Molecular insights into the composition, sources, and aging of atmospheric brown carbon

Chemical Society Reviews, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 1, 2025

The light-absorbing chemical components of atmospheric organic aerosols are commonly referred to as Brown Carbon (BrC), reflecting the characteristic yellowish brown appearance aerosol.

Language: Английский

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Decay Kinetics and Absorption Changes of Methoxyphenols and Nitrophenols during Nitrate-Mediated Aqueous Photochemical Oxidation at 254 and 313 nm

ACS Earth and Space Chemistry, Journal Year: 2022, Volume and Issue: 6(4), P. 1115 - 1125

Published: March 28, 2022

Brown carbon (BrC) absorbs radiation in the near-UV and visible ranges, affecting atmospheric photochemistry radiative forcing. Our understanding on photochemical transformation of BrC is still limited, especially when mixed with abundant photochemically labile inorganic salt, nitrate. Herein, we investigate reactions four chromophores, including two methoxyphenols nitrophenols. Experiments were conducted absence presence different concentrations H2O2 nitrate lights 254 313 nm. The results show that pseudo-first-order decay rate constants (k) these compounds at nm illumination approximately 10 times lower than those nm, demonstrating longer lifetimes chromophores under tropospherically relevant irradiation. Photo-enhancement range was observed most experiments, lasting longer, indicating prolonged effects nascent transformed Methoxyphenols had higher averaged k values nitrophenols during direct photolysis or lights, but for high-nitrate (or high-H2O2) conditions approached methoxyphenols. photo-enhancement substantially contributed by nitro products, while mainly hydroxylated and/or dimerized products. reveal similarity difference between nitrophenols, which may help better understand aging types model representation their

Language: Английский

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Molecular characteristics, sources, and formation pathways of organosulfur compounds in ambient aerosol in Guangzhou, South China

Atmospheric chemistry and physics, Journal Year: 2022, Volume and Issue: 22(10), P. 6919 - 6935

Published: May 30, 2022

Abstract. Organosulfur compounds (OrgSs), especially organosulfates, have been widely reported to be present in large quantities particulate organic matter found various atmospheric environments. Despite hundreds of organosulfates and their formation mechanisms being previously identified, a fraction OrgSs remain unexplained at the molecular level, better understanding pathways critical environmental parameters is required explain variations concentrations. In this study, abundance composition fine samples collected Guangzhou were reported. The results revealed that ratio annual average mass sulfur total was 33 ± 12 %, had positive correlations with SO2 (r=0.37, p<0.05) oxidant (NOx + O3, r=0.40, p<0.01). A Fourier transform ion cyclotron resonance spectrometry (FT-ICR MS) analysis more than 80 % sulfur-containing formulas detected elemental o/(4s+3n)≥1, indicating they largely form oxidized or nitrooxy organosulfates. Many tentatively identified as having biogenic anthropogenic origins also freshly emitted aerosols derived from combustion sources. indicated through an epoxide intermediate pathway could account for up 46 upper bound estimation, levels 20 variation sulfur. our dataset FT-ICR MS suggested relative humidity, oxidation volatile via ozonolysis, NOx-related organosulfate major reasons OrgSs, possibly highlighting importance acid-catalyzed ring-opening epoxides, processes, heterogeneous reactions involving either uptake into additional unrecognized OrgSs.

Language: Английский

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Investigation of the Binding Fraction of PFAS in Human Plasma and Underlying Mechanisms Based on Machine Learning and Molecular Dynamics Simulation

Environmental Science & Technology, Journal Year: 2022, Volume and Issue: 57(46), P. 17762 - 17773

Published: Oct. 25, 2022

More than 7000 per- and polyfluorinated alkyl substances (PFAS) have been documented in the U.S. Environmental Protection Agency's CompTox Chemicals database. These PFAS can be used a broad range of industrial consumer applications but may pose potential environmental issues health risks. However, little is known about emerging bioaccumulation to assess their chemical safety. This study focuses specifically on large high-quality data set fluorochemicals from related pharmaceutical chemicals databases, machine learning (ML) models were developed for classification prediction unbound fraction compounds plasma. A comprehensive evaluation ML shows that best blending model yields an accuracy 0.901 test set. The predictions suggest most (∼92%) high binding Introduction alkaline amino groups likely reduce affinities with plasma proteins. Molecular dynamics simulations indicate clear distinction between low fractions PFAS. computational workflows predict are also helpful molecular design prevent release high-bioaccumulation into environment.

Language: Английский

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Nitroaromatic Compounds from Secondary Nitrate Formation and Biomass Burning Are Major Proinflammatory Components in Organic Aerosols in Guangzhou: A Bioassay Combining High-Resolution Mass Spectrometry Analysis

Environmental Science & Technology, Journal Year: 2023, Volume and Issue: 57(51), P. 21570 - 21580

Published: Nov. 21, 2023

The limited characterization and detection capacity of unknown compounds hinder our understanding the molecular composition toxic in PM2.5. present study applied Fourier transform ion cyclotron resonance mass spectrometry coupled with negative positive electrospray ionization sources (ESI–/ESI+ FT-ICR-MS) to probe characteristics dynamic formation processes effective proinflammatory components organic aerosols (OAs) PM2.5 Guangzhou for one year. We detected abundant molecules OAs, mainly classified as CHON (compounds composed C, H, O, N atoms) elemental nitroaromatic (NACs) structures. From perspective process, we discovered that these molecules, especially NACs, were largely driven by secondary nitrate biomass burning (in emission source), well SO2 atmospheric evolution). In addition, results indicated had replaced primary main contributing source OAs. This highlights importance community measures control production derived from urban areas.

