ABSTRACT
This chapter explores several approximate mass balance models that are applicable to long-lived trace gases, both natural and anthropogenic. The transport of trace gases is controlled by atmospheric motions which occur on various space and time scales, sometimes dominated by turbulent processes which are usually extremely complex. A large class of atmospheric trace gases, including CH4, CO, and CH3CCl,, are oxidized in the atmosphere by reacting with OH radicals. The subjects of this discussion not only provide information on several areas of current interest in atmospheric chemistry, but are chosen primarily to illustrate the previous discussions of simplified models of chemical transport in the atmosphere. Alternatively, concentrations of inert species may also be used to determine transport coefficients that can be extended to mass balances of other gases. The chapter discusses specific models which are currently in use, and which continue to provide insights into modern problems of global pollution, mass balances, biogeochemical cycles of trace gases, and related areas.
