Abstract: Addition of a labile sulphur donor to light sensitive silver halide microcrystals results in the formation of a distribution of silver sulphide clusters on the crystal surface. These silver sulphide clusters enhance the efficiency of image formation during the photographic process. Their activity towards the capturing of light photons, however, is very critical to their size (aggregation number) and concentration. By incorporating gold ions into silver sulphide clusters it was possible to monitor the size distribution by measuring the amount of gold reacted. From these experiments, no evidence was found for aggregation of the reacted sulphur entities on the surface. The uptake of gold ions at different sulphur concentrations could well be fitted with a simulated size distribution when a catalyzed deposition of sulphur was assumed, with a reactivity of the surface equal to 1.0 % for the microcrystals studied. From a simulation of the silver sulphide cluster size distribution a correlation could also be found between increasing aggregation numbers and the absorption at increasing wavelengths in diffuse reflectance spectroscopy.

Abstract: The paper presents the results of the study of atmospheric aerosols in the Siberian region. This research was focused on studying the chemical and biological characteristics of both natural and pollution aerosols in this vast territory of the Asian part of the former Soviet Union (FSU). The data received within the frame of this project formed the basis for the evaluation of the impact of these aerosols on the Arctic region and the global climate. The Asian part of FSU is of scientific interest in the context of environmental chemistry, air pollution and study of atmospheric aerosols, The specific relevance of aerosol research in Siberia is as follows. There are areas that are very remote from industrial or densely populated centres, In these circumstances, aerosol characterization contributes to the definition of global continental “background”) or “baseline” aerosol, i.e, the aerosol which should occur in natural circumstances and on which all pollution is superimposed. Recently, in the context of global and long-term climatic changes, baseline aerosols and long-range transport of particulate air pollutants have become a topic of much debate, This is because it has been thought that aerosols might compensate for the well-known greenhouse effect to a significant. In this context, more and more attention is being paid to long-range effects of continental aerosols on the polar regions. Research in Norway and Alaska showed that Western or Central Siberia may be a very important source of pollutants affecting the air composition in the Arctic region. Cities and regions in south Siberia are enormously polluted by heavy metals, the level of pollution being many times higher than in the Western world, thus the health of local population is seriously affected. In most cases, gigantic point sources are in the area, which is simple from the viewpoint of environmental chemistry and unambiguous results should be obtained easily. Atmospheric deposition is a possible cause of the existence of heavy metals in the southern part of Lake Baikal. in the northern part of the lake, the environment is unpolluted. However in the southern part of the lake is considerably threatened by pollution from Baikalsk wood-pulp mill and industrial enterprises of Irkutsk, Angarsk,