Determination of the sources of nitrate contamination in karst springs using isotopic and chemical indicators

S. V. Panno; K. C. Hackley; H. H. Hwang; W. R. Kelly

doi:10.1016/S0009-2541(01)00318-7

Determination of the sources of nitrate contamination in karst springs using isotopic and chemical indicators

S. V. Panno, K. C. Hackley, H. H. Hwang, W. R. Kelly

Illinois State Water Survey

Research output: Contribution to journal › Article › peer-review

Abstract

The sources of nitrate (NO^-₃) in groundwater of the shallow karst aquifer in southwestern Illinois' sinkhole plain were investigated using chemical and isotopic techniques. The groundwater in this aquifer is an important source of potable water for about half of the residents of the sinkhole plain area. Previous work has shown that groundwater from approximately 18% of the wells in the sinkhole plain has NO^-₃ concentrations in excess of the USEPA's drinking water standard of 10 mg N/1. Relative to background levels, the NO^-₃ concentrations in water from 52% of the wells, and probably all of the springs in the study area, are anomalously high, suggesting that sources other than naturally occurring soil organic matter have contributed additional NO^-₃ to groundwater in the shallow karst aquifer. This information, and the dominance of agriculture in the study area, suggest that agrichemical contributions may be significant. To test this hypothesis, water samples from 10 relatively large karst springs were collected during four different seasons and analyzed for inorganic constituents, dissolved organic carbon, atrazine, and δ¹⁵N and δ¹⁸O of the NO^-₃ ions. The isotopic data were most definitive and suggested that the sources of NO^-₃ in spring water are dominated by N-fertilizer with some possible influence of atmospheric NO^-₃ and, to a much lesser extent, human and/or animal waste. Differences in the isotopic composition of NO^-₃ and some of the chemical characteristics were observed during the four consecutive seasons in which spring water samples were collected. Isotopic values for δ¹⁵N and δ¹⁸O of the NO^-₃ ranged from 3.2‰ to 19.1‰ and from 7.2‰ to 18.7‰, respectively. The trend of δ¹⁵N and δ¹⁸O data for NO^-₃ also indicated that a significant degree of denitrification is occurring in the shallow karst hydrologic system (within the soil zone, the epikarst and the shallow karst aquifer) prior to discharging to springs.

Original language	English (US)
Pages (from-to)	113-128
Number of pages	16
Journal	Chemical Geology
Volume	179
Issue number	1-4
DOIs	https://doi.org/10.1016/S0009-2541(01)00318-7
State	Published - 2001

Keywords

Fertilizers
Groundwater
Groundwater chemistry
Karst springs
Nitrate isotopes

ASJC Scopus subject areas

Geology
Geochemistry and Petrology

Online availability

10.1016/S0009-2541(01)00318-7

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title = "Determination of the sources of nitrate contamination in karst springs using isotopic and chemical indicators",

abstract = "The sources of nitrate (NO-3) in groundwater of the shallow karst aquifer in southwestern Illinois' sinkhole plain were investigated using chemical and isotopic techniques. The groundwater in this aquifer is an important source of potable water for about half of the residents of the sinkhole plain area. Previous work has shown that groundwater from approximately 18% of the wells in the sinkhole plain has NO-3 concentrations in excess of the USEPA's drinking water standard of 10 mg N/1. Relative to background levels, the NO-3 concentrations in water from 52% of the wells, and probably all of the springs in the study area, are anomalously high, suggesting that sources other than naturally occurring soil organic matter have contributed additional NO-3 to groundwater in the shallow karst aquifer. This information, and the dominance of agriculture in the study area, suggest that agrichemical contributions may be significant. To test this hypothesis, water samples from 10 relatively large karst springs were collected during four different seasons and analyzed for inorganic constituents, dissolved organic carbon, atrazine, and δ15N and δ18O of the NO-3 ions. The isotopic data were most definitive and suggested that the sources of NO-3 in spring water are dominated by N-fertilizer with some possible influence of atmospheric NO-3 and, to a much lesser extent, human and/or animal waste. Differences in the isotopic composition of NO-3 and some of the chemical characteristics were observed during the four consecutive seasons in which spring water samples were collected. Isotopic values for δ15N and δ18O of the NO-3 ranged from 3.2‰ to 19.1‰ and from 7.2‰ to 18.7‰, respectively. The trend of δ15N and δ18O data for NO-3 also indicated that a significant degree of denitrification is occurring in the shallow karst hydrologic system (within the soil zone, the epikarst and the shallow karst aquifer) prior to discharging to springs.",

keywords = "Fertilizers, Groundwater, Groundwater chemistry, Karst springs, Nitrate isotopes",

author = "Panno, {S. V.} and Hackley, {K. C.} and Hwang, {H. H.} and Kelly, {W. R.}",

note = "Funding Information: We thank G. Gardner (Missouri Department of Transportation) and Joan Bade (Illinois Department of Natural Resources) for showing us the locations of numerous springs in the sinkhole plain and introducing us to their owners. We also thank P. Kremmell of the US Department of Agriculture for data on nutrient and pesticide application rates for southwestern Illinois, and C.P. Weibel (Illinois State Geological Survey) for preparing our spring location figure. This research was supported by a grant from the Illinois Groundwater Consortium, the Illinois Department of Natural Resources Conservation 2000 program through the Monroe Co. Soil and Water Conservation District and by state funds from the Department of Natural Resources, Illinois State Geological Survey division. Publication of this article has been authorized by the Chief of the Illinois State Geological Survey.",

year = "2001",

doi = "10.1016/S0009-2541(01)00318-7",

language = "English (US)",

volume = "179",

pages = "113--128",

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TY - JOUR

T1 - Determination of the sources of nitrate contamination in karst springs using isotopic and chemical indicators

AU - Panno, S. V.

