Spatial and temporal variation of urban air pollutants and their concentrations in relation to meteorological conditions at four sites in Busan, South Korea

This study is based on 10-year period (2005–2014) hourly measurements of six air pollutants (NO, NO2, O3, SO2, CO and PM10) in four different sites (traffic, urban background, commercial and rural background) of Busan, the second largest city in South Korea. An integrated analysis, considering various time periods (annual, seasonal and diurnal as a function of seasons and weekdays/weekends) and a statistical analysis of concentrations in relation to local meteorological conditions has been conducted. Comparable downward trends for air pollutants over 10 years has been found across the study sites, with the exception for O3 which increases at a rate of ∼0.7 ppbv/year. NO, NO2 and CO show a seasonal variation with winter enhancement, and this pattern is most obvious at the traffic site. Ozone has an annual cycle with a spring peak, showing higher peak amplitude at the rural background site. Summer enhancement of SO2 is identified at the site in the proximity of harbours when prevailing air masses have been transported from shipping regions. The distance from sources, particularly road transportation tends to produce spatial variations in the diurnal cycle, and this is particularly evident in the broader and delayed rush hour peak at the rural background site. The meteorological conditions and source strength expressed as weekdays/weekend drive the diurnal variations in terms of peak size, showing the winter enhancement for NO, NO2, SO2 and CO with lower weekend concentrations. Highest daily peak for PM10 is observed in the spring with reduced level on weekends.