Correcting Concentrations For Altitude
Atmospheric pollutant concentrations expressed as mass per unit volume of atmospheric air (e.g., mg/m³, µg/m³, etc.) at sea level will decrease with increasing altitude because the atmospheric pressure decreases with increasing altitude.
The change of atmospheric pressure with altitude can be obtained from this equation:
Given an atmospheric pollutant concentration at an atmospheric pressure of 1 atmosphere (i.e., at sea level altitude), the concentration at other altitudes can be obtained from this equation:
| where: | |
| = altitude, in hundreds of meters | |
| = atmospheric pressure at altitude , in atmospheres | |
| = Concentration at sea level altitude, in mass per unit volume | |
| = Concentration at altitude, in mass per unit volume |
As an example, given a concentration of 260 mg/m³ at sea level, calculate the equivalent concentration at an altitude of 1,800 meters:
Ca = 260 × 0.9877 18 = 208 mg/m³ at 1,800 meters altitude
Read more about this topic: Useful Conversions And Formulas For Air Dispersion Modeling
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