Measurement report: Exploring NH<sub>3</sub> behavior in urban and suburban Beijing: comparison and implications

Abstract

Abstract. Ammonia (NH3) plays an important role in particulate matter formation; hence, its atmospheric level is relevant to human health and climate change. Due to different relative distributions of NH3 sources, concentrations of atmospheric NH3 may behave differently in urban and rural areas. However, few parallel long-term observations of NH3 exist to reveal the different behaviors of NH3 concentrations at urban and rural sites in a same region. In this study, online ammonia analyzers were used to continuously observe atmospheric NH3 concentrations at an urban site and a suburban site in Beijing from 13 January 2018 to 13 January 2019. The observed mixing ratio of NH3 averaged 21±14 ppb (range of 1.6–133 ppb) at the urban site and 22±15 ppb (range of 0.8–199 ppb) at the suburban site. The NH3 mixing ratios at the urban and suburban sites exhibited similar seasonal variations, with high values in summer and spring and low values in autumn and winter. The hourly mean NH3 mixing ratios at the urban site were highly correlated (R=0.849, P<0.01) with those at the suburban site; however, the average diurnal variations in the NH3 mixing ratios at the urban and suburban sites differed significantly, which implies different contributions from NH3 sources and sinks at the urban and suburban sites. In addition to the emission sources, meteorological factors were closely related to the changes in the NH3 concentrations. For the same temperature (relative humidity) at the urban and suburban sites, the NH3 mixing ratios increased with relative humidity (temperature). Relative humidity was the factor with the strongest influence on the NH3 mixing ratio in different seasons at the two sites. The relationships between the NH3 concentrations and temperature (relative humidity) varied from season to season and showed differences between the urban and suburban sites. The reasons for the different relationships need to be investigated in future studies. Higher wind speed mainly from the northwest sector lowered the NH3 mixing ratios at both sites. Similarly to other primary pollutants in Beijing, the NH3 mixing ratios were high when impacted by air masses from the southern sector.

Vehicular Emissions Enhanced Ammonia Concentrations in Winter Mornings: Insights from Diurnal Nitrogen Isotopic Signatures

“…Overall, the hourly NH 3 concentrations ranged from 1.5 to 67.3 μg m –3 , with a year-round mean of 16.4 ± 10.3 μg m –3 . The average annual NH 3 concentration observed here is comparable with previous results in Beijing. , For seasonal variations, the NH 3 concentrations increased from spring to summer, peaking in July as 25.5 ± 9.0 μg m –3 , and then decreased gradually in autumn and winter, falling to 8.5 ± 5.8 μg m –3 in January. For diurnal variations, an early morning spike of NH 3 concentrations was observed in most months (except for November), in which the concentration of NH 3 rapidly increased after 05:00, peaked around 09:00, and then decreased until reaching the minimum at 17:00.…”

4D‐Var Inversion of European NH3 Emissions Using CrIS NH3 Measurements and GEOS‐Chem Adjoint With Bi‐Directional and Uni‐Directional Flux Schemes

“…While the bi-di scheme seems to better capture the diurnal variability at the background site in Germany, such improvements may not be ubiquitous. For comparison, different diurnal cycles were identified at urban and suburban sites at Beijing in Lan et al (2021), where generally higher concentrations of ammonia during the daytime and low concentrations during the nighttime were observed at a suburban site during most of the year except autumn, while the opposite condition was found at an urban site during non-spring seasons. As discussed therein, the complexity and variability of NH 3 diurnal cycles is owing to multiple competing factors including sources, chemical sinks, vertical mixing, horizontal transport, temperature, relative humidity, and other meteorological impacts; improvements made owing to bi-di alone may not lead to improved simulated diurnal variability in all conditions.…”

Chloride (HCl ∕ Cl−) dominates inorganic aerosol formation from ammonia in the Indo-Gangetic Plain during winter: modeling and comparison with observations

“…However, over India, the impact on reducing PM 2.5 might be limited because NH 3 emission reductions may be more challenging due to its diverse and area-wide sources. Ianniello et al (2010) and Lan et al (2021) have investigated the variation of atmospheric NH 3 at an urban and suburban site of Beijing with respect to meteorological factors, where RH was found to be a strong factor in influencing the NH 3 mixing ratio. A few studies over Asia have highlighted the gas-to-particle conversion of NH 3 in Delhi (Acharja et al, 2021;Saraswati et al, 2019) and China and its subsequent impact on the aerosol formation (Wang et al, 2015;Xu et al, 2020).…”