Sediments of two dam reservoirs in SE Poland, Zalew Zemborzycki (ZZ) and Brody Iłżeckie (BI) were studied. The sediments from both reservoirs were sampled in the transects perpendicular to the shoreline, at the river inflow and the frontal dam. The total concentration of Mn, Zn, Pb, Cd, Cu, Cr and Ni was determined by ICP-EAS method after the sample digestion in the mixture of concentrated HNO3 and HClO4 acids. The statistical analyses: value intervals, mean values, variation coefficient, the median and the skewed distribution were performed. To estimate differences between the means for transects, Tukey’s test was applied with least significant difference (LSD) determination. The maps of the metal spatial distribution were drawn and sediment quality according to the geochemical and ecotoxicological criteria evaluated. Differences between the reservoirs in terms of heavy metals concentration in bottom sediments, and regularities in their spatial distribution were found. In the ZZ sediments the concentration was at the level of geochemical background (Zn, Cr), slightly (Cd, Cu, Ni) or moderately (Pb) contaminated sediments. The metal concentration in the sediments of the BI was up to eight times higher as compared to the ZZ. Moreover, sediments from the BI reservoir showed a greater variability of metal concentration than those from ZZ, which resulted from the dredging operation performed in the part of the reservoir. Metal concentration in sediments of the dredged part was ca. 2–5 times lower than in the undredged one, which indicates that after the dredging operation, accumulation of these metals was slight. The concentrations of Zn, Pb and Cd from the undredged part of BI were at the level of contaminated sediments and exceeded the probable effects level (PEL). In the ZZ, the greatest accumulation of metals occurred in the upper part of the reservoir and at the frontal dam, and the lowest in the middle part of the reservoir. In BI, the lower outflow of water in this reservoir caused a lower metal concentration in the sediments at the frontal dam, as compared with the other sediments in the undredged part of the reservoir. The results indicate that in small and shallow reservoirs, areas of accumulation of heavy metals depend on such factors as a parent river current, reservoir depth, water waving, reservoir shape (narrowing, coves/bays), and type of water outflow.

The purpose of the paper is to analyze the spatial variability of precipitation in Poland in the years 1981–2010. The av-erage annual rainfall was 607 mm. Precipitation in Poland is characterized by high spatial and temporal variability. The lowest annual precipitation was recorded in the central part of the country, where they equaled 500 mm. The highest annual precipitation totals were determined in the south, equaling 970 mm. The average precipitation in the summer half-year is 382 mm (63% of the annual total). On the basis of data from 53 climate stations, maps were made of the spatial distribution of precipitation for the period of the year and winter and summer half-year. The kriging method was used to map rainfall distribution in Poland. In the case study, cross-validation was used to compare the prediction performances of three periods. Kriging, with exponential type of semivariogram, gave the best performance in the statistical sense. Their application is justices especially in areas where landform is very complex. In accordance with the assumptions, the mean prediction error (ME), mean standardized prediction error (MSE), and root mean-square standardized prediction error (RMSSE) values are approximately zero, and root-mean-square prediction error (RMSE) and average standard error (ASE) reach values well below 100.