Secondary organic material formed by methylglyoxal in aqueous aerosol mimics – Part 1: Surface tension depression and light-absorbing products

Schwier, A. N.; Shapiro, E. L.; Sareen, Neha; McNeill, V. Faye

doi:10.5194/acpd-9-15541-2009

Cited by 3 publications

(2 citation statements)

References 80 publications

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“…Emerging research suggests that a variety of particulate OM can absorb radiation, particularly at the shorter visible and UV wavelengths (Adler et al, 2009;Barnard et al, 2008;Dinar et al, 2008;Hoffer et al, 2006;Kirchstetter et al, 2004;Rincon et al, 2009;Roden et al, 2006;Schnaiter et al, 2006;Schwier et al, 2009;Shapiro et al, 2009;Sun et al, 2007;Yang et al, 2009). In fact the mass absorption cross-section (MAC) of this so-called "brown carbon" (C Brown ) has been estimated to be of the same order as BC at 400 nm (Barnard et al, 2008;Clarke et al, 2007).…”

Section: Black Carbon and Brown Coatingsmentioning

confidence: 99%

Impact of brown and clear carbon on light absorption enhancement, single scatter albedo and absorption wavelength dependence of black carbon

2010

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Abstract. The presence of clear coatings on atmospheric black carbon (BC) particles is known to enhance the magnitude of light absorption by the BC cores. Based on calculations using core/shell Mie theory, we demonstrate that the enhancement of light absorption (E Abs ) by atmospheric black carbon (BC) when it is coated in mildly absorbing material (C Brown ) is reduced relative to the enhancement induced by non-absorbing coatings (C Clear ). This reduction, sensitive to both the C Brown coating thickness and imaginary refractive index (RI), can be up to 50% for 400 nm radiation and 25% averaged across the visible radiation spectrum for reasonable core/shell diameters. The enhanced direct radiative forcing possible due to the enhancement effect of C Clear is therefore reduced if the coating is absorbing. Additionally, the need to explicitly treat BC as an internal, as opposed to external, mixture with C Brown is shown to be important to the calculated single scatter albedo only when models treat BC as large spherical cores (> 50 nm). For smaller BC cores (or fractal agglomerates) consideration of the BC and C Brown as an external mixture leads to relatively small errors in the particle single scatter albedo of <0.03. It has often been assumed that observation of an absorption Angström exponent (AAE)>1 indicates absorption by a non-BC aerosol. Here, it is shown that BC cores coated in C Clear can reasonably have an AAE of up to 1.6, a result that complicates the attribution of observed light absorption to C Brown within ambient particles. However, an AAE<1.6 does not exclude the possibility of C Brown ; rather C Brown cannot be confidently assigned unCorrespondence to: D. A. Lack (daniel.lack@noaa.gov) less AAE>1.6. Comparison of these model results to various ambient AAE measurements demonstrates that large-scale attribution of C Brown is a challenging task using current in-situ measurement methods. We suggest that coincident measurements of particle core and shell sizes along with the AAE may be necessary to distinguish absorbing and non-absorbing OC.

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Section: Black Carbon and Brown Coatingsmentioning

confidence: 99%

Impact of brown and clear carbon on light absorption enhancement, single scatter albedo and absorption wavelength dependence of black carbon

2010

View full text Add to dashboard Cite

show abstract

“…Emerging research suggests that a variety of particulate OM can absorb radiation, particularly at the shorter visible and UV wavelengths (Adler et al, 2009;Barnard et al, 2008;Dinar et al, 2008;Hoffer et al, 2006;Kirchstetter et al, 2004;Rincon et al, 2009;Roden et al, 2006;Schnaiter et al, 2006;Schwier et al, 2009;Shapiro et al, 2009;Sun et al, 2007;Yang et al, 2009). In fact the mass absorption cross-section (MAC) of this so-called "brown carbon" (C Brown ) (Andreae and Gelencser, 2006) has been estimated to be of the same order as BC at 400 nm (Barnard et al, 2008;Clarke et al, 2007).…”

Section: Black Carbon and Brown Coatingsmentioning

confidence: 99%

Impact of brown and clear carbon on light absorption enhancement, single scatter albedo and absorption wavelength dependence of black carbon

Lack¹,

Cappa²

2010

Preprint

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Abstract. The presence of clear coatings on atmospheric black carbon (BC) particles is known to enhance the magnitude of light absorption by the BC cores. Based on calculations using core/shell Mie theory, we demonstrate the enhancement of light absorption (EAbs) by atmospheric black carbon (BC) when coated in mildly absorbing material (CBrown) is reduced, relative to the enhancement by non-absorbing coatings (CClear). This reduction, sensitive to CBrown shell thickness and imaginary refractive index (RI), can be up to 50% for 400 nm radiation and 25% averaged across the visible radiation spectrum for reasonable core/shell diameters. The enhanced direct radiative forcing possible due to the enhancement effect of CClear is therefore reduced if the coating is absorbing. Additionally, the need to explicitly treat BC as an internal, as opposed to external, mixture with CBrown is shown to be important to the calculated single scatter albedo only whensub models treat BC as large spherical cores (>50 nm). For smaller BC cores (or fractal agglomerates) consideration of the BC and CBrown as an external mixture leads to relatively small errors in the particle single scatter albedo of <0.03. It is often assumed that observation of an absorption Angstrom exponent (AAE) >1 indicates non-BC absorption. Here, it is shown that BC cores coated in CClearcan reasonably have an AAE of up to 1.6, a result that complicates the attribution of observed light absorption to CBrown within ambient particles. However, an AAE<1.6 does not exclude the possibility of CBrown, rather CBrown cannot be confidently assigned unless AAE>1.6. Comparison of these results to some ambient AAE data shows that large-scale attribution of CBrown is a challenging task using current in-situ measurement methods. We suggest that coincident measurements of particle core and shell sizes along with the AAE may be necessary to distinguish absorbing and non-absorbing OC.

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Secondary organic material formed by methylglyoxal in aqueous aerosol mimics – Part 2: Product identification using Aerosol-CIMS

Sareen¹,

Shapiro²,

Schwier³

et al. 2009

Preprint

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Abstract. We used chemical ionization mass spectrometry with a volatilization flow tube inlet (Aerosol-CIMS) to characterize secondary organic material formed by methylglyoxal with ammonium sulfate in aqueous aerosol mimics. Bulk reaction mixtures were diluted and atomized to form submicron aerosol particles. Organics were detected using Aerosol-CIMS in positive and negative ion mode using I− and H3O+·(H2O)n as reagent ions. The results are consistent with aldol condensation products, carbon-nitrogen species, sulfur-containing compounds, and oligomeric species up to 759 amu. These results support previous observations by us and others that ammonium sulfate plays a critical role in the SOA formation chemistry of dicarbonyl compounds.

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Secondary organic material formed by methylglyoxal in aqueous aerosol mimics – Part 1: Surface tension depression and light-absorbing products

Cited by 3 publications

References 80 publications

Impact of brown and clear carbon on light absorption enhancement, single scatter albedo and absorption wavelength dependence of black carbon

Impact of brown and clear carbon on light absorption enhancement, single scatter albedo and absorption wavelength dependence of black carbon

Impact of brown and clear carbon on light absorption enhancement, single scatter albedo and absorption wavelength dependence of black carbon

Secondary organic material formed by methylglyoxal in aqueous aerosol mimics – Part 2: Product identification using Aerosol-CIMS

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