Pinonaldehyde and some other organics in rain and snow in central Japan

Solvent-extractable organic compounds in the rain and snow collected at loc al cities in the mountainous region in central Japan, were analyzed by GC/M S and GC. Pinonaldehyde (2,2-dimethyl-3-acetyl-cyclobutyl-ethanal), an atmo spheric reaction product of alpha -pinene, was detected in the rain and sno w for the first time, and n-alkanes (C-17-C-33), fatty acids (C-8-C-23), an d benzoic acid were also detected as major organic components. Concentratio ns of pinonaldehyde, C-17-C-33 n-alkanes, C-8-C-11 fatty acids, C-12-C-13 f atty acids and benzoic acid ranged between <0.02-13, 0.10-35, 0.55-5.7, 4.2 -19 and <0.02-6.0 mug/l, respectively. Their composition showed some differ ence in summer and winter. In summer, fatty acids and benzoic acid were mor e abundant, while pinonaldehyde and n-alkanes were much less. Higher photoc hemical reactivity and higher bioactivity in summer could explain these sea sonal changes except for pinonaldehyde, which would suffer from further oxi dation in the atmosphere after its photochemical production from alpha -pin ene. Predominance of pinonaldehyde and C-12-C-23 fatty acids in the rain an d snow showed a remarkable contrast to n-alkanes in aerosol phase, which we re the most abundant components. It indicated that oxygenated products from biogenic compounds might be important as cloud condensation nuclei in fore st areas. (C) 2001 Elsevier Science Ltd. All rights reserved.