The physical and optical properties of an atmospheric aerosol mixture depend on a number of factors. The relative humidity influences the size of hydroscopic particles and the effective radius of an aerosol mixture. In consequence, values of the aerosol extinction, the aerosol optical thickness and theÅngström coefficient are modified. A similar effect is observed when the aerosol composition changes. A higher content of small aerosol particles causes the effective radius of an aerosol mixture to decrease and theÅngström coefficient to increase. Both effects are analysed in this paper. The parameters of the size distribution and the type of components used to represent natural atmospheric aerosol mixtures are based on experimental data. The main components are sea-salts (SSA), anthropogenic salts (WS, e.g. NH 4 HSO 4 , NH 4 NO 3 , (NH 4 ) 2 SO 4

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Cyanobacteria, otherwise known as blue-green algae, are oxygenic, photosynthetic prokaryotes. They occur naturally in many fresh, marine and brackish waters worldwide and play an important role in global carbon and nitrogen cycles. In their long history, cyanobacteria have developed structures and mechanisms that enable them to survive and proliferate under different environmental conditions. In the Baltic Sea, the mass development of cyanobacteria is compounded by a high level of eutrophication. The dominant species in the Baltic, the filamentous Aphanizomenon flos-aquae and Nodularia spumigena, can fix dissolved atmospheric N 2 , as a result of which they can outcompete other phytoplankton organisms. Heterocystous, filamentous cyanobacteria also make a significant contribution The complete text of the paper is available at http://www.iopan.gda.pl/oceanologia/ 294 H. Mazur-Marzec, M. Pliński to the internal nutrient loading in the Baltic. The blooms of N. spumigena are of particular concern, as this cyanobacterium produces nodularin (NOD), a hepatotoxic peptide. The concentration of the toxin in the sea is regulated mainly by dilution with uncontaminated water, photolysis, sorption to sediments and microbial degradation. The transfer of the toxin in the Baltic trophic chain through zooplankton, mussels, fish and birds has been reported, but biodilution rather than bioconcentration has been observed. Cyanobacterial blooms are thought to pose a serious threat to the ecosystem. Their harmful effects are related to the occurrence of a high biomass, oxygen depletion, a reduction in biodiversity, and the production of toxic metabolites.

I n t e r n a t i o n a l J o u r n a l o f O c e a n o g r a p h y a n d H y d r o b i o l o g y AbstractThe paper presents petroleum concentration in coastal waters of Gdańsk Bay, which was measured in 2006 -2012. The oil concentration ranges from below the detection limit, i.e. 1 μg kg -1 to almost 120 μg kg -1 . The concentration does not usually exceed 60 μg kg -1 and its average value is 11.7 μg kg -1 . The presence of petroleum in coastal water is characterized by seasonality, with the lowest values in summer and the highest in winter. The conducted research showed that the coastal zone is not the source of petroleum contamination of the sea. The main reason for the presence of petroleum in the coastal water is the migration of polluted water within the bay. The inflow of pollutants from the mainland is yet another source of the contamination in the sea.

This paper presents studies of the total spectra (fluorescence-excitation matrix) of petroleum with regard to the utilization of fluorescence for determining petroleum pollutants. Thorough testing of one group, comprising almost forty lubricating oils in the form of their hexane solutions, points out their discrimination.