Preprints
https://doi.org/10.5194/egusphere-2023-500
https://doi.org/10.5194/egusphere-2023-500
14 Apr 2023
 | 14 Apr 2023
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

First Measurements of the Nitrogen Stable Isotope Composition (δ15N) of Ship-emitted NOx

Zeyu Sun, Zheng Zong, Yang Tan, Chongguo Tian, Zeyu Liu, Fan Zhang, Rong Sun, Yingjun Chen, Jun Li, and Gan Zhang

Abstract. The nitrogen stable isotope composition (δ15N) of nitrogen oxides (NOx) is a powerful indicator for source apportionment of atmospheric NOx; however, δ15N–NOx values emitted from ships have not been reported, affecting the accuracy of source partitioning of atmospheric NOx in coastal zones with a lot of ocean vessel activity. This study systemically analyzed the δ15N–NOx variability and main influencing factors of ship emissions. Results showed that δ15N–NOx values from ships ranged from −35.8 ‰ to 2.04 ‰ with a mean ± standard deviation of −18.5 ± 10.9 ‰. The δ15N–NOx values increased monotonically with the ongoing tightening of emission regulations, presenting a significantly negative logarithmic relationship with NOx concentrations (p < 0.01). The selective catalytic reduction (SCR) system was the most important factor affecting changes in δ15N–NOx values, compared with fuel types and operation states of ships. Based on the relationship between δ15N–NOx values and emission regulations observed in this investigation, the temporal variation in δ15N–NOx values from ship emissions in the international merchant fleet was evaluated by developing a mass-weighted model. These simulated δ15N–NOx values can be used to select suitable δ15N–NOx values for a more accurate assessment of the contribution of ship-emitted exhaust to atmospheric NOx.

Zeyu Sun et al.

Status: open (until 21 Jun 2023)

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Zeyu Sun et al.

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Short summary
This is the first report of ship-emitted nitrogen stable isotope composition (δ15N) of nitrogen oxides (NOx). Results showed that δ15N–NOx from ships was −18.5 ± 10.9 ‰ and increased monotonically with tightening emission regulations. The selective catalytic reduction system was the most vital factor. The temporal variation in δ15N–NOx was evaluated and can be used to select suitable δ15N–NOx for a more accurate assessment of the contribution of ship-emitted exhaust to atmospheric NOx.