Abstract
High concentration of suspended particulate matters (SPM) occurs frequently from late autumn to early winter in the urban areas of central Japan. In this paper photochemical formation of particulate organic matter in late autumn was investigated for inland mid-size and small-size cities far from large emission areas. Field observations were made in November to December 1989 at Okaya and November 1990 at Nagano. Organic matters in the form of airborne aerosols were collected on a quartz fiber filter using a high-volume air sampler in the daytime (1200-1700 JST) and at night (1700-1200 JST). After the filter was extracted with dichloromethane and subsequently with methanol, the extracted organic matters were analyzed by GC/FID equipped with a capillary column.
At first organic carbon (OC) and elementary carbon (EC) in the airborne aerosols were determined and then pinonaldehyde, C17-C33 n-alkanes, C12-C23 fatty acids, dicarboxylic acids, benzoic acid, lower molecular unresolved complex mixture (LUCM) and higher molecular unresolved complex mixture (HUCM) were detected. Then, concentrations of these organic matters in total attained to 1.4μg/m3 at Okaya and 3.4μg/m3 at Nagano, and they were about 20% of OC at both sites. Concentrations of pinonaldehyde, dicarboxylic acids, benzoic acid and LUCM increased in the daytime, and fractions of these matters formed by photochemical reactions in the daytime were estimated to be more than 50%. These results suggested that a significant amount of particulate organic matters is produced photochemically in the daytime even in the late autumn.
