MEASUREMENT OF VOLATILE ORGANIC-CHEMICALS AT SELECTED SITES IN CALIFORNIA

Urban air concentrations of 24 selected volatile organic chemicals that may be potentially hazardous to human health and environment were measured during field experiments conducted at two California locations, at Houston, TX, and at Denver, CO. Chemicals measured included chlorofluorocarbons, halomethanes, haloethanes, halopropanes, chloroethylenes and aromatic hydrocarbons. With emphasis on California sites, data from these studies are anlaysed and interpreted with respect to variabilities in ambient air concentrations, diurnal changes, relation to prevailing meteorology, sources and trends. Except in a few instances, mean concentrations are typically between 0 and 5 ppb. Significant variabilities in atmospheric concentrations associated with intense sources and adverse meteorological conditions are shown to exist. In addition to short-term variability, there is evidence of systematic diurnal and seasonal trends. In some instances it is possible to detect declining trends (e.g. ethylene dibromide and chloroethylenes) resulting from the effectiveness of control strategies.