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

Atmospheric chemistry and physics, Journal Year: 2020, Volume and Issue: 20(4), P. 2513 - 2532

Published: March 2, 2020

Abstract. Brown carbon (BrC) plays an essential impact on radiative forcing due to its ability absorb sunlight. In this study, the optical properties and molecular characteristics of water-soluble methanol-soluble organic (OC; MSOC) emitted from simulated combustion biomass coal fuels vehicle emissions were investigated using ultraviolet–visible (UV–vis) spectroscopy, excitation–emission matrix (EEM) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) coupled with electrospray ionization (ESI). The results showed that these smoke aerosol samples burning (BB) (CC) had a higher absorption efficiency at 365 nm (MAE365) than emission samples. A stronger MAE365 value was also found in MSOC (WSOC), indicating low polar compounds would possess light capacity. Parallel factor (PARAFAC) analysis identified six types fluorophores (P1–6) WSOC including two humic-like substances (HULIS-1) (P1 P6), three protein-like (PLOM) (P2, P3, P5), one undefined substance (P4). HULIS-1 mainly aging exhaust particles; P2 only abundant BB aerosols; P3 ubiquitous all tested P4 fossil P5 more intense fresh particles. chromophores (six components; C1–6) exhibited consistent WSOC, suggesting method could be used indicate origins chromophores. FT-ICR spectra CHO CHON most components but S-containing appeared abundance CC aerosols aerosols, while considerably fewer largely detected MSOC. unique formulas different sources van Krevelen (VK) diagram presented distributions. To specific, medium H ∕ C O ratio, opposite ratio. Moreover, capacity positively associated unsaturation degree weight source aerosols. above are potentially applicable further studies EEM-based or molecular-characteristic-based apportionment atmospheric

Language: Английский

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Molecular Dynamics and Light Absorption Properties of Atmospheric Dissolved Organic Matter

Environmental Science & Technology, Journal Year: 2021, Volume and Issue: 55(15), P. 10268 - 10279

Published: July 21, 2021

The light-absorbing organic aerosol referred to as brown carbon (BrC) affects the global radiative balance. linkages between its molecular composition and light absorption properties how environmental factors influence BrC are not well understood. In this study, atmospheric dissolved matter (ADOM) in 55 samples from Guangzhou was characterized using Fourier transform ion cyclotron resonance mass spectrometry measurements. abundant components ADOM were aliphatics peptide-likes (in structure), or nitrogen- sulfur-containing compounds elemental composition). of positively correlated with levels unsaturated aromatic structures. Particularly, 17 nitrogen-containing species, which identified by a random forest, variation well. Aggregated boosted tree model nonmetric multidimensional scaling analysis show that largely driven meteorological conditions anthropogenic activities, among biomass burning (BB) OH radical two important factors. often accumulate elevated BB emissions related secondary processes, whereas photolysis/photooxidation usually occurs under high solar radiance/•OH concentration. This study first illuminated at level provided clues for molecular-level research future.

Language: Английский

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Characterization of the light-absorbing properties, chromophore composition and sources of brown carbon aerosol in Xi'an, northwestern China

Atmospheric chemistry and physics, Journal Year: 2020, Volume and Issue: 20(8), P. 5129 - 5144

Published: April 30, 2020

Abstract. The impact of brown carbon aerosol (BrC) on the Earth's radiative forcing balance has been widely recognized but remains uncertain, mainly because relationships among BrC sources, chromophores and optical properties are poorly understood. In this work, light absorption chromophore composition were investigated for samples collected in Xi'an, northwestern China, from 2015 to 2016. Both Ångström exponent (AAE) mass efficiency (MAE) show distinct seasonal differences, which could be attributed differences sources BrC. Three groups light-absorbing organics found important chromophores, including compounds that have multiple peaks at wavelengths > 350 nm (12 polycyclic aromatic hydrocarbons their derivatives) a single peak < (10 nitrophenols nitrosalicylic acids 3 methoxyphenols). These measured contribute average about 1.1 % 3.3 methanol-soluble 365 summer winter, respectively, 7 5 times higher than corresponding fractions total organic carbon. resolved by positive matrix factorization (PMF) using these instead commonly used non-light-absorbing markers as model inputs. Our results vehicular emissions secondary formation major (∼ 70 %) spring, coal combustion fall, biomass burning become 80 dominates 60 summer.

