Atmospheric aerosol formation by chemical reactions

Abstract

This paper is a review of several aspects of aerosol formation processes that occur in the earth's atmosphere. Important contributors to atmospheric aerosol chemistry are the sulfates, nitrates, and organic compounds, which are considered to be formed mainly by reactions of trace reactive gases in air. The phenomenology of the evolution of aerosols by such chemical processes is illustrated by recent observations taken in Los Angeles smog. The results of this program show the strong relationships between sulfate, nitrate, and organic carbon formation and gas phase processes of photochemical smog. Suspected mechanisms of secondary aerosol production are summarized, with consideration for both homogeneous and heterogeneous processes. These mechanisms are examined in the light of laboratory simulations and the knowledge of atmospheric behavior to deduce the potential importance of certain classes of reactions for explaining aerosol evolution. Such considerations illustrate well the complexities of gas-particle interactions in atmospheric chemistry.