151. Isotopic Constraints on the Atmospheric Sources and Formation of Nitrogenous Species in Biomass-Burning-Influenced Clouds
- Author
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Jianmin Chen, Moritz F. Lehmann, Jiarong Li, Yan-Lin Zhang, Xiao-Yao Zhai, Chao Zhu, Chongguo Tian, Linlin Song, Yunhua Chang, Yunting Fang, Tong Huang, Wenqi Zhang, and Yu-Chi Lin
- Subjects
Atmosphere ,chemistry.chemical_compound ,Dinitrogen pentoxide ,Nitrate ,chemistry ,δ18O ,Environmental chemistry ,chemistry.chemical_element ,Environmental science ,Coal combustion products ,Nitrogen ,NOx ,Aerosol - Abstract
The interpretation of tropospheric cloud formation rests on understanding the sources and processes affecting aerosol constituents of the atmosphere that are preserved in cloudwater. However, this challenge is difficult to be quantitatively addressed based on the sole use of bulk chemical properties. Nitrogenous aerosols, mainly ammonium (NH4+) and nitrate (NO3−), play an important role in tropospheric cloud formation. Here we collected cloudwater samples at the summit of Mt. Tai (1545 m above sea level) in Eastern China during a long-lasting biomass burning (BB) event, and measured for the first time the isotopic compositions (mean ± 1σ) of cloudwater nitrogen species (δ15N-NH4+ = −6.53 ± 4.96 ‰, δ15N-NO3− = −2.35 ± 2.00 ‰, δ18O-NO3− = 57.80 ± 4.23 ‰), allowing insights into their sources and potential transformation mechanism within the clouds. Large contributions of BB to the cloudwater NH4+ (32.9 ± 4.6 %) and NO3− (28.2 ± 2.7 %) inventories were confirmed through a Bayesian isotopic mixing model, coupled with our newly-developed computational quantum chemistry module. Despite an overall reduction in total anthropogenic NOx emission due to effective emission control actions and stricter emission standards for vehicles, the observed cloud δ15N-NO3− values suggest that NOx emissions from transportation may have exceeded emissions from coal combustion. δ18O-NO3− values imply that the reaction of OH with NO2 is the dominant pathway of NO3− formation (57 ± 11 %), yet the contribution of heterogeneous hydrolysis of dinitrogen pentoxide was almost as important (43 ± 11 %).
- Published
- 2018