Abstract
Highly time-resolved aerosol measurements and analysis are necessary for a proper aerosol characterization in many polluted regions, because aerosol concentrations in polluted environments can change over time scales of minutes. However, many urban measuring sites have measuring devices that provide time resolved average aerosol concentrations over a day or two at best. Light-scattering properties of mineral dust and soot particles in the El Paso-Juárez Airshed were analyzed with an improved methodology, using the T-matrix, a maximum likelihood estimator (MLE), and data from both an acoustic extinctiometer and a laser particle counter. The hourly inter-comparisons of the scattering coefficients’ results between the model and those obtained using the instruments at a wavelength of 0.87 μm show good agreement. This methodology has been applied in the El Paso-Juárez Airshed successfully, and it could be used in other cities where mineral dust and soot are major components of the aerosol concentrations.
Highlights
Medina et al [1] developed a novel methodology to characterize the optical properties of mineral dust and soot particles, that was based on T-matrix theory [2]
We present an improved method based on hourly inter-comparisons of scattering coefficients, to provide a highly time-resolved methodology needed to provide a high-standard approximation and correlation of observations of aerosol airshed loading, which can change within minutes or less of time
A minimal 1 L/min aerosol sample is collected into the photoacoustic extinctiometer (PAX) through an internal vacuum pump controlled by two critical orifices
Summary
Medina et al [1] developed a novel methodology to characterize the optical properties of mineral dust and soot particles, that was based on T-matrix theory [2]. The T-matrix model was used to calculate the scattering and extinction cross sections for the aerosols present in the El Paso-Juarez Airshed. The T-matrix theory was selected because it could be applied to randomly oriented, non-spherical rotational symmetric particles. The study inter-compared daily mean scattering coefficients through the analysis of data from an acoustic extinctiometer and a laser particle counter, in conjunction with a non-spherical scattering model, the T-matrix that was used to obtain the scattering coefficients. The comparisons of the calculated values with data showed that the agreement was good.
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