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The Dobson unit (DU) is a unit of measurement of the amount of a trace gas in a vertical column through the Earth's atmosphere.It originated by, and continues to be primarily used in respect to, the study of atmospheric ozone, whose total column amount, usually termed "total ozone", and sometimes "column abundance", is dominated by the high concentrations of ozone in the stratospheric ozone layer.
The PSI chart below is ... there is a discontinuous jump of one AQI unit. To convert from concentration to AQI ... The ozone AQI between 100 and 300 is computed by ...
For example, such a regulation might limit the concentration of NOx to 55 ppmv in a dry combustion exhaust gas corrected to 3 volume percent O 2. As another example, a regulation might limit the concentration of particulate matter to 0.1 grain per standard cubic foot (i.e., scf) of dry exhaust gas corrected to 12 volume percent CO 2.
Ozone (/ ˈ oʊ z oʊ n /) (or trioxygen) is an inorganic molecule with the chemical formula O 3.It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope O
Air pollutant concentrations expressed as mass per unit volume of atmospheric air (e.g., mg/m 3, μg/m 3, etc.) at sea level will decrease with increasing altitude. The concentration decrease is directly proportional to the pressure decrease with increasing altitude.
If all of the ozone in the atmospheric column one was measuring were compressed to STP, the thickness of the compressed atmosphere in mm would equal an answer in Dobson Units divided by 100. The vertical distribution of ozone is derived using the Umkehr method. This method relies on the intensities of reflected, rather than direct, UV light ...
Ground-level ozone (O 3), also known as surface-level ozone and tropospheric ozone, is a trace gas in the troposphere (the lowest level of the Earth's atmosphere), with an average concentration of 20–30 parts per billion by volume (ppbv), with close to 100 ppbv in polluted areas.
These units express the concentration of air pollution in terms of the mass or volume of the pollutant, and they are commonly used for measurements of both gaseous pollutants, such as nitrogen dioxide, and coarse (PM 10) and fine (PM 2.5) particulates.