Volume 33, Issue 6 pp. 1219-1235

STRUCTURAL EQUATION MODELING OF DYNAMICS OF NITRATE CONTAMINATION IN GROUND WATER1

Zhi-Jun Liu

Zhi-Jun Liu

Respectively, Postdoctoral Fellow, Smithsonian Environmental Research Center, P.O. Box 28, Edgewater, Maryland 21037–0028; Associate Director, University Hygienic Laboratory, The University of Iowa, 102 Oakdale Campus, H101 OH, Iowa City, Iowa 52242–5002; and Professor, Department of Geography, The University of Iowa, Iowa City, Iowa 52242–1316.

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George R. Hallberg

George R. Hallberg

Respectively, Postdoctoral Fellow, Smithsonian Environmental Research Center, P.O. Box 28, Edgewater, Maryland 21037–0028; Associate Director, University Hygienic Laboratory, The University of Iowa, 102 Oakdale Campus, H101 OH, Iowa City, Iowa 52242–5002; and Professor, Department of Geography, The University of Iowa, Iowa City, Iowa 52242–1316.

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George P. Malanson

George P. Malanson

Respectively, Postdoctoral Fellow, Smithsonian Environmental Research Center, P.O. Box 28, Edgewater, Maryland 21037–0028; Associate Director, University Hygienic Laboratory, The University of Iowa, 102 Oakdale Campus, H101 OH, Iowa City, Iowa 52242–5002; and Professor, Department of Geography, The University of Iowa, Iowa City, Iowa 52242–1316.

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First published: 08 June 2007
Citations: 14
1

Paper No. 96157 of the Journal of the American Water Resources Association (formerly Water Resources Bulletin). Discussions are open until August 1, 1998.

Abstract

ABSTRACT: Most research on the temporal aspect of nitrate pollution in water resources has focused on surface water. Comprehensive studies on the dynamics of nitrate in ground water are lacking, especially on a drainage basin scale and for relatively long periods of time. In this study, structural equation modeling is applied in investigating the influences of climate, hydrology, and nitrogen management in agricultural production on nitrate concentration in the Big Spring Basin, Iowa, over a 10-year period. The study shows that for given hydrogeological settings, nitrogen management practices and climate are the two most important factors that affect nitrate dynamics. The long-term trend of nitrate is closely related to the nitrogen input primarily determined by management practices. The potential effects of nitrogen management, however, are contingent on the variations of climate. The improvements in water quality (reduced nitrate concentration and loads) in relation to improved nitrogen management are often overshadowed by the impact of climate, especially in extremely dry or wet years. The variations of climate and hydrology have much greater impacts on the nitrate dynamics than the changes in nitrogen input. This study reveals significant seasonal variation in the relations between nitrate concentration and influencing factors, which is also closely related to the seasonal variation in climate. Assessment of management practices and resultant water quality should consider the impact of short- and long-term climate dynamics.

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