The scientific study of the relationships and interactions of the substances in the gases around the earth. Examples would be determination of the concentrations, sources, and sinks of ozone in the troposphere and stratosphere and the greenhouse gases that surround earth. This includes all reactions of and sources and sinks on the surface of the earth of particles released in the air. [Journal of Physical Chemistry A; v110; 7777-7786; 2006] [Atmospheric Environment; v41; 2319-2334; 2007.] [Science of The Total Environment; v360; 5-25; 2006.]