Atmospheric Ion Mobility Spectra Research Articles

Estimation of aerosol size distribution from ion mobility spectra using the KL model

Atmospheric ion mobility spectra were measured at Maitri, Antarctica, using an indigenously fabricated ion mobility spectrometer in January–February 2005 during the 24th Indian Antarctic Expedition. The ion mobility spectrometer was fabricated and tested at the Indian Institute of Tropical Meteorology, Pune, India. As the ion mobility depends on the diameter of the particles, the aerosol size distribution was derived from the observed ion mobility spectra using the KL model. The model was tested by comparing the derived spectra with the observed spectra using the Scanning Mobility Particle Sizer and the Aerodynamic Particle Sizer. We show that the KL model can reasonably reproduce the observed size distribution except in the accumulation mode. Relevant meteorological parameters are also reported, which aid in the interpretation of the results.

Variability in aerosol and air ion composition in the Arctic spring atmosphere

Systematic measurement results of aerosol dispersity in the size range from 0.004 to 10 μm in diameter, element composition, and the mobility spectrum of atmospheric ions in the range from 0.00032 to 5 cm 2/V s in the surface atmospheric layer at Zigler Island (Western Arctic, Franz–Joseph Archipelago, March–April 1994) are presented. A comparison is made with data obtained using similar methods and instruments at Wrangel Island (Eastern Arctic, March–April 1985), in Antarctica (Molodezhnaya station, January–May 1983), over the Pamir mountains (Fedchenko glacier, September 1989) and in the vicinity of Moscow (Obninsk, April–May 1994)). The form and variability of the aerosol size and air ion mobility spectra at different regions of the Arctic and Antarctic, as well as in mountain and forest steppe regions, do not differ significantly. The stratification of the atmospheric boundary layer and wind speed are the main factors of variability of the arctic aerosols and ions. Inflows of air from the mainland do not change these positions.

Atmospheric ion mobility spectra near the ground

The mobility spectra of positive and negative ions artificially produced in the ambient air near the ground were measured by using a newly constructed mobility spectrometer having parallel plate electrodes. The negative mobility spectra obtained by this spectrometer have a very sharp peak at 1.80 cm 2 volt −1 s −1, and the average negative ion mobility is estimated to be 2.40 cm 2 volt −1 s −1. In the positive ion mobility spectra, on the other hand, a rather broad peak is seen at 1.25 cm 2 volt −1 s −1. The average positive ion mobility is estimated to be 1.69 cm 2 volt −1 s −1. By comparing the result with recent mass spectrometric measurements and a model calculation, detailed discussions are given. Additional experiments were made to test for changes of the mobility spectra by using nitric acid and ammonia vapours, and gases in tobacco smoke.

Formation of atmospheric ultrafine particles and ions from trace gases

Firstly, the importance of ultrafine particles in the atmospheric aerosol is reviewed. Based on conventional nucleation theory, it is shown that water vapor alone cannot initiate the formation of such particles. We consider a mixture of water vapor and sulfuric acid and, pursuant to a discussion of theoretical results obtained by various writers, we consider the case under atmospheric conditions. We demonstrate that this leads to orders of magnitude which compare with the results of simulation experiments now under way. Secondly, we study the mobility spectrum of atmospheric ions, based on mobility mass correlations, and we demonstrate that Thomson's conventional theory, calling upon only the presence of water vapor in the atmosphere, does not allow for the interpretation of the atmospheric ions' mobility spectrum observed in our experiment. This spectrum is qualitatively interpreted by generalizing the theory of Thomson and by introducing in it the simultaneous presence of water vapor and sulfuric acid.