Light Absorption Properties of Organic Aerosol from Wood Pyrolysis: Measurement Method Comparison and Radiative Implications

Li, Xinghua; Xiao, Maodong; Xu, Xuezhe; Zhou, Jiacheng; Yang, Kaiqiang; Wang, Zihao; Zhang, Weijun; Hopke, Philip K.; Zhao, Weixiong

doi:10.1021/acs.est.0c01475

Cited by 29 publications

(11 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It should be noted that the comparison would not be influenced by the difference in BrC measurement method between this study and FIREX, as b abs values (and thus MAE) derived from the optical closure and methanol extraction approaches were shown to be generally equivalent by an intercomparison study. 47 In addition, a negative dependence of MAE* on POA BB /BC was also evident in source emission studies based on the methanol extraction approach, 48,49 although the observations were typically performed for limited biofuel types and POA BB /BC ranges.…”

Section: ■ Results and Discussionmentioning

confidence: 98%

Strong Impacts of Legitimate Open Burning on Brown Carbon Aerosol in Northeast China

Cheng

Cao

et al. 2021

Environ. Sci. Technol. Lett.

View full text Add to dashboard Cite

The massive agricultural sector in Northeast China results in a huge amount of crop residues, which have long been disposed mainly through “illegal” open burning. A transition of local policy occurred in 2018, with a window of approximately 3 months issued for agricultural fires. Here, we investigated the responses of brown carbon (BrC) to the new policy. Persistently high levels of BrC mass (estimated as methanol-soluble organic carbon) and absorption coefficient were observed during the “legitimate burning” period. Agricultural fires, the major driver responsible for the elevated BrC levels, were found to be distinctive with relatively low combustion efficiencies and resulted in BrC with less light absorptivity, compared to residential burning of crop residues. The agricultural fire emissions also led to overestimation of elemental carbon (EC) mass, by a factor of up to 1.6. This in turn resulted in substantial underestimation of f BrC/EC, the fraction of solar energy absorbed by BrC relative to EC. This study indicates that the new open burning policy could not be considered successful with respect to either air quality improvement or climate change mitigation.

show abstract

Section: ■ Results and Discussionmentioning

confidence: 98%

Strong Impacts of Legitimate Open Burning on Brown Carbon Aerosol in Northeast China

Cheng

Cao

et al. 2021

Environ. Sci. Technol. Lett.

View full text Add to dashboard Cite

show abstract

“…Filter-based measurements were found to report high attenuation coefficients in comparison with the optical closure . ATN corrected by the artifacts such as the multiple scattering effect and shadowing effect and the realistic mass absorption efficiency (MAE) values are preferable in calculating the BC or BrC mass; however, the lack of parameter values and high variations in a few studies − resulted in high uncertainties in its calculation.…”

Section: Methodsmentioning

confidence: 99%

Optically Measured Black and Particulate Brown Carbon Emission Factors from Real-World Residential Combustion Predominantly Affected by Fuel Differences

Zhang

Luo

et al. 2020

Environ. Sci. Technol.

View full text Add to dashboard Cite

Residential solid fuel use is an important source of black carbon (BC) but also a main source of uncertainty in BC emission inventories, as reliable real-world emission factors (EFs) and data on consumption of noncommercial household fuels are limited. In this study, particulate BC and brown carbon (BrC) for real-world indoor coal and biomass burning were evaluated using a SootScan model OT21 optical transmissometer from a field campaign including 343 biomass/coal combustion events. The highest BC EF from the burning of coal cake (a mixed fuel locally made from coal and clay) was 1.6–6.4 higher than that of other fuels, and BC EFs were higher for coal combustion than for biomass burning. The highest particulate BrC EF was from charcoal burning and was 1.5–4.3 times higher than that from other biomass and coals. Burning fuel in iron stoves had lower BC and BrC EFs, at approximately 15–66% and 40–54%, respectively, compared with burning in other stove types. The difference between heating and cooking activities was statistically insignificant (p > 0.05). A generalized linear model coupled with dominance analysis evidenced that the EFs were significantly associated with fuel and stove types, with the fuel difference being a major influencing factor explaining 68% of the variation. This suggests that a clean fuel transition would have beneficial impacts on air pollution associated with the residential sector in China. The absorption EFs differed by 2–3 orders of magnitude across different fuel–stove combinations. The Absorption Ångström Exponent values for the particulate from residential solid fuel combustions ranged from 0.92 to 3.7.

