Soot reference materials for instrument calibration and intercomparisons: a workshop summary with recommendations

TLDR

Soot from biomass and fossil fuel combustion is linked to climate change and health, yet scientists lack standardized reference materials to calibrate diverse measurement techniques. The workshop aimed to review soot measurement knowledge, identify uncertainties caused by missing SRMs, and define desirable SRM attributes to reduce errors. A 2011 workshop of 50 experts examined existing soot SRMs and produced recommendations for developing and implementing new SRMs tailored to various measurement methods. The workshop found that while some techniques, such as the SP2 laser‑induced incandescence, have suitable SRMs (e.g., fullerene soot), other methods like filter‑based light absorption and thermal optical analysis lack satisfactory reference materials. Abstract.

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.