Cite this article: Schauer, G., Kasper-Giebl, A. and Močnik, G. (2016). Increased PM Concentrations during a Combined Wildfire and Saharan Dust Event Observed at High-Altitude Sonnblick Observatory, Austria.
Aerosol Air Qual. Res.
16: 542-554. https://doi.org/10.4209/aaqr.2015.05.0337
PM originating from mineral dust and wildfires was decoupled using on-line methods.
Calculated contributions from both sources were compared to measured values.
Absorptions exponents characteristic for mineral dust and wildfires were deduced.
A relationship between αSSA and the calculated contribution of mineral dust is shown.
Enhancement ratios PM/CO were determined for time periods dominated by wildfires.
A period of increased particulate matter concentrations was observed at the high-altitude Sonnblick Observatory in August 2013. Trajectory analysis, wildfire maps and the evaluation of aerosol measurements revealed a combined and sometimes alternating influence of long-range transport of Saharan dust and emissions of wildfires. The occurrence of Saharan dust was confirmed by an increase of coarse particle number concentration and a negative exponent of the single scattering albedo wavelength dependence, determined by Nephelometer and Aethalometer measurements. During time periods less influenced by Saharan dust, number concentration of accumulation mode particles increased and a marked correlation of aerosol mass concentrations and CO mixing ratios was observed. By analyzing the wavelength dependence of the absorption coefficients determined with a seven wavelength Aethalometer, the influence of the two aerosol sources was decoupled. Therefore, absorption exponents of 3 and 1.3 were assumed for Saharan dust and wildfires, respectively. Mass concentrations of particulate matter caused by Saharan dust and wildfire emissions were estimated, with the contribution of Saharan dust to overall particulate matter mass ranging from 5% to 80%.
Keywords: Saharan dust; Wildfires; Background aerosols; Long range transport; Absorption exponent