Reduction in biomass burning aerosol light absorption upon humidification: roles of inorganically-induced hygroscopicity, particle collapse, and photoacoustic heat and mass transfer

Lewis, K.; Arnott, W. P.; Moosmüller, Hans; Chakrabarty, Rajan K.; Carrico, Christian M.; Kreidenweis, Sonia M.; Day, Derek E.; Malm, William C.; Laskin, Alexander; Jiménez, José; Ulbrich, I. M.; Huffman, J. A.; Onasch, T. B.; Trimborn, A.; Liu, L.; Mishchenko, Michael I.

doi:10.5194/acp-9-8949-2009

Cited by 126 publications

(132 citation statements)

References 53 publications

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“…Garland et al (2007) parameterized the relative humidity dependence of light extinction at 532 nm for inorganic ammonium sulfate aerosols, Baynard et al (2006) looked at mixtures of NaCl and ammonium sulfate with a few dicarboxylic acids, and Fierz-Schmidhauser et al (2010) measured the scattering dependence of ammonium sulfate and sodium chloride. Conversely, we could only find two recent studies (Hasenkopf et al, 2011;Lewis et al, 2009) which dealt with the optical growth of slightly absorbing particles. Hasenkopf et al (2011) focused on the optical growth at 532 nm of organic particles likely to have been present on early Earth and Titan, and Lewis et al (2009) studied the scattering and absorption increase (or reduction) at 530 and 870 nm using three different types of smoke particles.…”

Section: Introductionmentioning

confidence: 95%

“…Conversely, we could only find two recent studies (Hasenkopf et al, 2011;Lewis et al, 2009) which dealt with the optical growth of slightly absorbing particles. Hasenkopf et al (2011) focused on the optical growth at 532 nm of organic particles likely to have been present on early Earth and Titan, and Lewis et al (2009) studied the scattering and absorption increase (or reduction) at 530 and 870 nm using three different types of smoke particles.…”

Section: Introductionmentioning

confidence: 95%

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Absorbing aerosols at high relative humidity: linking hygroscopic growth to optical properties

et al. 2012

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Abstract. One of the major uncertainties in the understanding of Earth's climate system is the interaction between solar radiation and aerosols in the atmosphere. Aerosols exposed to high humidity will change their chemical, physical, and optical properties due to their increased water content. To model hydrated aerosols, atmospheric chemistry and climate models often use the volume weighted mixing rule to predict the complex refractive index (RI) of aerosols when they interact with high relative humidity, and, in general, assume homogeneous mixing. This study explores the validity of these assumptions. A humidified cavity ring down aerosol spectrometer (CRD-AS) and a tandem hygroscopic DMA (differential mobility analyzer) are used to measure the extinction coefficient and hygroscopic growth factors of humidified aerosols, respectively. The measurements are performed at 80 % and 90 %RH at wavelengths of 532 nm and 355 nm using size-selected aerosols with different degrees of absorption; from purely scattering to highly absorbing particles. The ratio of the humidified to the dry extinction coefficients (f RH ext (%RH, Dry)) is measured and compared to theoretical calculations based on Mie theory. Using the measured hygroscopic growth factors and assuming homogeneous mixing, the expected RIs using the volume weighted mixing rule are compared to the RIs derived from the extinction measurements.We found a weak linear dependence or no dependence of f RH(%RH, Dry) with size for hydrated absorbing aerosols in contrast to the non-monotonically decreasing behavior with size for purely scattering aerosols. No discernible difference could be made between the two wavelengths used. Less than 7 % differences were found between the real parts of the complex refractive indices derived and those calculated using the volume weighted mixing rule, and the imaginary parts had up to a 20 % difference. However, for substances with growth factor less than 1.15 the volume weighted mixing rule assumption needs to be taken with caution as the imaginary part of the complex RI can be underestimated.

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Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 95%

Absorbing aerosols at high relative humidity: linking hygroscopic growth to optical properties

et al. 2012

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“…For a non-spherical particle, such as a fresh soot agglomerate, the mobility diameter (D mob ) as measured by a DMA is normally larger than the geometric volume/mass equivalent diameter (D ve ) (DeCarlo et al, 2004). However, it has been widely reported that the coating on soot aggregates will modify its morphology (Weingartner et al, 1997;Zhang et al, 2008;Lewis et al, 2009;Pagels et al, 2009;Kiselev et al, 2010) by causing the soot aggregate to collapse and to become less fractal and more compact. The modification of the particle morphology will change its physical mobility properties, and therefore measurements of D mob .…”

Section: Htdma-sp2 Systemmentioning

confidence: 99%

“…by exposing hygroscopic soot to elevated RH conditions will cause enhanced reconstruction effect (i.e. Lewis et al, 2009). The undermined shape effect on ρ eff leads to a challenge in explicitly explaining the hygroscopic growth of BC particles.…”

