To investigate and quantify the ice nucleation activity of soil dust, we conducted a series of laboratory measurements with five different soil dust samples at the cloud simulation chamber AIDA (Aerosol Interactions and Dynamics in the Atmosphere). The chamber operates under atmospherically relevant conditions over wide ranges of temperature, pressure and humidity. By controlled adiabatic expansions, the ascent of an air parcel in the troposphere is simulated. In combination with supplementary INP measurements, we thus attained a robust data set on the ice nucleation activity of soil dust aerosol over a wide temperature range in the immersion freezing regime.
In addition, the role of primary biological particles and organic matter was examined in more detail to investigate the origin of the enhanced ice nucleation activity of arable soil dust. For example, the soil dust samples were exposed to dry heat for pyrolysis of organic compounds. Additional instrumentation allowed us to characterize the untreated and the heat treated total aerosol particles as well as the ice residuals received from immersion freezing and deposition nucleation experiments.
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