scholarly journals Light absorption by polar and non-polar aerosol compounds from laboratory biomass combustion

2018 ◽  
Author(s):  
Deep Sengupta ◽  
Vera Samburova ◽  
Chiranjivi Bhattarai ◽  
Elena Kirillova ◽  
Lynn Mazzoleni ◽  
...  
Keyword(s):  
Light Absorption ◽  
Flow Reactor ◽  
Soluble Fraction ◽  
Chemical Properties ◽  
Water Soluble ◽  
Biomass Combustion ◽  
Absorption Properties ◽  
Oxidation Processes ◽  
Aerosol Mass ◽  
Physical Processing

Abstract. Fresh and atmospherically aged biomass-burning (BB) aerosol mass is mostly comprised of black carbon (BC) and organic carbon (OC) with its light-absorbing fraction – brown carbon (BrC). There is a lack of data on the physical and chemical properties of atmospheric BB aerosols, leading to high uncertainties in estimates of the BB impact on air quality and climate, especially for BrC. The polarity of chemical compounds influences their fate in the atmosphere including wet/dry deposition and chemical and physical processing. So far, most of the attention has been given to the water-soluble (polar) fraction of BrC, while the non-polar BrC fraction has been largely ignored. In the present study, the light absorption properties of polar and non-polar fractions of fresh and aged BB emissions were examined to estimate the contribution of different-polarity organic compounds to the light absorption properties of BB aerosols. In our experiments, four globally and regionally important fuels were burned under flaming and smoldering conditions in DRI’s combustion chamber. To mimic atmospheric oxidation processes (5–7 days), BB emissions were aged using an oxidation flow reactor (OFR). Fresh and OFR-aged BB aerosols were collected on filters and extracted with water and hexane to study absorption properties of polar and non-polar organic species. Spectrophotometric measurements over the 190 to 900 nm wavelength range showed that the non-polar (hexane-soluble) fraction is 2–3 times more absorbing than the polar (water-soluble) fraction. However, an increased absorbance was observed for the water extracts of oxidized/aged emissions while the absorption of the hexane extracts was lower for the aged emissions. Comparing the absorption Ångström Exponent (AAE) values, we observed changes in the light absorption properties of BB aerosols with aging that was dependent on the fuel types. The light absorption by HUmic LIke Substances (HULIS) was found to be higher in fuels characteristic of the southwestern USA. The absorption of the HULIS fraction was lower for OFR-aged BB emissions. Comparison of the light absorption properties of different polarity extracts (water, hexane, HULIS) provides insight into the chemical nature of BB BrC and its transformation during oxidation processes.

scholarly journals Light absorption by polar and non-polar aerosol compounds from laboratory biomass combustion

2018 ◽  
Vol 18 (15) ◽  
pp. 10849-10867 ◽  
Author(s):  
Deep Sengupta ◽  
Vera Samburova ◽  
Chiranjivi Bhattarai ◽  
Elena Kirillova ◽  
Lynn Mazzoleni ◽  
...  
Keyword(s):  
Light Absorption ◽  
Flow Reactor ◽  
Soluble Fraction ◽  
Solar Spectrum ◽  
Chemical Properties ◽  
Water Soluble ◽  
Biomass Combustion ◽  
Absorption Properties ◽  
Oxidation Processes ◽  
Flaming Combustion

