ثنائي أكسيد النيتروجين
Assimilative capacity of the atmosphere is defined as the maximum load of pollutants that can be added without compromise of its resources. Meteorologists calculate assimilative capacity through the atmosphere using ventilation coefficient or through the pollution potential. The ventilation coefficient is calculated by multiply the mixing height (the height at which vigorous mixing of gasses occur) with the average wind speed. Atmospheric concentrations change rapidly as gasses move due to winds, convection current and dispersion of gasses. The pollution potential is determined by calculating the concentration of pollutants and comparing that to the acceptable limits. This way of calculating takes into consideration the current level of pollutants and assesses how much more can be added in order to reach the assimilative capacity. Sulphur dioxide (SO2), Nitrogen monoxide (NO) and Nitrogen dioxide (NO2) and suspended particulate matter (SPM) are important pollutants to measure. High concentrations sulphur dioxide can cause acid rain which damages structures and increases acidity of soils and bodies of water. High concentrations nitrogen monoxide and nitrogen dioxide can cause photochemical smog which has adverse effects on those with compromised lungs. High concentrations of suspended particulate matter can be absorbed by the lungs into the bloodstream can cause pneumonia.