Aging of Atmospheric Brown Carbon Aerosol

ACS Earth and Space Chemistry, Journal Year: 2021, Volume and Issue: 5(4), P. 722 - 748

Published: April 5, 2021

Emitted by numerous primary sources and formed secondary sources, atmospheric brown carbon (BrC) aerosol is chemically complex. As BrC ages in the atmosphere via a variety of chemical physical processes, its composition optical properties change significantly, altering impacts on climate. Research past decade has considerably expanded our understanding reactions both gas condensed phases. We review these recent advances aging chemistry with focus phase leading to formation, aqueous in-cloud particle reactions. Connections are made between single component proxies more complex mixtures as well laboratory field measurements chemistry. General conclusions that can darken particles over short time scales hours close source considerable photobleaching oxidative whitening will occur when day or removed from source.

Language: Английский

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Molecular Analysis of Secondary Brown Carbon Produced from the Photooxidation of Naphthalene

Environmental Science & Technology, Journal Year: 2022, Volume and Issue: 56(6), P. 3340 - 3353

Published: March 1, 2022

We investigate the chemical composition of organic light-absorbing components, also known as brown carbon (BrC) chromophores, formed in a proxy anthropogenic secondary aerosol generated from photooxidation naphthalene (naph-SOA) absence and presence NOx. High-performance liquid chromatography equipped with photodiode array detector electrospray ionization high-resolution mass spectrometer is employed to characterize naph-SOA its BrC components. provide molecular-level insights into optical properties individual components their relevance. This work reveals formation strongly absorbing nitro-aromatic chromophores under high-NOx conditions describes degradation during atmospheric aging. NOx addition enhanced light absorption while reducing wavelength-dependence, seen by coefficient (MAC) Ångström exponent (AAE). Optical parameters low- showed range values MACOM 405nm ∼ 0.12 m2 g–1 AAE300–450nm 8.87 (low-NOx) 0.19 7.59 (high-NOx), consistent "very weak" "weak" classes, respectively. The weak-BrC class commonly attributed biomass smoldering emissions, which appear have comparable naph-SOA. Molecular contributing were identified substantial nitro-aromatics, indicating that these species may be used source-specific markers related emissions.

Language: Английский

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Nitrogen-Containing Compounds Enhance Light Absorption of Aromatic-Derived Brown Carbon

Environmental Science & Technology, Journal Year: 2022, Volume and Issue: 56(7), P. 4005 - 4016

Published: Feb. 22, 2022

The formation of secondary brown carbon (BrC) is chemically complex, leading to an unclear relationship between its molecular composition and optical properties. Here, we present in-depth investigation molecular-specific properties aging BrC produced from the photooxidation ethylbenzene at varied NOx levels for first time. Due pronounced unsaturated products, mass absorption coefficient (MAC) organic aerosols (ESOA) 365 nm was higher than that biogenic SOA by a factor 10. A high level ([ethylbenzene]0/[NOx]0 < 10 ppbC ppb–1) found significantly increase average MAC300–700nm ESOA 0.29 m2 g–1. data two complementary high-resolution spectrometers quantum chemical calculations suggested nitrogen-containing compounds were largely responsible enhanced light high-NOx ESOA, multifunctional nitroaromatic (such as C8H9NO3 C8H9NO4) identified important chromophores. High-NOx underwent photobleaching upon direct exposure ultraviolet light. Photolysis did not lead significant decomposition C8H9NO4, indicating may serve relatively stable nitrogen reservoirs would effectively absorb solar radiation during daytime.

Language: Английский

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pH-Dependent Aqueous-Phase Brown Carbon Formation: Rate Constants and Implications for Solar Absorption and Atmospheric Photochemistry

Environmental Science & Technology, Journal Year: 2024, Volume and Issue: 58(2), P. 1236 - 1243

Published: Jan. 3, 2024

Aqueous-phase reactions of α-dicarbonyls with amines or ammonium have been identified as important sources secondary brown carbon (BrC). However, the kinetics BrC formation and effects pH are still not very clear. In this study, by aqueous (glyoxal methylglyoxal) ammonium, amino acids, alkylamines in bulk solution at different values investigated. Our results reveal pH-parameterized production rate constants, kBrCII (m–1 [M]−2 s–1), based on light absorption between 300 500 nm: log10(kBrCII) = (1.0 ± 0.1) × – (7.4 1.0) for glyoxal (6.3 0.9) methylglyoxal. The linear slopes closing to 1.0 indicate that is governed nitrogen nucleophilic addition pathway. Consequently, absorptivities produced increase exponentially pH. from methylglyoxal higher (≥6.5) exhibits optical properties comparable biomass burning coal combustion, categorized "weakly" absorbing BrC, while lower (<6.0) (pH 5.0–7.0) falls into "very weakly" BrC. pH-dependent feature significantly affects solar ability thus atmospheric photochemical processes, e.g., 7.0 absorbs 14–16 times more power compared 5.0, which turn could lead a decrease 1 order magnitude photolysis constants O3 NO2.

