Persistent Nonagricultural and Periodic Agricultural Emissions Dominate Sources of Ammonia in Urban Beijing: Evidence from 15N Stable Isotope in Vertical Profiles

Ammonia (NH3) emission reduction is key to limiting the deadly PM2.5 pollution globally. However, studies of long-term source apportionment of vertical NH3 are relatively limited. On the basis of the one-year measurements of weekly vertical profiles of δ 15N–NH3 at 5 heights (2, 15, 102, 180, and 32...

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Bibliographic Details
Published in:Environmental science & technology 2020-01, Vol.54 (1), p.102-109
Main Authors: Zhang, Yangyang, Benedict, Katherine B, Tang, Aohan, Sun, Yele, Fang, Yunting, Liu, Xuejun
Format: Article
Language:English
Subjects:
Ammonia
Apportionment
Emissions
Emissions control
Fertilization
Fossil fuels
Human influences
Particulate matter
Seasonal variations
Stable isotopes
Vertical distribution
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Summary:Ammonia (NH3) emission reduction is key to limiting the deadly PM2.5 pollution globally. However, studies of long-term source apportionment of vertical NH3 are relatively limited. On the basis of the one-year measurements of weekly vertical profiles of δ 15N–NH3 at 5 heights (2, 15, 102, 180, and 320 m) on a 325-m meteorological tower in urban Beijing, we found that vertical profiles of NH3 concentrations generally remained stable with height. δ 15N–NH3 increased obviously as a function of height in cold seasons (with heating) and decreased in warm seasons (with fertilization), indicating a stronger human-induced seasonal variation via regional transport at higher altitudes. Relatively stable δ 15N–NH3 near the ground surface suggested the strong local emission. The results of isotopic mixing model (SIAR) indicate that source apportionment using measured δ 15N–NH3 only would overestimate the contribution of agricultural emissions to NH3. By using an estimation of initial δ 15N–NH3, we found that nonagricultural sources contributed ∼72% of NH3 on average. Our study suggests that (i) both persistent nonagricultural and periodic agricultural emissions drive atmospheric NH3 concentration and its vertical distribution in urban Beijing; and (ii) source apportionment based on measured δ 15N–NH3 only likely underestimates fossil fuel source contribution, if the combined NH x isotope effects are not considered.
ISSN:0013-936X
1520-5851
DOI:10.1021/acs.est.9b05741