Laura M. Bexfield

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Pesticide data for ground water sampled across the United States between 1993-1995 and 2001-2003 by the U.S. Geological Survey National Water-Quality Assessment Program were evaluated for trends in detection frequency and concentration. The data analysis evaluated samples collected from a total of 362 wells located in 12 local well networks characterizing(More)
Concentrations of halogenated volatile organic compounds ͑VOCs͒ were determined by gas chromatography ͑GC͒ with an electron-capture detector ͑GC-ECD͒ and by gas chromatography with mass spectrometry ͑GC-MS͒ in 109 groundwater samples from five study areas in the United States. In each case, the untreated water sample was used for drinking-water purposes or(More)
The age distribution of water from a public-supply well in a deep alluvial aquifer was estimated and used to help explain arsenic variability in the water. The age distribution was computed using a ternary mixing model that combines three lumped parameter models of advection-dispersion transport of environmental tracers, which represent relatively recent(More)
Seasonal variability in groundwater pumping is common in many places, but resulting effects of seasonal pumping stress on the quality of water produced by public-supply wells are not thoroughly understood. Analysis of historical water-quality samples from public-supply wells completed in deep basin-fill aquifers in Modesto, California (134 wells) and(More)
"Global patterns and environmental controls of perchlorate and nitrate co-occurrence in arid and semi-arid environments" (2015). Abstract Natural perchlorate (ClO 4 À) is of increasing interest due to its widespread occurrence on Earth and Mars, yet little information exists on the relative abundance of ClO 4 À compared to other major anions, its stability,(More)
11. Location map of the Albuquerque area showing locations of the temperature profile sites. IV INTRODUCTION In 1995, the Water Resources Division (WRD) of the U.S. Geological Survey (USGS) published initial groundwater flow models of the aquifer system in the Albuquerque area that indicated significantly less water available for municipal consumption than(More)
An understanding of the occurrence and sources of arsenic in ground water of the Middle Rio Grande Basin (MRGB), central New Mexico, is essential to the establishment of drinking-water supplies that will consistently meet the new standard of 10 micrograms per liter established by the U.S. Environmental Protection Agency for arsenic in drinking water. New(More)
Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted material contained within this report. Figures 1. Albuquerque Bernalillo County Water(More)
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