Specifying the light-absorbing properties of aerosol particles in fresh snow samples, collected at the Environmental Research Station Schneefernerhaus (UFS), Zugspitze

Abstract

Abstract. Atmospheric aerosol particles like mineral dust, volcanic ash and combustion particles can reduce Earth's snow and ice albedo considerably even by very small amounts of deposited particle mass. In this study, a new laboratory method is applied to measure the spectral light absorption coefficient of airborne particles that are released from fresh snow samples by an efficient nebulizing system. Three-wavelength photoacoustic absorption spectroscopy is combined with refractory black carbon (BC) mass analysis to determine the snow mass-specific and BC mass-specific absorption cross sections. Fullerene soot in water suspensions are used for the characterization of the method and for the determination of the mass-specific absorption cross section of this BC reference material. The analysis of 31 snow samples collected after fresh snowfall events at a high-altitude Alpine research station reveals a significant discrepancy between the measured snow mass-specific absorption cross section and the cross section that is expected from the BC mass data, indicating that non-BC light-absorbing particles are present in the snow. Mineral dust and brown carbon (BrC) are identified as possible candidates for the non-BC particle mass based on the wavelength dependence of the measured absorption. For one sample this result is confirmed by environmental scanning electron microscopy and by single-particle fluorescence measurements, which both indicate a high fraction of biogenic and organic particle mass in the sample.

The Light Absorption Heating Method for Measurement of Light Absorption by Particles Collected on Filters

“…The LAHM instrument showed substantially more absorption per unit mass of soot on the filter as compared to filters with the same mass of fullerene soot indicating that the MAC for the propane soot particles was significantly higher than the MAC for fullerene soot. The values in the literature suggest that propane soot can have an MAC on the order of 12-15 m 2 /g [12,14], while fullerene soot has been reported to have a MAC value between 7 and 10 m 2 /g [15]. Figure 5 shows the temperature increase for the LAHM calibration filters made with fullerene soot along with several propane soot filters as a function of micrograms of BC of each type.…”

Can the Aerosol Absorption Ångström Exponent Represent Aerosol Color in the Atmosphere: A Numerical Study

“…Observational research and numerical simulation are two common methods used to reveal aerosol colors. Observation by using instruments such as scanning or transmission electron microscopes can offer intuitive appearances of a single aerosol particle [10][11][12]. The colors of aerosol samples are usually shown as photos.…”