Absorption of light by soot particles: determination of the absorption coefficient by means of aethalometers

Weingärtner, E.; Saathoff, H.; Schnaiter, M.; Streit, N.; Bitnar, Bernd; Baltensperger, Urs

doi:10.1016/s0021-8502(03)00359-8

Cited by 1,110 publications

(1,113 citation statements)

References 20 publications

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“…During Saharan dust events (SDE) they found Angström exponents of absorption of 1.5 to 1.8 between λ=370 nm and λ=590 nm which were significantly larger than the usual Angström exponents of 1.0 to 1.2 from nonSaharan background aerosol. Reflections on the filter were corrected by an empirical correction factor, which was calculated for different aerosol types by Weingartner et al (2003). As already mentioned in the previous section the determination of Angström exponents of absorption for our dust samples based on the PAS absorption measurements at λ=532 nm and λ=266 nm results in relatively high values between 4.2 (Morocco) and 5.3 (Cairo 2).…”

Section: Discussionmentioning

confidence: 97%

Optical properties and mineralogical composition of different Saharan mineral dust samples: a laboratory study

Linke¹,

Möhler²,

et al. 2006

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Abstract. In aerosol chamber experiments optical properties of resuspended mineral dust samples of defined size distributions were measured. Extinction coefficients (b ext ) and mass specific extinction cross sections (σ ext ) were determined for Saharan dust samples from different locations. The results for σ ext were not very sensitive to the type of dust and varied at λ=550 nm between 3.3±0.4 m 2 g −1 and 3.7±0.4 m 2 g −1 .The absorption coefficients (b abs ) and mass specific absorption cross sections (σ abs ) were determined with a novel multiwavelength photo-acoustic absorption spectrometer (PAS). The single scattering albedo was close to 1 (0.98 to 0.99) at 532 nm and 1064 nm, but significantly lower (0.63 to 0.76) at 266 nm. Additionally the chemical and mineralogical composition of the dust samples were analysed with special regard to the iron oxide phases hematite and goethite. At λ=266 nm the mineral dust sample without any detectable iron oxides showed a significantly higher SSA compared to the sample with a hematite content of 0.6 wt-%.

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Section: Discussionmentioning

confidence: 97%

Optical properties and mineralogical composition of different Saharan mineral dust samples: a laboratory study

Linke¹,

Möhler²,

et al. 2006

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“…In other words, dust is unlikely to have caused the aforementioned CN-to-HH elevation of σ ap . Regarding brown carbon, a wavelength of 880 nm was used in the aethalometer for BC quantification, at which brown carbon is theoretically almost invisible (Andreae and Gelencsér 2006;Weingartner et al 2003). Consequently, brown carbon is also unlikely to play a strong role in the elevation of CN-to-HH σ ap .…”

Section: Exploratory Probe Of the Bc/ec Divergence In The Hh Periodmentioning

confidence: 99%

“…Considering that total ATN incorporates not only b ap but also filter-induced light attenuation (mainly light scattering due to the filter matrix and the particles embedded in the filter matrix) (Arnott et al 2005;Petzold et al 1997;Weingartner et al 2003;Chow et al 2009), the abovementioned BC/EC ratios of 1.88±0.30 for the HH week and 0.92 ±0.14 for the CN week can suggest an enhancement factor of approximately two for the attenuation efficiency, σ ATN-a , but not for σ ap .…”

Section: In Situ Light Absorption Measurements Neededmentioning

confidence: 99%

“…Two methods can be used to obtain b ap . For the first method, a nephelometer can be used to monitor aerosol scattering (b scat ) simultaneously with an aethalometer to monitor ATN; b ap can then be calculated using a correction procedure (Arnott et al 2005;Coen et al 2010;Schmid et al 2006;Weingartner et al 2003). In the second approach, b ap can be monitored directly using non-filter-based instruments.…”

Section: In Situ Light Absorption Measurements Neededmentioning

confidence: 99%

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Comparison of elemental and black carbon measurements during normal and heavy haze periods: implications for research

