The Roles of N, S, and O in Molecular Absorption Features of Brown Carbon in PM_2.5 in a Typical Semi‐Arid Megacity in Northwestern China

Abstract

Brown carbon (BrC) is a nonnegligible chemical component of organic aerosols and has great influences on radiative forcing, regional and global climates, and even human health (Lin et al., 2018). BrC can be released from a variety of emission sources such as traffic, biomass burning, and coal combustion, and formed from secondary transformation (Fleming et al., 2020;Soleimanian et al., 2020). BrC formed through different mechanisms could have unique light absorption capacities (Lei et al., 2019;Lukacs et al., 2007). The formations of BrC with sulfur (S), nitrogen (N), and oxygen (O)-containing precursors simulated in chamber experiments have been widely reported in the last decade (

Molecular Characterization of Water-Soluble Aerosol Particle Extracts by Ultrahigh-Resolution Mass Spectrometry: Observation of Industrial Emissions and an Atmospherically Aged Wildfire Plume at Lake Baikal

“…Nevertheless, plotting of the summed CHON 1 class intensity (ESI+, r S = 0.68, p < 0.05) as well as the CHOS class (ESI–, r S = 0.62, p < 0.05) with AAE in Figure S5 shows how an increase in UV light absorption is related to the relative abundance of the CHON and CHOS compound classes. Especially nitrogen-containing compounds are in the focus for being a part of BrC responsible for a significant share of light absorption due to their molecular properties. , This formation of BrC species during atmospheric aging may be driven by the presence of ammonia or ammonium salts as found for laboratory aging of VOCs in the gas phase or aqueous phase, counteracting photobleaching. , Similar sum formulae are also found in this study.…”

“…Together with the selectivity of the ionization modes, the higher relative abundance in ESI+ can be explained by the detection of nitro or amino groups as well as basic aromatic nitrogen (e.g., pyridine), which fit the limit of O/N and show sufficient proton affinity. Nitrogen compounds with CN and C–N functional groups and low O/N ratio were identified as the two most important chemical bonding structures of BrC in summer in methanol filter extracts from a Chinese megacity . On the other hand, in ESI–, the abundance of higher oxidized molecules is higher (O/N = 3–5, 52 ± 3 and 62 ± 3%, ESI±, respectively), which could be explained by the ionization of organic nitrates in combination with other acidic oxygen-containing functional groups.…”

“…Nitrogen compounds with CN and C−N functional groups and low O/N ratio were identified as the two most important chemical bonding structures of BrC in summer in methanol filter extracts from a Chinese megacity. 67 On the other hand, in ESI−, the abundance of higher oxidized molecules is higher (O/N = 3−5, 52 ± 3 and 62 ± 3%, ESI±, respectively), which could be explained by the ionization of organic nitrates in combination with other acidic oxygencontaining functional groups. Sum formulae with an even higher O/N ratio of larger than 5 could be assigned to peroxyacetyl nitrate (PAN) compounds, which can act as a way of transporting NO x to remote areas by long-range transport.…”

Molecular Characterization of Nitrogen-Containing Compounds in Humic-like Substances Emitted from Biomass Burning and Coal Combustion

“…N-containing organic compounds (NOCs) have been substantially identified in HULIS and are proposed to affect the atmospheric system in many ways. ,− For example, nitroaromatic compounds (e.g., nitrophenols) are a significant fraction of light-absorbing brown carbon (BrC) in aerosols, which have important influences on the radiative balance and photochemical reactions in the atmosphere. − Meanwhile, the reduced nitrogen such as N-bases (e.g., aliphatic and aromatic amides and N-heterocyclic compounds) is also identified in ambient aerosols, which can act as a H-bonding acceptor to enhance the ROS generation by HULIS. ,− Among them, some aromatic N-heterocyclic compounds have significant light absorption and can contribute to radiative forcing even at low atmospheric concentrations . Moreover, as a significant fraction of total nitrogen in aerosols, NOCs have important effects on the nitrogen deposition to the terrestrial and aquatic ecosystems and are essential parts of the total nitrogen cycle on Earth. , Therefore, a detailed understanding of molecular characteristics of NOCs in HULIS is necessary for assessing their environmental and climate impacts.…”

Factors Influencing the Molecular Compositions and Distributions of Atmospheric Nitrogen‐Containing Compounds

“…Because of spatial and temporal heterogeneity, this proportion varies from below 10% to over 80% on a global scale, without clear spatiotemporal patterns (Cornell, 2011;Jickells et al, 2013;Yu et al, 2020). Moreover, NOCs (e.g., nitroaromatic compounds and some N-heterocyclic compounds) are major constituents of the total brown carbon in aerosols and cloud water and laboratory-generated biogenic and anthropogenic secondary organic aerosols (SOAs; Desyaterik et al, 2013;Lin et al, 2017;Zeng et al, 2020Zeng et al, , 2021; thus, NOCs profoundly influence regional and global radiative forcing and climate changes (Laskin et al, 2015).…”