Language: Английский

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

Environmental Science & Technology, Journal Year: 2021, Volume and Issue: 56(1), P. 119 - 130

Published: Dec. 9, 2021

N-containing organic compounds (NOCs) in humic-like substances (HULIS) emitted from biomass burning (BB) and coal combustion (CC) were characterized by ultrahigh-resolution mass spectrometry the positive electrospray ionization mode. Our results indicate that NOCs include CHON+ CHN+ groups, which are detected as a substantial fraction both BB- CC-derived HULIS, suggest not only BB but also CC is potential important source of atmosphere. The mainly consist reduced nitrogen with other oxygenated functional straw- coal-smoke HULIS exhibit lower degree oxidation than pine-smoke HULIS. In addition, higher N atoms (N2 and/or N3) generally bear modified aromaticity index (AImod) values contained especially straw-smoke whereas atom (N1) always have relatively AImod dominant These findings imply primary emission may be significant N1 compounds, high number (e.g., N2–3) could associated materials. Further study warranted to distinguish more sources.

Language: Английский

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Chemical Fingerprinting of HULIS in Particulate Matters Emitted from Residential Coal and Biomass Combustion

Environmental Science & Technology, Journal Year: 2021, Volume and Issue: 55(6), P. 3593 - 3603

Published: March 3, 2021

Identification of humic-like substances (HULIS) structures and components is still a major challenge owing to their chemical complexity. This study first employed complementary method with the combination two-dimensional gas chromatography-time-of-flight mass spectrometry liquid chromatography-quadrupole-time-of-flight address low-polarity polar HULIS in PM2.5 (particulate matter an aerodynamic diameter less than 2.5 μm), respectively. The showed significant correlation identifying overlapping species performed well uncovering complexity HULIS. A total 1246 compound (65.6-81.0% for each sample), approximately 1 order magnitude more compounds that reported previous studies, were addressed collected real-world household biomass coal combustion. Aromatics most abundant (37.4-64.1% 34.5-70.0% samples) all samples according carbon skeleton determination, while included phenols (2.6-21.1%), ketones (6.0-17.1%), aldehydes (1.1-6.8%), esters (2.9-20.0%), amines/amides (3.2-8.5%), alcohols (3.8-17.0%), acids (4.7-15.1%). Among identified species, 11-36% 11-41% chromophores, another 22-35 23-29% chromophore precursors, shows promise fingerprinting.

Language: Английский

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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

Journal of Geophysical Research Atmospheres, Journal Year: 2021, Volume and Issue: 126(16)

Published: Aug. 9, 2021

Abstract Brown Carbon (BrC) absorbs light in wavelength of 300–400 nm, and BrC molecule (BrCM) is a fundamental component responsible for aerosol radiative forcing. In this study, Fourier‐transform ion cyclotron resonance mass spectrometry (FT‐ICR MS) coupled with electrospray ionization (ESI) was used to determine methanol extracted BrCM PM 2.5 collected Xi'an, China. The absorption individual quantified through partial least square regression (PLSR) method. Results showed that 77.5% 91.8% winter summer BrCMs were weak absorptive. top 60.4% 84.6%, respectively, the absorbances winter. nitrogen (N)‐containing organic molecules identified be critical components light‐absorbing matters both two seasons, outlining significance N chromogenesis BrC. more closely related ‐(O)NO 2 originated from NO engaged reactions winter, ‐NH formed NH 3 summer. Sulfur (S)‐containing functional groups not chromophoric while sulfur dioxide (SO ) triggered N‐containing S‐free formations under high oxides (NOx) concentration levels relative humidity (RH) Hypochromicity oxygen (O) discovered because photobleaching oxidation highly oxidized molecules.

Language: Английский

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Nitrogen Enrichment during Soil Organic Matter Burning and Molecular Evidence of Maillard Reactions

Environmental Science & Technology, Journal Year: 2022, Volume and Issue: 56(7), P. 4597 - 4609

Published: March 9, 2022

Wildfires in forested watersheds dramatically alter stored and labile soil organic matter (SOM) pools the export of dissolved (DOM). Ecosystem recovery after wildfires depends on microbial communities revegetation therefore is limited by availability nutrients, such as nitrogen-containing labile, water-soluble compounds. However, SOM byproducts produced at different wildfire intensities are poorly understood, leading to difficulties assessing severity predicting ecosystem recovery. In this work, water-extractable (WEOM) from laboratory microcosms burned discrete temperatures was characterized ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry study impacts fire temperature DOM composition. The molecular composition derived burn indicated that were enriched with heating composed a wide range aromatic features oxidation states. Mass difference-based analysis also suggested products formed during could be modeled using transformations along Maillard reaction pathway. enrichment N-containing burning has important implications for downstream water quality.