Abstract. Fresh and atmospherically aged biomass-burning (BB) aerosol mass is mostly comprised of strongly light-absorbing black carbon (BC) and of organic carbon (OC) with its light-absorbing fraction – brown carbon (BrC). There is a lack of data on the physical and chemical properties of atmospheric BB aerosols, leading to high uncertainties in estimates of the BB impact on air quality and climate, especially for BrC. The polarity of chemical compounds influences their fate in the atmosphere including wet/dry deposition and chemical and physical processing. So far, most of the attention has been given to the water-soluble (polar) fraction of BrC, while the non-polar BrC fraction has been largely ignored. In the present study, the light absorption properties of polar and non-polar fractions of fresh and aged BB emissions were examined to estimate the contribution of different-polarity organic compounds to the light absorption properties of BB aerosols. In our experiments, four globally and regionally important fuels were burned under flaming and smoldering conditions in the Desert Research Institute (DRI) combustion chamber. To mimic atmospheric oxidation processes (5–7 days), BB emissions were aged using an oxidation flow reactor (OFR). Fresh and OFR-aged BB aerosols were collected on filters and extracted with water and hexane to study absorption properties of polar and non-polar organic species. Results of spectrophotometric measurements (absorption weighted by the solar spectrum and normalized to mass of fuel consumed) over the 190 to 900 nm wavelength range showed that the non-polar (hexane-soluble) fraction is 2–3 times more absorbing than the polar (water-soluble) fraction. However, for emissions from fuels that undergo flaming combustion, an increased absorbance was observed for the water extracts of oxidized/aged emissions while the absorption of the hexane extracts was lower for the aged emissions for the same type of fuels. Absorption Ångström exponent (AAE) values, computed based on absorbance values from spectrophotometer measurements, were changed with aging and the nature of this change was fuel dependent. The light absorption by humic-like substances (HULIS) was found to be higher in fuels characteristic of the southwestern USA. The absorption of the HULIS fraction was lower for OFR-aged BB emissions. Comparison of the light absorption properties of different-polarity extracts (water, hexane, HULIS) provides insight into the chemical nature of BB BrC and its transformation during oxidation processes.

scholarly journals Chemical characterization of fine particular matter in Changzhou, China and source apportionment with offline aerosol mass spectrometry

2016 ◽  
Author(s):  
Zhaolian Ye ◽  
Jiashu Liu ◽  
Aijun Gu ◽  
Feifei Feng ◽  
Yuhai Liu ◽  
...  
Keyword(s):  
Trace Elements ◽  
Organic Matter ◽  
Organic Carbon ◽  
Source Apportionment ◽  
Major Ions ◽  
Chemical Properties ◽  
Chemical Characterization ◽  
Water Soluble ◽  
Traffic Emissions ◽  
Aerosol Mass

Abstract. Knowledge on aerosol chemistry in densely populated regions is critical for reduction of air pollution, while such studies haven't been conducted in Changzhou, an important manufacturing base and polluted city in the Yangtze River Delta (YRD), China. This work, for the first time, performed a thorough chemical characterization on the fine particular matter (PM2.5) samples, collected during July 2015 to April 2016 across four seasons in Changzhou city. A suite of analytical techniques were employed to characterize organic carbon / elemental carbon (OC / EC), water-soluble organic carbon (WSOC), water-soluble inorganic ions (WSIIs), trace elements, and polycyclic aromatic hydrocarbons (PAHs) in PM2.5; in particular, an Aerodyne soot particle aerosol mass spectrometer (SP-AMS) was deployed to probe the chemical properties of water-soluble organic aerosols (WSOA). The average PM2.5 concentrations were found to be 108.3 μg m−3, and all identified species were able to reconstruct ~ 80 % of the PM2.5 mass. The WSIIs occupied about half of the PM2.5 mass (~ 52.1 %), with SO42−, NO3− and NH4+ as the major ions. On average, nitrate concentrations dominated over sulfate (mass ratio of 1.21), indicating influences from traffic emissions. OC and EC correlated well with each other and the highest OC / EC ratio (5.16) occurred in winter, suggesting complex OC sources likely including both secondarily formed and primarily emitted OA. Concentrations of eight trace elements (Mn, Zn, Al, B, Cr, Cu, Fe, Pb) can contribute up to 6.0 % of PM2.5 during winter. PAHs concentrations were also high in winter (140.25 ng m−3), which were predominated by median/high molecular weight PAHs with 5- and 6-rings. The organic matter including both water-soluble and water-insoluble species occupied ~ 20 % PM2.5 mass. SP-AMS determined that the WSOA had an average atomic oxygen-to-carbon (O / C), hydrogen-to-carbon (H / C), nitrogen-to-carbon (N / C) and organic matter-to-organic carbon (OM / OC) ratios of 0.36, 1.54, 0.11, and 1.74, respectively. Source apportionment of WSOA further identified two secondary OA (SOA) factors (a less oxidized and a more oxidized OA) and two primary OA (POA) factors (a nitrogen enriched hydrocarbon-like traffic OA and a cooking-related OA). On average, the POA contribution overweighed SOA (55 % vs. 45 %), indicating the important role of local anthropogenic emissions to the aerosol pollution in Changzhou. Our measurement also shows the abundance of organic nitrogen species in WSOA, and the source analyses suggest these species likely associated with traffic emissions, which warrants more investigations on PM samples from other locations.

