scholarly journals Influence of Ammonium Sulfate Seed Particle on Optics and Compositions of Toluene Derived Organic Aerosol in Photochemistry

Atmosphere ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 961
Author(s):  
Tingting Lu ◽  
Mingqiang Huang ◽  
Weixiong Zhao ◽  
Changjin Hu ◽  
Xuejun Gu ◽  
...  
Keyword(s):  
Ammonium Sulfate ◽  
Light Absorption ◽  
Radiative Forcing ◽  
Fine Particles ◽  
Complex Refractive Index ◽  
Organic Aerosol ◽  
Urban Atmosphere ◽  
Seed Particle ◽  
Optical Parameters ◽  
High Concentration

Aromatic secondary organic aerosol (SOA) particles are known to contribute to radiative forcing and light absorption of atmosphere. However, the complex refractive index (CRI), single-scattering albedo (SSA) and other optical parameters of aromatic SOA are not well understood. SOA generated from photooxidation of toluene with a variety concentration of ammonium sulfate ((NH4)2SO4) seed particles in a smog chamber were investigated in the current study. The real part CRI of toluene SOA without seeds derived and based on aerosol albedometer measurements is 1.486 ± 0.002 at λ = 470 nm, showing a good agreement with available experimental data, and its SSA was measured to be 0.92 ± 0.02 at λ = 470 nm, indicating that the SOA particles without seeds have strong scattering ability. The SSA of SOA formed in the presence of 300 μg/m3 (NH4)2SO4 seed was 0.81 ± 0.02 at λ = 470 nm, less than the SSA of SOA without seed. SSA of SOA decreased, while the imaginary part of CRI (k) of SOA increased with increasing concentration of (NH4)2SO4 seed, demonstrating that the adsorption capacity of SOA formed in the presence of (NH4)2SO4 seed is enhanced. Different from the carboxyl compounds measured in the SOA without seed, imidazoles with strong chromophores of C=N that are responsible for the light absorption were detected as the principal constituents of SOA formed in the presence of (NH4)2SO4 seed. These would provide valuable information for discussing the optics and components of aromatic SOA in the urban atmosphere containing a high concentration of (NH4)2SO4 fine particles.

scholarly journals Size-resolved characterization of organic aerosol in the North China Plain: new insights from high resolution spectral analysis

2021 ◽  
Author(s):  
Weiqi Xu ◽  
Chun Chen ◽  
Yanmei Qiu ◽  
Conghui Xie ◽  
Yunle Chen ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
North China Plain ◽  
North China ◽  
Fine Particles ◽  
Large Fraction ◽  
Organic Aerosol ◽  
Size Distributions ◽  
The North ◽  
The Impact

Organic aerosol (OA), a large fraction of fine particles, has a large impact on climate radiative forcing and human health, and the impact depends strongly on size distributions. Here we...

scholarly journals Chemical characteristics of brown carbon in atmospheric particles at a suburban site near Guangzhou, China

2018 ◽  
Vol 18 (22) ◽  
pp. 16409-16418 ◽  
Author(s):  
Yi Ming Qin ◽  
Hao Bo Tan ◽  
Yong Jie Li ◽  
Zhu Jie Li ◽  
Misha I. Schurman ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Absorption Coefficient ◽  
Light Absorption ◽  
Radiative Forcing ◽  
Chemical Characterization ◽  
Organic Aerosol ◽  
Atmospheric Particles ◽  
Chemical Characteristics ◽  
Brown Carbon ◽  
Suburban Site

