Sources and nitrogen isotope fractionation mechanisms of atmospheric amino acids

doi:10.13745/j.esf.sf.2025.3.25

Abstract

Abstract:

In recent years, amino acids in aerosols, including free amino acids (FAAs) and combined amino acids (CAAs), have attracted widespread attention. This is due to the significant roles these proteinaceous substances play in global climate change, the removal efficiency of air pollutants, the bioavailability of atmospheric nitrogen, the formation of secondary organic aerosols, and their effects on human health. This paper focuses on the application of stable nitrogen isotopes of compound-specific amino acids, a new technique, in tracing the sources and transformation processes of atmospheric amino acids. It reviews the stable nitrogen isotope characteristics of individual amino acids in potential atmospheric protein emission sources, as well as the mechanisms of stable nitrogen isotope fractionation during combustion processes and atmospheric transformations. Future research should further investigate the isotopic fractionation mechanisms of individual amino acid under different particle sizes, meteorological conditions, and special pollution events. This will help clarify the role and contribution of amino acids in cloud and precipitation formation, climate change, and pollution events.

Key words: free amino acids, combined amino acids, stable nitrogen isotopes, fractionation mechanisms

CLC Number:

P402

ZHU Renguo, XIAO Huayun. Sources and nitrogen isotope fractionation mechanisms of atmospheric amino acids[J]. Earth Science Frontiers, 2025, 32(3): 362-374.

Figures/Tables 5

Fig.1 The average of δ15N for free Gly from major emission sources. Adapted from [25]. NA represents not detected.

Table 1 Nitrogen isotope values of major sources of free and combined glycine release (modified after [27])

源	样本数量	δ¹⁵N值/‰
源	样本数量	平均值	分析精度	最小值	最大值
植物源中游离Gly	21	-13.4	3.0	-19.3	-7.6
土壤源中游离Gly	5	5.2	3.5	1.2	9.4
生物质燃烧源游离Gly	6	22.4	4.4	16.9	27.3
植物源中结合Gly	5	-11.1	2.7	-13.2	-6.6
土壤源中结合Gly	7	2.6	4.6	-1.6	7.8
生物质燃烧源结合Gly	6	19.2	0.6	18.1	19.8

Fig.2 Distribution of free amino acid and combined amino acids in biomass burning, soil, plant sources, and PM2.5. Modified after [27].

Fig.3 Photochemical and microbial processes that proteins may undergo in the atmosphere. Modified after [25,27].

Fig.4 Chemical reactions that proteinaceous compounds may undergo during combustion. Modified after [25,91].

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