Relating Nitrogen Sources and Aquifer Susceptibility to Nitrate in Shallow Ground Waters of the United States

Relating Nitrogen Sources and Aquifer Susceptibility to Nitrate in Shallow Ground Waters of the... Characteristics of nitrogen loading and aquifer susceptibility to contamination were evaluated to determine their influence on contamination of shallow ground water by nitrate. A set of 13 explanatory variables was derived from these characteristics, and variables that have a significant influence were identified using logistic regression (LR). Multivariate LR models based on more than 900 sampled wells predicted the probability of exceeding 4 mg/L of nitrate in ground water. The final LR model consists of the following variables: (1) nitrogen fertilizer loading (p‐value = 0.012); (2) percent cropland‐pasture (p < 0.001); (3) natural log of population density (p < 0.001); (4) percent well‐drained soils (p = 0.002); (5) depth to the seasonally high water table (p = 0.001); and (6) presence or absence of a fracture zone within an aquifer (p = 0.002). Variables 1–3 were compiled within circular, 500 m radius areas surrounding sampled wells, and variables 4–6 were compiled within larger areas representing targeted land use and aquifers of interest. Fitting criteria indicate that the full logistic‐regression model is highly significant (p < 0.001), compared with an intercept‐only model that contains none of the explanatory variables. A goodness‐of‐fit test indicates that the model fits the data well, and observed and predicted probabilities of exceeding 4 mg/L nitrate in ground water are strongly correlated (r2= 0.971). Based on the multivariate LR model, vulnerability of ground water to contamination by nitrate depends not on any single factor but on the combined, simultaneous influence of factors representing nitrogen loading sources and aquifer susceptibility characteristics. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Ground Water Wiley

Relating Nitrogen Sources and Aquifer Susceptibility to Nitrate in Shallow Ground Waters of the United States

Ground Water, Volume 39 (2) – Mar 1, 2001

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Publisher
Wiley
Copyright
Copyright © 2001 Wiley Subscription Services, Inc., A Wiley Company
ISSN
0017-467X
eISSN
1745-6584
D.O.I.
10.1111/j.1745-6584.2001.tb02311.x
Publisher site
See Article on Publisher Site

Abstract

Characteristics of nitrogen loading and aquifer susceptibility to contamination were evaluated to determine their influence on contamination of shallow ground water by nitrate. A set of 13 explanatory variables was derived from these characteristics, and variables that have a significant influence were identified using logistic regression (LR). Multivariate LR models based on more than 900 sampled wells predicted the probability of exceeding 4 mg/L of nitrate in ground water. The final LR model consists of the following variables: (1) nitrogen fertilizer loading (p‐value = 0.012); (2) percent cropland‐pasture (p < 0.001); (3) natural log of population density (p < 0.001); (4) percent well‐drained soils (p = 0.002); (5) depth to the seasonally high water table (p = 0.001); and (6) presence or absence of a fracture zone within an aquifer (p = 0.002). Variables 1–3 were compiled within circular, 500 m radius areas surrounding sampled wells, and variables 4–6 were compiled within larger areas representing targeted land use and aquifers of interest. Fitting criteria indicate that the full logistic‐regression model is highly significant (p < 0.001), compared with an intercept‐only model that contains none of the explanatory variables. A goodness‐of‐fit test indicates that the model fits the data well, and observed and predicted probabilities of exceeding 4 mg/L nitrate in ground water are strongly correlated (r2= 0.971). Based on the multivariate LR model, vulnerability of ground water to contamination by nitrate depends not on any single factor but on the combined, simultaneous influence of factors representing nitrogen loading sources and aquifer susceptibility characteristics.

Journal

Ground WaterWiley

Published: Mar 1, 2001

References

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