Amounts of Constituents in the Atmosphere

There are two ways in atmospheric chemistry to represent the amount (or mass) of a substance the concentration and the mixing ratio. The concentration is the amount (or mass) of a substance in a given volume divided by that volume. The mixing ratio is 

Component Formula ppmv mgm 3 Main source of selected components 

Notes Substances considered as atmospheric pollutants are denoted by the superscript a. 

Substances denoted by the superscript b can even occur at higher values than those in the table. 

Water concentration is also reported as humidity (absolute or relative) relative humidity is expressed by the fraction of specific humidity to the maximum specific humidity possible for a given pressure and temperature. The main sources of atmospheric gases are further explained in the text. 

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