Zhi

Chen

Xue

et al. 2014

Environ Monit Assess

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Studies specifically addressing the elemental carbon (EC)/black carbon (BC) relationship during the transition from clean-normal (CN) air quality to heavy haze (HH) are rare but have important health and climate implications. The present study, in which EC levels are measured using a thermal-optical method and BC levels are measured using an optical method (aethalometer), provides a preliminary insight into this issue. The average daily EC concentration was 3.08±1.10 μg/m 3 during the CN stage but climbed to 11.77±2.01 μg/m 3 during the HH stage. More importantly, the BC/EC ratio averaged 0.92±0.14 during the CN state and increased to 1.88± 0.30 during the HH state. This significant increase in BC/ EC ratio has been confirmed to result partially from an increase in the in situ light absorption efficiency (σ ap ) due to an enhanced internal mixing of the EC with other species. However, the exact enhancement of σ ap was unavailable because our monitoring scheme could not acquire the in situ absorption (b ap ) essential for σ ap calculation. This reveals a need to perform simultaneous measurement of EC and b ap over a time period that includes both the CN and HH stages. In addition, the sensitivity of EC to both anthropogenic emissions and HH conditions implies a need to systematically study how to include EC complex (EC concentration, OC/EC ratio, and σ ap ) as an indicator in air quality observations, in alert systems that assess air quality, and in the governance of emissions and human behaviors.

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“…All filter-based optical methods exhibit loading effects (Bond et al, 1999;Weingartner et al, 2003;Virkkula, 2010;Virkkula et al, 2005Virkkula et al, , 2007Collaud Coen et al, 2010;Park et al, 2010;Hyvärinen et al, 2013). The relationship between attenuation and BC surface loading is linear for low attenuation values.…”

Section: Introductionmentioning

confidence: 99%

The "dual-spot" Aethalometer: an improved measurement of aerosol black carbon with real-time loading compensation

et al. 2015

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Abstract. Aerosol black carbon is a unique primary tracer for combustion emissions. It affects the optical properties of the atmosphere and is recognized as the second most important anthropogenic forcing agent for climate change. It is the primary tracer for adverse health effects caused by air pollution. For the accurate determination of mass equivalent black carbon concentrations in the air and for source apportionment of the concentrations, optical measurements by filter-based absorption photometers must take into account the "filter loading effect". We present a new real-time loading effect compensation algorithm based on a two parallel spot measurement of optical absorption. This algorithm has been incorporated into the new Aethalometer model AE33. Intercomparison studies show excellent reproducibility of the AE33 measurements and very good agreement with post-processed data obtained using earlier Aethalometer models and other filterbased absorption photometers. The real-time loading effect compensation algorithm provides the high-quality data necessary for real-time source apportionment and for determination of the temporal variation of the compensation parameter k.

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Absorption of light by soot particles: determination of the absorption coefficient by means of aethalometers

Cited by 1,110 publications

References 20 publications

Optical properties and mineralogical composition of different Saharan mineral dust samples: a laboratory study

Optical properties and mineralogical composition of different Saharan mineral dust samples: a laboratory study

Comparison of elemental and black carbon measurements during normal and heavy haze periods: implications for research

The "dual-spot" Aethalometer: an improved measurement of aerosol black carbon with real-time loading compensation

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Absorption of light by soot particles: determination of the absorption coefficient by means of aethalometers

Cited by 1,110 publications

References 20 publications

Optical properties and mineralogical composition of different Saharan mineral dust samples: a laboratory study

Optical properties and mineralogical composition of different Saharan mineral dust samples: a laboratory study

Comparison of elemental and black carbon measurements during normal and heavy haze periods: implications for research

The &quot;dual-spot&quot; Aethalometer: an improved measurement of aerosol black carbon with real-time loading compensation

Contact Info

Product

Resources

About

The "dual-spot" Aethalometer: an improved measurement of aerosol black carbon with real-time loading compensation