Optimizing Thermal-Optical Methods for Measuring Atmospheric Elemental (Black) Carbon: A Response Surface Study

Conny, Joseph M.; Klinedinst, Donna B.; Wight, Scott A.; Paulsen, Jeffrey L.

doi:10.1080/02786820300920

Cited by 60 publications

(51 citation statements)

References 31 publications

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“…4, during the CN week, the variations in BC was similar to those of EC, and the average BC/EC ratio was 0.92±0.14, which is very close to 1. This result conforms to the general viewpoint that EC is a major contributor to ambient aerosol light absorption and explains why EC is often used interchangeably with BC when the aerosol effect on climate is considered, when an aethalometer needs calibrating, or when BC emission inventories are developed (Conny et al 2003;Vignati et al 2010;Petzold et al 1997). However, the trends shifted abruptly during the HH week, with the BC levels consistently higher than the corresponding EC levels.…”

Section: Variation Of Ec and Bc Concentrations For Cn And Hh Periodssupporting

confidence: 84%

“…BC cannot be measured directly but must be inferred from the particle light absorption (b ap ) through a conversion factor that is used to translate b ap to the BC mass concentration (Chow et al 2009;Biswas et al 2003). According to the literature, both EC and BC are considered to assume a graphitic structure and are therefore thermally refractory and light-absorbing in nature (Bond and Bergstrom 2006;Salako et al 2012;Conny et al 2003;Turpin et al 1990). It seems that both EC and BC describe nearly the same fraction of carbonaceous aerosols; however, according to traditional practice, their values are dependent on specified determination methods which focus on different properties, e.g., thermal stability or light absorption (Birch 1998;Chow et al 1993;Hansen et al 1984).…”

Section: Introductionmentioning

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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Section: Variation Of Ec and Bc Concentrations For Cn And Hh Periodssupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

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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“…It is anticipated that as sites were changed from the CSN OC/ EC approach to the IMPROVE approach a step change is likely to be observed, potentially with slightly lower OC and higher EC; total carbon will likely change little Schmid et al, 2001;Conny et al, 2003;Watson et al, 2005;Cheng et al, 2011). This change also resulted in better precision and lower MDL values for OC, EC, and OC fractions as seen in Table 11 when comparing 2006 to 2012.…”

Section: Csn and Improve Program Historiesmentioning

confidence: 97%

“…Beginning with samples collected in January 2005, IMPROVE provides both TOR and TOT results (DRI, 2005;Chow et al, 2007). Several studies have been conducted comparing the IMPROVE, CSN, and in some cases other protocols for OC and EC Schmid et al, 2001;Conny et al, 2003;Chow et al, 2004;Watson et al, 2005;Cheng et al, 2011).…”

Section: Carbonmentioning

confidence: 99%

U.S. National PM_2.5Chemical Speciation Monitoring Networks—CSN and IMPROVE: Description of networks

Solomon

Crumpler

Flanagan

et al. 2014

Journal of the Air & Waste Management Association

228

173

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“…The response of the thermal or thermal-optical techniques to the light-absorbing substances in biomass smoke has not been adequately characterized, but seems to be very dependent on the instrumental settings (Conny et al, 2003). Birch and Cary (1996) note that with an "optimized" setting they find only 0.86% EC a in cigarette smoke, while with a "less than optimal" setting 20-30% of the carbon in cigarette smoke was designated elemental.…”

Section: Thermochemical Analysis ("Ec")mentioning

confidence: 99%

Black carbon or brown carbon? The nature of light-absorbing carbonaceous aerosols

Andreae

Gelencsér²

2006

Atmos. Chem. Phys.

1,791

1,033

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Abstract. Although the definition and measurement techniques for atmospheric "black carbon" ("BC") or "elemental carbon'' ("EC") have long been subjects of scientific controversy, the recent discovery of light-absorbing carbon that is not black ("brown carbon, Cbrown") makes it imperative to reassess and redefine the components that make up light-absorbing carbonaceous matter (LAC) in the atmosphere. Evidence for the atmospheric presence of Cbrown comes from (1) spectral aerosol light absorption measurements near specific combustion sources, (2) observations of spectral properties of water extracts of continental aerosol, (3) laboratory studies indicating the formation of light-absorbing organic matter in the atmosphere, and (4) indirectly from the chemical analogy of aerosol species to colored natural humic substances. We show that brown carbon may severely bias measurements of "BC" and "EC" over vast parts of the troposphere, especially those strongly polluted by biomass burning, where the mass concentration of Cbrown is high relative to that of soot carbon. Chemical measurements to determine "EC" are biased by the refractory nature of Cbrown as well as by complex matrix interferences. Optical measurements of "BC" suffer from a number of problems: (1) many of the presently used instruments introduce a substantial bias into the determination of aerosol light absorption, (2) there is no unique conversion factor between light absorption and "EC" or "BC" concentration in ambient aerosols, and (3) the difference in spectral properties between the different types of LAC, as well as the chemical complexity of Cbrown, lead to several conceptual as well as practical complications. We also suggest that due to the sharply increasing absorption of Cbrown towards the UV, single-wavelength light absorption measurements may not be adequate for the assessment of absorption of solar radiation in the troposphere. We discuss the possible consequences of these effects for our understanding of tropospheric processes, including their influence on UV-irradiance, atmospheric photochemistry and radiative transfer in clouds.

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Optimizing Thermal-Optical Methods for Measuring Atmospheric Elemental (Black) Carbon: A Response Surface Study

Cited by 60 publications

References 31 publications

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

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

U.S. National PM_2.5Chemical Speciation Monitoring Networks—CSN and IMPROVE: Description of networks

Black carbon or brown carbon? The nature of light-absorbing carbonaceous aerosols

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Optimizing Thermal-Optical Methods for Measuring Atmospheric Elemental (Black) Carbon: A Response Surface Study

Cited by 60 publications

References 31 publications

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

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

U.S. National PM2.5Chemical Speciation Monitoring Networks—CSN and IMPROVE: Description of networks

Black carbon or brown carbon? The nature of light-absorbing carbonaceous aerosols

Contact Info

Product

Resources

About

U.S. National PM_2.5Chemical Speciation Monitoring Networks—CSN and IMPROVE: Description of networks