Vehicular exhaust contributions to high NH3 and PM2.5 concentrations during winter in Tokyo, Japan. (1st June 2019)

• Record Type: Journal Article
• Authors: Osada, Kazuo; Saito, Shinji; Tsurumaru, Hiroshi; Hoshi, Junya
• Is Part Of: Atmospheric environment. Volume 206(2019)
• Page Start: 218
• Page End: 224
• Publication Date: 2019-06-01
• Subjects: Hourly measurement -- Motor vehicle exhaust -- NH3 -- Urban source; Air -- Pollution -- Periodicals; Air -- Pollution -- Meteorological aspects -- Periodicals; 551.51
• DOI: 10.1016/j.atmosenv.2019.03.008
• Languages: English
• ISSNs: 1352-2310

Abstract

Abstract: Concentrations of PM2.5 in Tokyo, a densely populated megacity, often increase because of NH4 NO3 formation under low-wind conditions during winter. To obtain source information of NH3 as a NH4 NO3 precursor, hourly NH3 and NH4 + concentrations were measured at an urban site in Tokyo in December 2017. Results show that PM2.5 and NH4 + concentrations increased simultaneously under low-wind and low-temperature conditions along with NH3, NOx, CO, and optical black carbon (OBC) concentrations. The remaining NH4 + (herein, ΔNH4 + ) subtracted from observed NH4 + to equivalent SO4 2− concentration correlated well with NO3 − in PM2.5, indicating the existence of fine NH4 NO3 particles. Regression analysis of hourly NH3 + ΔΝH4 + concentrations with CO, NOx, and OBC showed significant correlation. Virtual emission rates (VER) of NH3 per motor vehicle in Tokyo were estimated using observed relations between NH3 + ΔΝH4 + and OBC, etc. with data from vehicular statistics: they were 3.7–32 mg/km. The regression of NH3 + ΔΝH4 + with OBC concentrations indicated an intercept of about 3.2 ppb, which is about half of the monthly average in December. This result implies that the non-vehicular source strength was nearly the same strength as the bulk vehicular emissions of NH3 during winter in Tokyo. Highlights: Considering excess NH4 + concentrations over SO4 2− was useful to study urban NH3 . Virtual emission rates of NH3 per vehicle in Tokyo were 3.7–32 mg/km. Non-vehicular NH3 sources contributed almost equally to winter vehicular emissions.