title: Long term trends of methane, non methane hydrocarbons, and carbon monoxide in urban atmosphere.
abstract: The concentrations of methane (CH4), non-methane hydrocarbons (NMHC), and carbon monoxide (CO) were measured at two urban locations (Guro (GR) and Nowon (NW)) in Seoul, Korea between 2004 and 2013. The mean amount fractions of CH4, NMHC, and CO, measured at GR over this period were 2.06±0.02, 0.32±0.03, and 0.61±0.05 ppm, respectively, while at NW they were 2.08±0.06, 0.33±0.05, and 0.54±0.06 ppm, respectively. The ratio of CH4 to the total hydrocarbon amount fraction remained constant across the study years: 0.82 to 0.90 at GR and 0.81 to 0.89 at NW. Similarly, stable ratios were also observed between NMHC and THC at the two sites. In contrast, the annual mean ratios for CH4/NMHC showed a larger variation: between 4.55 to 8.67 at GR and 4.25 to 8.45 at NW. The seasonality of CO was characterized by wintertime maxima, while for CH4 and NMHC the highest amount fractions were found in fall. The analysis of their long-term trends based on Mann-Kendall and Sen's methods showed an overall increase of THC and CH4, whereas a decreasing trend was observed for NMHC and CO.
authors: Department of Civil & Environmental Engineering, Hanyang University, 222 Wangsimni-Ro, Seoul 133-791, Republic of Korea.
authors: Ezaz
authors: E
authors: Ahmed
authors: Department of Civil & Environmental Engineering, Hanyang University, 222 Wangsimni-Ro, Seoul 133-791, Republic of Korea. Electronic address: kkim61@hanyang.ac.kr.
authors: Ki-Hyun
authors: KH
authors: Kim
authors: Department of Environment & Energy, Sejong University, Seoul 143-747, Republic of Korea.
authors: Eui-Chan
authors: EC
authors: Jeon
authors: Analytical Science Division, National Physical Laboratory, Hampton Rd., Teddington, TW11 0LW UK.
authors: Richard J C
authors: RJ
authors: Brown
keywords: Carbon; Long-term; Methane; Non-methane hydrocarbon; Total hydrocarbon; Urban