scholarly journals Effects of SO<sub>2</sub> on optical properties of secondary organic aerosol generated from photooxidation of toluene under different relative humidity

2019 ◽  
Author(s):  
Wenyu Zhang ◽  
Weigang Wang ◽  
Junling Li ◽  
Chao Peng ◽  
Kun Li ◽  
...  
Keyword(s):  
Climate Change ◽  
Optical Properties ◽  
Relative Humidity ◽  
Secondary Organic Aerosol ◽  
Complex Refractive Index ◽  
Organic Aerosol ◽  
Conjugated Oligomers ◽  
Atmospheric Conditions ◽  
Multiphase Reaction ◽  
532 Nm

Abstract. Secondary organic aerosol (SOA) have great impacts on air quality, climate change and human health. The composition and physicochemical properties of SOA differ a lot for they originated under different atmospheric conditions and from various precursors and oxidations. In this work, photooxidation experiments of toluene were performed under four conditions (dry, dry with SO2, wet, and wet with SO2) to investigate the effect of SO2 under different relative humidity on the composition and optical properties of SOA at the wavelength of 375 nm and 532 nm. According to our results, the increase of humidity enhances not only light absorption, but also scattering property of SOA. Highly conjugated oligomers formed through multiphase reaction might be the reasons of this phenomenon. Adding SO2 slightly lower the real part of complex refractive index (n) of SOA: ndry, SO2 

scholarly journals Effects of SO<sub>2</sub> on optical properties of secondary organic aerosol generated from photooxidation of toluene under different relative humidity conditions

2020 ◽  
Vol 20 (7) ◽  
pp. 4477-4492 ◽  
Author(s):  
Wenyu Zhang ◽  
Weigang Wang ◽  
Junling Li ◽  
Chao Peng ◽  
Kun Li ◽  
...  
Keyword(s):  
Climate Change ◽  
Refractive Index ◽  
Optical Properties ◽  
Secondary Organic Aerosol ◽  
Aldol Condensation ◽  
Complex Refractive Index ◽  
Organic Aerosol ◽  
Atmospheric Conditions ◽  
Radiative Balance ◽  
Dry Conditions

Abstract. Secondary organic aerosol (SOA) has great impacts on air quality, climate change and human health. The composition and physicochemical properties of SOA differ greatly because they form under different atmospheric conditions and from various precursors as well as differing oxidation. In this work, photooxidation experiments of toluene were performed under four conditions (dry, dry with SO2, wet and wet with SO2) to investigate the effect of SO2 under different relative humidities on the composition and optical properties of SOA at wavelengths of 375 and 532 nm. According to our results, the increase in humidity enhances not only light absorption but also the scattering property of the SOA. Oligomers formed through multiphase reactions might be the reason for this phenomenon. Adding SO2 slightly lowers the real part of the complex refractive index, RI(n), of toluene-derived SOA (RI(n)dry,SO2<RI(n)dry, RI(n)wet,SO2<RI(n)wet), which might be a result of the partitioning of low-oxidation-state products. The imaginary part of the complex refractive index, RI(k), is enhanced under dry conditions with SO2 compared to that of only dry conditions, which might be due to acid-catalyzed aldol condensation reactions. Wet conditions with SO2 shows the combined effect of SO2 and humidity. The extinction properties of toluene-derived SOA under wet conditions with SO2 increased by approximately 30 % compared to that of toluene-derived SOA formed under dry conditions. Our results suggest that various atmospheric conditions will affect the composition and optical proprieties of SOA, which has significant implications for evaluating the impacts of SOA on the rapid formation of regional haze, global radiative balance and climate change.

scholarly journals Relating hygroscopicity and optical properties to chemical composition and structure of secondary organic aerosol particles generated from the ozonolysis of α-pinene

