Biogenic Trace Gas Exchanges

Abstract

Biogenic trace gases are defined as those gases of biological origin whose atmospheric mixing ratios (concentrations by volume) are less than a few parts per million by volume (ppmv). In the past several decades, knowledge of trace gas exchanges between terrestrial or aquatic systems and the atmosphere, and of the biological, physical, and chemical processes that control them, has increased dramatically. The increased attention and research effort in this area stems primarily from the fact that the atmospheric concentrations of a number of trace gases are increasing. The increases of some of the less reactive gases such as nitrous oxide (N2O) and methane (CH4) are documented in the 20-year or longer record of atmospheric measurements at sampling stations throughout the world (e.g., Prinn et al. 1990, Steele et al. 1992) and by the long-term record provided through the analysis of gases trapped in glacial ice (e.g., Raynaud et al. 1988); increases in some reactive trace gases such as oxides of nitrogen (NOX) and ozone have been determined via ground-based ambient concentration measurements, ground- or aircraft-based flux measurements and atmospheric models. The consequences of these atmospheric changes are felt at a variety of scales; some contribute to the radiative balance of Earth and hence climate change, and others have critical roles in regional and global atmospheric chemistry.