Light absorption properties of elemental carbon (EC) and water-soluble brown carbon (WS–BrC) in the Kathmandu Valley, Nepal: A 5-year study

2020 ◽  
Vol 261 ◽  
pp. 114239 ◽  
Author(s):  
Pengfei Chen ◽  
Shichang Kang ◽  
Lekhendra Tripathee ◽  
Kirpa Ram ◽  
Maheswar Rupakheti ◽  
...  
Keyword(s):  
Light Absorption ◽  
Elemental Carbon ◽  
Water Soluble ◽  
Kathmandu Valley ◽  
Absorption Properties ◽  
Brown Carbon

Optical and chemical properties of wintertime light-absorbing aerosols in the eastern Indo-Gangetic Plain, India

2020 ◽  
Author(s):  
Supriya Dey ◽  
Archita Rana ◽  
Prashant Rawat ◽  
Sayantan Sarkar
Keyword(s):  
Organic Carbon ◽  
Light Absorption ◽  
Mass Concentration ◽  
Chemical Properties ◽  
Water Soluble ◽  
Chemical Extraction ◽  
Aerosol Formation ◽  
Gangetic Plain ◽  
Indo Gangetic Plain ◽  
And Chemical Properties

<p>Light-absorbing carbonaceous aerosols such as black and brown carbon (BC and BrC) and humic-like substances (HULIS) have pronounced effects on the earth’s radiative balance and tropospheric photochemistry. In India, large heterogeneities exist for BC and organic carbon (OC) emission inventories, which necessitates regionally-representative ground-based measurements. Such measurements are spatially scattered for BC, rare for BrC and non-existent for HULIS. This severely limits a robust understanding of the optical and chemical properties of these aerosols, and consequently, their climate effects. To address this issue, the present study reports optical and chemical properties of wintertime (December 2018-February 2019) BC, BrC and HULIS at a rural receptor site in the highly polluted eastern Indo-Gangetic Plain (IGP), India. A 7 wavelength aethalometer was deployed to measure time-resolved BC mass concentration, and absorption coefficients (b<sub>abs</sub>) and Angstrom exponent (AE) of BrC. Separation of aqueous and organic BrC (BrC<sub>aq</sub> and BrC<sub>org</sub>) and HULIS fractions via a multi-step chemical extraction procedure followed by optical measurements (UV-Vis, fluorescence and FT-IR), and supplementary measurements of OC, water-soluble organic carbon (WSOC) and ionic species led to better insights into the potential chromophore composition and their relative importance in constraining aerosol optical properties.</p><p>The daily averaged BC mass concentration was 15.4±9.5 μg m<sup>-3</sup> during winter, where the biomass burning (BB) contribution was 25±5%. The diurnal profile of BC<sub>BB</sub> and BrC light absorption coefficient (b<sub>abs_BrC</sub>) showed a prominent morning peak (0700-0800 H) characterized by mixed fossil fuel and biofuel emission and a gradual increase towards night due to enhanced primary BB emission from cooking activities and lowering of the mixing depth. The regionally transported BB plume from northwestern IGP contributed substantial BC and BrC to this receptor location in the eastern end of the corridor, which was supported by concentration-weighted air mass trajectories (CWTs).</p><p>The BrC<sub>org</sub> light absorption at 365 nm (b<sub>abs_BrC_org</sub>) was almost 2 times compared to that of BrC<sub>aq</sub> (b<sub>abs_BrC_aq</sub>) (36±7.1 vs 18.3±4.3 Mm<sup>-1</sup>), which suggested a dominance of non-polar polyconjugated BrC chromophores. This was also supported by the increasing trend of water-insoluble BrC from 49±10% at 365 nm to 64±21% at 550 nm, with averaged contributions of 49±8% at 300-400 nm and 67±9% at 400-550 nm, respectively. A strong correlation between WSOC and NO<sub>3</sub><sup>- </sup>(r=0.78, p<0.01) and WSOC and NH<sub>4</sub><sup>+</sup> (r=0.63, p<0.01) indicated the possibility of nighttime secondary organic aerosol formation. A prominent fluorescence peak at ~409 nm for BrC<sub>aq </sub>confirmed the presence of HULIS, and b<sub>abs_BrC_aq</sub> was dominated by the low-polarity HULIS-n fraction. AE of individual HULIS fractions increased by 7-36% towards the more polar HULIS-a and highly-polar water-soluble organic matter (HPWSOM) compared to the less polar HULIS-n for the 300-700 nm range. Distinct FTIR peaks at 3400 cm<sup>-1</sup>, 1710 cm<sup>-1</sup> and 1643 cm<sup>-1</sup> suggested abundance of C-H, C=O and C=C functional groups, respectively, in the BrC chromophores. Overall, it appeared that the regionally transported BB plume significantly enriches BrC and HULIS in the eastern part of the IGP corridor.   </p>

