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Optical properties of selected components of mineral dust aerosol processed with organic acids and humic material
Author(s) -
Alexander Jennifer M.,
Grassian V. H.,
Young M. A.,
Kleiber P. D.
Publication year - 2015
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2014jd022782
Subject(s) - calcite , oxalic acid , chemistry , mineral , quartz , mineralogy , humic acid , chemical engineering , inorganic chemistry , materials science , organic chemistry , composite material , fertilizer , engineering
Visible light scattering phase function and linear polarization profiles of mineral dust components processed with organic acids and humic material are measured, and results are compared to T‐matrix simulations of the scattering properties. Processed samples include quartz mixed with humic material, and calcite reacted with acetic and oxalic acids. Clear differences in light scattering properties are observed for all three processed samples when compared to the unprocessed dust or organic salt products. Results for quartz processed with humic acid sodium salt (NaHA) indicate the presence of both internally mixed quartz‐NaHA particles and externally mixed NaHA aerosol. Simulations of light scattering suggest that the processed quartz particles become more moderate in shape due to the formation of a coating of humic material over the mineral core. Experimental results for calcite reacted with acetic acid are consistent with an external mixture of calcite and the reaction product, calcium acetate. Modeling of the light scattering properties does not require any significant change to the calcite particle shape distribution although morphology changes cannot be ruled out by our data. It is expected that calcite reacted with oxalic acid will produce internally mixed particles of calcite and calcium oxalate due to the low solubility of the product salt. However, simulations of the scattering for the calcite‐oxalic acid system result in rather poor fits to the data when compared to the other samples. The poor fit provides a less accurate picture of the impact of processing in the calcite‐oxalic acid system.