Work

Refining δ15N isotopic fingerprints of local NO for accurate source identification of nitrate in PM2.5

Year: 2025

Type: article

Abstract: • The six typical NO x sources were collected in Tianjin, China, and the δ 15 N-NO x values exhibit distinct regional characteristics of China; • δ 15 N values from local NO x sources can more accurately trace the origins of NO 3 − in PM 2.5 ; • Excluding industrial NO x sources could result in an overestimation of the contributions from other sources by more than 10%; Stable nitrogen isotopic composition ( δ 15 N) has proven to be a valuable tool for identifying sources of nitrates (NO 3 – ) in PM 2.5 . However, the absence of a systematic study on the δ 15 N values of domestic NO x sources hinders accurate identification of NO 3 – sources in China. Here, we systematically determined and refined δ 15 N values for six categories of NO x sources in Tianjin using an active sampling method. Moreover, the δ 15 N values of NO 3 – in PM 2.5 were measured during pre-heating, mid-heating and late-heating periods, which are the most heavily polluted in Tianjin. The results indicate that the isotopic fingerprints of the six types of NO x sources in Tianjin are indicative of the regional characteristics of China, particularly the North China Plain. The Bayesian isotope mixing (MixSIAR) model demonstrated that coal combustion, biomass burning, and vehicle exhaust collectively contributed more than 60 %, dominating the sources of NO 3 – during sampling periods in Tianjin. However, failure to consider the isotopic signatures of local NO x sources could result in an overestimation of the contribution from natural gas 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 10 %. Notably, as the number of sources input to the model increased, the contribution of various NO x sources was becoming more stable, and the inter-influence between various sources significantly reduced. This study demonstrated that the refined isotopic fingerprint in China could more effectively distinguish source of NO 3 – , thereby providing valuable insights for controlling NO 3 – pollution.

Source: Environment International

DOI: 10.1016/j.envint.2025.109317

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

Institutions: Tianjin University, Shanghai Jiao Tong University, Henan University

Language: English

Topic: Atmospheric chemistry and aerosols

Subfield: Atmospheric Science

Field: Earth and Planetary Sciences

Domain: Physical Sciences

SDG: Climate action

Open Access status: gold

Estimated APC paid: $4,750