Language: Английский

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Formation of Secondary Nitroaromatic Compounds in Polluted Urban Environments

Journal of Geophysical Research Atmospheres, Journal Year: 2022, Volume and Issue: 127(10)

Published: May 14, 2022

Abstract Nitroaromatic compounds (NACs) are important light absorption contributors to atmospheric brown carbon; however, their formation pathways and the key influential factors in polluted urban atmospheres largely unknown. Herein, we present molecular characterization of particulate NACs Shanghai by applying ultra‐high‐performance liquid chromatography coupled Orbitrap mass spectrometry, investigated seasonal diel variations pathways. The total number abundance increased significantly during air pollution episodes, these exhibited greatest relative among CHON compounds. 12 quantified higher levels winter (52.3 ± 29.1 ng m −3 ) than summer (7.83 3.30 ), owing masses mostly passing through northern heating regions. Among NACs, 4‐nitrophenol 4‐nitrocatechol were most abundant species. Most enhanced via photooxidation day summer, while day‐night not as obvious. Further analysis relevance suggested that nitrophenol its methylated derivatives mainly formed gas‐phase photochemical reactions, whereas aqueous‐phase oxidation processing could be an pathway form methyl‐nitrocatechols. Formation was relatively sensitive NO 2 under low‐NO x conditions, became independent high‐NO conditions. A larger fraction transformed into inorganic nitrate products when less abundant, implying would play more roles aerosol properties with decline concentrations.

Language: Английский

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Unveiling the Molecular Characteristics, Origins, and Formation Mechanism of Reduced Nitrogen Organic Compounds in the Urban Atmosphere of Shanghai Using a Versatile Aerosol Concentration Enrichment System

Environmental Science & Technology, Journal Year: 2024, Volume and Issue: 58(16), P. 7099 - 7112

Published: March 27, 2024

Reduced nitrogen-containing organic compounds (NOCs) in aerosols play a crucial role altering their light-absorption properties, thereby impacting regional haze and climate. Due to the low concentration levels of individual NOCs air, utilization accurate detection quantification technologies becomes essential. For first time, this study investigated diurnal variation, chemical characteristics, potential formation pathways urban ambient Shanghai using versatile aerosol enrichment system (VACES) coupled with HPLC-Q-TOF-MS. The results showed that accounted over 60% identified components aerosols, O/N < 3 being major contributors (>70%). predominance positive ionization mode suggested prevalence reduced NOCs. Higher relative intensities number fractions were observed during nighttime, while CHO an opposite trend. Notably, correlation between intensity ammonium nighttime was observed, suggesting reaction form imines may be pathway for nighttime. Seven prevalent types autumn winter characterized by CH2 long-chain homologues. These included alkyl, cyclic, aromatic amides CHON compounds, as well heterocyclic or cyclic amines aniline homologue series CHN which associated anthropogenic activities capable forming light-absorbing chromophores posing harm human health. findings highlight significant contributions both primary emissions chemistry, particularly amination processes, pollution Shanghai's atmosphere.

Language: Английский

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Molecular Characterization of Water‐Soluble Brown Carbon Chromophores in Beijing, China

Journal of Geophysical Research Atmospheres, Journal Year: 2020, Volume and Issue: 125(15)

Published: June 30, 2020

Abstract High abundance and strong light absorption of atmospheric brown carbon (BrC) have been reported in East Asia, especially northern China. However, the molecular‐level understanding BrC chromophores this area is still limited quite challenging. In study, elemental composition individual was first investigated megacity Beijing, China, using a powerful platform for characterization chromophores, with combination high‐performance liquid chromatography coupled to UV/Vis absorbance detector time‐of‐flight mass spectrometer an electrospray ionization source. The results from study showed that S‐containing compounds (e.g., CHOS CHONS) significantly increased highly polluted days compared lightly days, probably due emissions sources such as coal combustion favorable conditions organosulfates formation. It found CHON CHO were most abundant water‐soluble organic Beijing during wintertime. Nitroaromatic major three C 6 H 5 NO 3 , 7 4 ) under all conditions, while other specific CHON‐ CHO‐containing formulas identified varied different seasons pollution conditions. Overall, explained about 2%–18% bulk over wavelength range 300–400 nm. In‐depth studies on exploring more well their chemical structures, related sources, formation mechanisms should be conducted future.

Language: Английский

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