2014 ◽  
Vol 14 (7) ◽  
pp. 10543-10596 ◽  
Author(s):  
C. Denjean ◽  
P. Formenti ◽  
B. Picquet-Varrault ◽  
E. Pangui ◽  
P. Zapf ◽  
...  
Keyword(s):  
Optical Properties ◽  
Secondary Organic Aerosol ◽  
Complex Refractive Index ◽  
Glassy State ◽  
Particle Surface ◽  
Chemical Properties ◽  
Organic Aerosol ◽  
Atomic Ratio ◽  
Scattering Coefficient ◽  
Size Growth

Abstract. Secondary Organic Aerosol (SOA) were generated from the ozonolysis of α-pinene in the CESAM simulation chamber. The formation and ageing of the SOA were studied by following their optical, hygroscopic and chemical properties. The optical properties investigated by determining the particle Complex Refractive Index (CRI). The hygroscopicity was quantified by measuring the effect of RH on particle size (Growth Factor, GF) and scattering coefficient (f(RH)). The oxygen to carbon (O : C) atomic ratio of the particle surface and bulk were used as a sensitive parameter to correlate the changes in hygroscopic and optical properties of the SOA composition in CESAM. The real CRI at 525 nm wavelength decreased from 1.43–1.60 (±0.02) to 1.32–1.38 (±0.02) during the SOA formation. The decrease in real CRI correlates with a decrease in the O : C ratio of SOA from 0.68 (±0.20) to 0.55 (±0.16). In contrast, the GF stayed roughly constant over the reaction time, with values of 1.02–1.07 (±0.02) at 90% (±4.2) RH. Simultaneous measurements of O : C ratio of the particle surface revealed that the SOA was not composed of a homogeneous mixture, but with less oxidised species at the surface which would limit the water adsorption onto particle. In addition, an apparent change of both mobility diameter and scattering coefficient with increasing RH from 0 to 30% was observed for SOA after 16 h reaction. We postulate that this change could be due to a change in the viscosity of the SOA from a predominantly glassy state to a predominantly liquid state.

scholarly journals Relating hygroscopicity and optical properties to chemical composition and structure of secondary organic aerosol particles generated from the ozonolysis of α-pinene

2015 ◽  
Vol 15 (6) ◽  
pp. 3339-3358 ◽  
Author(s):  
C. Denjean ◽  
P. Formenti ◽  
B. Picquet-Varrault ◽  
E. Pangui ◽  
P. Zapf ◽  
...  
Keyword(s):  
Optical Properties ◽  
Growth Factor ◽  
Secondary Organic Aerosol ◽  
Complex Refractive Index ◽  
Glassy State ◽  
Particle Surface ◽  
Organic Aerosol ◽  
Scattering Coefficient ◽  
The Real ◽  
Simulation Chamber

Abstract. Secondary organic aerosol (SOA) were generated from the ozonolysis of α-pinene in the CESAM (French acronym for Experimental Multiphasic Atmospheric Simulation Chamber) simulation chamber. The SOA formation and aging were studied by following their optical, hygroscopic and chemical properties. The optical properties were investigated by determining the particle complex refractive index (CRI). The hygroscopicity was quantified by measuring the effect of relative humidity (RH) on the particle size (size growth factor, GF) and on the scattering coefficient (scattering growth factor, f(RH)). The oxygen to carbon atomic ratios (O : C) of the particle surface and bulk were used as a sensitive parameter to correlate the changes in hygroscopic and optical properties of the SOA composition during their formation and aging in CESAM. The real CRI at 525 nm wavelength decreased from 1.43–1.60 (±0.02) to 1.32–1.38 (±0.02) during the SOA formation. The decrease in the real CRI correlated to the O : C decrease from 0.68 (±0.20) to 0.55 (±0.16). In contrast, the GF remained roughly constant over the reaction time, with values of 1.02–1.07 (±0.02) at 90% (±4.2%) RH. Simultaneous measurements of O : C of the particle surface revealed that the SOA was not composed of a homogeneous mixture, but contained less oxidised species at the surface which may limit water absorption. In addition, an apparent change in both mobility diameter and scattering coefficient with increasing RH from 0 to 30% was observed for SOA after 14 h of reaction. We postulate that this change could be due to a change in the viscosity of the SOA from a predominantly glassy state to a predominantly liquid state.