Abstract. Light-absorbing organic carbon (or brown carbon, BrC) in atmospheric particles has received much attention for its potential role in global radiative forcing. While a number of field measurement campaigns have differentiated light absorption by black carbon (BC) and BrC, the chemical characteristics of BrC are not well understood. In this study, we present co-located real-time light absorption and chemical composition measurements of atmospheric particles to explore the relationship between the chemical and optical characteristics of BrC at a suburban site downwind of Guangzhou, China, from November to December 2014. BrC and BC contributions to light absorption were estimated using measurements from a seven-wavelength aethalometer, while the chemical composition of non-refractory PM1 was measured with a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). Using the absorption Ångström exponent (AAE) method, we estimated that BrC contributed 23.6 % to the total aerosol absorption at 370 nm, 18.1 % at 470 nm, 10.7 % at 520 nm, 10.7 % at 590 nm, and 10.5 % at 660 nm. Biomass burning organic aerosol (BBOA) has the highest mass absorption coefficient among sources of organic aerosols. Its contribution to total brown carbon absorption coefficient decreased but that of low-volatility oxygenated organic aerosol (LVOOA) increased with increasing wavelength, suggesting the need for wavelength-dependent light absorption analysis for BrC in association with its chemical makeup. Clear correlations of N-containing ion fragments with absorption coefficient were observed. These correlations also depended on their degrees of unsaturation/cyclization and oxygenation. While the current study relates light absorption by BrC to ion fragments, more detailed chemical characterization is warranted to constrain this relationship.

scholarly journals Wavelength and NO<sub>x</sub> dependent complex refractive index of SOAs generated from the photooxidation of toluene

2012 ◽  
Vol 12 (6) ◽  
pp. 14551-14589 ◽  
Author(s):  
T. Nakayama ◽  
K. Sato ◽  
Y. Matsumi ◽  
T. Imamura ◽  
A. Yamazaki ◽  
...  
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Organic Compounds ◽  
Cross Sections ◽  
Light Absorption ◽  
Complex Refractive Index ◽  
Urban Atmosphere ◽  
Radiation Balance ◽  
Limited Information ◽  
K Value

Abstract. Recently, secondary organic aerosols (SOAs) generated from anthropogenic volatile organic compounds have been proposed as a possible source of lightabsorbing organic compounds "brown carbon" in the urban atmosphere. However, the atmospheric importance of these SOAs remains unclear due to limited information about their optical properties. In this study, the complex refractive index (RI, m=n − ki) values at 405, 532, and 781 nm of the SOAs generated during the photooxidation of toluene (toluene-SOAs) under a variety of initial nitrogen oxide (NOx= NO + NO2) conditions were examined by photoacoustic spectroscopy (PAS) and cavity ring down spectroscopy (CRDS). The complex RI values obtained in the present study and reported in the literature indicate that the k value, which represents the light absorption of the toluene-SOAs steeply increased to shorter wavelengths at <405 nm, while the n value gradually increased to shorter wavelengths from 781 to 355 nm. The k values at 405 nm were found to increase from 1.8 × 10−3 to 7.2 × 10−3 with increasing initial NOx concentration from 109 to 571 ppbv. The nitrate to organics ratio of the SOAs determined using a highresolution time-of-flight aerosol mass spectrometer (H-ToF-AMS) also increased with increasing initial NOx concentration. The RI values of the SOAs generated during the photooxidation of 1,3,5-trimethylbenzene in the presence of NOx (1,3,5-TMB-SOAs) were also determined to investigate the influence of the chemical structure of the precursor on the optical properties of the SOAs, and it was found that the light absorption of the 1,3,5-TMB-SOAs is negligible at all of the wavelengths investigated (405, 532, and 781 nm). These results can be reasonably explained by the hypothesis that nitro-aromatic compounds such as nitro-cresols are the major contributors to the light absorption of the toluene-SOAs. Using the obtained RI values, mass absorption cross sections of the toluene-SOAs at 405 and 532 nm were estimated to be 0.08–0.48 and 0.002–0.081 m2 g−1, respectively, under typical conditions in an urban atmosphere during the daytime. These results indicate that light absorption by the SOAs potentially contributes to the radiation balance at ultraviolet wavelengths below ~400 nm, specifically when the mass concentrations of the anthropogenic SOAs are significant compared with those of black carbon particles.

scholarly journals Influence of organic aerosol composition determined by offline FIGAERO-CIMS on particle absorptive properties in autumn Beijing

