Photooxidation of α-pinene at high relative humidity in the presence of increasing concentrations of NOx

Photooxidation of alpha -pinene at high relative humidity in the presence of increasing concentrations of nitrogen oxides (NO sub(x)) was investigated. The size distributions and number concentrations of the particles formed by the photochemistry were measured using a scanning mobility particle sizer (SMPS) consisting of either a nano or long differential mobility analyzer (DMA) and a condensation particle counter (CPC). Trace compounds such as HCHO formed during photooxidation in air were shown to be more sensitive measures of model performance than was ozone and organic nitrates could fulfill a similar role. The results showed that in addition to a complex mixture of gaseous and particulate oxygenated organics, organic nitrates were components of both the gas and particle phases.