10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Measured In-situ Mineral Due Absorption Spectra
CHRISTOPHER ZANGMEISTER, James Radney, National Institute of Standards and Technology
Abstract Number: 925 Working Group: Remote/Regional Atmospheric Aerosol
Abstract Depending upon the locality, mineral dust aerosols generated from wind-blown soils can represent a significant fraction of local aerosol mass loadings. These aerosols are also capable of significantly affecting local energy budgets and radiative forcings. However, little is known about the absorption spectra of these particles. Of the published findings most focus on mineral dusts from desert regions. Here, we will present laboratory absorption spectra of aerosolized soil samples from locations across the United Sates (CA, IA, MD and MN) with land uses encompassing agriculture, forest and gravel roadbed road surfaces. Spectra were collected using a photoacoustic spectrometer with both a supercontinuum laser with a tunable wavelength and bandwidth filter and a diode laser allowing spectra to be measured from λ = 405 nm to 840 nm. We find that the measured spectra can be broadly grouped as either red clay-like or brown/gray dirt-like and possessing Absorption Angstrom Exponents (AAE) of > 7 or ≈ 3.5, respectively. Mass absorption coefficients (MAC) of sub-micron particles were also directly measured at 405 nm using a tandem differential mobility analyzer-aerosol particle mass analyzer with a photoacoustic spectrometer and condensation particle counter. MAC values were all less than 0.5 m2/g and exhibited a moderate correlation with AAE. FT-IR spectra of each mineral dust enabled identification of materials within the sample set and were correlated to aerosol absorption spectra.