as did the one of the wells near the application field of the Swine Farm (well 5) and the dry well located in southern field of the UGA Poultry Complex (well 12). Ammonium concentrations were also lowest in soil cores from well 3, generally less than 2 mg/L, and these can be considered background concentrations. Ammonium concentrations were high by comparison in the soil columns from the wells located downslope from the Swine Farm lagoons (wells 8a, 8b) (Figure 6). In addition, ammonia concentrations were relatively high throughout the soil columns in the application fields of the Swine Farm (well 5) and at the Poultry Complex ( dry well 12). Yet, the concentrations of ammonia were relatively low in the soils from the wells south of the Poultry Complex (wells 1, 2), with the exception of two depths. Concentrations of copper were highest in the soil columns from the Swine Farm application fields (wells 5, 6) (Figure 7).
Figure 5 Nitrate-Nitrogen (mg/L) concentrations in soil profile from well installations in Orange Trail Creek watershed
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Figure 6 Ammonia-Nitrogen (mg/L) concentrations within soil profiles of wells in Orange Trail Creek watershed
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Figure 7 Copper (mg/kg) concentrations in soil profiles from well installations in Orange Trail Creek watershed
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Discussion The high nitrate concentrations in wells in the area surrounding Orange Trail Creek clearly indicate that groundwater is the source of the nitrate in the stream (and not runoff). This is consistent with the finding that the highest nitrate concentrations in the streams are near the headwaters where springs seem to be present. All of the nitrate concentrations in the stream were similar to the concentrations in the surrounding groundwater wells, with the exception of stream sample E which was below the detection limit (Figure 3). One of the sources appeared to the lagoons at the Swine Farm. Wells down-slope of the second lagoon from the north (wells 8a and 8b) had one of the highest nitrate concentrations. These wells were the only wells with high ammonium concentrations. Since ammonium is a cation with limited mobility in soil and ground water, this probably indicates that lagoon water is leaking through fractures in the bedrock below the lagoons to the headwaters of the stream in this area down-slope of the lagoons. We attempted to install wells immediately downslope (within 30 ft of the edge) of the third lagoon from the north, but encountered hard bedrock at less than 10 ft. The same thing happened when we tried to install a well just north of this lagoon near an area where manure had been composted. Therefore it is very likely that when this lagoon, and perhaps others, were installed the lagoon bottom was very close to bedrock. Ammonium concentrations in the soil at 8a and 8b were not high near the surface, but they increased below the surface. This is evidence that the lagoons were leaking from the bottom into groundwater and not overflowing running off to the stream. The lagoons could cause the high nitrate concentrations seen in the eastern branches of Orange Trail Creek. Another source appeared to be the spray field at the UGA Swine Farm. Well 5 at the edge of the spray field and well 6 down-slope of the spray field had high nitrate concentrations. The soil cores from well 5 also had high ammonium concentrations. The presence of high copper concentrations at these same wells may be due to the addition of copper to swine feed, used as an antibiotic. If the direction of groundwater flow follows surface topography in this area, groundwater from the spray field area would flow to the northeast branch of Orange Trail Creek which starts near the road into the Botanical Gardens (Figure 1 and 2). A third source appeared to be coming from the hill north of Orange Trail Creek where the Poultry Complex is located. The two wells installed upslope of the northwest branch of Orange Trail Creek (wells 1 and 2) had high nitrate concentrations (Figures 2 and 3). There is a ridge that separates the northeast and northwest branches and it is unlikely that groundwater would flow from the Swine Farm spray field area to the northwest branch. Furthermore, the presence of the high nitrate and ammonium concentrations in the soil column from the dry well in the southern field of the Poultry Complex (dry well 12) indicated that there was another source of nitrogen in the area. According to Dr. Michael Lacy, Poultry Science Department Head, poultry litter was stacked in this area during the 1980's when it was made available for nearby garden plots. However, the stacks were
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thought to be along the tree line at the base of the hill and this is down slope of dry well 12. Dr. Lacy also said that wastewater from a poultry lagoon on the north face of this hill was pumped onto a field just to the west of the field where dry well 12 was located, but this only happened about five times. This could also have been a source even though the poultry litter stacks were removed before 1992 and the lagoon wastewater has not been applied to the nearby field since the late 1980's. Groundwater travel times to springs in the Piedmont region can be several decades as shown in a study by Rose (1992)1. Other potential sources of nitrate from the hill to the north concentrations to the Orange Trail Creek watershed that were considered included the UGA landfill located to the northwest of the watershed. However, the landfill is located over a ridge and groundwater in the area flows to the west and not towards the Orange Trail Creek, according to a study by Brown and Caldwell2. The Botanical Gardens complex did not appear to be a source of the high nitrate in Orange Trail Creek in that the well between the creek and the complex (well 3) had the lowest nitrate concentration observed in the groundwater wells (Figures 2 and 3). Also, the land to the south of the UGA Swine Farm did not appear to be a source in that the southeastern branch of Orange Trail Creek had nitrate concentrations below detection (stream sample E, Figures 2 and 3). Regulatory Framework The nitrate concentrations in the groundwater do not represent a threat to human health in that there are no drinking wells installed in this area (the EPA limit on nitrate-nitrogen concentrations in drinking water is 10 mg/L). Furthermore, no state regulations have been violated that we are aware of in that at the time Swine Farm lagoons were installed (1971-1984), there was no requirement for installing liners to prevent leakage. Current state regulations for swine operations vary depending on the size of the operation and whether it is a new or existing operation. The primary requirement for the UGA Swine Farm is to implement a comprehensive nutrient management plan, which it does. Recommendations The primary objective for future work in this watershed should be to stop the contaminant source before it reaches the Oconee River. This could be done in part by restoring the wetland that once existed at the confluence of the Orange Trail Creek and the Oconee River. The Swine Farm lagoons should be closed as soon as possible using the practices recommended by the Natural Resource Conservation Service for decommissioning lagoons. Furthermore, the swine operations should be moved as soon as possible to the new farm being developed by the College of Agricultural and Environmental Sciences. Lastly, the exact source of nitrate that appears to be somewhere within Poultry Science
1 Rose, S. 1992. Tritium in groundwater of the Georgia Piedmont: Implications for recharge and flow paths. Hydrological Processes. 6:67-78. 2 Brown and Caldwell. 1996. Bedrock Characterization Study; Milledge Avenue Site, University of Georgia.
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complex should be identified. This could probably be done with additional soil sampling of the area.
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Appendix A: Participating Scientists Jim Affolter, Associate Professor, Horticulture and Botanical Gardens Research
Coordinator Mark Bakker, Associate Research Scientist, Biological and Agricultural Engineering Thomas Bass, Program Specialist, Biological and Agricultural Engineering Robert Dove, Associate Professor, Animal and Dairy Sciences John Dowd, Assistant Professor, Geology Rhett Jackson, Associate Professor, Warnell School of Forest Resources Maria Khun, Laboratory Manager, Environmental Safety Division Karin Lichtenstein, Research Technician, Crop and Soil Sciences Steve Nickerson, Professor, Animal and Dairy Sciences Valentine Nzengung, Associate Professor, Geology David Radcliffe, Professor, Crop and Soil Sciences Todd Rassmussen, Associate Professor, Warnell School of Forest Resources Mark Risse, Associate Professor, Biological and Agricultural Engineering Jill Stachura, Senior Scientist, Brown and Caldwell David Wenner, Associate Research Scientist, Geology