INFLUENCE OF LARGE TRIBUTARIES ON THE CHEMICAL COMPOSITION OF WATERS OF THE MIDDLE OB RIVER

The comparative analysis of the data on the chemical compound of river waters in the mouth sites of the Tom, the Chulym, the Parabel, the Vasyugan and the Ob rivers in sections located above and below the river mouth is executed. The purpose of the research is estimation of influence of the basic tributaries on the hydrochemical condition of the main river (Ob) in its middle current. During the research the following hydrochemical parameters were used:pH., the sum of the main ions, concentrations of Ca2+, Mg2+, Na+, K+, HCO3-, SO42-, Cl-, NO3-, NO2-, NH4+, PO43-, Si, organic acids, hydrocarbons ("mineral oil"), carbon of organic substances.org, Fe, Pb, Hg, Cu, Zn, Cd, Li, Cr, Al, Mn, Ba, Sr, Th, U, Sc, La. The initial information came from Tomsk Polytechnic University, Tomsk branch of Institute of Oil and Gas Geology and Geophysics of the Siberian Branch of the Russian Academy of Science and the open society "Tomskgeomonitor" during the summer and autumn period in 1991, 1999 and 2006. As a result, it has been established that influence of the Tom, the Chulym, the Parabel and the Vasugan rivers on the chemical composition and quality of the Ob river waters is ambiguous owing to changes (at the juncture of the rivers) in conditions of interaction between river waters and deposits, river-bed sediments and atmospheric air. It shows mainly in the increase of the concentration of the main ions after the confluence with the Chulym; of the content of carbon of organic substances after the confluence with the Parabel and the Vasyugan. On the whole, the quality of waters of the Ob and its basic tributaries is estimated as unsatisfactory. It is also necessary to note that during recent decades the discrepancy of quality of waters to specifications is very frequently automatically equated to their pollution, which, at least, is incorrect. For example, iron is practically always present in the surface and underground waters of the region in the quantities exceeding the maximum concentration limit and, as a rule, irrespective of proximity of any sources of pollution. Besides, the parameter of quality of water of Sigma C/(maximum concentration limit) used in the given work and stated in the sanitary rules and norms of the Russian Federation should be equal or less than 1. For group of 15-20 parameters this condition is achievable only when the concentration of each of them accordingly is 15-20 times less than the maximum concentration limit.