A yearlong study of water-soluble organic carbon in Beijing II: Light absorption properties

2014 ◽  
Vol 89 ◽  
pp. 235-241 ◽  
Author(s):  
Zhenyu Du ◽  
Kebin He ◽  
Yuan Cheng ◽  
Fengkui Duan ◽  
Yongliang Ma ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Light Absorption ◽  
Water Soluble ◽  
Absorption Properties ◽  
Water Soluble Organic Carbon ◽  
Soluble Organic Carbon

scholarly journals Contributions of nitrated aromatic compounds to the light absorption of water-soluble and particulate brown carbon in different atmospheric environments in Germany and China

2016 ◽  
Author(s):  
Monique Teich ◽  
Dominik van Pinxteren ◽  
Michael Wang ◽  
Simonas Kecorius ◽  
Zhibin Wang ◽  
...  
Keyword(s):  
Light Absorption ◽  
Strong Influence ◽  
Water Soluble ◽  
Absorption Properties ◽  
Brown Carbon ◽  
Light Absorption Coefficient ◽  
Alkaline Conditions ◽  
Acidic Conditions ◽  
The Mean ◽  
Biogenic Aerosols

Abstract. The relative contribution of eight nitrated aromatic compounds (NACs, nitrophenols + nitrated salicylic acids) to the light absorption of aqueous particle extracts and particulate brown carbon were determined from aerosol particle samples collected in Germany and China. High-volume filter samples were collected during six campaigns, performed at five locations in two seasons: (I) two campaigns with strong influence of biomass burning (BB) aerosol – at the TROPOS institute (winter, 2014, urban background, Leipzig, Germany) and the Melpitz research site (winter, 2014, rural background); (II) two campaigns with strong influence from biogenic emissions – at Melpitz (summer, 2014) and the forest site Waldstein (summer, 2014, Fichtelgebirge, Germany), and (III) two CAREBeijing-NCP campaigns – at Xianghe (summer, 2013, anthropogenic polluted background) and Wangdu (summer, 2014, anthropogenic polluted background with a distinct BB-episode), both in the North China Plain. The filter samples were analyzed for NAC concentrations and the light absorption of aqueous filter extracts was determined. Light absorption properties of particulate brown carbon were derived from a seven-wavelength Aethalometer during the campaigns at TROPOS (winter) and Waldstein (summer). The light absorption of the aqueous filter extracts was found to be pH dependent: at pH 10, the aqueous light absorption coefficient Abs370 and the mass absorption efficiency (MAE370) at 370 nm were a factor of 1.6 and 1.4 larger than at pH 2, respectively. In general, Abs370 ranged from 0.21–21.8 Mm−1 under acidic conditions and 0.63–27.2 Mm−1 under alkaline conditions, over all campaigns. The observed MAE370 was in a range of 0.10–1.79 m2 g−1 and 0.24–2.57 m2 g−1 for acidic and alkaline conditions, respectively. For MAE370 and Abs370, the observed values were higher in winter than in summer, in agreement with other studies. Furthermore, it was found that the MAE370 values in winter in Germany exceeded those of the Chinese summer background stations (average of 0.85±0.24 m2 g−1 compared to 0.47±0.15 m2 g−1). The lowest MAE was observed for the Waldstein (summer) campaign (average of 0.17±0.03 m2 g−1), indicating that freshly emitted biogenic aerosols are only weakly absorbing. In contrast, a strong relationship was found between the light absorption properties and the concentrations of levoglucosan, corroborating findings from other studies. Regarding the particulate light absorption at 370 nm, a mean particulate light absorption coefficient babs,370 of 54 Mm−1 and 6.0 Mm−1 was determined for the TROPOS (winter) and Waldstein (summer) campaigns, respectively, with average contributions of particulate brown carbon to babs,370 of 46 % at TROPOS (winter) and 15 % at Waldstein (summer). The absorption Ångström exponent of the ambient aerosol during the campaigns at TROPOS (winter) and Waldstein (summer) was found to be 1.5±0.1 and 1.2±0.3, respectively. Thus, the Aethalometer measurements support the findings from aqueous filter extracts of only weakly absorbing biogenic aerosols in comparison to the more polluted and BB influenced aerosol at TROPOS (winter). The mean contribution of NACs to the aqueous extract light absorption over all campaigns ranged from 0.10 %–1.25 % under acidic conditions and 0.13 %–3.71 % under alkaline conditions. The high variability among the measurement sites showed that the emission strengths of light absorbing compounds and the composition of brown carbon were very different for each site. The mean contribution of NACs to the particulate brown carbon light absorption was 0.10±0.06 % (acidic conditions) and 0.13±0.09 % (alkaline conditions) during the Waldstein (summer) campaign and 0.25±0.21 % (acidic conditions) and 1.13±1.03 % (alkaline conditions) during the TROPOS (winter) campaign. A correlation of NAC concentrations with Abs370 was observed for the BB-influenced campaigns at TROPOS (winter) and Melpitz (winter). The average contribution of NACs to the aqueous extract light absorption over all campaigns was found to be 5 times higher than their mass contribution to water-soluble organic carbon indicating that even small amounts of light-absorbing compounds can have a disproportionately high impact on the light absorption properties of particles.

