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bromide ratios in leachate derived from farm-animal waste
Environmental Pollution 121 (2003) 23–25 www.elsevier.com/locate/envpol
Chloride/bromide ratios in leachate derived from farm-animal waste Paul F. Hudak* Department of Geography and Environmental Science Program, University of North Texas, PO Box 305279, Denton, TX 76203-5279, USA Received 14 November 2001; accepted 3 April 2002
‘‘Capsule’’: Results have important implications for identifying animal sources of contaminated groundwater.
Abstract Ratios of conservative chemicals have been used to identify sources of groundwater contamination. While chloride/bromide ratios have been reported for several common sources of groundwater contamination, little work has been done on leachate derived from farm-animal waste. In this study, chloride/bromide ratios were measured in leachate derived from longhorn-cattle, quarterhorse, and pygme-goat waste at a farm in Abilene, Texas, USA. (Minimum, median, and maximum) chloride/bromide ratios of (66.5, 85.6, and 167), (119, 146, and 156), and (35.4, 57.8, and 165) were observed for cattle, horses, and goats, respectively. These ratios are below typical values for domestic wastewater and within the range commonly observed for oilfield brine. Results of this study have important implications for identifying sources of contaminated groundwater in settings with significant livestock and/or oil production. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: Chloride/bromide ratios; Animal waste; Groundwater
1. Introduction Numerous natural and anthropogenic sources can contaminate groundwater. Effective aquifer remediation requires removing or controlling these contaminant source(s). However, identifying actual contaminant sources can be challenging in settings where many sources could have impacted the groundwater. Because they remain essentially constant from sources to receptors, ratios of conservative chemicals can be useful for identifying sources of contaminated groundwater. Several investigators have used chloride/bromide ratios for this purpose. Recent examples include Davis et al. (1998), Vengosh and Pankratov (1998), Andreasen and Fleck (1997), Whittemore (1995), and references therein. Davis et al. (1998) reviewed chloride/bromide ratios from studies at several places worldwide. They concluded that, in general, chloride/bromide ratios ranged from 50 to 150 in atmospheric precipitation, 300 to 600 in domestic sewage, 1000 to 10,000 in dissolved evapor-
* Corresponding author. Tel.: +1-940-565-4312; fax: +1-940-5654297. E-mail address: [email protected] (P.F. Hudak).
ites, and 10 to 100 in urban runoff. Observations for oilfield brine (relics of evaporated seawater) varied widely, but were typically in the range 100–300. Presentday seawater has a chloride/bromide ratio of approximately 290 (Hem, 1992). Vengosh and Pankratov (1998) reported slightly higher chloride/bromide ratios for domestic wastewater in Israel (ranging from 410 to 873, with a mean of 732). While chloride and bromide have similar chemical characteristics, chloride is much more prevalent in the environment and more frequently reported in water analyses. Despite infrequent reporting of bromide, there is a growing database of chloride/bromide ratios for domestic wastewater. However, the author could find no reports of chloride/bromide ratios in leachate derived from farm-animal waste. This is a significant research gap because animal-waste can potentially contaminate groundwater, especially in livestock farms above shallow aquifers. Potential sources of animal waste include unpaved feedlot floors, runoff holding ponds, manure treatment and storage lagoons, and manure stockpiles (Sweeten, 1992). The purpose of this study was to measure chloride and bromide concentrations and calculate chloride/bromide ratios in leachate derived from farm-animal waste.
0269-7491/03/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S0269-7491(02)00211-7
24
P.F. Hudak / Environmental Pollution 121 (2003) 23–25
2. Methods
3. Results and discussion
Fifteen manure samples were collected from longhorn cattle, quarter horses, and pygmy goats at a farm in Abilene, Texas, USA (Fig. 1). The horses consumed coastal bermudagrass and sweet feed (primarily oats, corn, and molasses). Cattle consumed coastal bermudagrass, millet, and creep feed (primarily corn, oats, cottonseed, and molasses). The goats also consumed coastal bermudagrass, along with sheep and goat feed (primarily corn, oats, and barley). Samples were sealed in plastic bags and transported to a research lab, where they were removed and immersed in beakers of distilled water for 6 days. Subsequently, leachates were filtered from the beakers, boiled, and delivered to an analytical lab certified by the State of Texas and United States Environmental Protection Agency (EPA). Leachates were analyzed following EPA Method 9056, ion chromatography.
