The Environmentalist 16, 307-312 (1996)
Nitrate levels in shallow groundwater of upstate New York, USA GLENN R. HARRIS*, BRIAN D. HENRY AND JEFFREY S. DEYETTE St. Lawrence University, Canton, NY 13617, USA This paper summarizes research evaluating nitrate levels in shallow groundwater of upstate New York, USA. Water from abandoned dug wells in six different land-use categories was analyzed for nitrate. Findings indicate that regardless of overlying land-use, shallow groundwater is susceptible to high levels of nitrate. Over 60 percent of the water samples tested, including at least one sample from each land-use category, had nitrate levels in excess of the United States drinking water standard of 10 mg I"I. Due to the potential threat of elevated nitrate levels, efforts should be made to eliminate abandoned dug wells in shallow groundwater as a source of water supply. Introduction
In St Lawrence County, New York, USA, most rural homes use private wells which are not tested regularly by any public health or environmental agency. This situation leaves residents susceptible to a number of harmful health effects if contaminants in drinking water unknowingly exceed current drinking water standards. The purpose of this paper is to summarize research evaluating nitrate levels in shallow groundwater in this largely rural and sparsely populated region. The most publicized health effect from exposure to nitrates is methemoglobinemia. This disorder of the bloodstream is particularly dangerous for infants, and is therefore often called blue-baby syndrome (Johnson and Kross, 1990). There have been recent cases of methemoglobinemia in infants reported in Iowa and Wisconsin (Knobeloch et aL, 1993; Kross et al., 1993). In response to this possible health effect, the United States Environmental Protection Agency (EPA) has established a maximum contaminant level (reel) for nitrate in drinking water at 10 mg 1-1 . Stomach cancer is a second possible health risk (Cuello et aL, 1976; Fraser et aL, 1980; Forman et aL, 1985). Although the EPA indicates that there is insufficient information to determine a *Glenn Harris is with the Environmental Studies Programme of S't Lawrence University in Canton, New York. Brian Henry is with the Department of Entomology at the University of Georgia in Athens, Georgia. Jeffrey Deyette is with the joint International Relations and Resource and Environmental Management Programme at Boston University in Boston, Massachusetts. This research was performed as a Community Service Project sponsored by the Mergardt Fund while Mr Henry and Mr Deyette were students under the supervision of Dr Harris at St Lawrence University. Correspondence and offprint requests should be addressed to Glenn Harris.
0251-1088 © 1996 Chapman & Hall
correlation between nitrates and stomach cancer, these studies suggest that such a link does exist. Other possible effects of nitrate exposure from drinking water include birth defects, stupor and coma (Knobeloch et aL, 1993). Nitrates can contaminate groundwater from both natural and human sources. In predominantly agricultural areas, such as St Lawrence County, major sources include chemical fertilizers, home sewage, feedlots and surface water runoff (Johnson and Kross, 1990). Wells are located in a variety of landuses in St Lawrence County: residential yards, ham yards, cropland, pasture and abandoned agricultural land reverting back to brush via ecological succession. Specific land-use practices can have a significant impact on groundwater quality. For example, livestock grazing and the landspreading of fertilizers can result in the distribution of chemicals that could pollute groundwater. Previous studies have demonstrated a correlation between nitrate levels in groundwater and various land-use categories. A 1993 United States Geological Survey (USGS) report on groundwater in east-central Minnesota documented a correlation between nitrate levels and overlying land-use. In this study 100 wells in four land-use categories (undeveloped sites, non-irrigated cultivated sites, irrigated sites and residential sites) were sampled and analyzed for nitrate concentrations. It was found that nitrate concentrations at non-irrigated cultivated sites (median 2.0 mg 1-1) were greater than levels at undeveloped sites (median less than 0.2 mg 1-1) (Anderson, 1993). Beck et al. (1985) tested 34 wells in southwest Georgia to determine the relationship between nitrate levels and land-uses such as forest, wetland and agriculture. They found higher nitrate concentrations in agricultural lands (4--6 mg 1-1) than in wells located in forest-covered areas (less than 1 mg 1-I) (Beck et aL, 1985). Our investigation focused on the relationship 307
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Fig. 1. Dug well located in pasture for dairy cattle and sheep, St Lawrence County, New York State.
