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\nparticles can reduce Earth s snow and ice albedo considerably even by very\nsmall amounts of deposited particle mass. In this study, a new laboratory\nmethod is applied to measure the spectral light absorption coefficient of\nairborne particles that are released from fresh snow samples by an efficient\nnebulizing system. Three-wavelength photoacoustic absorption spectroscopy is\ncombined with refractory black carbon (BC) mass analysis to determine the\nsnow mass-specific and BC mass-specific absorption cross sections.\nFullerene soot in water suspensions are used for the characterization of the\nmethod and for the determination of the mass-specific absorption cross\nsection of this BC reference material. The analysis of 31 snow samples\ncollected after fresh snowfall events at a high-altitude Alpine research\nstation reveals a significant discrepancy between the measured snow mass-specific absorption cross section and the cross section that is expected\nfrom the BC mass data, indicating that non-BC light-absorbing particles are\npresent in the snow. Mineral dust and brown carbon (BrC) are identified as\npossible candidates for the non-BC particle mass based on the wavelength\ndependence of the measured absorption. For one sample this result is\nconfirmed by environmental scanning electron microscopy and by single-particle fluorescence measurements, which both indicate a high fraction of\nbiogenic and organic particle mass in the sample.