Table 1 summarizes chloride/bromide ratios measured in the leachate samples. A Kruskal–Wallis (non-parametric ANOVA) test showed no significant difference (H=4.25, P=0.120) among median chloride/bromide ratios for cattle, horses, and goats. However, all of the animal observations were significantly lower than typical values reported for domestic wastewater. Higher chloride/bromide ratios in domestic wastewater reflect heavy usage of chloride salts as food preservatives and seasonings. Two important inferences can be drawn from these results. First, assuming that animal waste yields chloride/bromide ratios in water that are similar to those in domestic sewage is invalid. Such assumptions could lead to erroneous interpretations of contaminant sources and inadequate aquifer remediation schemes. For example, an investigator who measured chloride/bromide ratios in the 100–200 range, and who assumed any contamination from feedlots would be manifested by much higher ratios in groundwater, might fail to consider feedlots a plausible contaminant source. Second, farm-animal waste yields chloride/bromide ratios similar to those reported for oilfield brine. Thus, chloride/bromide ratios cannot distinguish between oilfield brine and animal waste as sources of groundwater contamination. This is an important consideration for agricultural areas which produce livestock as well as oil and gas. Many examples can be found in Texas, USA. This study contributes one set of data to what will hopefully be a growing database of chloride/bromide ratios in water impacted by animal waste. Site-specific conditions including diet will undoubtedly influence ratios reported in future studies. Ultimately, a large database assembled from several studies worldwide could be a valuable tool for identifying sources of groundwater contamination, especially in rural or agricultural settings. For example, if nitrate was found in groundwater, one could compare measured chloride/ bromide ratios to those established for farm-animal waste, and thus determine whether animal waste was a potential source, or whether the investigation should focus on alternative nitrate sources such as septic systems or crop fertilizer.
Fig. 1. Location map showing Abilene (dot) and outline of Texas, USA.
Table 1 Observed chloride/bromide ratios
Median Mean S.D.b
Cattle
Horses
Goats
80.2 >93.0a 66.5 167 91.0
146 149 156 119 139
165 57.8 35.4 61.8 37.9
85.6a 101 45.0
146 142 14.1
57.8 71.6 53.5
a Bromide not detected ( <0.05 mg/l) in one sample. Median=91.0 including this sample. b S.D., standard deviation.
References Andreasen, D.C., Fleck, W.B., 1997. Use of bromide:chloride ratios to differentiate potential sources of chloride in a shallow, unconfined aquifer affected by brackish-water intrusion. Hydrogeology Journal 5 (2), 17–26. Davis, S.N., Whittemore, D.O., Fabryka-Martin, J., 1998. Uses of chloride/bromide ratios in studies of potable water. Ground Water 36 (2), 338–350. Hem, J.D., 1992. Study and interpretation of the chemical character-
P.F. Hudak / Environmental Pollution 121 (2003) 23–25 istics of natural water. United States Geological Survey Water Supply Paper 2254, 1–263. Sweeten, J.M., 1992. Groundwater Quality Protection for Livestock Feeding Operations. Texas Agricultural Extension Service, College Station, TX. Vengosh, A., Pankratov, I., 1998. Chloride/bromide and chloride/
25
fluoride ratios of domestic sewage effluents and associated contaminated groundwater. Ground Water 36 (5), 815–824. Whittemore, D.O., 1995. Geochemical differentiation of oil and gas brine from other saltwater sources contaminating water resources: Case studies from Kansas and Oklahoma. Environmental Geosciences 2 (1), 15–31.
