Measurements of atmospheric formaldehyde (HCHO) and acetaldehyde (CH3CHO) during POPCORN 1994 using 2.4-DNPH coated silica cartridges

The 2.-4-dinitrophenylhydrazine coated silica cartridge technique (DSC) was used for the measurements of HCHO and CH3CHO during the POPCORN campaign i n August 1994. A total number of 505 measurements was carried out using an automatic sampling system. The sampling time for each measurement was 30 mi nutes. During the first two weeks of the campaign samples were taken every 3 hours and during the last two weeks every 30 minutes. No significant diur nal variation of HCHO and CH3CHO was observed. The average mixing ratios of HCHO and CH3CHO were 1.8 +/- 1.0 ppb and 1.4 +/- 1.3 ppb. The results for HCHO are in a good agreement with simultaneous measurements by differential optical absorption Spectroscopy (DOAS). The absence of a strong diurnal va riation of the HCHO mixing ratio can be explained by production and destruc tion processes during day and night. The measured mixing ratios of HCHO and CH3CHO, especially the mixing ratios during night, are a strong indication that during the POPCORN campaign the maize was a local source of HCHO and CH3CHO.