scholarly journals Enhanced formation of secondary organic aerosol from photochemical oxidation during the COVID-19 lockdown in a background site in Northwest China

2021 ◽  
Vol 778 ◽  
pp. 144947
Author(s):  
Haobin Zhong ◽  
Ru-Jin Huang ◽  
Yunhua Chang ◽  
Jing Duan ◽  
Chunshui Lin ◽  
...  
Keyword(s):  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Northwest China ◽  
Photochemical Oxidation ◽  
Background Site

scholarly journals Characterization of aerosol and cloud water at a mountain site during WACS 2010: secondary organic aerosol formation through oxidative cloud processing

2012 ◽  
Vol 12 (2) ◽  
pp. 6019-6047 ◽  
Author(s):  
A. K. Y. Lee ◽  
K. L. Hayden ◽  
P. Herckes ◽  
W. R. Leaitch ◽  
J. Liggio ◽  
...  
Keyword(s):  
Aqueous Phase ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Cloud Water ◽  
Water Soluble ◽  
Photochemical Oxidation ◽  
Aerosol Formation ◽  
Aerosol Mass ◽  
Dissolved Organics ◽  
Organic Spectra

Abstract. The water-soluble fractions of aerosol samples and cloud water collected during Whistler Aerosol and Cloud Study (WACS 2010) were analyzed using an Aerodyne aerosol mass spectrometer (AMS). This is the first study to report AMS organic spectra of re-aerosolized cloud water, and to make direct comparison between the AMS spectra of cloud water and aerosol samples collected at the same location. In general, the aerosol and cloud organic spectra were very similar, indicating that the cloud water organics likely originated from secondary organic aerosol (SOA) formed nearby. By using a photochemical reactor to oxidize both aerosol filter extracts and cloud water, we find evidence that fragmentation of aerosol water-soluble organics increases their volatility during oxidation. By contrast, enhancement of AMS-measurable organic mass by up to 30% was observed during aqueous-phase photochemical oxidation of cloud water organics. We propose that additional SOA material was produced by functionalizing dissolved organics via OH oxidation, where these dissolved organics are sufficiently volatile that they are not usually part of the aerosol. This work points out that water-soluble organic compounds of intermediate volatility (IVOC), such as cis-pinonic acid, produced via gas-phase oxidation of monoterpenes, can be important aqueous-phase SOA precursors in a biogenic-rich environment.

scholarly journals Origin and transformation of ambient volatile organic compounds during a dust-to-haze episode in northwest China

2020 ◽  
Vol 20 (9) ◽  
pp. 5425-5436 ◽  
Author(s):  
Yonggang Xue ◽  
Yu Huang ◽  
Steven Sai Hang Ho ◽  
Long Chen ◽  
Liqin Wang ◽  
...  
Keyword(s):  
Secondary Organic Aerosol ◽  
Sharp Decrease ◽  
Fold Increase ◽  
Organic Aerosol ◽  
Northwest China ◽  
Photochemical Reactions ◽  
Urban Site ◽  
Vehicle Exhaust ◽  
Haze Pollution ◽  
Volatile Organic

Abstract. The high contribution of secondary organic aerosol to the loading of fine particle pollution in China highlights the roles of volatile organic compound (VOC) oxidation. In this respect, particulate active metallic oxides in dust, like TiO2 and Fe ions, were proposed to influence the photochemical reactions of ambient VOCs. A case study was conducted at an urban site in Xi'an, northwest China, to investigate the origin and transformation of VOCs during a windblown dust-to-haze pollution episode, and the assumption that dust would enhance the oxidation of VOCs was verified. Local vehicle exhaust (25 %) and biomass burning (18 %) were found to be the two largest contributors to ambient VOCs. In the dust pollution period, a sharp decrease in the loading of VOCs and the aging of their components were observed. Simultaneously, the secondary oxygenated VOC fraction (i.e., methylglyoxal) increased. Source strength, physical dispersion, and regional transport were eliminated as major factors for the variation of ambient VOCs. In another aspect, about a 2- to 3-fold increase in the loading of iron (Fe) and titanium (Ti) was found in the airborne particles, together with a fast decrease in trans-/cis-2-butene ratios, which demonstrated that dust can accelerate the oxidation of ambient VOCs and the formation of secondary organic aerosol (SOA) precursors.

scholarly journals Atmospheric oxidation of isoprene and 1,3-butadiene: influence of aerosol acidity and relative humidity on secondary organic aerosol

2015 ◽  
Vol 15 (7) ◽  
pp. 3773-3783 ◽  
Author(s):  
M. Lewandowski ◽  
M. Jaoui ◽  
J. H. Offenberg ◽  
J. D. Krug ◽  
T. E. Kleindienst
Keyword(s):  
Organic Carbon ◽  
Secondary Organic Aerosol ◽  
Absolute Humidity ◽  
Organic Aerosol ◽  
Photochemical Oxidation ◽  
Pronounced Increase ◽  
Acid Sensitivity ◽  
Aerosol Acidity ◽  
Acidic Sulfate ◽  
Secondary Organic Carbon

