From Measurements to Models: Toward Accurate Representation of Brown Carbon in Climate Calculations

Current Pollution Reports, Journal Year: 2020, Volume and Issue: 6(2), P. 90 - 104

Published: March 19, 2020

Language: Английский

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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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Formation of Secondary Brown Carbon in Biomass Burning Aerosol Proxies through NO₃ Radical Reactions

Environmental Science & Technology, Journal Year: 2019, Volume and Issue: 54(3), P. 1395 - 1405

Published: Nov. 15, 2019

Atmospheric brown carbon (BrC) is an important contributor to the radiative forcing of climate by organic aerosols. Because molecular diversity BrC compounds and their dynamic transformations, it challenging predictively understand optical properties. OH radical O3 reactions, together with photolysis, lead diminished light absorption lower warming effects biomass burning BrC. The night-time aging on properties aerosols are less known. To address this knowledge gap, NO3 chemistry tar from wood pyrolysis was investigated in a flow reactor. This study shows that change because transformations driven reactions form new absorbing species significant enhancement over ultraviolet–visible (UV-vis) range. overnight increases mass coefficients factor 1.3–3.2 between 380 nm 650 nm. Nitrated compounds, particularly nitroaromatics, were identified as main products contribute enhanced secondary Night-time represents source can have pronounced effect atmospheric air pollution.

Language: Английский

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Lifecycle of light-absorbing carbonaceous aerosols in the atmosphere

npj Climate and Atmospheric Science, Journal Year: 2020, Volume and Issue: 3(1)

Published: Oct. 21, 2020

Abstract Light-absorbing carbonaceous aerosols (LACs), including black carbon and light-absorbing organic (brown carbon, BrC), have an important role in the Earth system via heating atmosphere, dimming surface, modifying dynamics, reducing snow/ice albedo, exerting positive radiative forcing. The lifecycle of LACs, from emission to atmospheric evolution further deposition, is key their overall climate impacts uncertainties determining hygroscopic optical properties, burden, interactions with clouds, deposition on snowpack. At present, direct observations constraining some processes during LACs (e.g., between hydrometeors) are rather limited. Large inconsistencies directly measured LAC properties those used for model evaluations also exist. Modern models starting incorporate detailed aerosol microphysics evaluate transformation rates water solubility, chemical composition, phases which shown improved performance. However, process-level understanding modeling still poor particularly BrC, yet be sufficiently assessed due lack global-scale measurements. Appropriate treatments size- composition-resolved that influence both aerosol–cloud expected advance quantification light absorption system. This review summarizes recent advances up-to-date knowledge highlighting essential issues where measurements need improvement.

Language: Английский

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Global Measurements of Brown Carbon and Estimated Direct Radiative Effects

Geophysical Research Letters, Journal Year: 2020, Volume and Issue: 47(13)

Published: June 16, 2020

Abstract Brown carbon (BrC) is an organic aerosol material that preferentially absorbs light of shorter wavelengths. Global‐scale radiative impacts BrC have been difficult to assess due the lack observational data. To address this, filters were continuously collected with near pole‐to‐pole latitudinal coverage over Pacific and Atlantic basins in three seasons as part Atmospheric Tomography Mission. chromophores filter extracts measured. We find globally, was highly spatially heterogeneous, mostly detected air masses had transported from regions extensive biomass burning. calculate average direct effect absorption accounted for approximately 7% 48% top atmosphere clear‐sky instantaneous forcing by all absorbing carbonaceous aerosols remote atmosphere, indicating burning important component global balance.

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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Shortwave absorption by wildfire smoke dominated by dark brown carbon

Nature Geoscience, Journal Year: 2023, Volume and Issue: 16(8), P. 683 - 688

Published: Aug. 1, 2023

Wildfires emit large amounts of black carbon and light-absorbing organic carbon, known as brown into the atmosphere. These particles perturb Earth's radiation budget through absorption incoming shortwave radiation. It is generally thought that loses its absorptivity after emission in atmosphere due to sunlight-driven photochemical bleaching. Consequently, atmospheric warming effect exerted by remains highly variable poorly represented climate models compared with relatively nonreactive carbon. Given wildfires are predicted increase globally coming decades, it increasingly important quantify these radiative impacts. Here we present measurements ensemble-scale particle-scale smoke plumes from western United States. We find a type dark contributes three-quarters short visible light half long absorption. This strongly absorbing aerosol species water insoluble, resists daytime photobleaching increases night-time processing. Our findings suggest parameterizations need be revised improve estimation forcing associated warming.

