Size‐Resolved Characterization of the Chromophores in Atmospheric Particulate Matter From a Typical Coal‐Burning City in China

Abstract

This study reports the size‐resolved characterization of the chromophores in atmospheric particulate matter in Linfen, a typical coal‐burning city in China. The optical properties of both the water‐soluble and water‐insoluble chromophores in atmospheric particulates are studied using excitation‐emission matrix spectroscopy and follow the parallel factor analysis of excitation‐emission matrix data. The mass absorption efficiency and normalized fluorescence volume by mass concentration of the organic carbon in methanol‐soluble matter in the particulate samples are stronger than that of the water‐soluble matter. We found that the total absorption (Abs), fluorescence volume (FV), mass absorption efficiency, and normalized fluorescence volume of particle extracts with sizes less than 10 μm increased with the decreasing particle size. The total concentration of the selected seven polycyclic aromatic hydrocarbons was positively correlated with the Abs365 and FV of both the water‐soluble matter and methanol‐soluble matter, but the average contribution of the selected polycyclic aromatic hydrocarbons to the total Abs and FV was very small (<3%). This study is the first to report a size‐resolved characterization of the chromophores in atmospheric particulate matter. Humic‐like substances tend to be present in small particles, and tryptophan‐like and tyrosine‐like components tend to increase with increasing particle size.

Size-resolved exposure risk of persistent free radicals (PFRs) in atmospheric aerosols and their potential sources

“…3.2 of this study, this particulate matter is related to combustion, which indicates that coal combustion in winter may provide an important contribution to EPFRs. The EPFR concentration in the fine PM of Linfen reported above is equivalent to that in the fine PM of Xi'an, but it is 10 times smaller than that in the fine PM of Beijing (Yang et al, 2017;Chen et al, 2019b). Although the particle size distribution characteristics of EPFRs in winter and summer are different, their concentration levels are similar, which in- dicates that the EPFR concentration is not related to the PM concentration but is determined by the source characteristics.…”

“…EPFRs of different lifetimes are present in atmospheric PM, with only a few hours for short-lifetime EPFRs and several years for longlifetime EPFRs that show no signs of decay (Gehling and Dellinger, 2013;Chen et al, 2019c). Most studies indicate that sources of transportation and combustion may be the primary EPFR sources in atmospheric PM (Wang et al, 2018;Yang et al, 2017;Chen et al, 2019b). Chen et al (2018bChen et al ( , 2019b found that strong atmospheric photochemical effects in summer and dust particles may also be important sources of EPFRs.…”

“…Most studies indicate that sources of transportation and combustion may be the primary EPFR sources in atmospheric PM (Wang et al, 2018;Yang et al, 2017;Chen et al, 2019b). Chen et al (2018bChen et al ( , 2019b found that strong atmospheric photochemical effects in summer and dust particles may also be important sources of EPFRs. The process of electron transfer and stabilization between the surface of metal oxides (such as iron, copper, zinc and nickel) and substituted aromatic molecules under high temperatures is considered to be the main process for the formation of EPFRs in atmospheric particles (Truong, 2010;Vejerano et al, 2012a;Patterson et al, 2013;Vejerano et al, 2011Vejerano et al, , 2012b.…”

Molecular compositions and optical properties of dissolved brown carbon in biomass burning, coal combustion, and vehicle emission aerosols illuminated by excitation–emission matrix spectroscopy and Fourier transform ion cyclotron resonance mass spectrometry analysis

“…The EFs emitted from bituminous CC (PM = 9.1 × 10 −1 ± 6.5 × 10 −1 g kg −1 fuel, OC = 4.2 × 10 −1 ± 3.3 × 10 −1 g kg −1 fuel, and EC = 9.4 × 10 −2 ± 1.9 × 10 −1 g kg −1 fuel) were much higher than those of anthracite combustion (PM = 1.5 × 10 −1 ± 8.9 × 10 −2 g kg −1 fuel, OC = 1.2 × 10 −2 ± 4.5 × 10 −3 g kg −1 fuel, and EC = 1.6 × 10 −4 ± 1.4 × 10 −4 g kg −1 fuel) in the same stove. These differences could be attributed to the high volatile matter content of bituminous coal (Tian et al, 2017;Chen et al, 2005). Note that the CC smoke collection began when the flame had been ignited with one third of the material, and the rest was added.…”

“…The C5 and C6 components were more intense in vehicle exhaust particles (25 ± 6.8 % and 50 ± 6.8 %, respectively), suggesting they were the primary vehicle emission chromophores. The last study observed that the relative abundances of various chromophores in aerosols with different particle sizes were different (Chen et al, 2019). Therefore, the fluorescence technique is sensitive for chromophores with different sources, sizes, and chemical structures, and so on.…”