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Spatial and Temporal Variations in Nitrate Contamination of a Rural Aquifer, California
Author(s) -
Williams A. E.,
Johnson J. A.,
Lund L. J.,
Kabala Z. J.
Publication year - 1998
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1998.00472425002700050021x
Subject(s) - contamination , aquifer , groundwater , environmental science , nitrate , water quality , hydrology (agriculture) , watershed , spatial variability , pollution , structural basin , geology , ecology , paleontology , statistics , geotechnical engineering , mathematics , machine learning , computer science , biology
The quality of ground water in the Sierra Pelona watershed, California is examined as an example of a small rural groundwater basin in a mountainous area of arid climate. Water quality in this region has been seriously impacted by nitrate (NO 3 ) contamination with 42% of wells sampled exceeding the EPA public drinking water maximum contaminant level (MCL) of 10 mg/L as NO 3 ‐N at some point during 1992–1993. High NO 3 ‐N concentrations reported from this region suggest degradation of water quality due to anthropogenic activity. Dissolved ion concentrations, particularly NO 3 , chloride and calcium varied radically in 55% of well waters sampled prior to, following, and months after an unusually wet winter. Our extensive well sampling program, chemical results and delineation of spatial and temporal NO 3 ‐N variation allow us to constrain possible contamination sources and transport mechanisms active in the Sierra Pelona basin. The spatial distribution and temporal variability of NO 3 indicate three patterns of contamination: (i) isolated wells impacted by numerous, localized NO 3 sources which erratically affect a single well without significantly contaminating neighboring ones; (ii) a tight cluster of wells, unusually low in other ions but consistently high in NO 3 ; (iii) moderate and generally consistent NO 3 concentrations, found over a large, diffuse region of the Sierra Pelona alluvial aquifer. An understanding of the differing NO 3 source(s) and contamination mode(s) that contribute to these observed contaminant patterns is critical to development and success of any strategy for contaminant mitigation and/or remediation.