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Brodnax Water pollution • Any chemical, biological, or physical change in water quality that harms living organisms or makes water unsuitable for desired uses. Point sources • • • Why care about water Video Located at specific places Easy to identify, monitor, and regulate Examples: • Ditches, sewer lines, drain pipes, oil tankers, underground mines Nonpoint sources • • • • Broad, diffuse areas from which pollutants enter bodies of surface water or air Difficult to identify and control Expensive to clean up Examples • Runoff (chemical or biological) from feedlots, cropland, lawns, golf courses, logged forests, urban streets & parking lots (THINK BIG AREA) Point Source of Polluted Water in Gargas, France BIGGEST Sources of Water Pollution Agriculture activities • ***Sediment eroded from agricultural land*** • Fertilizers and pesticides • Bacteria from livestock and food processing wastes Industrial facilities • Organic and inorganic chemicals Mining • Sediment from eroding soil • Toxic chemicals Nonpoint Sediment from Unprotected Farmland Flows into Streams Other Sources of Water Pollution Other sources of water pollution • Parking lots • Build-up of toxins on surface • Human-made materials • Ex.: plastics – release polymers as they break down • Climate change due to global warming • will affect precipitation and change amounts of pollutants washing into the hydrological cycle Types of Water Pollution Video Parking lot pollutants will make their way into our water supply Major Water Pollutants have Harmful Effects Over 500 disease-causing agents can be spread through water vectors According to The World Health Organization (WHO): • 3.2 Million people die every year from water diseases or clean water shortages (most under 5) • In the developing world, diarrheal diseases kill a child under 5 every 18 SECONDS • 1.2 Billion people (1 out of 6) worldwide have no access to clean drinking water Water Quality There are 3 indicators of water quality: the concentrations of dissolved oxygen (DO), the biological oxygen demand (BOD), and the coliform bacteria count. Dissolved Oxygen (DO): the amount of oxygen gas dissolved in water. o At 68°F (20°C) and normal atmospheric pressure, the maximum DO level is 9 ppm (parts per million) and is healthy. o DO level is an important indication of the ecological health of a waterway. o If the DO level drops below 4.5 ppm, fish populations decline rapidly. o Can indicate the presence of oxygen demanding bacteria – a sign that the water is polluted by potentially disease causing agents Water Testing Video Biological Oxygen Demand (BOD): amount of dissolved oxygen gas required for bacterial decomposition of organic wastes in water. o Bacterial decomposition may reduce the BO content so much that some aquatic organisms die. o Water is seriously polluted when the BOD of the decomposers cause the DO to fall below 5 ppm. Coliform Bacteria: Escherichia coli are intestinal microbes found in soils and feces of humans and other animals. o Their presence indicates that other harmful microbes (that cause diseases such as viral hepatitis, cholera, dysentery, or encephalitis) may also be present o Bacteria can be grown in laboratories and counted o At a site where untreated sewage is dumped in a stream, bacteria start feasting on the sewage and the BOD increases enormously. Downstream, the DO levels drop drastically and fish die. Fish do not die from the sewage directly, rather from the lack of oxygen. Indicator species • Scientists can remove cattails from contaminated areas and test them for specific pollutants • Mussels can also be tested for pollutants since they are bottom-dwellers that filter the water with their bodies Genetic engineering • Scientists are creating bacteria and yeast that glow in the presence of a particular toxic chemical, like heavy metals or carcinogens. Measuring sediment • Scientists measure sediment amounts and analyze the water for color and turbidity • Turbidity – cloudiness of the water BOD (ppm) Pure water Typical fresh, natural water Domestic sewage Sewage after treatment 0 2-5 Hundreds 10-20 Chemical analysis of Fecal Coliform (per 100 mL) Testing Water for Pollutants Type of Water • For drinking = NO colonies • For swimming < 200 colonies • Raw sewage contains several million colonies Streams can cleanse themselves if we do not overload them Flowing rivers and streams can recover rapidly from moderate levels of degradable wastes through a combination of dilution and biodegradation of such wastes by bacteria. Chemical tests used in measuring water quality: phosphates, nitrates, pH, salinity, etc. • This process is hindered by excessive amounts of pollutants, drought, damming, or water diversions that reduce their flows • This process cannot remove slowly degradable (like DDT) and nondegradable pollutants (like lead and arsenic) Global Outlook Half of the world’s 500 rivers are polluted o Most of these are in developing countries Cannot afford waste treatment Cannot enforce water pollution laws Untreated sewage o Developing countries dump 80-90% of waste raw Industrial waste o Pollutes 2/3 of India’s rivers China’s rivers o 1/3 unsafe for agricultural & industrial use o 300 million people without access to potable (drinkable) H20 Water pollution in India Video Lakes are more vulnerable to pollution Lakes are less effective at diluting pollutants than streams o Stratified layers Little vertical mixing o Little or no water flow Trash truck dumping garbage into river in Peru Eutrophication of Lakes Oligotrophic lake • Low nutrients, clear water • Supports little plant life and fish species such as trout and small mouth bass • High DO levels Eutrophic lake • Nutrient-rich lake • Supports a great deal of plant life, which often chokes out other organisms • Low DO content • Large algae populations, and fish species such as carp and bullhead Eutrophication • Natural nutrient enrichment of a lake over time Cultural eutrophication • Accelerated nutrient enrichment due to human activities involving mostly nitrate and phosphate containing effluents Sources: feedlots, farmland, suburban yards, mining sites, untreated sewage Cultural Eutrophication Video Oligotrophic Lake Eutrophic Lake