AU - Hackley, K. C.

AU - Hwang, H. H.

AU - Kelly, W. R.

N1 - Funding Information: We thank G. Gardner (Missouri Department of Transportation) and Joan Bade (Illinois Department of Natural Resources) for showing us the locations of numerous springs in the sinkhole plain and introducing us to their owners. We also thank P. Kremmell of the US Department of Agriculture for data on nutrient and pesticide application rates for southwestern Illinois, and C.P. Weibel (Illinois State Geological Survey) for preparing our spring location figure. This research was supported by a grant from the Illinois Groundwater Consortium, the Illinois Department of Natural Resources Conservation 2000 program through the Monroe Co. Soil and Water Conservation District and by state funds from the Department of Natural Resources, Illinois State Geological Survey division. Publication of this article has been authorized by the Chief of the Illinois State Geological Survey.

PY - 2001

Y1 - 2001

N2 - The sources of nitrate (NO-3) in groundwater of the shallow karst aquifer in southwestern Illinois' sinkhole plain were investigated using chemical and isotopic techniques. The groundwater in this aquifer is an important source of potable water for about half of the residents of the sinkhole plain area. Previous work has shown that groundwater from approximately 18% of the wells in the sinkhole plain has NO-3 concentrations in excess of the USEPA's drinking water standard of 10 mg N/1. Relative to background levels, the NO-3 concentrations in water from 52% of the wells, and probably all of the springs in the study area, are anomalously high, suggesting that sources other than naturally occurring soil organic matter have contributed additional NO-3 to groundwater in the shallow karst aquifer. This information, and the dominance of agriculture in the study area, suggest that agrichemical contributions may be significant. To test this hypothesis, water samples from 10 relatively large karst springs were collected during four different seasons and analyzed for inorganic constituents, dissolved organic carbon, atrazine, and δ15N and δ18O of the NO-3 ions. The isotopic data were most definitive and suggested that the sources of NO-3 in spring water are dominated by N-fertilizer with some possible influence of atmospheric NO-3 and, to a much lesser extent, human and/or animal waste. Differences in the isotopic composition of NO-3 and some of the chemical characteristics were observed during the four consecutive seasons in which spring water samples were collected. Isotopic values for δ15N and δ18O of the NO-3 ranged from 3.2‰ to 19.1‰ and from 7.2‰ to 18.7‰, respectively. The trend of δ15N and δ18O data for NO-3 also indicated that a significant degree of denitrification is occurring in the shallow karst hydrologic system (within the soil zone, the epikarst and the shallow karst aquifer) prior to discharging to springs.

AB - The sources of nitrate (NO-3) in groundwater of the shallow karst aquifer in southwestern Illinois' sinkhole plain were investigated using chemical and isotopic techniques. The groundwater in this aquifer is an important source of potable water for about half of the residents of the sinkhole plain area. Previous work has shown that groundwater from approximately 18% of the wells in the sinkhole plain has NO-3 concentrations in excess of the USEPA's drinking water standard of 10 mg N/1. Relative to background levels, the NO-3 concentrations in water from 52% of the wells, and probably all of the springs in the study area, are anomalously high, suggesting that sources other than naturally occurring soil organic matter have contributed additional NO-3 to groundwater in the shallow karst aquifer. This information, and the dominance of agriculture in the study area, suggest that agrichemical contributions may be significant. To test this hypothesis, water samples from 10 relatively large karst springs were collected during four different seasons and analyzed for inorganic constituents, dissolved organic carbon, atrazine, and δ15N and δ18O of the NO-3 ions. The isotopic data were most definitive and suggested that the sources of NO-3 in spring water are dominated by N-fertilizer with some possible influence of atmospheric NO-3 and, to a much lesser extent, human and/or animal waste. Differences in the isotopic composition of NO-3 and some of the chemical characteristics were observed during the four consecutive seasons in which spring water samples were collected. Isotopic values for δ15N and δ18O of the NO-3 ranged from 3.2‰ to 19.1‰ and from 7.2‰ to 18.7‰, respectively. The trend of δ15N and δ18O data for NO-3 also indicated that a significant degree of denitrification is occurring in the shallow karst hydrologic system (within the soil zone, the epikarst and the shallow karst aquifer) prior to discharging to springs.

KW - Fertilizers

KW - Groundwater

KW - Groundwater chemistry

KW - Karst springs

KW - Nitrate isotopes

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DO - 10.1016/S0009-2541(01)00318-7

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SN - 0009-2541

VL - 179

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JO - Chemical Geology

JF - Chemical Geology

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ER -

Determination of the sources of nitrate contamination in karst springs using isotopic and chemical indicators

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