Tailored graphitized soot as reference material for EC/OC measurement validation

Abstract. The lack of standard reference materials for calibrating, troubleshooting and intercomparing techniques that measure the composition of black carbon, commonly referred to as soot, has been a major obstacle that hinders improved understanding of how climate and health is impacted by this ubiquitous component of the atmosphere. A different approach is offered here as a means of constructing precisely controlled material with fractions of organic carbon (OC) on the surface of elemental carbon (EC) whose structure reflects that of the combustion produced particles found in the atmosphere. The proposed soot reference material (SRM) uses EC as a basis substrate for surface coatings of organic compounds that are representative of the main classes of organics identified in the coverage of soot produced by fossil fuel burning. A number of methods are used to demonstrate the quality and stability of the reference EC and SRM. Comparison of the nominal fraction of OC deposited on the EC substrate with the fraction measured with thermal/optical analysis (TOA) shows excellent agreement. Application of this type of reference material for evaluating the different methods of carbon analysis may help resolve differences that currently exist between comparable measurement techniques when trying to separate OC and EC from ambient samples.