2021 ◽  
Author(s):  
Jing Cai ◽  
Cheng Wu ◽  
Jiandong Wang ◽  
Wei Du ◽  
Feixue Zheng ◽  
...  
Keyword(s):  
Optical Properties ◽  
Urban Environment ◽  
Light Absorption ◽  
Radiative Forcing ◽  
Dicarboxylic Acids ◽  
Organic Aerosol ◽  
Molecular Composition ◽  
Absorption Enhancement ◽  
Ionization Mass ◽  
Aerosol Composition

Abstract. Organic aerosol (OA) is a major component of fine particulate matter (PM) affecting air quality, human health, and the climate. The absorptive and reflective behavior of OA components contributes to determining particle optical properties and thus their effects on the radiative budget of the troposphere. There is limited knowledge on the influence of the molecular composition of OA on particle optical properties in the polluted urban environment. In this study, we characterized the molecular composition of oxygenated OA collected on filter samples in autumn of 2018 in Beijing, China, with a filter inlet for gases and aerosols coupled to a high-resolution time-of-flight chemical ionization mass spectrometer (FIGAERO-CIMS). Three haze episodes occurred during our sampling period with daily maximum concentrations of OA of 50, 30, and 55 µg m−3, respectively. We found that the signal intensities of dicarboxylic acids and sulfur-containing compounds increased during the two more intense haze episodes, while the relative contributions of wood-burning markers and other aromatic compounds were enhanced during the cleaner periods. We further assessed the optical properties of oxygenated OA components by combining the detailed chemical composition measurements with collocated particle light absorption measurements. We show that light-absorption enhancement (Eabs) of black carbon (BC) was mostly related to more oxygenated OA (e.g. dicarboxylic acids), likely formed in aqueous-phase reactions during the intense haze periods with higher relative humidity, and speculate that they might contribute to lensing effects. Aromatics and nitro-aromatics (e.g. nitrocatechol and its derivatives) were mostly related to a high light absorption coefficient (babs) consistent with light-absorbing (brown) carbon (BrC). Our results provide information on oxygenated OA components at the molecular level associated with BrC and BC particle light-absorption and can serve as a basis for further studies on the effects of anthropogenic OA on radiative forcing in the urban environment.

scholarly journals Evidence for Asian dust effects from aerosol plume measurements during INTEX-B 2006 near Whistler, BC

2008 ◽  
Vol 8 (5) ◽  
pp. 18531-18589 ◽  
Author(s):  
W. R. Leaitch ◽  
A. M. Macdonald ◽  
K. G. Anlauf ◽  
P. S. K. Liu ◽  
D. Toom-Sauntry ◽  
...  
Keyword(s):  
Organic Material ◽  
Fine Particle ◽  
Radiative Forcing ◽  
Fine Particles ◽  
Organic Aerosol ◽  
Dust Particles ◽  
Coarse Particles ◽  
Organic Mass ◽  
Source Regions ◽  
Scanning Transmission

Abstract. Several cases of aerosol plumes resulting from trans-Pacific transport were observed between 2 km and 5.3 km at Whistler, BC from 22 April 2006 to 15 May 2006. The fine particle (<1 μm) chemical composition of most of the plumes was dominated by sulphate that ranged from 1–5 μg m−3 as measured with a Quadrapole Aerosol Mass Spectrometer (Q-AMS). Coarse particles (>1 μm) were enhanced in all sulphate plumes. Fine particle organic mass concentrations were relatively low in most plumes and anti-correlated with the increases in the coarse particles. The chemistry of coarse particles sampled at Whistler Peak was dominated by calcium, sodium, nitrate, sulphate and formate. Scanning transmission X-ray microscopy of coarse particles sampled from the NCAR C-130 aircraft relatively close to Whistler indicated carbonate, potassium and organic functional groups, in particular the carboxyl group. Asian plumes reaching Whistler, BC during the INTEX-B study were not only significantly reduced of fine particle organic material, but organic compounds were attached to coarse particles in significant quantities. Scavenging of organic aerosol precursors by dust near source regions is suggested, and any formation of secondary organic aerosol (SOA) during transport from Asian source regions across the Pacific was principally associated with the coarse particles. An average of profiles indicates that trans-Pacific transport between 2 and 5 km during this period increased ozone by about 10 ppbv and fine particle sulphate by 0.2–0.5 μg m−3. The mean sizes of the fine particles in the sulphate plumes were larger when dust particles were present and smaller when the fine particle organic mass concentration was larger and dust was absent. The coarse particles of dust act to accumulate sulphate, nitrate and organic material in larger particles, diminishing the role of these compounds in indirect radiative forcing, but potentially enhancing their roles in direct radiative forcing.