Language: Английский

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Brown Carbon in Primary and Aged Coal Combustion Emission

Environmental Science & Technology, Journal Year: 2021, Volume and Issue: 55(9), P. 5701 - 5710

Published: April 7, 2021

Smog chamber experiments were conducted to characterize the light absorption of brown carbon (BrC) from primary and photochemically aged coal combustion emissions. Light was measured by UV–visible spectrophotometric analysis water methanol extracts filter samples. The single-scattering albedo at 450 nm 0.73 ± 0.10 for emissions 0.75 0.13 coefficient 365 higher than that a factor 10 7 This suggests majority BrC is water-insoluble even after aging. mass efficiency this (MAE365) OA (POA) dependent on conditions, with an average 0.84 0.54 m2 g–1, which significantly (0.24 0.18 g–1). Secondary (SOA) dominated decreased MAE365 aging indicates SOA less absorbing POA and/or bleached (oxidized) estimated (0.14 0.08 g–1) much lower POA. A comparison residential other anthropogenic sources are among strongest organics.

Language: Английский

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Characteristics and evolution of brown carbon in western United States wildfires

Atmospheric chemistry and physics, Journal Year: 2022, Volume and Issue: 22(12), P. 8009 - 8036

Published: June 21, 2022

Abstract. Brown carbon (BrC) associated with aerosol particles in western United States wildfires was measured between July and August 2019 aboard the NASA DC-8 research aircraft during Fire Influence on Regional to Global Environments Air Quality (FIREX-AQ) study. Two BrC measurement methods are investigated, highly spectrally resolved light absorption solvent (water methanol) extracts of collected filters situ bulk particle at three wavelengths (405, 532 664 nm) a photoacoustic spectrometer (PAS). A light-absorption closure analysis for 300 700 nm performed. The combined pure black material, including enhancements due internally mixed materials, plus soluble Mie-predicted factor conversion BrC, compared spectra from power law fit PAS wavelengths. For various parameters used, wavelength roughly 400 they agreed, lower individual component-predicted significantly exceeded higher consistently but more variable. Limitations extrapolation data below 405 missing species low solubility that strongly absorb may account differences. Based measurements closest fires, emission ratio PAS-measured relative monoxide (CO) average 0.13 Mm−1 ppbv−1; ratios also provided. As smoke moved away burning regions, evolution over time observed be complex; enhancement, depletion or constant levels age were all first 8 h after different plumes. Within following emissions, 4-nitrocatechol, well-characterized chromophore commonly found particles, largely depleted BrC. In descending plume where temperature increased by 15 K, 4-nitrocatechol dropped, possibly temperature-driven evaporation, remained unchanged. Evidence reactions ozone, related species, as pathway secondary formation under both high oxides nitrogen (NOx) conditions, while bleached regions ozone NOx, consistent complex behaviors laboratory studies. Although hours is variable, limited number aged (15 30 h) indicate net loss It yet determined how near-field affects characteristics longer timescales spatial scales, its environmental impacts likely greater.

Language: Английский

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Measuring light absorption by freshly emitted organic aerosols: optical artifacts in traditional solvent-extraction-based methods

Atmospheric chemistry and physics, Journal Year: 2019, Volume and Issue: 19(13), P. 8817 - 8830

Published: July 11, 2019

Abstract. Recent studies have shown that organic aerosol (OA) could a nontrivial role in atmospheric light absorption at shorter visible wavelengths. Good estimates of OA are therefore necessary to better estimate radiative forcing due these aerosols climate models. One the common techniques used measure is solvent extraction technique from filter samples which involves use spectrophotometer bulk absorbance by solvent-soluble fraction particulate matter. Measured solvent-phase subsequently converted particle-phase coefficient using scaling factors. The conventional view apply correction factor 2 coefficients obtained solvent-extracted based on Mie calculations. appropriate factors function biases incomplete carbon (OC) solvents and size-dependent properties OA. range for along with their potential dependence burn conditions an unexplored area research. Here, we performed comprehensive laboratory study involving three (water, methanol, acetone) investigate bias solvent-extraction-based photometry as compared situ freshly emitted biomass burning. We correlated OC∕TC (total carbon) mass ratio single scattering albedo (SSA) observed conventionally water methanol-extracted might not be extensible all systems, suggest caution while such coefficients. Furthermore, linear correlation between SSA was also established. Finally, spectroscopic data, analyzed differences Ångström exponents (AÅE) solution- particulate-phase measurements. noted AÅE measurements deviate significantly counterparts.

Language: Английский

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