Processes Determining Surface Water Chemistry

This chapter gives a brief overview of the main parameters and indicators influencing the surface water quality as well as an average data characterizing their temporal spatial distribution within the main river basins of Ukraine.

Chapter describes main hydrological processes forming hydrological regime of surface water and consequently influencing water quality. Considered hydrological processes include the transport of substances within the river basin; influence of water discharge on surface water chemical composition; hydrodynamic processes; characteristic of hydrophysical parameters; sedimentation (role of bottom deposits in water quality forming). Dependence of surface water mineralization and concentrations of the main ions within different river basins and physical-geographical zones of Ukraine is discussed. It is shown that hydrodynamic processes and different types of water flow like laminar and turbulent lead to differences in chemical substances distribution and water masses mixing in rivers, reservoirs and regulated water objects. Role of water turbidity, color, and bottom deposits in hydrochemical regime of surface water objects is also discussed. Extended information on concentrations of chemical substances in bottom deposits (solid phase) and pore solutions (liquid phase) is presented and analyzed.

Main physico-chemical processes regarding to surface water are summarized and discussed in this chapter in details focusing on acid-base balance; dissociation of acids and bases; hydrolysis of metal ions, complexation processes with inorganic and organic ligands; processes of sorption-desorption in “water-particulates – bottom sediments” system. Theoretical considerations illustrated with respective formulas and graphs are supplemented with extensive field data and results of computations. Chapter can serve as a valuable source of reference information in the field of natural water chemistry and water quality assessment from the point of view of chemical substances transformations.

Role of biological processes in forming of surface water chemical composition in particular influence of hydrobionts on pH value of water environment, concentration of dissolved oxygen and redox potential, nutrients concentrations and dynamics is discussed. Major attention is paid to the role of hydrobionts in forming of nutrients composition in surface water objects. It is shown that water plants are one of the most important sources of hydrocarbons, protein compounds, aminoacids and compounds of phenol origin as well as different classes and groups of organic substances inflow into the water. Results of studies of hydrobionts impact on metals migration in surface water, transformation of their co-existing forms and characteristics of their distribution among biotic and abiotic components of water ecosystems are considered.

Characteristic of different anthropogenic factors influencing quality of surface water is given in this Chapter. By the nature of the affect on surface water the anthropogenic factors could be divided into two groups. The first group includes the regulation of rivers and construction of hydropower stations and reservoirs, construction of thermal and nuclear power plants. These factors affect primarily hydrological and biological processes, causing changes in the concentration of dissolved substances, including oxygen, settling of suspended organo-mineral substances with toxic compounds adsorbed on them, decrease in turbidity, temperature changes and biological productivity of water masses. The second group of factors includes industrial, municipal and agricultural wastewater and petroleum products, affecting mainly the physico-chemical and biological processes. Analysis of these factors is given illustrated by information of surface water chemical composition being under influence of urban agglomerations.