scholarly journals Chemical characteristics of brown carbon in atmospheric particles at a suburban site near Guangzhou, China

2018 ◽  
Author(s):  
Yi Ming Qin ◽  
Hao Bo Tan ◽  
Yong Jie Li ◽  
Zhu Jie Li ◽  
Misha I. Schurman ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Absorption Coefficient ◽  
Light Absorption ◽  
Radiative Forcing ◽  
Chemical Characterization ◽  
Organic Aerosol ◽  
Atmospheric Particles ◽  
Chemical Characteristics ◽  
Brown Carbon ◽  
Suburban Site

Abstract. Light-absorbing organic carbon (or brown carbon, BrC) in atmospheric particles has received much attention for its potential role in global radiative forcing. While a number of field measurement campaigns have differentiated light absorption by black carbon (BC) and BrC, the chemical characteristics of BrC are not well understood. In this study, we present co-located real-time light absorption and chemical composition measurements of atmospheric particles to explore the relationship between the chemical and optical characteristics of BrC at a suburban site downwind of Guangzhou, China from November to December 2014. BrC and BC contributions to light absorption were estimated using measurements from a seven-wavelength aethalometer, while the chemical composition of non-refractory PM1 was measured with a high resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). Using the Absorption Angstrom Exponent (AAE) method, we estimated that BrC contributed 23.6 % to the total aerosol absorption at 370 nm, 18.1 % at 470 nm, 10.7 % at 520 nm, 10.7 % at 590 nm, and 10.5 % at 660 nm. Biomass burning organic aerosol (BBOA) has the highest mass absorption coefficient among sources of organic aerosols. Its contribution to total brown carbon absorption coefficient decreased but that of low-volatility oxygenated organic aerosol (LVOOA) increased with increasing wavelength, suggesting the need for wavelength-dependent light absorption analysis for BrC in association with its chemical makeup. Clear correlations of N-containing ion fragments with absorption coefficient were observed. These correlations also depended on their degrees of unsaturation/cyclization and oxygenation. While the current study relates light absorption by BrC to ion fragments, more detailed chemical characterization is warranted to constrain this relationship.

scholarly journals Wavelength and NO<sub>x</sub> dependent complex refractive index of SOAs generated from the photooxidation of toluene

2013 ◽  
Vol 13 (2) ◽  
pp. 531-545 ◽  
Author(s):  
T. Nakayama ◽  
K. Sato ◽  
Y. Matsumi ◽  
T. Imamura ◽  
A. Yamazaki ◽  
...  
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Organic Compounds ◽  
Cross Sections ◽  
Light Absorption ◽  
Complex Refractive Index ◽  
Urban Atmosphere ◽  
Radiation Balance ◽  
Limited Information ◽  
K Value

