Transcript Document
Water Pollution Chapter 20 20-1 What Are the Causes and Effects of Water Pollution? Concept 20-1A Water pollution causes illness and death in humans and other species and disrupts ecosystems. Concept 20-1B The chief sources of water pollution are agricultural activities, industrial facilities, and mining, but growth in population and resource use make it increasingly worse. Water Pollution Comes from Point and Nonpoint Sources Water pollution is any chemical, biological, or physical change in water quality that has a harmful effect on living organisms or makes water unsuitable for desired uses. Water quality, or its chemical and physical makeup, depends upon its intended use. • Drinking water needs to be as pure H2O and possible • Water used for washing your car or watering your lawn can be of lower quality Water Pollution Comes from Point and Nonpoint Sources Point source: specific location or from a single point • Drain pipes, ditches, sewer lines, spills • Fairly easy to identify, monitor, and regulate Nonpoint source: cannot be traced to a single site of discharge • Atmospheric deposition, runoff from agricultural / industrial / residential lands • Difficult to identify and control and expensive to clean up because of the many diffuse sources Water Pollution Comes from Point and Nonpoint Sources Major sources of water pollution are: 1) Agricultural activities are by far the leading cause of water pollution. • Sediment eroded from agricultural lands, fertilizers, pesticides, bacteria from livestock, salts from irrigation 2) Industrial facilities release a variety of harmful organic and inorganic chemicals. 3) Surface mining disturbs the Earth’s surface causing runoff of sediments and toxic chemicals. Major Water Pollutants and Their Sources Science Focus: Testing Water for Pollutants There are a variety of tests to determine water quality: • • • • • • • • • • • Temperature pH Dissolved Oxygen Total Dissolved Solids Flow Rate Phosphates Nitrates Chlorides Color and turbidity of the water Coliform bacteria: E. coli Biological Assessment • Indicator species 20-2 What Are the Major Water Pollution Problems in Streams and Lakes? Concept 20-2A While streams are extensively polluted worldwide by human activities, they can cleanse themselves of many pollutants if we do not overload them or reduce their flows. Concept 20-2B Addition of excessive nutrients to lakes from human activities can disrupt lake ecosystems, and prevention of such pollution is more effective and less costly than cleaning it up. Streams Can Cleanse Themselves If We Do Not Overload Them Flowing streams can recover from a moderate level of water pollution if they are not overloaded with pollutants and their flows are not reduced. • In a flowing stream, the breakdown of degradable wastes by bacteria depletes dissolved oxygen and creates an oxygen sag curve. • Biodegradation of wastes by bacteria takes time • This reduces or eliminates populations of organisms that require high amounts of oxygen until the stream is cleansed of wastes. Dilution and Decay of Degradable, Oxygen-Demanding Wastes in a Stream Similar oxygen sag curves can result from thermal pollution. Stream Pollution in Developed Countries Most developed countries have sharply reduced point-source pollution but water contamination is still a problem. • Accidental or deliberate releases of toxic chemicals by industries, mines, malfunctioning sewage treatment plants • Non-point runoff of pesticides and nutrients from cropland and livestock Stream Pollution in Developing Countries Stream pollution in most developing countries is a major problem. • Untreated sewage, infectious agents, industrial wastes Most countries cannot afford water treatment plants. Many don’t have water quality laws or the laws are not enforced. Problems are made worse by the fact that many people in developing countries drink, bath, and wash clothes in rivers. Case Study: India’s Ganges River: Religion, Poverty, Population Growth, and Health Daily, more than 1 million Hindus in India bathe, drink from, or carry out religious ceremonies in the highly polluted Ganges River. Case Study: India’s Ganges River: Religion, Poverty, Population Growth, and Health Religious beliefs, cultural traditions, poverty, and a large population interact to cause severe pollution of the Ganges River in India. • Very little of the sewage is treated • Animal wastes and carcasses are thrown into river • Hindu believe in cremating the dead to free the soul and throwing the ashes in the holy Ganges. • Some are too poor to afford the wood to fully cremate • Decomposing bodies promote disease and depletes DO Low Water Flow and Too Little Mixing Makes Lakes Vulnerable to Water Pollution Dilution of pollutants in lakes is less effective than in most streams because most lake water is not mixed well and has little flow. • Lakes