Preprints
https://doi.org/10.5194/egusphere-2024-1621
https://doi.org/10.5194/egusphere-2024-1621
27 Jun 2024
 | 27 Jun 2024
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Technical note: Refining δ15N isotopic fingerprints of local NOx for accurate source identification of nitrate in PM2.5

Hao Xiao, Qinkai Li, Shiyuan Ding, Wenjing Dai, Gaoyang Cui, and Xiaodong Li

Abstract. Stable nitrogen isotopic composition (δ15N) has proven to be a valuable tool for identifying sources of nitrates (NO3) in PM2.5. However, the absence of a systematic study on the δ15N values of domestic NOx sources hinders accurate identification of NO3 sources in China. Here, we systematically determined and refined δ15N values for six categories of NOx sources in the local Tianjin area using an active sampling method. Moreover, the δ15N values of NO3 in PM2.5 were measured during pre-heating, mid-heating and late-heating periods, which are the most heavily polluted in Tianjin. Results shown that the representative nature and region-specific characteristics of isotopic fingerprints for six categories of NOx sources in Tianjin. The Bayesian isotope mixing (MixSIAR) model demonstrated that coal combustion, biomass burning, and vehicle exhaust collectively contributed more than 60 %, dominating the sources of NO3 during sampling periods in Tianjin. However, failure to consider the isotopic signatures of local NOx sources could result in an underestimation of the contribution from coal combustion. Additionally, the absence of industrial sources, an uncharacterized source in previous studies, may directly result in the contribution fraction of other sources being overestimated by the model more than 15 %. Notably, as the number of sources input to the model increased, the contribution of various NOx sources was becoming more stable, and the inter-influence between various sources significantly reduced. This study demonstrated that the refined isotopic fingerprint in a region-specific context could more effectively distinguish source of NO3, thereby providing valuable insights for controlling NO3 pollution.

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Hao Xiao, Qinkai Li, Shiyuan Ding, Wenjing Dai, Gaoyang Cui, and Xiaodong Li

Status: open (until 09 Aug 2024)

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  • RC1: 'Comment on egusphere-2024-1621', Anonymous Referee #1, 24 Jul 2024 reply
Hao Xiao, Qinkai Li, Shiyuan Ding, Wenjing Dai, Gaoyang Cui, and Xiaodong Li
Hao Xiao, Qinkai Li, Shiyuan Ding, Wenjing Dai, Gaoyang Cui, and Xiaodong Li

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Short summary
This study established a refined isotopic fingerprint of NOx sources in local Tianjin, which included previously uncharacterized sources in China. Results shown that the representative nature and region-specific characteristics of isotopic fingerprints for six categories of NOx sources in Tianjin. A reasonable source-resolved structure of NO3 could obtained by MixSIAR model using the δ15N values of NOx source established in this study, suggest the important of the refined isotopic fingerprint.