Abstract. Recently, secondary organic aerosols (SOAs) generated from anthropogenic volatile organic compounds have been proposed as a possible source of light-absorbing organic compounds, "brown carbon," in the urban atmosphere. However, the atmospheric importance of these SOAs remains unclear due to limited information about their optical properties. In this study, the complex refractive index (RI, m = n-ki values at 405, 532, and 781 nm of the SOAs generated during the photooxidation of toluene (toluene-SOAs) under a variety of initial nitrogen oxide (NOx = NO + NO2) conditions were examined by photoacoustic spectroscopy (PAS) and cavity ring-down spectroscopy (CRDS). The complex RI-values obtained in the present study and reported in the literature indicate that the k-value, which represents the light absorption of the toluene-SOAs, increased to shorter wavelengths at <532 nm, and the n-value also increased to shorter wavelengths from 781 to 355 nm. The k-values at 405 nm were found to increase from 0.0018 to 0.0072 with increasing initial NOx concentration from 109 to 571 ppbv. The nitrate to organics ratio of the SOAs determined using a high-resolution time-of-flight aerosol mass spectrometer (H-ToF-AMS) also increased with increasing initial NOx concentration. The RI-values of the SOAs generated during the photooxidation of 1,3,5-trimethylbenzene in the presence of NOx (1,3,5-TMB-SOAs) were also determined to investigate the influence of the chemical structure of the precursor on the optical properties of the SOAs, and it was found that the light absorption of the 1,3,5-TMB-SOAs is negligible at all of the wavelengths investigated (405, 532, and 781 nm). These results can be reasonably explained by the hypothesis that nitroaromatic compounds, such as nitrocresols, are the major contributors to the light absorption of the toluene-SOAs. Using the obtained RI-values, mass absorption cross sections of the toluene-SOAs at 405 nm were estimated to be 0.08–0.52 m2g−1 under typical conditions in an urban atmosphere during the daytime. These results indicate that light absorption by the SOAs potentially contributes to the radiation balance at ultraviolet wavelengths below ~400 nm, specifically when the mass concentrations of the anthropogenic SOAs are significant compared with other light-absorbing particles.

scholarly journals Effect of salt seed particle surface area, composition and phase on secondary organic aerosol mass yields in oxidation flow reactors

2019 ◽  
Vol 19 (4) ◽  
pp. 2701-2712 ◽  
Author(s):  
Erik Ahlberg ◽  
Axel Eriksson ◽  
William H. Brune ◽  
Pontus Roldin ◽  
Birgitta Svenningsson
Keyword(s):  
Ammonium Sulfate ◽  
Surface Area ◽  
Residence Time ◽  
Maximum Yield ◽  
Particle Surface ◽  
Organic Aerosol ◽  
Seed Particle ◽  
Particle Surface Area ◽  
Flow Reactors ◽  
Seed Particles

Abstract. Atmospheric particulate water is ubiquitous, affecting particle transport and uptake of gases. Yet, research on the effect of water on secondary organic aerosol (SOA) mass yields is not consistent. In this study, the SOA mass yields of an α-pinene and m-xylene mixture, at a concentration of 60 µg m−3, were examined using an oxidation flow reactor operated at a relative humidity (RH) of 60 % and a residence time of 160 s. Wet or dried ammonium sulfate and ammonium nitrate seed particles were used. By varying the amount of seed particle surface area, the underestimation of SOA formation induced by the short residence time in flow reactors was confirmed. Starting at a SOA mass concentration of ∼5 µg m−3, the maximum yield increased by a factor of ∼2 with dry seed particles and on average a factor of 3.2 with wet seed particles. Hence, wet particles increased the SOA mass yield by ∼60 % compared to the dry experiment. Maximum yield in the reactor was achieved using a surface area concentration of ∼1600 µm2 cm−3. This corresponded to a condensational lifetime of 20 s for low-volatility organics. The O:C ratio of SOA on wet ammonium sulfate was significantly higher than when using ammonium nitrate or dry ammonium sulfate seed particles, probably due to differences in heterogeneous chemistry.

scholarly journals Haze Optical Properties from Long-Term Ground-Based Remote Sensing over Beijing and Xuzhou, China

2018 ◽  
Vol 10 (4) ◽  
pp. 518 ◽  
Author(s):  
Kai Qin ◽  
Luyao Wang ◽  
Jian Xu ◽  
Husi Letu ◽  
Kefei Zhang ◽  
...  
Keyword(s):  
Optical Properties ◽  
Radiative Forcing ◽  
Fine Particles ◽  
Global Climate ◽  
Complex Refractive Index ◽  
Eastern China ◽  
Single Scattering ◽  
Dust Particles ◽  
Haze Pollution

