Benzene and toluene in New Zealand air

Benzene concentrations in the New Zealand urban environment may be higher than in the past, and as a result of changes in urban sources we could expect increases in rural environments. Recent work in New Zealand gives typical concentration values for benzene in the urban, rural and marine environments in the ranges 300-600, 0-900 and 0-100 parts per trillion, respectively. Seasonal variations above and below the mean concentrations of 10 ppt are evident in background levels and the measured concentrations at a non-urban site are very sensitive to wind direction. Corresponding measurements of toluene have been made at a clean site and the relationship between toluene and benzene has been used to identify the contributions to samples from background and from urban.