Hydrochemistry

the science of the chemical composition of natural waters and the laws governing the changes in composition as a result of the chemical, physical, and biological processes occurring in the surrounding environment. Since it is the science of the chemistry of the hydrosphere, hydrochemistry is part of both geochemistry and hydrology.

Hydrochemistry is important for the development of a number of related sciences, including petrology, mineralogy, soil science, hydrogeology, and hydrobiology. Knowledge of the chemical composition of water (which determines its quality) is necessary for such areas of practical activity as water supply, irrigation, and fish culture. Hydrochemical data are important in evaluating the corrosion of construction materials (concrete and metal), in analyzing mineral waters, in mineral prospecting (petroleum, ore deposits, and radioactive substances), and the like. The study of the chemical composition of water becomes particularly important when combatting the pollution of water basins by waste waters.

In Russia, the origin of the study of hydrochemistry is connected with the work of M. V. Lomonosov and the so-called Academy expeditions of the 18th century. At present, the study of the chemical composition of water is conducted at various scientific and higher educational institutions, in laboratories of industrial and transportation enterprises, in public health establishments and inspectorates, and in laboratories of the water supply system. Particularly important is hydrochemical work conducted at (sea, river, and lake) stations of the hydrometeorological network of the Hydrometeorological Service. In the USSR a large number of works on hydrochemistry have been published, and there is a regularly published organ, Gidrokhimicheskie materialy (from 1915). In 1921 the only hydrochemical scientific research institute in the world was organized; now there are hydrochemistry courses in appropriate institutions of higher learning.

Three subdivisions of hydrochemistry can be distinguished in its present stage of development.

(1) The first subdivision deals with the formation of the chemical composition of natural waters. It includes the study of water as a solvent for the complex of minerals of the earth’s crust and the study of the chemical processes that occur in water as it interacts with rocks, soils, organisms, and the atmosphere. Investigations are also carried out on the solubility of substances found in nature, their state in solution and their stability, as well as on the sorption, exchange, and oxidation-reduction processes. In this subdivision, closely related to geochemistry, we must include the general questions of the cycle of substances and the migration of elements in the hydrosphere.

(2) The second subdivision deals with the chemical composition and hydrochemical cycle of certain forms of natural water and the dependence of their changes on the physicogeographical conditions of the surrounding environment. This broad subdivision borders closely on hydrology, and it is divided into the chemistry of rivers and lakes, chemistry of the sea, and the chemistry of underground water and atmospheric water.

The chemistry of surface waters studies the chemical composition of water in rivers, lakes, and artificial reservoirs, changes in the composition with land or water area and with depth, seasonal diurnal variations, and the conditions of the determination of its composition in its dependence on the surrounding environment. It is of great importance to predict the chemical composition of water reservoirs built in arid regions and to combat pollution in reservoirs. Investigations of salt lakes, rich in minerals, is very important for the chemical industry.

The chemistry of the sea is closely related to oceanography. In addition to the study of the dependence salinity, biogenic substances, and dissolved gases on hydrodynamic, hydrometeorological, and hydrobiological factors, it also studies the form and content of trace elements, the origin of organic substances, the processes of the metamorphization of organic substances, and the processes of the interaction of seawater with river and sea bottom sediments.

The chemistry of underground waters includes the study of the chemical composition of ground, stratal, artesian, and mineral waters and of the waters from petroleum deposits. Particularly stressed are the formation of the composition of waters and the processes of the interaction of water with the surrounding rocks, which take place at high pressures and often at elevated temperatures with retarded water exchange and characteristic microbiological conditions. For a long time, the study of mineral waters, quite varied in composition and origin, has been of great importance.

(3) The third subdivision consists of the methods used in hydrochemical investigations. This subdivision is a special branch of analytical chemistry, as applied to the characteristics of the analysis of natural waters. At present, fiydro-chemistry makes extensive use of spectroscopy, chromatography, polarography, tagged atoms, and other physico-chemical methods. A large subdivision of analysis is the determination of the components of polluted water.