Regionality and particularity of a survey site from the viewpoint of the SO2 and SO42− concentrations in ambient air in a 250-km×250-km region of Japan

We reviewed the data on the atmospheric SO2 and SO42− concentrations measured in a survey conducted by the Japan Environmental Laboratories Association (JELA). The data collected in the Tokai–Kinki–Hokuriku branch, which covers a 250-km×250-km region, were reviewed as one of the activities of the Tokai–Kinki–Hokuriku branch. The atmospheric SO2 and SO42− concentrations were measured using the four-stage filter-pack method. The data collected for 3 years (Campaign III by JELA) were reviewed. The SO2 concentration was affected by the eruption episode of the Miyakejima Volcano. In contrast, the SO42− concentration (annual mean in 1999: 35.0 nmol m−3) was scarcely affected by the eruption episode. The SO42− concentration level was within or slightly higher than the level of the European Monitoring Evaluation Program (EMEP) (lower than 30 nmol m−3) and that of mid-latitude North America. The particularity of the site would be potentially clarified by the relationship of the SO42−/(SO2+SO42−) ratio with the SO2 concentration and the correlation with the results of the Community Multi-scale Air Quality (CMAQ). The peculiar pattern of the monthly variation of the SO2 concentration clarified the particularity of the site, which was deeply associated to the spatial relationship with an express highway with heavy traffic and the wind rose.