Summary: On the basis of an analysis of literature and of own investigations, the state of metalions in natural waters is described as essential for the properties. There are investigated especially: hydrolysis, polymerization and complexation with humic substances. An analytical method for determining the degree of dispersion and the shares of free and complexed metal-ions as well as their charge and molar mass is presented.The present interest in the thorough study of the state of metal ions in natural waters and the rapid growth of the knowledge on them are attributed to the important role they play in various geochemical, geological and biological processes.The knowledge of the forms of existence and regularities of metal migration in natural waters and in other complex-composition media is important both in scientific and especially in practical respects for the decision of many problems arising a t the creation of a reliable technology of the metal compounds removal for drinking and service water treatment, at the development of effective methods for the valuable metals removal from sewage waters and their mixtures with natural waters, a t the development of hydrochemical methods for minerals and metal ores prospecting and in a number of other cases, related to the rational multipurpose use of water resources. This knowledge is also necessary t o interpret the mechanism of the biometals assiniilation by aquatic organisms and to assess water quality b y means biotesting methods.From the point of view of the content in natural waters the metals can be divided into two groups. The first group consists of niacrocoinponents -the ions of alkaline (Na+, K + ) and alkaline earth (Ca2+, Mg2+) elements, whose concentrations fluctuate within a rather wide range -from ppm in fresh waters t o ppt in sea a n d ocean waters. The rest of metals (microelements) whose content in natural waters is less than 1 nrg/l belongs to the second group. Such a division is to soiiie extent relative since under certain conditions (change of medium pH, of oxidative-reduction potential (EH), availability of complexing compounds a. 0.) the concentrations of some metals, e. g., iron, manganese, sometimes exceed 1 mg/l. This is especially characteristic of the dissolved-oxygen-poor underground waters and the bottom layers of deep waters of seas, lakes and reservoirs (ALYORIN ; DENISOVA). Table 1 shows the average concentrations of microelements in the water and suspended matter of oceans, seas, lakes, reservoirs and rivers (KONOVALOV e t al.; VINOGRA-DOV; GORDEEV and LISITSYN; MOROZOV; BOWEN). It should be noted that in the concrete water bodies, especially in the rivers and reservoirs, in various hydrological phases the concentrations of metal compounds can differ by several orders froiii the averagc values given in the table.
337Xatural waters are complex, varying-in-time chemicobiological systems, where nietal ions can exist as suspensions, colloids and truly dissolved compounds (simple hydrated ions or aquacomplexes, hydrolytic forms, c...