Extinction coefficients from aerosol measurements

TL;DR

This paper introduces a simple electrodynamics-based model to determine aerosol light extinction coefficients using aerosol and light measurements, highlighting differences from literature values and proposing a practical measurement approach.

Contribution

A novel, straightforward model combining aerosol and light measurements to accurately determine aerosol extinction coefficients with minimal input parameters.

Findings

Mass-specific extinction varies significantly between aerosol types.

Results differ more than threefold from literature values.

Proposed method simplifies future aerosol extinction measurements.

Abstract

In this contribution, we develop a model based on classical electrodynamics that describes light extinction in the presence of arbitrary aerosols. We do this by combining aerosol and light-intensity measurements performed with the well-proven measuring systems ELPI+ and MIREX, respectively. The developed model is particularly simple and depends on only a few input parameters, namely on densities and refractive indices of the constituting aerosol particles. As proof of principle, the model is in first applications used to determine extinction coefficients as well as mass-specific extinction for an infrared light source with a peak wave length of ${\lambda} = 0.88\ {\mu}m$. In doing so, detailed studies concentrate on two aerosols exemplary for characteristic values of the input parameters: a non-absorbing paraffin aerosol in a bench-scale setup and soot from a flaming n-heptane fire in a room-scale setup (test fire TF5 according to standard EN54). As main results, we find numerical values for mass-specific extinction that are first of all different in the two considered cases. Moreover, obtained results differ in part more than a factor of three from literature values typically used in practical applications. Based on the developed model, we explicitly address and assess underlying reasons for the deviations found. Finally, we propose a simple way how future light-extinction studies can be performed comparatively easily by means of the ELPI+-system or measuring devices that work in a similar way.