Biomedical Engineering Reference
In-Depth Information
Vapor intrusion
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Migration of volatile chemicals from the subsurface into overlying
buildings.
Vapor pressure
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A measure of a substance's propensity to evaporate. The force per unit area
exerted by vapor in an equilibrium state with surroundings at a given pressure. It increases
exponentially with an increase in temperature. A relative measure of chemical volatility, vapor
pressure is used to calculate water partition coefficients and volatilization rate constants.
Vinyl chloride (VC)
CHCl) that is highly toxic and believed to
be oncogenic. A colorless compound and an important industrial chemical chiefly used to
produce the polymer polyvinyl chloride (PVC).
‐
A chemical compound (CH
2
¼
Viscosity
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The molecular friction within a fluid that produces flow resistance.
Volatilization
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Transfer of a chemical from the liquid to the gas phase (as in evaporation).
Volatile organic compound (VOC)
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Any organic compound that has a high enough vapor
pressure under normal conditions to significantly vaporize and enter the atmosphere.
Water solubility
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The maximum possible concentration of a chemical compound dissolved in
water. If a substance is water soluble, it can very readily disperse through the environment.
Water table
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The top of an unconfined aquifer. Indicates the level below which subsurface
solids and rock are saturated with water.
Wellhead
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The assembly of fittings, valves, and controls located at the surface and connected
to the flow lines, tubing, and casing of the well so as to control the flow from the reservoir.
Xenobiotic
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A substance that is not normally found in the environment.