Analysis of air pollution in two major Korean cities: trends, seasonal variations, daily 1-hour maximum versus other hour-based concentrations, and standard exceedances

This study considers the characteristics of carbon monoxide (CO), nitrogen dioxide (NO2), ozone (O-3) and sulfur dioxide (SO2) in two major South Korean cities, including the capital city of Seoul, over a time period of 7-8 years. Changes in the annual mean and percentiles of the daily 1-h maximum and other hour-based concentrations varied according to the compound and city type. Seasonal variations varied according to the compound,:yet not with the city type. Both Seoul and Taegu exhibited lower O-3 concentrations in July compared to other summer months. There was a high degree of correlation between the daily 1- and 8-h maximum or daily mean concentrations of all compounds in both cities, with an R-2 Of 0.66-0.90 at p < 0.0001. It was indicated that for CO and O-3, the 8-h standard was more stringent than the 1-h standard, while for NO2 and SO2, the 1-h standard was more stringent than the 24-h standard. The correlation coefficients between the daily 1-h maximum and daily mean concentrations decreased as the maximum concentration values of NO2, O-3, and SO2 increased in the two cities. For all the target compounds, Seoul recorded a substantially higher frequency of days with concentrations above the relevant 1-, 8-, and 24-h standards compared to Taegu. (C) 2000 Elsevier Science Ltd. All rights reserved.