TRACE ELEMENTS IN A VALLEY OF UPPER RIVER NAREW AND ITS SELECTED TRIBUTARIES, NE POLAND

The catchment of the upper river Narew (NE Poland) was studied. Investigations were carried out in March, May, August, and October 2006. The study was aimed at evaluating total cadmium, lead, zinc, chromium, nickel, and cobalt content as well as their forms dissolved in bottom sediments of the upper river Narew and its selected tributaries. Also the attempts to recognize the influence of the catchment management on concentration of the elements studied in bottom sediments of the upper river Narew were undertaken by using the neural networks. Metal concentrations were determined by means of AAS technique. Human economic and household activities, along with a surface runoff, are responsible for the metals deposited in sediments of the rivers under analysis, which was confirmed by statistical computations. The sediments were described as not contaminated (I class) with nickel, zinc, copper, chromium, cobalt, and lead, whereas cadmium concentration slightly exceeded that typical of the I geochemical class in about 20% of the samples studied. Contents of other elements under investigation occurred at the level of geochemical background. The highest metal concentrations were recorded in the alluvia of the river Horodnianka that flows through the area situated near municipal waste dump in Hryniewicze. Studies using artificial neural networks gave the opportunity and efficiency to predict the heavy metals contents in bottom sediments of the river Narew and allowed us to assess its efficiency taking into account many parameters at the same time.