Abstract
Abstract. Soot, which is produced from biomass burning and the incomplete combustion of fossil and biomass fuels, has been linked to regional and global climate change and to negative health problems. Scientists measure the properties of soot using a variety of methods in order to quantify source emissions and understand its atmospheric chemistry, reactivity under emission conditions, interaction with solar radiation, influence on clouds, and health impacts. A major obstacle currently limiting progress is the absence of established standards or reference materials for calibrating the many instruments used to measure the various properties of soot. The current state of availability and practicability of soot standard reference materials (SRMs) was reviewed by a group of 50 international experts during a workshop in June of 2011. The workshop was convened to summarize the current knowledge on soot measurement techniques, identify the measurement uncertainties and limitations related to the lack of soot SRMs, and identify attributes of SRMs that, if developed, would reduce measurement uncertainties. The workshop established that suitable SRMs are available for calibrating some, but not all, measurement methods. The community of users of the single-particle soot-photometer (SP2), an instrument using laser-induced incandescence, identified a suitable SRM, fullerene soot, but users of instruments that measure light absorption by soot collected on filters did not. Similarly, those who use thermal optical analysis (TOA) to analyze the organic and elemental carbon components of soot were not satisfied with current SRMs. The workshop, and subsequent, interactive discussions, produced a number of recommendations for the development of new SRMs, and their implementation, that would be suitable for the different soot measurement methods.
Highlights
Soot, a product of incomplete combustion of any carbon containing fuels under hot and air-starved conditions, is a constituent of atmospheric aerosol particles that has received the attention of the climate and health research communities because of the impact of soot-containing aerosol on modifying radiative fluxes and increasing the susceptibility to diseases that affect the respiratory, cardiovascular and nervous systems of humans
The thermal optical analysis (TOA) method evaluates mixtures of organic carbon (OC) and elemental carbon (EC) and the incandescence technique looks at refractory black carbon, a form of carbon directly related to EC
The calibration, validation and intercomparison of techniques that measure soot properties require standard reference materials (SRM) whose properties are related to the characteristic being measured. At this time there are no SRMs that meet all criteria established by internationally recognized organizations that set reference standards
Summary
A product of incomplete combustion of any carbon containing fuels under hot and air-starved conditions, is a constituent of atmospheric aerosol particles that has received the attention of the climate and health research communities because of the impact of soot-containing aerosol on modifying radiative fluxes and increasing the susceptibility to diseases that affect the respiratory, cardiovascular and nervous systems of humans. The actions taken by the Steering Committee for BC reference materials, while a positive step, have not produced a noticeable movement in the atmospheric sciences community, i.e. those doing air quality, climate and health research, towards establishing a consensus with respect to soot SRMs. An explanation for the lack of progress in developing SRMs in the environmental sciences community is beyond the scope of this review article; a significant number of those in this community who do soot research have recognized for some time the need to take definitive action to rectify this situation. That there is no presumption that all of the material presented here meets with the complete acceptance of those who are co-authoring this article, sections that are written in quotations indicate material that might not reflect 100 % agreement of the participants
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