show abstract

“…, ( ) at four AE33 wavelengths (370 nm, 470 nm, 520 nm, and 590 nm) with Mie code programmed in the software package Igor Pro (WaveMetrics). These calculations assume that the absorbing (BrC-containing) non-refractory particles are spherical with homogeneous internal composition in the particle phase (Sumlin et al, 2018;Li et al, 2020). In literature, a constant MAC/MAE ratio of 1.8-2.0 is often used to proceed from absorption measured in dilute solutions to absorption in the particle phase (Liu et al, 2013;Washenfelder et al, 2015;Shamjad et al, 2017;Zeng et al, 2020).…”

Section: Determination Of Particulate Brc Absorptionmentioning

confidence: 99%

Source-specific light absorption by carbonaceous components in the complex aerosol matrix from yearly filter-based measurements

Moschos¹,

Gysel²,

Modini³

et al. 2020

Preprint

View full text Add to dashboard Cite

Abstract. Understanding the sources of light-absorbing organic (brown) carbon (BrC) and its interaction with black carbon (BC) and other non-refractory particulate matter (NR-PM) fractions is important for reducing uncertainties in the aerosol direct radiative forcing. In this study, we combine multiple filter-based techniques to achieve long-term, spectrally-resolved, source- and species-specific atmospheric absorption closure. We determine the total aerosol absorption at seven wavelengths based on the Aethalometer attenuation measurements, calibrated with the multi-wavelength absorption analyzer. We measure the spectrally-resolved imaginary part of the refractive index, k, for methanol extracts and determine the source-specific k for organic aerosol (OA) fractions using positive matrix factorization. The average k at 370 nm is found to be 0.06 for fresh biomass smoke, 0.03 for winter-oxygenated OA, and 0.006 for other less absorbing OA, which translates to corresponding mass absorption efficiencies (MAE) in dilute bulk solutions of 1.4, 0.7 and 0.13 m2 g−1. We apply Mie calculations to estimate the contributions of these fractions to total aerosol absorption. While enhanced absorption in the near-UV has been traditionally attributed to primary biomass smoke, here we show that anthropogenic oxygenated OA may be as important for BrC absorption during winter, especially at an urban background site. We demonstrate the absence of tar-balls in residential biomass burning particles of this study, and attribute the totality of the NR-PM absorption at shorter wavelengths to methanol-extractable BrC. As for BC, we show that the mass absorption cross-section (MAC) of this fraction is independent of its source, while we observe evidence for a lensing effect associated with the presence of NR-PM components. We find that bare BC has a MAC of 6.3 m2 g−1 at 660 nm and an absorption Ångström exponent (AAE) of 0.93 ± 0.16, while in the presence of coatings its absorption is enhanced by a factor of ~1.4. This falls within the global average enhancement factor of 1.5 ± 0.3 from filter-based techniques. Based on Mie-calculations of closure between observed and predicted total light absorption, we provide the first experimental evidence for a suppression of the lensing effect by BrC. The total absorption suppression remains modest, ~10–20 % at 370 nm, and is restricted to shorter wavelengths where BrC absorption is significant. Our long-term observations at locations representative of European urban background and rural Alpine sites show that extractable particulate BrC accounts for ~30 % of the absorption in the near-UV range (370 nm) on a yearly basis. However, if lensing suppression occurred due to internal mixing of BC and BrC as apparently the case for many samples in our study, then the additional absorption by BrC (vs transparent OA) would be partially compensated by a concurrent BC lensing factor reduction, which manifests as lower than expected total aerosol AAE values. Overall, when integrated with the solar spectrum at 300–900 nm, bare BC is found to contribute around two thirds of the solar radiation absorption by total carbonaceous aerosols, amplified by the lensing effect (with an interquartile range, IQR, of 8–27 %), while the IQR of yearly average contributions by particulate BrC is 6–13 % (13–20 % at the rural site during winter).

show abstract

Light Absorption Properties of Organic Aerosol from Wood Pyrolysis: Measurement Method Comparison and Radiative Implications

Cited by 29 publications

References 48 publications

Strong Impacts of Legitimate Open Burning on Brown Carbon Aerosol in Northeast China

Strong Impacts of Legitimate Open Burning on Brown Carbon Aerosol in Northeast China

Optically Measured Black and Particulate Brown Carbon Emission Factors from Real-World Residential Combustion Predominantly Affected by Fuel Differences

Source-specific light absorption by carbonaceous components in the complex aerosol matrix from yearly filter-based measurements

Contact Info

Product

Resources

About