2015 summertime characteristic variations of NMHCs in Seoul

Abstract:

Nonmethane hydrocarbons(NMHCs) is well known as a precursor of ozone and organic aerosols along with nitrogen oxides compounds. Recently, SOA(secondary Organic Aerosol) dominant fine particles and episodic high O₃ are frequently observed throughout major cities of the East Asia, especially SMA(Seoul Metropolitan Area). Even though NMHCs play an important role in their producions, we still have great uncertainties of it’s emission, transport and chemistry. During MAPS-Seoul 2015 (Magacity Air Pollution Studies- Seoul)/KORUS-AQ(Korea-US Air Quality Study), we measured NMHCs using automated dual column/FID GC system with thermal desorption unit to address science questions both defined in KORUS-AQ and MAPS-Seoul White papers. One column was designed to separate low boiling point NMHC(C₂~C₆), the other for high boiling point NMHC(C₇~C₁₂). 56 NMHC compounds were measured from 18^th May to 12^th June, 2015 at an urban site in hill top of Korea Institute of Science and Technology campus.

During the observation period, sum of NMHCs ranged from 27.6 ppbv to 54.1 ppbv. Among them, the mean concentrations of ethane was the highest (7.0 ppbv), and propane(6.7 ppbv), toluene(4.9ppbv), n-butane(3.3 ppbv) were followed. These four species represented 54% of total NMHCs concentration. The detailed behaviors of NMHC species were discussed further.