Chloride/bromide ratios in leachate derived from farm-animal waste Paul F. Hudak* Department of Geography and Environmental Science Program, University of North Texas, PO Box 305279, Denton, TX 76203-5279, USA Received 14 November 2001; accepted 3 April 2002
‘‘Capsule’’: Results have important implications for identifying animal sources of contaminated groundwater.
Abstract Ratios of conservative chemicals have been used to identify sources of groundwater contamination. While chloride/bromide ratios have been reported for several common sources of groundwater contamination, little work has been done on leachate derived from farm-animal waste. In this study, chloride/bromide ratios were measured in leachate derived from longhorn-cattle, quarterhorse, and pygme-goat waste at a farm in Abilene, Texas, USA. (Minimum, median, and maximum) chloride/bromide ratios of (66.5, 85.6, and 167), (119, 146, and 156), and (35.4, 57.8, and 165) were observed for cattle, horses, and goats, respectively. These ratios are below typical values for domestic wastewater and within the range commonly observed for oilfield brine. Results of this study have important implications for identifying sources of contaminated groundwater in settings with significant livestock and/or oil production. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: Chloride/bromide ratios; Animal waste; Groundwater
1. Introduction Numerous natural and anthropogenic sources can contaminate groundwater. Effective aquifer remediation requires removing or controlling these contaminant source(s). However, identifying actual contaminant sources can be challenging in settings where many sources could have impacted the groundwater. Because they remain essentially constant from sources to receptors, ratios of conservative chemicals can be useful for identifying sources of contaminated groundwater. Several investigators have used chloride/bromide ratios for this purpose. Recent examples include Davis et al. (1998), Vengosh and Pankratov (1998), Andreasen and Fleck (1997), Whittemore (1995), and references therein. Davis et al. (1998) reviewed chloride/bromide ratios from studies at several places worldwide. They concluded that, in general, chloride/bromide ratios ranged from 50 to 150 in atmospheric precipitation, 300 to 600 in domestic sewage, 1000 to 10,000 in dissolved evapor-
* Corresponding author. Tel.: +1-940-565-4312; fax: +1-940-5654297. E-mail address: [email protected] (P.F. Hudak).
ites, and 10 to 100 in urban runoff. Observations for oilfield brine (relics of evaporated seawater) varied widely, but were typically in the range 100–300. Presentday seawater has a chloride/bromide ratio of approximately 290 (Hem, 1992). Vengosh and Pankratov (1998) reported slightly higher chloride/bromide ratios for domestic wastewater in Israel (ranging from 410 to 873, with a mean of 732). While chloride and bromide have similar chemical characteristics, chloride is much more prevalent in the environment and more frequently reported in water analyses. Despite infrequent reporting of bromide, there is a growing database of chloride/bromide ratios for domestic wastewater. However, the author could find no reports of chloride/bromide ratios in leachate derived from farm-animal waste. This is a significant research gap because animal-waste can potentially contaminate groundwater, especially in livestock farms above shallow aquifers. Potential sources of animal waste include unpaved feedlot floors, runoff holding ponds, manure treatment and storage lagoons, and manure stockpiles (Sweeten, 1992). The purpose of this study was to measure chloride and bromide concentrations and calculate chloride/bromide ratios in leachate derived from farm-animal waste.
0269-7491/03/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S0269-7491(02)00211-7
24
P.F. Hudak / Environmental Pollution 121 (2003) 23–25
2. Methods
3. Results and discussion
Fifteen manure samples were collected from longhorn cattle, quarter horses, and pygmy goats at a farm in Abilene, Texas, USA (Fig. 1). The horses consumed coastal bermudagrass and sweet feed (primarily oats, corn, and molasses). Cattle consumed coastal bermudagrass, millet, and creep feed (primarily corn, oats, cottonseed, and molasses). The goats also consumed coastal bermudagrass, along with sheep and goat feed (primarily corn, oats, and barley). Samples were sealed in plastic bags and transported to a research lab, where they were removed and immersed in beakers of distilled water for 6 days. Subsequently, leachates were filtered from the beakers, boiled, and delivered to an analytical lab certified by the State of Texas and United States Environmental Protection Agency (EPA). Leachates were analyzed following EPA Method 9056, ion chromatography.
