Smog chamber studies on the air chemistry of biogenic hydrocarbons in the presence of ozone, NOx and SO2

: Nolting, F.; Zetzsch, C.

Abstract
The influence of SO sub 2 on the photochemical degradation processes of the biogenic hydrocarbon alpha-pinene was studied with respect to the present forest decline. For that purpose premixed air was irradiated with simulated sunlight in laboratory experiments using a modified smog chamber. In joint measurement campaigns with Israel and Böhm (TU Berlin) the performance of a novel semi continuous analyzer for H sub 2 SO sub 4/sulfate was tested for smog chamber studies of the transformation of SO sub 2 to sulfuric acid and sulfur containing aerosol. An influence of SO sub 2 on the formation of ozone was not detected. The rates of degradation cannot be described by gas phase reactions alone, and, in addition, they are faster in the presence of humidity. Depending on humidity, 30 - 50% of the consumed SO sub 2 can be recovered in the suspended aerosol. In the presence of 60% relative humidity the nearly exclusive product is sulfur aerosol that needs further characterization.