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Air pollutants

temperature: °C
pressure : hPa


molar mass =    g/mol

volume mixing ratio ppbv
volume mixing ratio ppmv
concentration (mass) µg/m3
concentration (mass) mg/m3
concentration (mol.) µmol/m3
concentration (molec.) molec./cm3
mass mixing ratio ppbm
partial pressure nbar


All results have been rounded to significant digits.

This is a converter for units used in the field of air pollution.

Usage: At first choose the pollutant from the pull-down-menu. You may choose O3, NO2, NO, SO2, CO, CO2, or H2O. For another substance ("?") you have to type its molar mass. Type the value you want to convert into the field, behind which you find the unit. Click on any free space of the window or the "calculate"-button. Read the results in the other fields. Move the mouse over a unit or click on it to read its full name. Use the "reset" button to delete your calculation.
For the calculation the temperature in degree Celsius and the pressure in hPa are needed. Without a new entry standard values are used.

In science, calculations are often made in the unit volume mixing ratio (ppmv, ppbv), while administrations often use concentrations (mg/m3), for example when they define threshold values. Sometimes it is common to apply simple factors to convert one unit into the other (e.g. 1 ppb O3 corresponds to about 2 µg/m3). Or the exact conversion factor at a single temperature (e.g. 20 °C) and standard pressure is used. ATTENTION: Unfortunately it is seldom mentioned, how conversions have been made. An exact reconversion with this converter might lead to wrong results.
For the calculation of the mass mixing ratio a mean molar mass of air has to be assumed (here 28.9644).
The conversion from volume mixing ratio to molecular concentration and partial pressure is independant of the molar mass.

Examples: What is the volume mixing ratio of ozone when the concentration is 180 µg/m3? Probably "ozone" is chosen by default in the pull-down-menu. Type "180" into the field in front of "µg/m3". Click on any free space of the window or the "calculate"-button. Find the result in the field in front of "ppbv" (90.208 ppbm at 20°C and 1013.25 hPa).

What is the concentration of NO2 when the volume mixing ratio is 20 ppbv at 0°C and 800 hPa, for example on top of a mountain ? At first change the values for temperature and pressure and choose "nitrogen dioxide" in the pull-down-menu. Type "20" into the field in front of "ppbv". Click on any free space of the window or the "calculate"-button. Find the result in the field in front of "µg/m3" (32.412 µg/m3).

Remarks:
- Large and small numbers are written exponentially. As example 2.3e5 = 2.3⋅105 = 230000 or 4.5e-5 = 4.5⋅10-5 = 0.000045.
- There is no warranty for the conversion. Cactus2000 is not responsible for damage of any kind caused by wrong results.
- Please send an email if you have suggestions or if you would like to see more conversions to be included.

- A collection of all Cactus2000-converters running offline may be ordered for a price of € 15.-. A test version is available for download for free.

© Bernd Krüger, 20.12.2009

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