Fig. 2. Dug well surrounded by cropland of corn and alfalfa, St Lawrence County, New York State.
between land-use activity and nitrate levels in shallow groundwater. Published literature indicates that nitrate has become a prevalent contaminant in shallow groundwater. The 1993 east-central Minnesota study found that concentrations of nitrates are greatest near the water table and decrease with the depth of the groundwater (Anderson, 1993). Additionally, in a recent survey of well water quality across the state of Iowa, investigators reported that the average nitrate concentration in wells less than 15 m deep was 11.2 mg 1-I, with 35 percent in excess of the reel (Kross et al., 1993). Similarly, research in two counties of New Jersey, USA, revealed higher levels of nitrates in wells less than 15 m than in wells between 15 and 30 m (median 4.15 mg 1-l compared to 0.30 mg 1-t), with even lower concentrations in wells more than 30 m deep (median 0.10 mg 1-1 ) (Murphy, 1992).
into deeper aquifers of both surficial and bedrock geology. In all, 23 shallow wells that fit into several categories of land-use (abandoned agricultural land, pasture (Fig. 1), cropland (Fig. 2), barnyard, residential yard and commercial land) were chosen for study. The depth to groundwater ranged between 0.3 and 10.2 m (Fig. 3). The authors selected abandoned wells, in order to provide easy access to the groundwater for sampling purposes. Often, these wells were located in the vicinity of shallow wells still in use for water supply. Two sets of water samples were taken; the first on 6 and 13 October 1993 and the second on 10 November 1993. Water was collected from wells using a LamottT M sampler (Fig. 4) and returned to the laboratory for nitrate analysis on the same day. Nitrate analysis was performed using a Bausch and LombTM spectrophotometer. Nitraver-five was added to the water samples in order to determine the amount of nitrate present. Light transmittance was recorded and then converted to mg 1-1 of nitrate. The data were analyzed using analysis of variance (ANOVA) to determine if groundwater quality varied as a function of overlying land-use. In addition, pairwise testing of intermediary values was performed for all possible combinations of land-use.
Methods In the nineteenth and early twentieth centmfies, the water needs of both human and livestock populations relied on dug wells in the glacial deposits of St Lawrence County. In some, but not all, situations these wells have since been replaced by wells drilled 308
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Nitrate levels in shallow groundwater of upstate New York, USA
Fig. 3. Dug well showing construction with large boulders. Shallow groundwater approximately six feet (2 m) below ground surface, St Lawrence County, New York State, USA. Results
Table 1 presents nitrate concentrations at all wells for both sampling periods. The range for the first set of nitrate readings was 0.0-63.8 mg 1-~, with a mean of 24.0 mg 1-l and a median of 16.6 mg 1-t . Both the mean and the median were above the maximum contaminant level. In total, 15 of 23 samples (65.2 percent) were above the mcl. Wells having a nitrate concentration in excess of the mcl were located in all six of the land-use types under investigation. Data for the second nitrate analysis ranged from 0.0-67.6 mg 1-1, with a mean of 21.0 mg t -a and a median of 12.6 mg 1-1. Again, the mean and median were above the incl. The second analysis showed 13 wells (56.5 percent) above the mcl. These wells were the same as those exceeding the mcl in the first set of tests. Table 2 shows that the mean concentration of nitrates in each of six different categories of land-use exceeded the mcl (abandoned, cropland, pasture, barnyard, residential yard and commercial land). The average levels of nitrate in the three wells located in barnyards were particularly problematic, exceeding the mcl by more than four times (41.9 mg
Fig. 4. Lamott sampler used to collect water from shallow wells in this study.
1-t and 48.8 mg 1-t ). The average concentrations of nitrate for the four wells located in residential yards were also notably high, exceeding the mcl by more than two-and-a-half times (28.5 mg 1-1 and 27 mg 1-1). ANOVA resulted in no statistically significant differences among categories of land-use. Discussion
The data reveal that with respect to shallow groundwater, there is no significant difference for nitrate concentrations across a range of land-uses. Over half of the dug wells in the research, including at least one well from each of the six categories of land-use, had nitrate levels in excess of the drinking water standard. Regardless of overlying land-use, shallow groundwater is susceptible to high levels of nitrate. The findings have some similarity to the study in New Jersey (Murphy, 1992), which did not find significantly different nitrate levels in shallow wells beneath agricultural and residential areas. However, the New Jersey study did find lower levels of nitrate under pasture and woodland (Murphy, 1992). Wells located in barnyards and croplands showed high concentrations of nitrate. A prominent
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Table 1. Nitrate concentrations at all monitoring wells, St Lawrence County, New York State, USA.
