Smog chamber study on the reactions of terpenes with ozone and OH

Although biogenic compounds like isoprene and terpenes constitute a significant portion of the organic compounds released, the influence of biogenic hydrocarbons on the formation of ozone and photooxidants remains still uncertain. In order to simulate the photochemical behaviour of these compounds a smog chamber facility was designed and tested. The smog chamber is equipped with a solar simulator with matched tropospheric uv spectrac distribution with up to threefold intensity. The chamber is thermostated in order to achieve long enclosure times of aerosols for future investigations. Using a cryogenic enrichment technique the decay of the hydrocarbons (up to 20 compounds simultaneously) is monitored in the ppb level by gas chromatography. Reactions with the active species, O3 and OH, are investigated either in the dark or in the irradiated chamber: In dark experiments low concentrations of O3 are produced by uv photolysis of O2 using a mercury pen ray lamp in an external photoreactor. OH radicals are produced by the photosmog reactions in humid (50% r.h.) NOx-mixtures (O - 200 ppb) in purified air. (ITA)