Aerosol haze pollution has had a significant impact on both global climate and the regional air quality of Eastern China, which has a high proportion of high level pollution days. Statistical analyses of aerosol optical properties and direct radiative forcing at two AERONET sites (Beijing and Xuzhou) were conducted from 2013 to 2016. Results indicate: (1) Haze pollution days accounted for 26% and 20% of days from 2013 to 2016 in Beijing and Xuzhou, respectively, with the highest proportions in winter; (2) The averaged aerosol optical depth (AOD) at 550 nm on haze days were about 3.7 and 1.6 times greater than those on clean days in Beijing and Xuzhou, respectively. At both sites, the maximum AOD occurred in summer; (3) Hazes were dominated by fine particles at both sites. However, as compared to Xuzhou, Beijing had larger coarse mode AOD and higher percentage of small α. This data, together with an analysis of size distribution, suggests that the hazes in Beijing were more susceptible to coarse dust particles than Xuzhou; (4) During hazes in Beijing, the single scattering albedo (SSA) is significantly higher when compared to clean conditions (0.874 vs. 0.843 in SSA440 nm), an increase much less evident in Xuzhou. The most noticeable differences in both SSA and the imaginary part of the complex refractive index between Beijing and Xuzhou were found in winter; (5) In Beijing, the haze radiative forcing produced an averaged cooling effect of −113.6 ± 63.7 W/m2 at the surface, whereas the averaged heating effect of 77.5 ± 49.7 W/m2 within the atmosphere was at least twice as strong as clean days. In Xuzhou, such a radiative forcing effect appeared to be much smaller and the difference between haze and clean days was insignificant. Derived from long-term observation, these findings are more significant for the improvement of our understanding of haze formation in China and the assessment of its impacts on radiative forcing of climate change than previous short-term case studies.

scholarly journals How Different Calculations of the Refractive Index Affect Estimates of the Radiative Forcing Efficiency of Ammonium Sulfate Aerosols

2011 ◽  
Vol 68 (9) ◽  
pp. 1845-1852 ◽  
Author(s):  
Carynelisa Erlick ◽  
Jonathan P. D. Abbatt ◽  
Yinon Rudich
Keyword(s):  
Refractive Index ◽  
Black Carbon ◽  
Ammonium Sulfate ◽  
Radiative Forcing ◽  
Radiative Properties ◽  
Refractive Indices ◽  
Mixing Rule ◽  
High Concentration ◽  
Aerosol Forcing ◽  
The Difference

Abstract Calculations of the radiative properties of hydrated ammonium sulfate (AS) aerosols often employ the conventional volume mixing rule, in which the refractive indices of AS and water are linearly averaged, weighted by their respective volume fractions in solution, and the real part of the refractive index of pure AS is taken to be 1.52–1.55, based on measurements of dry crystalline AS. However, there are significant differences between the refractive indices of AS–water solutions calculated using the conventional volume mixing rule and empirically derived refractive indices. The authors use a simple model for calculating the direct solar radiative forcing efficiency (RFE; radiative forcing divided by optical depth) of an optically thin layer of aerosols to investigate the magnitude of these differences. The difference between the conventional volume mixing rule and empirically derived refractive indices amounts to a modest difference in the direct solar RFE of AS aerosols at the top of the atmosphere at 0.550-μm wavelength and at relative humidities of 37%–99.9%. Without black carbon, the difference in RFE is up to −0.42 W m−2 for relative humidities less than around 66% and up to 0.25 W m−2 for relative humidities greater than 66%, whereas with 2% black carbon by volume, the range of difference in RFE is up to −0.59 W m−2 for relative humidities less than 66% and up to 0.30 W m−2 for relative humidities greater than 66%. Although modest, this difference in RFE may become important when investigating regional aerosol forcing in areas with a high concentration of urban and industrial pollution.

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