Environmental Pollution, Journal Year: 2018, Volume and Issue: 240, P. 60 - 67
Published: May 3, 2018
Language: Английский
Analytical Chemistry, Journal Year: 2018, Volume and Issue: 90(21), P. 12493 - 12502
Published: Oct. 8, 2018
Light-absorbing components of atmospheric organic aerosols, which are collectively termed "brown carbon" (BrC), ubiquitous in the atmosphere. They affect absorption solar radiation by aerosols atmosphere and human health as some them have been identified potential toxins. Understanding sources, formation, evolution, environmental effects BrC requires molecular identification characterization light-absorption properties chromophores. Identification is challenging due to complexity aerosols. In this study, we employ two complementary ionization techniques, pressure photo (APPI) electrospray (ESI), obtain broad coverage both polar nonpolar using high-resolution mass spectrometry (HRMS). These techniques combined with chromatographic separation compounds high performance liquid chromatography (HPLC), their light a photodiode array (PDA) detector, chemical composition HRMS. We demonstrate that approach enables more comprehensive biomass burning (BBOAs) emitted from test burns sage brush biofuel. particular, found chromophores such PAHs only detected positive mode APPI. Meanwhile, negative ESI results detection nitroaromatics, aromatic acids, phenols. For material examined over 40% solvent-extractable attributed water insoluble, semipolar derivatives, require APPI for identification. contrast, polar, water-soluble compounds, ESI, account less than 30% BrC.
Language: Английский
Citations
268
Environmental Science & Technology, Journal Year: 2018, Volume and Issue: 52(5), P. 2575 - 2585
Published: Jan. 31, 2018
Water-soluble humic like substances (HULIS) in smoke particles emitted from combustion of biomass materials and coal were characterized by ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry. The formulas identified classified into four main groups: CHO, CHON, CHOS, CHONS. average H/C O/C ratios are 1.13–1.33, 1.01–1.13, 1.26–1.48, 1.09–1.24 0.21–0.41, 0.27–0.45, 0.41–0.46, 0.44–0.61 for the CHONS groups, respectively. CHO compound was predominant component (43%–72%) HULIS burning (BB) combustion, followed CHON group BB-smoke S-containing groups (i.e., CHOS CHONS) coal-smoke HULIS. These results indicate that primary contain a high abundance species, which appear to be made up mainly oxidized nitrogen functional such as nitro compounds and/or organonitrates. contained more with relatively low molecular weight aromaticity index (AImod). They significantly enriched double bond equivalent (≥4), O/S suggest they most likely aromatic organosulfates nitrooxy usually found polluted atmospheres. findings imply emissions fuels potential sources water-soluble an atmospheric matrix is especially important source sulfate compounds.
Language: Английский
Citations
231
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
Citations
186
Atmospheric chemistry and physics, Journal Year: 2020, Volume and Issue: 20(4), P. 1901 - 1920
Published: Feb. 20, 2020
Abstract. Carbonaceous aerosols significantly affect global radiative forcing and climate through absorption the scattering of sunlight. Black carbon (BC) brown (BrC) are light-absorbing carbonaceous aerosols. The direct effect (DRE) BrC is uncertain. A recent study suggests that comparable to BC in upper troposphere over biomass burning regions resulting heating tends stabilize atmosphere. Yet current models do not include proper physical chemical treatments BrC. In this study, we derived a emission inventory on basis Global Fire Emissions Database version 4 (GFED4), developed module simulate light Community Atmosphere Model 5 (CAM5) Earth System (CESM), investigated photobleaching convective transport Studies Emissions, Atmospheric Composition, Clouds Climate Coupling by Regional Surveys (SEAC4RS) Deep Convective Chemistry Project (DC3) measurements. model simulations were also evaluated using HIAPER (High-Performance Instrumented Airborne Platform for Environmental Research) Pole-to-Pole Observations (HIPPO) We found globally significant absorber, DRE which 0.10 W m−2, more than 25 % (+0.39 m−2). Most significantly, results indicated atmospheric tropical mid larger BC. source mainly from wildfires, prevalent higher latitudes release much relative industrial sources. While skewed towards northern mid-latitude lower atmosphere, centered free troposphere. possible mechanism enhanced hydrophobic high molecular weight becomes fraction less easily activated cloud as aerosol ages. contribution Hadley circulation latitudinal expansion tropics likely heating.
