Factors regulating the distribution of O3 and NOx at two mountainous sites in Seoul, Korea

Özet

The concentrations of ozone (O3) and nitrogen oxides (NOx) were measured at two mountainous sites in Buk-Han(BH)andGwan-Ak(GA)andatareferencesiteinGwang-Jin(GJ),allinSeoul,SouthKorea,overa four-year period (2010e2013). The mean concentration (ppb) of NOx was comparable at the mountainous sites (22.9 ± 20.7 (BH) and 20.9 ± 16.9 (GA)) but about half the concentration at the reference site in GJ (47.8±36.4).Incontrast,themeanvalue(ppb)forO3 atthethreesitesexhibitedareversedpatternsuchas 40.2±19.7atGA,28.6±15.4atBH,and21.8±18.3atGJ.TheconcentrationofNOxwashigherinwinter/fall relativetosummer/springatallthreesites.Likethecleardistinctionsobservedfromthespatialdistribution patterns, the seasonal trends conrasted sharply between NOx and O3. Results of a correlation analysis suggested that the distribution of O3 was significantly affected by meteorological parameters (e.g., TEMP, UV,andsolarradiation).Accordingtoabacktrajectoryanalysis,thehighestO3 levelsatbothmountainous sites were caused byair masses passingovermarine areas, while the effects of ozone precursors on ozone concentration were attributed to air masses originating from China and/or the mainland (S. Korea).