Water Pollution notes - Chapter21:WaterPollution...

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Chapter 21: Water Pollution Water Pollution: Sources, Types, and Effects Water pollution and Its Sources Water pollution degrades water quality and can come from single sources and larger dispersed sources. Water pollution Any chemical, biological, or physical change in water quality that has a harmful effect on living organisms or makes water unsuitable for desired uses Point sources Discharge pollutants at specific location through drain pipes, ditches, or sewer lines into bodies of surface water Factories, sewage treatment plants (which remove some but not all pollutants, underground mines, and oil tankers Nonpoint sources Scattered and diffuse and cannot be traced to any single site of discharge Deposition form the atmosphere and runoff of chemicals and sediments into surface water from cropland, livestock feedlots, logged forests, surface mines and urban streets, lawns, golf courses, and parking lots Major sources of water pollution Agricultural activities By far the leading cause of water pollution Sediment eroded from agricultural lands is the largest source Fertilizers and pesticides, bacteria from livestock and food processing wastes, and excess salt from soils of irrigated cropland Industrial facilities Mining Surface mining disturbs the earth’s surface, creating a major source of eroded sediments and runoff of toxic chemicals Major Water Pollutants and Their Effects Water is polluted by disease­causing agents, oxygen­demanding wastes, plant nutrients, organic and inorganic chemicals, sediment, and excess heat. Major water pollution problems *pg 495 Exposure to infectious disease organisms (pathogens) from having to drink contaminated water Not having enough water for effective sanitation Excessive inputs of oxygen­demanding wastes can deplete the level of dissolved oxygen (DO) in water Scientists can use chemical analysis to determine the presence and concentrations of specific organic chemicals in polluted water They can also monitor water pollution by using living organisms as indicator species Genetic pollution Not native species Pollution of Freshwater Streams Water Pollution Problems of Streams
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Flowing streams can recover from a moderate level of degradable water pollutants if they are not overloaded and their flows are not reduced. Rivers and other flowing streams can recover rapidly from moderate levels of degradable, oxygen­demanding wastes and excess heat through a combination of dilution and biodegradation such wastes by bacteria. Stream Pollution in Developed Countries Most developed countries have sharply reduced point­source pollution but toxic chemicals and pollution from nonpoint sources are still a problem.
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