Hydrocarbons in the atmosphere

Trace concentrations of highly reactive hydrocarbons of biogenic origin have been proposed for some time as being important in aerosol formation processes in the atmosphere. More recently, assessments of potential photochemical reactions in the troposphere have proposed a role in the atmospheric ozone cycle for hydrocarbons, even for compounds such as methane that had previously been considered nonreactive. An assessment of the atmospheric hydrocarbon reaction system has been limited by a lack of observational information on the nature of conditions in the remote or non-urban atmosphere. Recent data on terpene concentrations and other biogenic hydrocarbon compounds are presented. Data on ethane and acetylene from aircraft samples taken over the north and south Pacific Ocean show concentrations in the 0.5 to 1 /m³ range for ethane and in the 0.05 to 0.3 g/m³ range for acetylene. A concentration gradient is present for these compounds between the northern and southern hemisphere. A rudimentary global concentration pattern for these C₂ compounds has been developed on the basis of recent data.