0000000000412071
AUTHOR
Annette Worringen
Environmental scanning electron microscopy (ESEM) as a new technique to determine the ice nucleation capability of individual atmospheric aerosol particles
Abstract Heterogeneous ice nucleation on synthetic silver iodide, natural kaolinite and montmorillonite particles via condensation, freezing and deposition modes was studied by environmental scanning electron microscopy (ESEM) in the temperature range of 250–270 K. By increasing the H2O pressure in the sample chamber at constant temperature, ice formation can be studied in situ and can be related to the chemical composition of the particles that can be determined simultaneously. For silver iodide and kaolinite, supersaturation values of first ice formation are in good agreement (1–2% absolute) with diffusion chamber experiments. For both substances, threshold temperatures for the condensati…
Inadvertent climate modification due to anthropogenic lead
Atmospheric particles are thought to initiate the majority of terrestrial precipitation. Field-based measurements of ice-crystal residues, together with controlled environment experiments on artificial clouds, suggest that anthropogenic lead-containing particles are among the most efficient ice-forming substances in the atmosphere.
Ice nucleation properties of the most abundant mineral dust phases
[1] The ice nucleation properties of the nine most abundant minerals occurring in desert aerosols (quartz, albite, microcline, kaolinite, montmorillonite, illite, calcite, gypsum, and hematite) were investigated by environmental scanning electron microscopy (ESEM). In this instrument, the pure minerals are exposed to water vapor at variable pressures and temperatures. The crystallization of ice on the mineral particles is observed by secondary electron imaging, and the supersaturation for an activated particle fraction of 1–3% is determined as function of temperature. In all experiments, condensation of water prior to ice formation was not observed within detectable limits, even at water su…