Significant contributions of combustion-related sources to ammonia emissions.

Chen, Zhi-Li; Song, Wei; Hu, Chao-Chen; Liu, Xue-Jun; Chen, Guan-Yi; Walters, Wendell W; Michalski, Greg; Liu, Cong-Qiang et al. · Nat Commun · 2022

basic_science · Level V

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Abstract

Atmospheric ammonia (NH<sub>3</sub>) and ammonium (NH<sub>4</sub><sup>+</sup>) can substantially influence air quality, ecosystems, and climate. NH<sub>3</sub> volatilization from fertilizers and wastes (v-NH<sub>3</sub>) has long been assumed to be the primary NH<sub>3</sub> source, but the contribution of combustion-related NH<sub>3</sub> (c-NH<sub>3</sub>, mainly fossil fuels and biomass burning) remains unconstrained. Here, we collated nitrogen isotopes of atmospheric NH<sub>3</sub> and NH<sub>4</sub><sup>+</sup> and established a robust method to differentiate v-NH<sub>3</sub> and c-NH<sub>3</sub>. We found that the relative contribution of the c-NH<sub>3</sub> in the total NH<sub>3</sub> emissions reached up to 40 ± 21% (6.6 ± 3.4 Tg N yr<sup>-1</sup>), 49 ± 16% (2.8 ± 0.9 Tg N yr<sup>-1</sup>), and 44 ± 19% (2.8 ± 1.3 Tg N yr<sup>-1</sup>) in East Asia, North America, and Europe, respectively, though its fractions and amounts in these regions generally decreased over the past decades. Given its importance, c-NH<sub>3</sub> emission should be considered in making emission inventories, dispersion modeling, mitigation strategies, budgeting deposition fluxes, and evaluating the ecological effects of atmospheric NH<sub>3</sub> loading.

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