Optical Properties of Secondary Organic Aerosol from cis-3-Hexenol and cis-3-Hexenyl Acetate: Effect of Chemical Composition, Humidity, and Phase

2016 ◽  
Vol 50 (10) ◽  
pp. 4997-5006 ◽  
Author(s):  
Rebecca M. Harvey ◽  
Adam P. Bateman ◽  
Shashank Jain ◽  
Yong Jie Li ◽  
Scot Martin ◽  
...  
Keyword(s):  
Optical Properties ◽  
Chemical Composition ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Hexenyl Acetate

scholarly journals A biogenic secondary organic aerosol source of cirrus ice nucleating particles

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Martin J. Wolf ◽  
Yue Zhang ◽  
Maria A. Zawadowicz ◽  
Megan Goodell ◽  
Karl Froyd ◽  
...  
Keyword(s):  
Laboratory Experiments ◽  
Secondary Organic Aerosol ◽  
Global Climate ◽  
Compositional Analysis ◽  
Field Measurements ◽  
Organic Aerosol ◽  
Cloud Formation ◽  
Ambient Atmosphere ◽  
Atmospheric Conditions ◽  
Mass Fractions

Abstract Atmospheric ice nucleating particles (INPs) influence global climate by altering cloud formation, lifetime, and precipitation efficiency. The role of secondary organic aerosol (SOA) material as a source of INPs in the ambient atmosphere has not been well defined. Here, we demonstrate the potential for biogenic SOA to activate as depositional INPs in the upper troposphere by combining field measurements with laboratory experiments. Ambient INPs were measured in a remote mountaintop location at –46 °C and an ice supersaturation of 30% with concentrations ranging from 0.1 to 70 L–1. Concentrations of depositional INPs were positively correlated with the mass fractions and loadings of isoprene-derived secondary organic aerosols. Compositional analysis of ice residuals showed that ambient particles with isoprene-derived SOA material can act as depositional ice nuclei. Laboratory experiments further demonstrated the ability of isoprene-derived SOA to nucleate ice under a range of atmospheric conditions. We further show that ambient concentrations of isoprene-derived SOA can be competitive with other INP sources. This demonstrates that isoprene and potentially other biogenically-derived SOA materials could influence cirrus formation and properties.

scholarly journals α-Pinene secondary organic aerosol yields increase at higher relative humidity and low NO<sub><i>x</i></sub> conditions

2016 ◽  
Author(s):  
Lisa Stirnweis ◽  
Claudia Marcolli ◽  
Josef Dommen ◽  
Peter Barmet ◽  
Carla Frege ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Relative Humidity ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Liquid Water Content ◽  
Strong Increase ◽  
Chemical Compositions ◽  
Scanning Mobility Particle Sizer ◽  
Equilibrium Partitioning ◽  
Phase Partitioning

Abstract. Secondary organic aerosol (SOA) yields from the photooxidation of α-pinene were investigated in smog chamber (SC) experiments at low (23–29 %) and high (60–69 %) relative humidity (RH), various NOx/VOC ratios (0.04–3.8) and with different aerosol seed chemical compositions (acidic to neutralized sulfate-containing or hydrophobic organic). A combination of a scanning mobility particle sizer and an Aerodyne high resolution time-of-flight aerosol mass spectrometer was used to determine SOA mass concentration and chemical composition. We present wall-loss-corrected yields as a function of absorptive masses combining organics and the bound liquid water content. High RH increased SOA yields by up to six times (1.5–6.4) compared to low RH. The yields at low NOx/VOC ratios were in general higher compared to yields at high NOx/VOC ratios. This NOx dependence follows the same trend as seen in previous studies for α-pinene SOA. A novel approach of data evaluation using volatility distributions derived from experimental data served as basis for thermodynamic phase partitioning calculations of model mixtures in this study. These calculations predict liquid-liquid phase separation into organic-rich and electrolyte phases. At low NOx conditions, equilibrium partitioning between the gas and liquid phases can explain most of the increase in SOA yields at high RH. This is indicated by the model results, when in addition to the α-pinene photooxidation products described in the literature, more fragmented and oxidized organic compounds are added to the model mixtures. This increase is driven by both the increase in the absorptive mass due to the additional particulate water and the solution non-ideality described by the activity coefficients. In contrast, at high NOx, equilibrium partitioning alone could not explain the strong increase in the yields with increased RH. This suggests that other processes including the reactive uptake of semi-volatile species into the liquid phase may occur and be enhanced at higher RH, especially for compounds formed under high NOx conditions such as carbonyls.

