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Scientific Investigations Report 2012–5141


Estimates of Tracer-Based Piston-Flow Ages of Groundwater from Selected Sites: National Water-Quality Assessment Program, 2006–10


Conversion Factors, Datums, and Abbreviations and Acronyms


Conversion Factors


Inch/Pound to SI

Multiply By To obtain
Length
foot (ft) 0.3048 meter (m)
mile (mi) 1.609 kilometer (km)

SI to Inch/Pound

Multiply By To obtain
Volume
liter (L) 0.2642 gallon (gal)
cubic centimeter (cm3) 0.06102 cubic inch (in3)
Mass
gram (g) 0.03527 ounce, avoirdupois (oz)
kilogram (kg) 2.205 pound avoirdupois (lb)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:


°F=(1.8×°C)+32.


Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (µS/cm at 25°C).


Concentrations of most chemical constituents in water are given either in milligrams per liter (mg/L) or micrograms per liter (µg/L).


Chlorofluorocarbon (CFC) concentrations are given in units of picograms per kilogram (pg/kg) and picomoles per kilogram (pmol/kg). One picogram is 10-12 grams. One picomole is 10-12 moles. One mole contains 6.022 × 1023 atoms or molecules of a substance. Sulfur hexafluoride (SF6) concentrations are given in units of femtograms per kilogram (fg/kg) and femtomoles per kilogram (fmol/kg). One femtogram is 10-15 grams. One femtomole is 10-15 moles. CFC and SF6 concentrations also are given in units of parts per trillion by volume (pptv), which represents the atmospheric concentration that would have yielded a measured aqueous concentration assuming equilibrium partitioning between atmosphere and water under the specified conditions (recharge temperature, recharge elevation, and excess air concentration). 


Tritium concentrations are given in units of Tritium Units (TU). Based upon a tritium half-life of 12.32 years (Lucas and Unterweger, 2000), 1 TU is equal to 3.22 picocuries per liter.


Helium-3 (3He) data are reported as δ values computed from the formula


-

where Rx is the ratio of 3He to 4He in the sample, RSTD is the 3He to 4He ratio of the reference standard air (1.384 × 10-6), and δ3He is expressed in percent.


Excess air concentrations (see Glossary) are reported in units of cubic centimeters at standard temperature and pressure (STP) per kilogram of water (cc STP/kg), and helium (He) and neon (Ne) concentrations are reported in units of cubic centimeters (at standard temperature and pressure) per gram of water (cc STP/g). One cc STP of He or Ne is equal to 2.6868 × 1019 atoms. 


Datum


Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 (NGVD 29).


Altitude, as used in this report, refers to distance above the vertical datum.


Abbreviations and Acronyms

Ar argon
14C carbon-14
CFC chlorofluorocarbon
CH4 methane
CO2 carbon dioxide
DWH NAWQA Data Warehouse
Fe Iron
FSS Flow System Study
FY fiscal year
He helium
3H tritium
3He helium-3
4He helium-4
LUS Land-Use Study
MAAT mean annual air temperature
MAS Major-Aquifer Study
Mn Manganese
N2 nitrogen (in the form dnitrogen)
NAWQA National Water-Quality Assessment Program
Ne neon
O2 oxygen (in the form dioxygen)
REF Reference well
SF6 sulfur hexafluoride
SIO Scripps Institution of Oceanography
SIP standard temperature and pressure
SUS Study-Unit SUrvey
TU tritium unit
UA unfractionated air
USGS U.S. Geological Survey

First posted July 31, 2012

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