Hydrocarbon emissions from natural vegetation in Californiaʹs South Coast Air Basin

Hydrocarbon emissions from ten native plant species with high contributions to the biomass of Californiaʹs South Coast Air Basin (SOCAB) were measured using a flow-through chamber enclosure technique. Camphor and cineole and other oxygenated hydrocarbons were observed to be large emissions from certain aromatic sage and sagebrush species. Representative emission rate measurements for these species were difficult to obtain using the enclosure technique. Sesquiterpenes were found to be a high proportion of the emissions from Black Sage plants from late February to April. The isoprene emission rates measured for Interior Live Oak (Quercus wislizenii) and Scrub Oak (Quercus dumosa) were lower than most previously examined Quercus sp. However, estimated emissions of isoprene and terpenes from natural plant species in the SOCAB suggest that it may be difficult to reduce anthropogenic hydrocarbons sufficiently to meet ambient air quality standards for ozone and support the position that stringent controls on NOx as well as hydrocarbons will be required.