Water

Abstract

The physical-chemical properties of water as a solvent are tabulated. The magnitude of the main reservoirs and fluxes in the hydrological cycle, with special attention given to the human appropriation of renewable fresh water, are given. The acquisition of solutes in the water is discussed in the context of circulation of water with rocks, atmosphere, and biota, with special attention given to chemical weathering, the biogeochemical cycle, chemical equilibria, and the chemical speciation of the elements. Factors affecting stream quality and general principles of stream water geochemistry are given. Ideally, water is controlled by the alteration of rock minerals through chemical weathering processes, which liberate soluble products. These processes are controlled or influenced by climatic factors, such as rainfall, air temperature, and evaporation associated with biological or biochemical processes. Human activity impacts water quality in an ever increasing manner. Carbon, sulfur, and nitrogen are present in the hydrologic cycle and their increase or decrease is an indication of water quality. There are many techniques for water analysis. A great deal, however, can be determined by a few physical and chemical tests. This article deals with fresh water analysis primarily and may not be suitable for saline water. Tests for physical properties include: temperature, specific conductance, color, turbidity, taste and odor, dissolved solids and suspended solids, and pH. There are many principal mineral constituents and gases that can be determined. Information is given for the determination of alkalinity, acidity, hardness, sodium and potassium, chloride, sulfate, nitrate and nitrite, fluoride, phosphate, boron and borates, silica and oxygen. Analysis of minor mineral constituent and gases, BOD, detergents, pesticides, and radioactive materials, both artificial and natural, and identification of bacteria round out the section on analysis.

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