title: Characteristics of ammonia gas and fine particulate ammonium from two distinct urban areas: Osaka, Japan, and Ho Chi Minh City, Vietnam.
abstract: Continuous and simultaneous measurements of ammonia gas (NH3) and fine particulate ammonium (PM2.5NH4+) were performed in two distinct urban areas: Osaka, Japan, and Ho Chi Minh City (HCMC), Vietnam. Measurements were performed using a new online instrument. Two measurement periods were conducted during February 11-March 12, 2015 (cold period), and July 1-September 14, 2015 (warm period), at the urban site in Osaka, while 17 days of measurements, from May 21 to June 8, 2015, were conducted at the urban site in HCMC. The average NH3concentration at the HCMC site was much higher than that at the Osaka site. The differences in the NH3levels between the two cities are a result of their different emission sources. Traffic emission is a significant contributor to the NH3levels within the urban area in Osaka. Conversely, the contribution of traffic emission to the NH3levels in the HCMC urban area is negligible. With a population of around 8.5 million people living in the urban area of HCMC, the high NH3level is due to human sources and poor waste management systems, especially because of the high temperature (30 °C) and dense population of the city (density up to 42,000 inhabitants per km2). In contrast to the NH3levels, the highest PM2.5NH4+level occurred during the cold period at the Osaka site, and the average level at this site was higher than that at the HCMC site. The availability of atmospheric acids, low temperature, and high humidity facilitates the formation of ammonium. Our results indicate that NH3plays a key role in secondary inorganic aerosol formation; therefore, it contributes to a significant amount of PM2.5at the Osaka site. In contrast, the high levels of PM2.5observed at the HCMC site are likely from road traffic emission, mainly motorcycles, rather than secondary inorganic aerosol formation.
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai-shi, Osaka, 599-8531, Japan. dhhuy@hcmus.edu.vn.|Faculty of Environmental Science, University of Science, Vietnam National University, 227 Nguyen Van Cu Street, District 5, Ho Chi Minh City, Vietnam. dhhuy@hcmus.edu.vn.
authors.forename: Duong Huu
authors.initials: DH
authors.lastname: Huy
authors.affiliation: Faculty of Environmental Science, University of Science, Vietnam National University, 227 Nguyen Van Cu Street, District 5, Ho Chi Minh City, Vietnam.
authors.forename: Le Tu
authors.initials: LT
authors.lastname: Thanh
authors.affiliation: Faculty of Environmental Science, University of Science, Vietnam National University, 227 Nguyen Van Cu Street, District 5, Ho Chi Minh City, Vietnam.
authors.forename: To Thi
authors.initials: TT
authors.lastname: Hien
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai-shi, Osaka, 599-8531, Japan.
authors.forename: Kazushi
authors.initials: K
authors.lastname: Noro
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai-shi, Osaka, 599-8531, Japan.
authors.forename: Norimichi
authors.initials: N
authors.lastname: Takenaka
mesh_terms: D000336:Aerosols; D000393:Air Pollutants / Q000032:analysis*; D000641:Ammonia / Q000032:analysis*; D064751:Ammonium Compounds / Q000032:analysis*; D002947:Cities; D004784:Environmental Monitoring / Q000379:methods; D006813:Humidity; D007564:Japan; D052638:Particulate Matter / Q000032:analysis*; D013696:Temperature; D014744:Vietnam
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D064751:Ammonium Compounds; D052638:Particulate Matter; D000641:Ammonia
keywords: Ammonia; Ammonium; Ho Chi Minh City; Osaka; PM2.5; Traffic emission; Urban