ECOLOGICAL WATER QUALITY
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Abstract
Water quality – is a description of water’s chemical and biological composition and physical properties, which characterize it as an abiotic component of aquatic ecosystem and determine its suitability for specific consumption purposes. Ecological water quality (environmental water quality) – refers to the ecological well-being of an aquatic ecosystem, with the main focus on protection of the aquatic environment and human life and health. It comprises a complex of physical, chemical, biological and other parameters reflecting specific features of abiotic and biotic components of aquatic ecosystems. The requirements for physical, chemical and biological properties of water are set in the water quality standards, which may be developed by particular countries or introduced by international organizations. Ecological water quality depends upon natural and human factors. Natural factors are in their turn divided into abiotic (for example, geological, meteorological, hydrological) and biotic (for example, the ratio of primary production and organic matter destruction). The main human factors affecting water quality include artificial modification of aquatic ecosystems’ hydrological conditions and their pollution with diverse chemical compounds. There are a lot of approaches to ecological water quality assessment according to both abiotic (physical and chemical) and biological parameters. Physical and chemical methods take into account such parameters as water transparency, suspended particulate matter concentration (turbidity), ion composition, water hardness, total dissolved salts content, nutrients and organic matter content, dissolved gases concentration, pH. Biological methods are based upon assessing the living organisms’ (biological indicators’) response to mineral and organic substances, present in water. Various living organisms can be used as biological indicators: algae, in particular – diatoms, higher aquatic plants, different species of aquatic invertebrates and fishes. While physical and chemical methods characterize water quality at the moment of sampling, biological methods provide an integral picture of water quality for a certain time period. Besides, biological methods are more informative, because they reflect the aquatic ecosystem’s response to pollution. On the whole, the most reliable data on ecological water quality can be obtained by combining physical, chemical and biological methods.