The size distribution of amino acids (AAs) in atmospheric particles determines the atmospheric allergenicity, which may have deleterious effects on human health. This paper explores the use of compound-specific δ15N patterns of hydrolyzed amino acid (HAA), δ15N values of total hydrolyzed amino acid (THAA), degradation index (DI), and the variance within trophic AAs (ΣV) as markers to examine the sources and processing history of different sizes particle in the atmosphere. 2-weeks of daily aerosol samples from five sampling sites in the Nanchang area (Jiangxi Province, China) and samples of main emission sources of AAs in aerosols (biomass burning, soil and plants) were collected (Zhu et al., 2020). Here, we measured the concentrations and δ15N values of each HAA in two size segregated aerosol particles (> 2.5 μm and PM2.5). Our results showed that the average concentrations of THAA in fine particles was nearly 6 times higher than that in coarse particles (p δ15N values of hydrolyzed glycine (Gly) in both fine (−1.0 ‰ to +20.3 ‰) and coarse particles (−0.8 ‰ to +15.7 ‰) exhibited wide ranges, but both fall within the ranges of Gly from biomass burning, soil and plant sources. Similarly, δ15N values of THAA in both fine (+0.7 ‰ to +13.3 ‰) and coarse particles (−2.3 ‰ to +10.0 ‰) were typically in the range of THAA from these three emission sources. Moreover, the average difference in the δ15NTHAA value between fine and coarse particles was smaller than 1.5 ‰. These results suggested that the sources of atmospheric AAs for fine and coarse particles might be similar, which are dominated by AAs from biomass burning, soil, and plant sources. Meanwhile, compared to fine particles, significantly lower DI values (p scattered δ15N distribution in Trophic-AA and higher ΣV values (p δ15N values of Source-AA (Gly, Ser, Phe and Lys) and THAA (δ15NTHAA) between coarse particles and fine particles was relatively small. It is likely that AAs in coarse particles have advanced bacterial degradation state compared to fine particles. Besides that, the significant increase in DI values and a decrease in ΣV values for coarse particles were observed at the onset of the rainfall events (p fresh AAs in coarse particles were mainly released at the onset of the precipitation and decayed swiftly.