Language: Английский

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Aqueous-Phase Reactions of Anthropogenic Emissions Lead to the High Chemodiversity of Atmospheric Nitrogen-Containing Compounds during the Haze Event

Environmental Science & Technology, Journal Year: 2023, Volume and Issue: 57(43), P. 16500 - 16511

Published: Oct. 16, 2023

Nitrogen-containing organic compounds (NOCs), a type of important reactive-nitrogen species, are abundant in aerosols haze events observed Northern China. However, due to the complex nature NOCs, sources, formation, and influencing factors still ambiguous. Here, molecular composition matters (OMs) hourly PM2.5 samples collected during event China was characterized using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). We found that CHON (formulas containing C, H, O, N atoms) dominated OM fractions showed high chemodiversity transformability. Relying on newly developed revised-workflow oxidation-hydrolyzation knowledge for compounds, 64% major aromatic (>80%) could be derived from oxidization or hydrolyzation processes. Results FT-ICR MS data analysis further aerosol liquid water (ALW)-involved aqueous-phase reactions distribution aromatic-CHON besides coal combustion, ALW-involved compound formation daytime nighttime different. Our results improve understanding composition, potential which can help advance evolution, control haze.

Language: Английский

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Insight into the Role of NH₃/NH₄⁺ and NO_x/NO₃^– in the Formation of Nitrogen-Containing Brown Carbon in Chinese Megacities

Environmental Science & Technology, Journal Year: 2024, Volume and Issue: unknown

Published: Feb. 23, 2024

Particulate brown carbon (BrC) plays a crucial role in the global radiative balance due to its ability absorb light. However, effect of molecular formation on light absorption properties BrC remains poorly understood. In this study, atmospheric samples collected from six Chinese megacities winter and summer were characterized through ultrahigh-performance liquid chromatography coupled with Orbitrap mass spectrometry (UHPLC-Orbitrap MS) measurements. The average values coefficient at wavelength 365 nm (babs365) approximately 4.0 times higher than those summer. Nitrogen-containing organic molecules (CHNO) identified as critical components light-absorbing substances both seasons, underscoring importance N-addition BrC. These nitrogen-containing chromophores more closely related nitro-containing compounds originating biomass burning nitrogen oxides (NOx)/nitrate (NO3–) reactions winter. summer, they reduced N-containing formed ammonia (NH3)/ammonium (NH4+) reactions. NH3/NH4+-mediated contributed secondary winter, particularly southern cities. Compared O/Cw, lower molecule conjugation indicator (double bond equivalent, DBE), babs365 suggest possible bleaching mechanism during oxidation process. findings strengthen connection between composition BrC, providing insights into mechanisms across northern cities different seasons.

Language: Английский

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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

ACS Earth and Space Chemistry, Journal Year: 2022, Volume and Issue: 6(4), P. 1095 - 1107

Published: March 29, 2022

Air pollution over Lake Baikal originating from anthropogenic emissions as well wildfire events and secondary organic aerosol (SOA) formation poses a threat to this world heritage ecosystem. During ship expedition in 2018, ambient particles were sampled on filters at different locations of extracted obtain the fraction water-soluble (WSOA). Subsequent analysis by Fourier transform ion cyclotron resonance (FTICR) mass spectrometry with direct-infusion electrospray ionization (ESI) both modes provides insights into molecular composition polar high-molecular-weight species WSOA. Light absorption spectral dependence determined Ångstrom exponent (AAE) is correlated summed compound class abundancies identify light-absorbing compounds. Most detected are heavily oxidized, associated intense atmospheric aging, contain significant amounts nitrogen or sulfur, most abundant classes being CHO, CHON, CHOS. Nitrogen-containing more frequently found positive ESI correlate AAE. Oxygen-to-nitrogen ratios (O/N) larger than 3 indicate nitrates, also less oxidized can be linked brown carbon (BrC). complementary information with, one hand, sensitive detection high average oxidation state (OSC) low-volatility negative mode, other lower OSC (OSC < 0) oligomers potential biomass burning mode. Additionally, great overlap sum formulae was all sampling sites along route, regardless primary emission sources, indicating strong aging mixing, leading similar (OOA) sources.

Language: Английский

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Molecular Signatures and Sources of Fluorescent Components in Atmospheric Organic Matter in South China

Environmental Science & Technology Letters, Journal Year: 2022, Volume and Issue: 9(11), P. 913 - 920

Published: Oct. 18, 2022

Excitation emission matrix (EEM) spectra coupled with parallel factor analysis (PARAFAC) have been used to characterize brown carbon (BrC). The molecular composition of PARAFAC components is not well understood in atmospheric science, which has impeded the accurate interpretation chemical changes and source apportionment BrC using EEM-PARAFAC methods. We assigned numerous formulas identified by Fourier transform ion cyclotron resonance mass spectrometry (both negative positive electrospray ionization modes) each PARAFAC-derived fluorescent component (FC) PM2.5 samples. Obvious differences characteristics sources were observed between hydrospheric FCs, indicating need for caution explaining FC based on FC. Previously protein-like (C4) less-oxidized humic-like (C1) associated mainly highly saturated photoresistant species less-polar anthropogenic emissions. Highly oxidized FCs aromatic unsaturated/phenolic compounds (high oxygen), potentially influenced biomass burning related secondary processes. seasonal variations light absorption similar those fluorescence intensity degree humification, oxygen). These linkages indicated potential investigating absorption, composition, BrC.

Language: Английский

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Molecular compositions and optical properties of water-soluble brown carbon during the autumn and winter in Guangzhou, China

Atmospheric Environment, Journal Year: 2022, Volume and Issue: 296, P. 119573 - 119573

Published: Dec. 30, 2022

Language: Английский

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