INTERCOMPARISON OF FORMALDEHYDE MEASUREMENTS IN THE TROPICAL ATMOSPHERE

An intercomparison of formaldehyde measurements at low concentrations (< 2.0 ppbv) was performed during the ASTROS '93 field campaign in Ven ezuela (Atmospheric Studies in the TROpical Savannah, September 1993). Formaldehyde was collected and measured by two different techniques: a porous membrane diffusion scrubber with fluorescent detection of the Hantzsch reaction product, and DNPH-traps (2,4-dinitrophenylhydrazine ) followed by high performance liquid chromatography with a UV/VIS abs orption detector. The time resolution for the diffusion scrubber instr ument was 5 min while the DNPH-trap samples were integrated over 30-60 min. The measured concentrations range from the detection limits (0.0 45 ppbv for the diffusion scrubber, 0.1 ppbv for the DNPH-traps) up to 2 ppbv. The correlation coefficient between the two techniques is r(2 ) = 0.80 (n = 48) and the slope equals unity (1.02 +/- 0.03). Both met hods are found to be suitable for field experiments in the low ppbv ra nge of formaldehyde.