scholarly journals Light absorption by secondary organic aerosol fromα-pinene: Effects of oxidants, seed aerosol acidity, and relative humidity

2013 ◽  
Vol 118 (20) ◽  
pp. 11,741-11,749 ◽  
Author(s):  
Chen Song ◽  
Madhu Gyawali ◽  
Rahul A. Zaveri ◽  
John E. Shilling ◽  
W. Patrick Arnott
Keyword(s):  
Relative Humidity ◽  
Light Absorption ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Aerosol Acidity ◽  
Seed Aerosol

scholarly journals Low-volatility compounds contribute significantly to isoprene secondary organic aerosol (SOA) under high-NO<sub><i>x</i></sub> conditions

2019 ◽  
Vol 19 (11) ◽  
pp. 7255-7278 ◽  
Author(s):  
Rebecca H. Schwantes ◽  
Sophia M. Charan ◽  
Kelvin H. Bates ◽  
Yuanlong Huang ◽  
Tran B. Nguyen ◽  
...  
Keyword(s):  
Ring Opening ◽  
Secondary Organic Aerosol ◽  
Inorganic Ions ◽  
Organic Aerosol ◽  
Organic Nitrates ◽  
Glyceric Acid ◽  
Mass Yield ◽  
Atmospheric Conditions ◽  
Ring Opening Reactions ◽  
The Impact

Abstract. Recent advances in our knowledge of the gas-phase oxidation of isoprene, the impact of chamber walls on secondary organic aerosol (SOA) mass yields, and aerosol measurement analysis techniques warrant reevaluating SOA yields from isoprene. In particular, SOA from isoprene oxidation under high-NOx conditions forms via two major pathways: (1) low-volatility nitrates and dinitrates (LV pathway) and (2) hydroxymethyl-methyl-α-lactone (HMML) reaction on a surface or the condensed phase of particles to form 2-methyl glyceric acid and its oligomers (2MGA pathway). These SOA production pathways respond differently to reaction conditions. Past chamber experiments generated SOA with varying contributions from these two unique pathways, leading to results that are difficult to interpret. This study examines the SOA yields from these two pathways independently, which improves the interpretation of previous results and provides further understanding of the relevance of chamber SOA yields to the atmosphere and regional or global modeling. Results suggest that low-volatility nitrates and dinitrates produce significantly more aerosol than previously thought; the experimentally measured SOA mass yield from the LV pathway is ∼0.15. Sufficient seed surface area at the start of the reaction is needed to limit the effects of vapor wall losses of low-volatility compounds and accurately measure the complete SOA mass yield. Under dry conditions, substantial amounts of SOA are formed from HMML ring-opening reactions with inorganic ions and HMML organic oligomerization processes. However, the lactone organic oligomerization reactions are suppressed under more atmospherically relevant humidity levels, where hydration of the lactone is more competitive. This limits the SOA formation potential from the 2MGA pathway to HMML ring-opening reactions with water or inorganic ions under typical atmospheric conditions. The isoprene SOA mass yield from the LV pathway measured in this work is significantly higher than previous studies have reported, suggesting that low-volatility compounds such as organic nitrates and dinitrates may contribute to isoprene SOA under high-NOx conditions significantly more than previously thought and thus deserve continued study.

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