Simultaneous measurement of atmospheric CH₂O, O₃, and NO₂ by differential optical absorption

TLDR

Formaldehyde mixing ratios were measured in rural Jülich and maritime north coast of Germany. Ground‑based UV‑optical absorption was used to simultaneously measure CH₂O, NO₂, and O₃ with detection limits of 0.1, 0.1, and 1 ppb, respectively. In Jülich, CH₂O varied from 0.1 to 6.5 ppb during May–October 1978, while maritime air showed ~0.2 ppb consistent with methane oxidation, indicating additional sources in Jülich.

Abstract

Formaldehyde mixing ratios are reported for rural areas around Jülich and for maritime air at the north coast of Germany. The measurements were made using a ground‐based UV‐optical absorption technique which allowed the simultaneous determination of CH 2 O, NO 2 , and O 3 with detection limits of 0.1, 0.1, and 1 ppb, respectively. In Jülich, 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 Jülich indicate other sources of formaldehyde.