Language: Английский
Citations
175
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
Citations
72
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
Citations
17
Atmospheric chemistry and physics, Journal Year: 2019, Volume and Issue: 19(1), P. 139 - 163
Published: Jan. 4, 2019
Abstract. Following wood pyrolysis, tar ball aerosols were laboratory generated from separated into polar and nonpolar phases. Chemical information of fresh balls was obtained a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) single-particle laser desorption/resonance enhanced multiphoton ionization spectrometry (SP-LD-REMPI-MS). Their continuous refractive index (RI) between 365 425 nm retrieved using broadband cavity spectroscopy (BBCES). Dynamic changes in the optical chemical properties for NOx-dependent photochemical process investigated an oxidation flow reactor (OFR). Distinct differences composition identified. Nonpolar contain predominantly high-molecular weight unsubstituted alkyl-substituted polycylic aromatic hydrocarbons (PAHs), while consist high number oxidized substances (e.g., methoxy-phenols, benzenediol) with higher O : C ratios carbon states. Fresh have light absorption characteristics similar to atmospheric brown (BrC) efficiency towards UV wavelengths. The average RI is 1.661+0.020i 1.635+0.003i aerosols, respectively, Ångström exponent (AAE) 5.7 7.8 detected wavelength range. fits volume mixing rule internally mixed nonpolar/polar balls. decreased increasing under oxidation. Photolysis by (254 nm), without strong oxidants system, slightly increased state Oxidation varying OH exposure levels absence NOx diminished (bleaching) ratio photobleaching via radical initiated mainly attributed decomposition chromophoric aromatics, nitrogen-containing organics, components aged particles. nitrous oxide (N2O) used simulate aging OFR. Under high-NOx conditions exposure, led formation organic nitrates, both degree aerosols. These observations suggest that secondary nitrate counteracts bleaching photooxidation eventually regain some implication climate effects upon various processes are briefly discussed.
Language: Английский
Citations
116
Atmospheric chemistry and physics, Journal Year: 2019, Volume and Issue: 19(5), P. 2899 - 2915
Published: March 7, 2019
Abstract. This study seeks to understand the compositional details of N-containing aromatic compounds (NACs) emitted during biomass burning (BB) and their contribution light-absorbing organic carbon (OC), also termed brown (BrC). Three laboratory BB experiments were conducted with two United States pine forest understory fuels typical those consumed prescribed fires. During experiments, submicron aerosol particles collected on filter media subsequently extracted methanol examined for optical chemical properties. Significant correlations (p<0.05) observed between BrC absorption elemental (EC)∕OC ratios individual burns data. However, pooled experimental data indicated that EC∕OC alone cannot explain absorption. Fourteen NAC formulas identified in samples, most which simulated secondary (SOA) from photooxidation volatile (VOCs) NOx. molecular structures associated identical formula SOA are different. In this work, NACs featured by methoxy cyanate groups predominately generated flaming phase. The mass concentrations quantified using authentic surrogate standards, contributions bulk light solvent-extractable OC calculated. matter (OM) significantly higher flaming-phase samples than smoldering-phase they correlated ratio both data, indicating formation largely depends burn conditions. average overall at 365 nm ranged 0.087±0.024 % 1.22±0.54 %, is 3–10 times OM (0.023±0.0089 0.18±0.067 %), so work likely strong chromophores. Further studies warranted identify more unknown fraction (>98 %)
Language: Английский
Citations
101
Environmental Pollution, Journal Year: 2018, Volume and Issue: 244, P. 38 - 46
Published: Oct. 8, 2018
Language: Английский
Citations
94
The Science of The Total Environment, Journal Year: 2020, Volume and Issue: 719, P. 137483 - 137483
Published: Feb. 21, 2020
Language: Английский
Citations
91