Table 1 summarizes chloride/bromide ratios measured in the leachate samples. A Kruskal–Wallis (non-parametric ANOVA) test showed no significant difference (H=4.25, P=0.120) among median chloride/bromide ratios for cattle, horses, and goats. However, all of the animal observations were significantly lower than typical values reported for domestic wastewater. Higher chloride/bromide ratios in domestic wastewater reflect heavy usage of chloride salts as food preservatives and seasonings. Two important inferences can be drawn from these results. First, assuming that animal waste yields chloride/bromide ratios in water that are similar to those in domestic sewage is invalid. Such assumptions could lead to erroneous interpretations of contaminant sources and inadequate aquifer remediation schemes. For example, an investigator who measured chloride/bromide ratios in the 100–200 range, and who assumed any contamination from feedlots would be manifested by much higher ratios in groundwater, might fail to consider feedlots a plausible contaminant source. Second, farm-animal waste yields chloride/bromide ratios similar to those reported for oilfield brine. Thus, chloride/bromide ratios cannot distinguish between oilfield brine and animal waste as sources of groundwater contamination. This is an important consideration for agricultural areas which produce livestock as well as oil and gas. Many examples can be found in Texas, USA. This study contributes one set of data to what will hopefully be a growing database of chloride/bromide ratios in water impacted by animal waste. Site-specific conditions including diet will undoubtedly influence ratios reported in future studies. Ultimately, a large database assembled from several studies worldwide could be a valuable tool for identifying sources of groundwater contamination, especially in rural or agricultural settings. For example, if nitrate was found in groundwater, one could compare measured chloride/ bromide ratios to those established for farm-animal waste, and thus determine whether animal waste was a potential source, or whether the investigation should focus on alternative nitrate sources such as septic systems or crop fertilizer.
Fig. 1. Location map showing Abilene (dot) and outline of Texas, USA.
Table 1 Observed chloride/bromide ratios
Median Mean S.D.b
Cattle
Horses
Goats
80.2 >93.0a 66.5 167 91.0
146 149 156 119 139
165 57.8 35.4 61.8 37.9
85.6a 101 45.0
146 142 14.1
57.8 71.6 53.5
a Bromide not detected ( <0.05 mg/l) in one sample. Median=91.0 including this sample. b S.D., standard deviation.
References Andreasen, D.C., Fleck, W.B., 1997. Use of bromide:chloride ratios to differentiate potential sources of chloride in a shallow, unconfined aquifer affected by brackish-water intrusion. Hydrogeology Journal 5 (2), 17–26. Davis, S.N., Whittemore, D.O., Fabryka-Martin, J., 1998. Uses of chloride/bromide ratios in studies of potable water. Ground Water 36 (2), 338–350. Hem, J.D., 1992. Study and interpretation of the chemical character-
P.F. Hudak / Environmental Pollution 121 (2003) 23–25 istics of natural water. United States Geological Survey Water Supply Paper 2254, 1–263. Sweeten, J.M., 1992. Groundwater Quality Protection for Livestock Feeding Operations. Texas Agricultural Extension Service, College Station, TX. Vengosh, A., Pankratov, I., 1998. Chloride/bromide and chloride/
25
fluoride ratios of domestic sewage effluents and associated contaminated groundwater. Ground Water 36 (5), 815–824. Whittemore, D.O., 1995. Geochemical differentiation of oil and gas brine from other saltwater sources contaminating water resources: Case studies from Kansas and Oklahoma. Environmental Geosciences 2 (1), 15–31.