Choosing the appropriate method of obtaining environmental data depends on the purpose of measurement, the required time and spatial resolution, the time variation of the analyzed pollutants, the required precision of the determinations.
Air monitoring primarily refers to the amount of pollutants in the environment, identified as immission.
Immission of pollutants or concentration of pollutants determines the amount of particulate or gaseous pollutants per unit of atmospheric air volume. The concentration of selected pollutants depends on the amount of emissions - which means the amount of pollutants entering the environment, as well as the dispersion conditions, including terrain topography and meteorological factors.
The concentration of gaseous pollutants is specified in certain units, usually it is determined in grams (grams and smaller units) per unit volume: ng / m3, µ/m3, g/m3, mg/m3, g/m3.The unit of mixing ratio may also be used: ppm (parts per million) or ppb (parts per billion).
- Method of converting the concentrations:
- 1000000 ppm = 100%
- 350 ppm = 35*10-3 % = 0,035 %
1 ppm – means one particle of pollution per million other particles (of air), so if we want to express the concentration in % of volume of air:
Conversion of the concentration given in ppm to the weight concentration requires the use of a formula and knowledge of the molar masses M of the selected pollutants. In the case of pollutant concentrations measured in atmospheric air it is more convenient to use a smaller unit of ppb (one per billion).