The vertical variability of ammonia in urban Beijing, China

• Main Authors: Y. Zhang, A. Tang, D. Wang, Q. Wang, K. Benedict, L. Zhang, D. Liu, Y. Li, J. L. Collett Jr., Y. Sun, X. Liu
• Format: Article
• Language: English
• Published: Copernicus Publications 2018-11-01
• Series: Atmospheric Chemistry and Physics
• Online Access: https://www.atmos-chem-phys.net/18/16385/2018/acp-18-16385-2018.pdf
• ISSN: 1680-7316; 1680-7324

<p>Weekly vertical profiles of ammonia (NH₃) were measured at 16 heights on the Beijing 325&thinsp;m meteorological tower for 1 year from March 2016 to March 2017. The average NH₃ concentrations exceeded 4&thinsp;µg&thinsp;m⁻³ at all heights with an overall average (±1<i>σ</i>) value of 13.3&thinsp;(±4.8)&thinsp;µg&thinsp;m⁻³. The highest NH₃ concentrations along the vertical profiles mostly occurred from 32 to 63 m, decreasing both towards the surface and at higher altitudes. Significant decreases in NH₃ concentrations were only found at the top two heights (280 and 320&thinsp;m). These results suggest an NH₃ rich atmosphere during all seasons in urban Beijing, from the ground to at least 320&thinsp;m. The highest seasonal NH₃ concentrations across the profile were observed in summer (18.2&thinsp;µg&thinsp;m⁻³) with high temperature, followed by spring (13.4&thinsp;µg&thinsp;m⁻³), autumn (12.1&thinsp;µg&thinsp;m⁻³) and winter (8.3&thinsp;µg&thinsp;m⁻³). A significant vertical variation in the NH₃ concentration was only found in summer. Source region analyses suggest that air masses from intensive agricultural regions to the south contribute most to the high NH₃ concentrations in Beijing. Local sources such as traffic emissions also appear to be important contributors to atmospheric NH₃ in this urban environment.</p>