The impact of the fuel feeding mode (continuous or periodic with different stand-by/operation time ratios) on carbon monoxide (CO) and nitrogen oxides (NO, NOx) concentration values in the flue gas was analysed for coniferous wood pellet firing. Experiments were performed in a 25 kW water boiler equipped with an over-fed wood pellet furnace located in a full scale heat station simulating real-life conditions. Influence of oxygen concentration and temperature in the combustion chamber on carbon monoxide and nitrogen oxide concentrations was presented in diagrams. Dust and hydrocarbon concentrations were also monitored. It was concluded that the commonly used periodic fuel supply does not necessarily cause a significant increase of carbon monoxide concentration, as compared to the continuous fuel feeding mode. Continuous fuel supply can even induce higher carbon monoxide concentrations when fuel mass stream is not chosen properly. Each time new fuel type is used in a specific furnace, one should perform experiments to determine the adequate settings (stand-by/operation time ratio, fuel mass streams, air stream) to obtain the optimal, lowest possible emission for a certain boiler heat output

The aim of the research was to study the influence of different tree stands on topsoil magnetic susceptibility and heavy metal contamination in the soil. The study was performed in the old park in Pruhonice (near Prague) in the Czech Republic. On the relatively small area of Pruhonice Park, five different coniferous tree species (pine, spruce, blue spruce, fir, Douglas fir) and five deciduous species (beech, red oak, common oak, hornbeam, birch) were found, growing in small clusters on the same geological background. Also other natural and anthropogenic factors such as distance from industrial and urban sources of pollution, type of soil, climate, etc. were similar. The magnetic susceptibility was measured directly in the field. Twenty topsoil cores 0.3 m long (2 under each tree species) were collected and also soil samples from under each tree (litter horizon) were taken. The magnetic susceptibility values of the topsoil profiles and of litter layer samples were obtained. Heavy metal analyses of surface samples (litter horizon) were also carried out. The field magnetic susceptibility (K) data are more or less comparable to the laboratory data (x). High heavy metal contents corresponding to high magnetic susceptibility values are observed in the litter horizon. A positive correlation between magnetic susceptibility and some heavy metals was observed. The results suggest that the type of forest may also influence the values of magnetic susceptibility and heavy metal content. Generally higher magnetic susceptibility values were observed in the coniferous forest, except for the surface layer (litter horizon) where the K values are lower than in the deciduous forest.

The paper presents the descriptions as well as drawings of three species of eriophyid mites found on coniferous plants as new in Poland: Trisetacus juniperinus (Nalepa) from Juniperus procumbens, Eriophyes junipereti Keifer from Juniperus communis L. 'Hibemica' and Cecidophyopsis psilaspis (Nalepa) from Taxus baccata L. Additionally, eriophyoid mites collected from Thuja occidentalis and Tsuga canadensis are discussed in this paper.