and reservoirs are often layered by temperature and undergo little mixing • Low flow makes them susceptible to runoff Rivers can be flushed of pollutants in days, compared to the years it would take to be removed from a lake. Various human activities can overload lakes with plant nutrients, which decrease DO and kill some aquatic species. Cultural Eutrophication Is Too Much of a Good Thing Eutrophication: natural nutrient enrichment of a shallow lake, estuary or slow moving stream, mostly from the runoff of plant nutrients from the surrounding land. • The opposite = Oligotrophic lake • Low nutrients, clear water Cultural eutrophication: when human activities accelerate the input of plant nutrients (mostly nitrates and phosphates) to a lake. • 85% of large lakes near major population centers in the U.S. have some degree of cultural eutrophication. Cultural Eutrophication Is Too Much of a Good Thing Eutrophication can lead to a large fish kill events. • Excessive nutrients cause out of control algae growth • Algae use up all the nutrients, die, and decompose • The decomposition process results in low oxygen levels and an oxygen sag is created • 1000’s or 10,000’s of fish can be killed at a time • In Iowa, fish kills are caused by large amounts of manure being spilled into rivers, streams, lakes 20-3 Pollution Problems Affecting Groundwater, Other Water Sources Concept 20-3A Chemicals used in agriculture, industry, transportation, and homes can spill and leak into groundwater and make it undrinkable. Concept 20-3B There are simple ways and complex ways to purify drinking water, but protecting it through pollution prevention is the least expensive and most effective strategy. Ground Water Cannot Cleanse Itself Very Well The drinking water for about half of the U.S. population and 95% of those in rural areas comes from groundwater. Common groundwater pollutants are gasoline, fertilizers, pesticides, and organic solvents Sources: spills, leaking underground pipes and tanks, seepage down from the surface Once a pollutant contaminates groundwater, it fills the pores between the sediment particles like a sponge • This makes removal and cleanup very difficult and costly Principal Sources of Groundwater Contamination in the U.S. Ground Water Cannot Cleanse Itself Very Well Direction of water flow When groundwater pollutants reach an aquifer, they spread out and form a specific shape called a plume. Ground Water Cannot Cleanse Itself Very Well Groundwater can become contaminated with a variety of chemicals because it cannot effectively cleanse itself or dilute and disperse pollutants. • • • • Slow flow: contaminants not diluted Less dissolved oxygen – less decomposition Fewer decomposing bacteria Colder temperatures slow down chemical reactions As a result, it can take 100’s to 1000’s of years for contaminated groundwater to cleanse itself of degradable wastes. • Non-degradable wastes (toxic lead, arsenic, flouride) are there permanently. Solutions: Groundwater Pollution, Prevention and Cleanup Groundwater contamination is the most clear situation where prevention is the only true solution. All cleanup methods are expensive and time consuming There Are Many Ways to Purify Drinking Water Centralized water treatment plants and watershed protection can provide safe drinking water for cities in developed countries. Simpler and cheaper ways can be used to purify drinking water for developing countries. • Boiling water or exposure to the sun’s UV rays for 3 hours can kill infectious microbes. While most developed countries have drinking water quality standards and laws, most developing countries do not. Using Laws to Protect Drinking Water Quality The U.S. Safe Drinking Water Act requires the EPA to establish national drinking water standards (maximum contaminant levels) for any pollutant that may have adverse effects on human health. • Originally, it only focused on standards for water treatment • Now, it includes protections for drinking water sources as well • rivers, lakes, springs, groundwater Using Laws to Protect Drinking Water Quality The U.N. estimates that 5.6 million Americans drink water that does not meet EPA standards. 1 in 5 Americans drinks water from a treatment plant that violated one or more safety standard. Industry pressures to weaken the Safe Drinking Act: • Eliminate national tests and public notification of violations • Allow rights to pollute if provider cannot afford to comply • Reduce EPA’s budget which limits its ability to monitor and enforce water quality standards Is Bottled Water the Answer? NO!! ¼ of bottled water is just tap water 40% of bottled water is lower quality than tap water and costs much more. Fossil fuels are used to make plastic bottles. • The oil used to produce plastic bottles in the U.S. each year would fuel 100,000 cars. • 1.4 million metric tons of plastic bottles are thrown away.