Nitrate concentrations (in mg 1-t) Well
6 and 13 October 1993
10 November 1993
I 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Mean:
0.0 16.6 49.8 40.0 55.6 53.6 24.2 63.8 10.6 54.6 0.0 38.0 34.0 3.8 4.8 0.0 9.6 20.4 4.8 5.8 39.0 12.6 10.8 24.0
0.0 27.1 50.8 27.1 66.6 52.6 21.4 67.6 0.0 45.6 0.0 45.6 40.0 2.8 0.0 0.0 0.I 12.6 0.0 0.0 46.0 5.8 13.6 21.0
Median: Range: Number of readings exceeding mcl (10 mg 1-1):
16.6 0.0-63.8
12.6 0.0-67.6
15
13
Table 2. Nitrate concentrations for various land-uses, St Lawrence County, New York State, USA. Land use
Abandoned Cropland Pasture Barnyard Residential yard Commercial land F-ratio for ANOVA P-value
Number of Mean nimonitoring trate concentration wells (in mg 1-t)
3 7 5 3 4 1
6 and 13 October 1993 12.7 24.4 18.3 41.9 28.5 12.6 0.73 0.6t
10 November 1993 14.3 17.3 11.6 48.8 27.0 5.8 1.27 0.32
trates can remain in groundwater from 30 to 40 years (Carey and Lloyd, 1985). Investigation of nitrate levels in shallow groundwater in St Lawrence County indicates that nitrate concentrations are frequently greater than the maximum contaminant level. Given the possible health effects for young children, Kross et al. (1993) recommended testing private well water for nitrates as part of the normal protocol for prenatal care by public health professionals. Due to substantial data demonstrating high levels of nitrate in shallow groundwater, it is recommended that shallow dug wells be avoided as a source of water supply. In addition to concerns for elevated nitrate concentrations, the drilling of deeper wells for water supply may be advantageous in avoiding microbial contamination. Finally, routine testing for nitrates and other possible contaminants is warranted when drinking water can only be obtained from dug wells in shallow groundwater. Acknowledgments
source of nitrate contamination is agricultural application of commercial fertilizers and livestock manure disposal (Kross et al., 1993). Additionally, the research revealed high nitrate levels in residential yards where fertilizers might be applied heavily. The 1993 USGS study in Minnesota also found high concentrations of nitrate (greater than 3.0 mg 1-1 ) in 63 percent of groundwater samples from residential sites (Anderson, 1993). The high levels of nitrate in shallow groundwater under abandoned agricultural and pasture lands reflects the capacity of nitrates to remain prevalent in groundwater for long periods of time. Reduction of nitrate levels in groundwater can occur through leaching and denitrification (Blackmer, 1987). However, these processes are very slow, especially when shallow groundwater is stagnant; ni-
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This research was part of a community service project made possible through the generous support of the family and friends of Michael Mergardt. The authors gratefully acknowledge Win Ghriskey, Kathleen Hitt, Karen Mackey, Erik Morland and Carla Ticconi for their work on the community service project. The authors also thank Dr Carolyn Johns for her assistance in the chemical analysis of water samples, as well as Paul Freeman and Nancy Alessi for their technical and general assistance.
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Nitrate levels in shallow groundwater of upstate New York, USA References Anderson, H.W. Jr. (1993) Effects of agricultural and residential land use on ground-water quality, Anoka sand plain aquifer, East-Central Minnesota. In United States Geological Survey Investigation. Report 93-4074, pp. 1-68. Beck, B.F., Asmussen, L. and Leonard, R. (1985) Relationship of geology, physiography, agricultural land use, and groundwater quality in Southwest Georgia. Groundwater 23(5), 627-34. Blackmer, A.M. (1987) Losses and transport of nitrogen from soils. In: D'Itri, F. and Wolfson, L. (eds) Rural Groundwater Contamination, pp. 85-103. Michigan: Lewis. Carey, M.A. and Lloyd, J.W. (1985) Modelling nonpoint sources of nitrate pollution of groundwater in the Great Ouse Chalk, UK Journal of Hydrology 78, 83-106. Cuello, C. , Correa, P., Haenzel, W., Cordillo, G., Brown, C., Archer, M. and Tannenbaum, S. (I976) Gastric cancer in Columbia: 1. Cancer risks and suspected environmental agents. Journal of the National Cancer Institute. 57,
1015-20. Forman, D., AI-Dabbagh, S. and Doll, R. (1985) Nitrates, nitrites and gastric cancer in Great Britain. Nature 313, 620-5. Fraser, P., Chilvers, C., Beral, V. and Hill, M.J. (1980) Nitrate and human cancer: a review of the evidence. International Journal of Epidemiology 9, 3-9. Johnson, C.J. and Kross, B.C. (1990) Continuing importance of nitrate contamination of groundwater and wells in rural areas. American Journal of Industrial Medicine 18, 449-56. Knobeloch, L., Krenz, K. and Anderson, H. (1993) Methemogtobinemia in an infant - Wisconsin, 1992. Morbidi~ and Mortali~ Weekly Report 42(12), 217-19. Kross, B.C., Hallberg, G.R., Bruner, D.R., Cherryholmes, K. and Johnson, J.K. (1993) The nitrate contamination of private well water in Iowa. American Journal of Public Health 83(2), 270-2. Murphy, E.A. (1992) Nitrate in drinking water wells in Burlington and Mercer Counties, New Jersey. Journal Soil and Water Conservation 47(2), 183-7.
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