Ü. Kikas

Statistical characteristics of aerosol in Baltic Sea region

The article presents the results of the aerosol measurements carried out on the eastern coast of the Baltic Sea during 1986 – 1993. Aerosol size distributions in the diameter range of 0.01–10 μm have been measured with the electric aerosol spectrometer (EAS). A short description of EAS is given. The majority of number distributions obtained by measurements were of monomodal shape. Modal diameter varied at 0.01–0.1 μm. Seven percent of all number distributions were of bimodal shape with modes at 0.010 – 0.032 μm and at 0.032 – 0.1 μm, separated with a minimum at 0.018 – 0.056 μm. The majority of aerosol mass distributions were of bimodal shape and consisted of an accumulation mode varying at 0.18 – 1.0 μm and of a coarse particle mode at 1.8 – 10 μm separated by a minimum varying at 0.56 – 3.2 μm. Parameters of the Junge distribution and the 4-parameter KL distribution have been obtained. The variability of aerosol concentrations and the stability of aerosol at a fixed site have been studied analyzing the time sequences of aerosol number distributions. The variability of concentrations depended on particle size. The variability was about 0.7 at 0.1 – 0.3 μm and rose toward both the smaller and larger diameters up to values 1.4 at 0.01 μm and 1.7 at 10 μm.

Observation of submicron aerosol, black carbon and visibility degradation in remote area at temperature range from −24 to 20°C

0.010–10 μm sized aerosol and black carbon werr measured in a remote Rautavaara site in periods in August, October and December by using electric aerosol spectrometer EAS and Aethalometers. During the study the lowest temperature was −24°C. The formation of new 0.010–0.030 μm sized aerosols was observed during decreasing temperatures below −10°C. Black carbon was seen to be strongly correlated with aerosols in the size range of 0.100–0.180 μm. The amount of black carbon was high at below 0°C. Visibility impairment could be coupled to rapid condensation of near micron-sized aerosols during the increasing temperature gradient. Solar flux changes and chemical composition of aerosols, especially black carbon, were shown to be strongly linked.

Atmospheric aerosol as an indicator of human polluting activity

Abstract The comparison of atmospheric aerosol spectra in urban and remote areas is made. The essential differences in particle concentrations, in their diurnal variations and in spectra shapes are found. Only the fine particles (below 0.1 μm) could be considered as appropriate indicators of local polluting activities. The larger particles are more influenced by air humidity and long scale transport and do not immediately reflect the changes in local photochemistry.