Section: Growth Factor Modellingmentioning

confidence: 99%

Ambient black carbon particle hygroscopic properties controlled by mixing state and composition

et al. 2013

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The wet removal of black carbon aerosol (BC) in the atmosphere is a crucial factor in determining its atmospheric lifetime and thereby the vertical and horizontal distributions, dispersion on local and regional scales, and the direct, semi-direct and indirect radiative forcing effects. The in-cloud scavenging and wet deposition rate of freshly emitted hydrophobic BC will be increased on acquisition of more-hydrophilic components by coagulation or coating processes. The lifetime of BC is still subject to considerable uncertainty for most of the model inputs, which is largely due to the insufficient constraints on the BC hydrophobic-to-hydrophilic conversion process from observational field data. This study was conducted at a site along UK North Norfolk coastline, where the BC particles were transported from different regions within Western Europe. A hygroscopicity tandem differential mobility analyser (HTDMA) was coupled with a single particle soot photometer (SP2) to measure the hygroscopic properties of BC particles and associated mixing state in real time. In addition, a Soot Particle AMS (SP-AMS) measured the chemical compositions of additional material associated with BC particles. The ensemble of BC particles persistently contained a less-hygroscopic mode at a growth factor (gf) of around 1.05 at 90% RH (dry diameter 163 nm). Importantly, a more-hygroscopic mode of BC particles was observed throughout the experiment, the gf of these BC particles extended up to ~1.4–1.6 with the minimum between this and the less hygroscopic mode at a gf ~1.25, or equivalent effective hygroscopicity parameter κ ~0.1. The gf of BC particles (gfBC) was highly influenced by the composition of associated soluble material: increases of gfBC were associated with secondary inorganic components, and these increases were more pronounced when ammonium nitrate was in the BC particles; however the presence of secondary organic matter suppressed the gfBC below that of pure inorganics. The Zdanovskii-Stokes-Robinson (ZSR) mixing rule captures the hygroscopicity contributions from different compositions within ±30% compared to the measured results, however is subject to uncertainty due to the complex morphology of BC component and potential artefacts associated with semivolatile particles measured with the HTDMA. This study provides detailed insights on BC hygroscopicity associated with its mixing state, and the results will importantly constrain the microphysical mixing schemes of BC as used by a variety of high level models. In particular, this provides direct evidence to highlight the need to consider ammonium nitrate ageing of BC particles because this will result in particles becoming hydrophilic on much shorter timescales than for sulphate formation, which is often the only mechanism considered

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“…We use the extinction-minus-scattering method in our lab. For highly absorbing particles, such as BC, this method is quite reasonable (Bond and Bergstrom, 2006), as it has been shown elsewhere (Lewis et al, 2009;Langridge et al, 2013) that PAS can include large errors under certain conditions. Additionally, our CRDS uses tunable lasers that provide a wide range of solar wavelengths (Singh et al, 2016), while most studies are limited to a single or a few specific wavelengths.…”

mentioning

confidence: 99%

Construction and Characterization of an Indoor Smog Chamber for the Measurement of the Optical and Physicochemical Properties of Aging Biomass Burning Aerosols Native to sub-Saharan Africa

Smith

Fiddler

Sexton

et al. 2018

Preprint

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Abstract. We describe here the construction and characterization of a new smog chamber facility (NCAT chamber) for studying the chemical and optical properties of biomass burning (BB) aerosols from biomass fuels native to sub-Saharan Africa. This facility is comprised of a ~9 m 3 fluorinated ethylene propylene film (FEP) reactor placed in a temperature-controlled room and coupled with a cavity ring-down spectrometer, nephelometer, condensation particle counter, differential mobility analyzer and other analytical instruments, such as NO X and O 3 20 analyzers, a GC, a filter sampler, and an impinger for collecting particles in water. Construction details and characterization experiments are described, including measurements of BB particulate size distribution and deposition rate, gas wall loss rates, dilution rate, light intensity, mixing speed, temperature and humidity variations, and air purification method. The wall loss rates for NO, NO 2 , and O 3 were found to be (7.40 ± 0.01) × 10 −4 , (3.47 ± 0.01) × 10 −4 , and (5.90 ± 0.08) × 10 −4 min −1 respectively. The NO 2 photolysis rate constant was 0.165 ±0.005 min -1 , 25 which corresponds to a flux of (7.72 ± 0.25) × 10 17 photons•nm•cm −2 •s −1 from 296.0−516.8 nm. Particle deposition rate was found to be (2.46 ± 0.11) x 10 −3 min −1 for pine at D p = 100 nm. After initial mixing in the chamber, with the ultraviolet (UV) light off, the particle size distribution for BB samples used for the initial work did not stabilize until ~7.5 hours after injection peaking near a mobility diameter of ~340 nm. The chamber demonstrated gas and particle loss rates, and other properties comparable to other similar indoor smog chambers 30

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Reduction in biomass burning aerosol light absorption upon humidification: roles of inorganically-induced hygroscopicity, particle collapse, and photoacoustic heat and mass transfer

Cited by 126 publications

References 53 publications

Absorbing aerosols at high relative humidity: linking hygroscopic growth to optical properties

Absorbing aerosols at high relative humidity: linking hygroscopic growth to optical properties

Ambient black carbon particle hygroscopic properties controlled by mixing state and composition

Construction and Characterization of an Indoor Smog Chamber for the Measurement of the Optical and Physicochemical Properties of Aging Biomass Burning Aerosols Native to sub-Saharan Africa

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