RÉSUMÉ

Results of long-term investigations of the co-existing forms of chromium in water bodies of various types (rivers, reservoirs, lakes, and ponds) are given in the paper. In the studied water bodies, the total concentration of chromium varies over a wide range accounting for 1.7–71.4 μg/L. The lower reservoirs of the Dnieper cascade located in the industrial zone proved to be most contaminated by its compounds. However, as compared to the 1980–1990s their concentration essentially decreased, which was conditioned by a decrease in the intensity of industrial production. A rather high content of chromium is observed in some lake systems of Kiev, which is conditioned by a high intensity of anthropogenic load. In the studied water bodies, with the exception of the rivers of the Pripyat River basin and the Ukrainian section of the Danube River, chromium migrates mainly in the dissolved state, where it is represented mainly by the compounds of Cr(III).The concentration of Cr(VI) is almost always lower than the limit of its detection by the photometric method. The absence of Cr(VI) is determined by its reduction under conditions of natural surface waters to non-toxic Cr(III). The complex compounds of chromium with organic substances of various chemical natures prevail in the composition of the dissolved form of chromium. Humic substances and carbohydrates are of considerable importance in complexation. The major portion of Cr(III) was found in the composition of complex compounds with the molecular mass of not more than 5.0 kDa.