U.S.
GEOLOGICAL SURVEY
Open-File Report 03-246
Prepared
in cooperation with
Virginia Department of Health
Office of Drinking Water
By David L. Nelms
and George E. Harlow, Jr.
The determination of aquifer susceptibility to
contamination from near-surface sources by the use of
ground-water dating techniques is a critical part of Virginia's Source Water
Assessment Program. As part of the Virginia Aquifer Susceptibility study,
water samples were collected between 1998 and 2000 from 145 wells and 6
springs in various hydrogeologic settings across the Commonwealth. Samples were analyzed
to determine water chemistry–including nitrate (NO3), dissolved organic
carbon (DOC), and radon-222 (222Rn), major dissolved and noble
gases–nitrogen (N2), argon (Ar), oxygen (O2), carbon dioxide
(CO2), methane (CH4), helium (He), and neon (Ne), environmental
tracers–chlorofluorocarbons (CFCs), sulfur hexafluoride (SF6),
tritium (3H), and tritium/helium-3 (3H/3He),
carbon isotopes–carbon-14 (14C) and carbon-13 (d13C),
and stable isotopes of oxygen (d18O) and hydrogen (d2H).
The chemical and isotopic composition, recharge temperatures, and apparent
ages of these water samples are presented in this report. Data collected
between 1999 and 2000 from 18 wells in Virginia as part of two other studies
by the U.S. Geological Survey also are presented. Most of the sites sampled
serve as public water supplies and are included in the comprehensive Source
Water Assessment Program for the Commonwealth.
CONTENTS
Abstract
Introduction
Purpose and scope
Definition of apparent
age
Sampling locations
Acknowledgements
Sample collection, analytical methods, and quality assurance
Water chemistry
Major dissolved and noble gases
Chloroflourocarbons
Sulfur hexaflouride
Tritium
Tritium/helium-3 and noble gases
Stable isotope ratios of oxygen and
hydrogen in water
Quality
assurance
Analytical and quality assurance data
Water chemistry
Major dissolved and noble gases,
recharge temperature, and excess air
Chlorofluorocarbon concentrations and
apparent ages
Sulfur hexafluoride concentrations
and apparent ages
Tritium, helium, and neon data, and
apparent tritium/helium-3 ages
Carbon isotope data and adjusted
radiocarbon ages
Stable isotope ratios of oxygen and
hydrogen in water
Quality assurance
References Cited
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Send questions or comments about this report to David Nelms (804) 261-2630.
For more information about USGS activities in Virginia, visit the USGS Virginia District home page.
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