Abstract. The effects of acidic seed aerosols on the formation of secondary organic aerosol (SOA) have been examined in a number of previous studies, several of which have observed strong linear correlations between the aerosol acidity (measured as nmol H+ m−3 air sample volume) and the percent change in secondary organic carbon (SOC). The measurements have used several precursor compounds representative of different classes of biogenic hydrocarbons including isoprene, monoterpenes, and sesquiterpenes. To date, isoprene has displayed the most pronounced increase in SOC, although few measurements have been conducted with anthropogenic hydrocarbons. In the present study, we examine several aspects of the effect of aerosol acidity on the secondary organic carbon formation from the photooxidation of 1,3-butadiene, and extend the previous analysis of isoprene. The photooxidation products measured in the absence and presence of acidic sulfate aerosols were generated either through photochemical oxidation of SO2 or by nebulizing mixtures of ammonium sulfate and sulfuric acid into a 14.5 m3 smog chamber system. The results showed that, like isoprene and β-caryophyllene, 1,3-butadiene SOC yields linearly correlate with increasing acidic sulfate aerosol. The observed acid sensitivity of 0.11% SOC increase per nmol m−3 increase in H+ was approximately a factor of 3 less than that measured for isoprene. The results also showed that the aerosol yield decreased with increasing humidity for both isoprene and 1,3-butadiene, although to different degrees. Increasing the absolute humidity from 2 to 12 g m−3 reduced the 1,3-butadiene yield by 45% and the isoprene yield by 85%.

scholarly journals Functionality-Based Formation of Secondary Organic Aerosol from m-Xylene Photooxidation

2021 ◽  
Author(s):  
Yixin Li ◽  
Jiayun Zhao ◽  
Mario Gomez-Hernandez ◽  
Renyi Zhang
Keyword(s):  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Single Scattering ◽  
High Reactivity ◽  
Urban Environments ◽  
Photochemical Oxidation ◽  
Chemical Mechanism ◽  
Ionic Dissociation ◽  
Heterogeneous Processes ◽  
High Yields

Abstract. Photooxidation of volatile organic compounds (VOCs) produces condensable oxidized organics (COOs) to yield secondary organic aerosol (SOA), but the fundamental chemical mechanism for gas-to-particle conversion remains uncertain. Here we elucidate the production of COOs and their roles in SOA and brown carbon (BrC) formation from m-xylene oxidation by simultaneous monitoring the evolutions of gas-phase products and aerosol properties in an environmental chamber. Four COO types with the distinct functionalities of dicarbonyls, carboxylic acids, polyhydroxy aromatics/quinones, and nitrophenols are identified from early-generation oxidation, with the yields of 25 %, 37 %, 5 %, and 3 %, respectively. SOA formation occurs via several heterogeneous processes, including interfacial interaction, ionic dissociation/acid-base reaction, and oligomerization, with the yields of (20 ± 4) % and (32 ± 7) % at 10 % and 70 % relative humidity (RH), respectively. Chemical speciation shows the dominant presence of oligomers, nitrogen-containing organics, and carboxylates at RH and carboxylates at low RH. The identified BrC includes N-heterocycles/N-heterochains and nitrophenols, as evident from reduced single scattering albedo. The measured uptake coefficient (γ) for COOs is dependent on the functionality, ranging from 3.7 × 10−4 to 1.3 × 10−2. A kinetic framework is developed to predict SOA production from the concentrations and uptake coefficients for COOs. This functionality-based approach well reproduces SOA formation from m-xylene oxidation and is broadly applicable to VOC oxidation for other species. Our results reveal that photochemical oxidation of m-xylene represents a major source for SOA and BrC formation under urban environments, because of its large abundance, high reactivity with OH, and high yields for COOs.

scholarly journals Molecular composition and volatility of isoprene photochemical oxidation secondary organic aerosol under low and high NO<sub>x</sub> conditions

2016 ◽  
Author(s):  
Emma L. D'Ambro ◽  
Ben H. Lee ◽  
Jiumeng Liu ◽  
John E. Shilling ◽  
Cassandra J. Gaston ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Group Contribution ◽  
Molecular Composition ◽  
Photochemical Oxidation ◽  
Organic Nitrates ◽  
Ionization Mass ◽  
Equilibrium Partitioning ◽  
Group Contribution Methods

