Lead poisoning, also called plumbism, deleterious effect of a gradual accumulation of lead in body tissues, as a result of repeated exposure to lead-containing substances. Causes And Symptoms In humans the main sources of lead are usually lead-based paint and drinking water carried through lead pipes; lead-based paints are especially harmful to children who chew on painted toys and furnishings and eat paint peelings…
Chlorine (Cl), chemical element, the second lightest member of the halogen elements, or Group 17 (Group VIIa) of the periodic table. Chlorine is a toxic, corrosive, greenish yellow gas that is irritating to the eyes and to the respiratory system. · · atomic number 17 atomic weight 35.453 melting point −103 °C (−153 °F) boiling point −34 °C (−29 °F) density…
Germ theory, in medicine, the theory that certain diseases are caused by the invasion of the body by microorganisms, organisms too small to be seen except through a microscope. The French chemist and microbiologist Louis Pasteur, the English surgeon Joseph Lister, and the German physician Robert Koch are given much of the credit for development and acceptance of the theory….
Water purification, process by which undesired chemical compounds, organic and inorganic materials, and biological contaminants are removed from water. That process also includes distillation (the conversion of a liquid into vapour to condense it back to liquid form) and deionization (ion removal through the extraction of dissolved salts). One major purpose of water purification is to provide clean drinking water….
Cast iron, an alloy of iron that contains 2 to 4 percent carbon, along with varying amounts of silicon and manganese and traces of impurities such as sulfur and phosphorus. It is made by reducing iron ore in a blast furnace. The liquid iron is cast, or poured and hardened, into crude ingots called pigs, and the pigs are subsequently remelted along with scrap and alloying…
Reservoir, an open-air storage area (usually formed by masonry or earthwork) where water is collected and kept in quantity so that it may be drawn off for use. reservoir Changes in weather cause the natural flow of streams and rivers to vary greatly with time. Periods of excess flows and valley flooding may alternate with low flows or droughts….
Sewer, conduit that carries wastewater from its source to a point of treatment and disposal. The wastewater may be domestic (sanitary) sewage, industrial sewage, storm runoff, or a mixture of the three. Large-diameter pipes or tunnels that carry a mixture of the three types of liquid wastes, called combined sewers, were commonly built in the 19th and early 20th…
Aqueduct, (from Latin aqua + ducere, “to lead water”), conduit built to convey water. In a restricted sense, aqueducts are structures used to conduct a water stream across a hollow or valley. In modern engineering, however, aqueduct refers to a system of pipes, ditches, canals, tunnels, and supporting structures used to convey water from its source to its main distribution point. Such systems…
Water cycle, also called hydrologic cycle, cycle that involves the continuous circulation of water in the Earth-atmosphere system. Of the many processes involved in the water cycle, the most important are evaporation, transpiration, condensation, precipitation, and runoff. Although the total amount of water within the cycle remains essentially constant, its distribution among the various processes is…
Groundwater, water that occurs below the surface of Earth, where it occupies all or part of the void spaces in soils or geologic strata. It is also called subsurface water to distinguish it from surface water, which is found in large bodies like the oceans or lakes or which flows overland in streams. Both surface and subsurface water are related through the hydrologic cycle (the continuous circulation…