SIMULTANEOUS MEASUREMENT OF ATMOSPHERIC CH2O, O3, AND NO2 BY DIFFERENTIAL OPTICAL-ABSORPTION

Formaldehyde mixing ratios are reported for rural areas around Julich and for maritime air at the north coast of Germany. The measurements were made using a ground-based UV-optical obsorption technique which allowed the simultaneous determination of CH//2O, NO//2, and O//3 with detection limits of 0. 1, 0. 1, and 1 ppb, respectively. In Julich, which may be regarded as typical for central European background atmosphere, mixing ratios varied from 0. 1 to 6. 5 ppb from May through October 1978. In maritime air under conditions when photochemical equilibrium was expected, formaldehyde concentrations of 0. 2 ppb were observed, which can be accounted for by photochemical oxidation of methane alone. However, the high concentrations of formaldehyde found at Julich indicate other sources of formaldehyde.