Abstract. We present measurements of secondary organic aerosol (SOA) formation from isoprene photochemical oxidation formed in an environmental simulation chamber using dry neutral seed particles, thereby suppressing the role of acid catalyzed multiphase chemistry, at a variety of oxidant conditions. A high-resolution time-of-flight chemical ionization mass spectrometer (HRToF-CIMS) utilizing iodide-adduct ionization coupled to the Filter Inlet for Gases and AEROsols (FIGAERO) allowed for the simultaneous online sampling of the gas and particle composition. Under high HO2 and low NO conditions, highly oxygenated (O : C ≥ 1) C5 compounds were major components (~ 50 %) of the SOA. The overall composition of the SOA evolved both as a function of time and as a function of input NO concentrations. As the level of input NO increased, organic nitrates increased in both the gas- and particle-phases, but the dominant non-nitrate particle-phase components monotonically decreased. We use comparisons of measured and predicted gas-particle partitioning of individual components to assess the validity of literature-based group-contribution methods for estimating saturation vapor concentrations. While there is evidence for equilibrium partitioning being achieved on the chamber residence time scale (5.2 hours) for some individual components, significant errors in group-contribution methods are revealed. In addition, > 30 % of the SOA mass, detected as low-molecular weight compounds, cannot be reconciled with equilibrium partitioning. These compounds desorb from the FIGAERO at unexpectedly high temperatures given their molecular composition, indicative of thermal decomposition of effectively lower volatility components, likely larger molecular weight oligomers. We use these insights from the laboratory and observations of the same SOA components made during the Southern Oxidant and Aerosol Study (SOAS) to assess the importance of isoprene photooxidation as a local SOA source.

scholarly journals Molecular composition and volatility of isoprene photochemical oxidation secondary organic aerosol under low- and high-NO<sub><i>x</i></sub> conditions

2017 ◽  
Vol 17 (1) ◽  
pp. 159-174 ◽  
Author(s):  
Emma L. D'Ambro ◽  
Ben H. Lee ◽  
Jiumeng Liu ◽  
John E. Shilling ◽  
Cassandra J. Gaston ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Group Contribution ◽  
Molecular Composition ◽  
Photochemical Oxidation ◽  
Organic Nitrates ◽  
Ionization Mass ◽  
Equilibrium Partitioning ◽  
Group Contribution Methods

Abstract. We present measurements of secondary organic aerosol (SOA) formation from isoprene photochemical oxidation in an environmental simulation chamber at a variety of oxidant conditions and using dry neutral seed particles to suppress acid-catalyzed multiphase chemistry. A high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS) utilizing iodide-adduct ionization coupled to the Filter Inlet for Gases and Aerosols (FIGAERO) allowed for simultaneous online sampling of the gas and particle composition. Under high-HO2 and low-NO conditions, highly oxygenated (O : C  ≥  1) C5 compounds were major components (∼ 50 %) of SOA. The SOA composition and effective volatility evolved both as a function of time and as a function of input NO concentrations. Organic nitrates increased in both the gas and particle phases as input NO increased, but the dominant non-nitrate particle-phase components monotonically decreased. We use comparisons of measured and predicted gas-particle partitioning of individual components to assess the validity of literature-based group-contribution methods for estimating saturation vapor concentrations. While there is evidence for equilibrium partitioning being achieved on the chamber residence timescale (5.2 h) for some individual components, significant errors in group-contribution methods are revealed. In addition, > 30 % of the SOA mass, detected as low-molecular-weight semivolatile compounds, cannot be reconciled with equilibrium partitioning. These compounds desorb from the FIGAERO at unexpectedly high temperatures given their molecular composition, which is indicative of thermal decomposition of effectively lower-volatility components such as larger molecular weight oligomers.

scholarly journals Nocturnal isoprene oxidation over the Northeast United States in summer and its impact on reactive nitrogen partitioning and secondary organic aerosol

2009 ◽  
Vol 9 (1) ◽  
pp. 225-269
Author(s):  
S. S. Brown ◽  
J. A. deGouw ◽  
C. Warneke ◽  
T. B. Ryerson ◽  
W. P. Dubé ◽  
...  
Keyword(s):  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Nitrogen Partitioning ◽  
Photochemical Oxidation ◽  
Reactive Nitrogen ◽  
Organic Nitrates ◽  
Isoprene Oxidation ◽  
Northeast Us ◽  
Aircraft Study

Abstract. Isoprene is the largest single VOC emission to the atmosphere. Although it is primarily oxidized photochemically during daylight hours, late-day emissions that remain in the atmosphere at sunset undergo oxidation by NO3 in regionally polluted areas with large NOx levels. A recent aircraft study examined isoprene and its nocturnal oxidants in a series of night flights across the Northeast US, a region with large emissions of both isoprene and NOx. Substantial amounts of isoprene that were observed after dark were strongly anticorrelated with measured NO3 and were the most important factor determining the lifetime of this radical. The products of photochemical oxidation of isoprene, methyl vinyl ketone and methacrolein, were more uniformly distributed, and served as tracers for the presence of isoprene at sunset, prior to its oxidation by NO3. Comparison of a determination of the mass of isoprene oxidized in darkness by NO3 to a calculation of integrated isoprene emissions showed that large amounts (>20%) of emitted isoprene may undergo nocturnal oxidation in this region. Organic nitrates produced from the NO3+isoprene reaction, though not directly measured, were estimated to account for 2–9% of total reactive nitrogen and 7–31% of other long-lived organic nitrates such as PAN. The mass of isoprene oxidized by NO3 was comparable to and correlated with the organic aerosol loading for flights with relatively low organic aerosol background. The contribution of nocturnal isoprene oxidation to secondary organic aerosol was determined in the range 1–17%, and isoprene SOA mass derived from NO3 was calculated to exceed that due to OH by approximately 50%.

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