Air Concentrations

In gas samples (normally air samples), concentrations cannot be expressed as simply as in water or soil , because gas volumes and densities are strongly dependent on temperature and pressure, whereas volumes and densities of liquids are not

1. To covert a gaseous pollutant concentration (Cpol) from ppmv to mg/m3, use

Udara1

2. To covert a gaseous pollutant concentration (Cpol) from mg/m3 to ppmv, use

Cpol

Where

Cpol         = pollutant concentration in the desired units

MVpol     = molecular weight of the pollutant in g/mol

Patm        = pressure of air (atm)

T               = actual air temperature (oC)

12.188 (K mol)/(L atm) = R-1, reciprocal of the ideal gas constant

Notes:

  1. P(atm) = P(mm Hg)/760 = P(torr)/760 = P(Pa)/101,325 = P(bar)/1.01325 = P(dyne/cm2)/1.01325 X 106 = P(psi)/14.696
  2. One percent by volume = 10,000 ppmv

Reference

Eugene R. Weiner. Application of Environmental Aquatic Chemistry. A Practical Guide. Third edition. CRC Press

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