Long term trends of methane, non methane hydrocarbons, and carbon monoxide in urban atmosphere

• Published in: The Science of the total environment 2015-06, Vol.518-519, p.595-604
• Main Authors: Ahmed, Ezaz, Kim, Ki-Hyun, Jeon, Eui-Chan, Brown, Richard J.C.
• Format: Article
• Language: English
• Subjects: Atmospheres; Carbon; Carbon monoxide; Constants; Hydrocarbons; Long-term; Maxima; Methane; Non-methane hydrocarbon; Total hydrocarbon; Trends; Urban
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2015.02.058

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±0.05ppm, respectively, while at NW they were 2.08±0.06, 0.33±0.05, and 0.54±0.06ppm, 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. •Despite the abundance, the population of airborne carbon species is poorly known except CO2.•The factors governing the distributions of diverse carbon species in air have been explored.•Over a long-term they are distinguished between increase (THC and CH4) vs. decrease (NMHC and CO).