Residence time

The residence time of the substance (gas, solid, or drops) in the atmosphere is the average amount of time that remains introduced into the atmosphere a particle or molecule of the substance in the atmosphere. It is determined by its weight (size), its solubility in water and its chemical composition.

Heavy solid particles or droplets fall to the ground faster than light. Depending on the water solubility of substances are more or less strongly washed out by rain. Substances in the atmosphere can be converted or degraded by chemical or physical processes (eg triggered by radical redox reactions or photolysis ). These and other factors determine the residence time of a substance in the atmosphere. Depending on the substance, this very short ( seconds or minutes) but is also very long ( several thousand years).

The concentration or increase in concentration of a substance in the atmosphere, such as a greenhouse gas which is established in a long -term equilibrium state by a certain ( anthropogenic ) emission rate is, in the simplest case is inversely proportional to its residence time. For many substances, in particular carbon dioxide, the relationships were more complicated (see carbon cycle ).