Language: Английский

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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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Optical Properties of Secondary Organic Aerosol Produced by Photooxidation of Naphthalene under NOx Condition

Environmental Science & Technology, Journal Year: 2022, Volume and Issue: 56(8), P. 4816 - 4827

Published: April 6, 2022

Secondary organic aerosols (SOAs) affect incoming solar radiation by interacting with light at ultraviolet and visible wavelength ranges. However, the relationship between chemical composition optical properties of SOA is still not well understood. In this study, complex refractive index (RI) produced from OH oxidation naphthalene in presence nitrogen oxides (NOx) was retrieved online range 315–650 nm bulk characterized an high-resolution time-of-flight mass spectrometer. addition, molecular-level brown carbon chromophores determined using high-performance liquid chromatography coupled to a photodiode array detector The real part RI increases both NOx/naphthalene ratio aging time, likely due increased mean polarizability decreased molecular weight fragmentation. Highly absorbing nitroaromatics (e.g., C6H5NO4, C7H7NO4, C7H5NO5, C8H5NO5) under higher NOx conditions contribute significantly absorption SOA. imaginary linearly NOx/VOCs formation nitroaromatic compounds. As function aging, O/C (slope = 0.024), mainly attributed achieved ratio, which favors light-absorbing nitroaromatics. enhancement as significant extensive it lower time opening aromatic rings reactions.

Language: Английский

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Measurement report: Optical properties and sources of water-soluble brown carbon in Tianjin, North China – insights from organic molecular compositions

Atmospheric chemistry and physics, Journal Year: 2022, Volume and Issue: 22(10), P. 6449 - 6470

Published: May 19, 2022

Abstract. Brown carbon (BrC) aerosols exert vital impacts on climate change and atmospheric photochemistry due to their light absorption in the wavelength range from near-ultraviolet (UV) visible light. However, optical properties formation mechanisms of ambient BrC remain poorly understood, limiting estimation radiative forcing. In present study, fine particles (PM2.5) were collected during 2016–2017 a day/night basis over urban Tianjin, megacity northern China. Light fluorescence water extracts PM2.5 investigated obtain seasonal diurnal patterns water-soluble BrC. There obvious seasonal, but no evident diurnal, variations winter, showed much stronger light-absorbing ability, with mass efficiency at 365 nm (MAE365) winter (1.54±0.33 m2 gC−1) that was 1.8 times larger than MAE365 summer (0.84±0.22 gC−1). Direct effects by relative black UV 54.3±16.9 % 44.6±13.9 summer, respectively. addition, five fluorescent components BrC, including three humic-like fluorophores two protein-like identified excitation–emission matrix spectrometry parallel factor (PARAFAC) analysis. The less oxygenated contributed more nighttime samples, while increased daytime samples. higher humification index (HIX), together lower biological (BIX) (FI), suggests chemical compositions associated high aromaticity degree photobleaching. Fluorescent indicate wintertime predominantly affected primary emissions fresh secondary organic aerosol (SOA), ones influenced aging processes. Results source apportionments using molecular same set reveal fossil fuel combustion processes, bioaerosol emission, biomass burning, biogenic anthropogenic SOA main sources Biomass burning nighttime, daytime. particular, our study highlights emission is an important Tianjin summer.

Language: Английский

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Atmospheric Brown Carbon on the Tibetan Plateau: Regional Differences in Chemical Composition and Light Absorption Properties

Environmental Science & Technology Letters, Journal Year: 2022, Volume and Issue: 9(3), P. 219 - 225

Published: Feb. 9, 2022

Fine particulate matter (PM2.5) filter samples were collected from two high-altitude remote sites located in the southern (QOMS) and northern (WLG) regions of Tibetan Plateau (TP) to explore regional differences brown carbon (BrC) properties. Chemical BrC composition representative these areas inferred molecular-level analysis PM2.5 using high-performance liquid chromatography coupled with photodiode array high-resolution mass spectrometry detectors. The results show that more polar chromophores abundant QOMS samples, while contributions less comparable WLG samples. A higher absorption coefficient was observed at than WLG. Strong identified as oxygenated aromatics nitrophenol compounds, organosulfate compounds found sample. this study indicate provide insights into their sources chemical processes, which should be considered for predictive understanding modeling radiative forcing aerosol TP area.

Language: Английский

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Quantifying the Light-Absorption Properties and Molecular Composition of Brown Carbon Aerosol from Sub-Saharan African Biomass Combustion

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

Published: Feb. 23, 2024

Sub-Saharan Africa is a hotspot for biomass burning (BB)-derived carbonaceous aerosols, including light-absorbing organic (brown) carbon (BrC). However, the chemically complex nature of BrC in BB aerosols from this region not fully understood. We generated smoke chamber through smoldering combustion common sub-Saharan African fuels (hardwoods, cow dung, savanna grass, and leaves). quantified aethalometer-based, real-time light-absorption properties BrC-containing organic-rich accounting variations wavelength, fuel type, relative humidity, photochemical aging conditions. In filter samples collected Botswana winter, we identified 182 species, classified into lignin pyrolysis products, nitroaromatics, coumarins, stilbenes, flavonoids. Using an extensive set standards, determined species-specific mass emission factors. Our analysis revealed linear relationship between combined species contribution to chamber-measured aerosol (0.4–14%) mass-absorption cross-section at 370 nm (0.2–2.2 m2 g–1). Hierarchical clustering resolved key molecular-level components matrix, with photochemically aged emissions leaf cow-dung showing fingerprints similar those found aerosols. These quantitative findings could potentially help refine climate model predictions, aid source apportionment, inform effective air quality management policies human health global climate.

Language: Английский

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Enhanced Light Absorption and Elevated Viscosity of Atmospheric Brown Carbon through Evaporation of Volatile Components

Environmental Science & Technology, Journal Year: 2024, Volume and Issue: 58(17), P. 7493 - 7504

Published: April 18, 2024

Samples of brown carbon (BrC) material were collected from smoke emissions originating wood pyrolysis experiments, serving as a proxy for BrC representative biomass burning emissions. The acquired samples, referred to "pyrolysis oil (PO

Language: Английский

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