Isotopic Variability of Ammonia (delta N-15-NH3) Slipped from Heavy-Duty Vehicles under Real-World Conditions

Chang, Yunhua and Cheng, Kai and Kuang, Yaqiong and Hu, Qingyao and Gao, Yaqing and Huang, Ru-Jin and Huang, Cheng and Walters, Wendell W. and Lehmann, Moritz F.. (2022) Isotopic Variability of Ammonia (delta N-15-NH3) Slipped from Heavy-Duty Vehicles under Real-World Conditions. Environmental Science and Technology Letters, 9 (9). pp. 726-732.

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Official URL: https://edoc.unibas.ch/92815/

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The widespread use of urea-SCR (selective catalytic reduction aftertreatment to meet stringent heavy-duty vehicle (HDV) NOx emission standards has worldwide led to increased exhaust ammonia (NH3) slip. A prerequisite for the nitrogen (N) stable isotope (delta N-15)-based source apportionment of ambient NH3 is that the N isotopic signatures of NH3 sources be well characterized. However, knowledge of delta N-15 values from HDV-emitted NH3 is still lacking. Using an on-board HDV emission measurement system, tailpipe-emitted gaseous NH3 from eight HDVs was collected during real-world driving conditions, and delta N-15 values were analyzed. We tentatively report an average delta N-15-NH3 [mean +/- 1 sigma = (-1.74 +/- 6.27)parts per thousand] that is significantly higher (and hence potentially of diagnostic value) than that of naturally occurring volatile NH3 sources (less than -26 parts per thousand) but only slightly lower than that of gasoline vehicles equipped with three-way catalytic converters. The observed variations in measured HDV delta N-15-NH3 can be largely explained by the differential N-isotope fractionation during NH3 formation and the extent of ammonia conversion. We found that minor changes in SCR efficiency can cause relatively large fluctuations in PN-NH3, highlighting the difficulties and/or limitations with regard to attributing a characteristic delta N-15 to tailpipe NH3 in N-isotope balances and source partitioning efforts.
Faculties and Departments:05 Faculty of Science > Departement Umweltwissenschaften > Geowissenschaften > Aquatic and Isotope Biogeochemistry (Lehmann)
UniBasel Contributors:Lehmann, Moritz F
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:American Chemical Society
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:19 Jan 2023 09:37
Deposited On:19 Jan 2023 09:37

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