Seasonal light absorption properties of water-soluble brown carbon in atmospheric fine particles in Nanjing, China

2018 ◽  
Vol 187 ◽  
pp. 230-240 ◽  
Author(s):  
Yanfang Chen ◽  
Xinlei Ge ◽  
Hui Chen ◽  
Xinchun Xie ◽  
Yuntao Chen ◽  
...  
Keyword(s):  
Light Absorption ◽  
Fine Particles ◽  
Water Soluble ◽  
Absorption Properties ◽  
Brown Carbon

scholarly journals Characterizing source fingerprints and ageing processes in laboratory-generated secondary organic aerosols using proton-nuclear magnetic resonance (<sup>1</sup>H-NMR) analysis and HPLC HULIS determination

2017 ◽  
Vol 17 (17) ◽  
pp. 10405-10421 ◽  
Author(s):  
Nicola Zanca ◽  
Andrew T. Lambe ◽  
Paola Massoli ◽  
Marco Paglione ◽  
David R. Croasdale ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
1H Nmr ◽  
Flow Reactor ◽  
Analytical Techniques ◽  
Water Soluble ◽  
Proton Nuclear Magnetic Resonance ◽  
Aerosol Mass ◽  
Polycarboxylic Acids ◽  
Nuclear Magnetic

Abstract. The study of secondary organic aerosol (SOA) in laboratory settings has greatly increased our knowledge of the diverse chemical processes and environmental conditions responsible for the formation of particulate matter starting from biogenic and anthropogenic volatile compounds. However, characteristics of the different experimental setups and the way they impact the composition and the timescale of formation of SOA are still subject to debate. In this study, SOA samples were generated using a potential aerosol mass (PAM) oxidation flow reactor using α-pinene, naphthalene and isoprene as precursors. The PAM reactor facilitated exploration of SOA composition over atmospherically relevant photochemical ageing timescales that are unattainable in environmental chambers. The SOA samples were analyzed using two state-of-the-art analytical techniques for SOA characterization – proton nuclear magnetic resonance (1H-NMR) spectroscopy and HPLC determination of humic-like substances (HULIS). Results were compared with previous Aerodyne aerosol mass spectrometer (AMS) measurements. The combined 1H-NMR, HPLC, and AMS datasets show that the composition of the studied SOA systems tend to converge to highly oxidized organic compounds upon prolonged OH exposures. Further, our 1H-NMR findings show that only α-pinene SOA acquires spectroscopic features comparable to those of ambient OA when exposed to at least 1  ×  1012 molec OH cm−3  ×  s OH exposure, or multiple days of equivalent atmospheric OH oxidation. Over multiple days of equivalent OH exposure, the formation of HULIS is observed in both α-pinene SOA and in naphthalene SOA (maximum yields: 16 and 30 %, respectively, of total analyzed water-soluble organic carbon, WSOC), providing evidence of the formation of humic-like polycarboxylic acids in unseeded SOA.

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