Chapter 22 Water Pollution

Types of Water Pollution Any physical or chemical change in water that adversely affects the health of humans and other organisms Varies in magnitude and type of pollutant by location Major water pollution issue globally Lack of disease-free water

Types of Water Pollution Eight categories Sewage Disease-causing agents Sediment pollution Inorganic plant and algal nutrients Organic compounds Inorganic chemicals Radioactive substances Thermal pollution Some categories are interrelated

Sewage The release of wastewater from drains or sewers Includes human wastes, soaps, and detergents Causes 2 serious environmental problems: Enrichment Increase in Biological Oxygen Demand (BOD)

Enrichment Fertilization of a body of water by high levels of plant and algal nutrients (nitrogen and phosphorus) Microorganisms decompose materials into CO2, water, other inoffensive materials Cellular respiration – requires oxygen

Biological Oxygen Demand Amount of oxygen needed by microorganisms to decompose biological wastes Expressed as mg of DO/L for a specific number of days at a given temperature As BOD increases Dissolved Oxygen (DO) decreases

Dissolved Oxygen Oxygen has a limited ability to dissolve in water When aquatic ecosystem contains a large amount of sewage, decomposing organisms use up most of DO Little left for fishes and other aquatic animals Extremely low DO, anaerobic microorganisms produce compounds with unpleasant odors Further deteriorates water quality

Dissolved Oxygen

Oligotrophic Lake Unenriched, clear water that supports small populations of aquatic organisms

Eutrophic Lake Slow-flowing stream, lake or estuary enriched by inorganic plant and algal nutrients such as phosphorus Often due to fertilizer or sewage runoff

Eutrophication Enrichment of lake, estuary, or slow-flowing stream by inorganic plant and algal nutrients Increased photosynthetic productivity Water becomes cloudy (pea soup-like) because of presence of algae and cyanobacteria

Eutrophication Over time, bodies of water become eutrophic naturally Slowly grow enriched, shallower Plants start to take root Becomes a marsh Artificial eutrophication – human-induced process Fertilizer runoff and sewage

Disease-causing Agents Infectious organisms that cause diseases Originate in the wastes of infected individuals Common bacterial or viral diseases: Typhoid, cholera, bacterial dysentery, polio, and infectious hepatitis

Disease-causing Agents Monitored by testing for presence of E. coli in the water via a fecal coliform test Indicates the presence of pathogenic organisms

E. Coli Safe drinking water – no more than 1 bacterium/100 mL Safe swimming water – no more than 200/100 mL Safe general recreation water (boating) – no more than 2000/100 mL Raw sewage – several million/100 mL

Sediment Pollution Excessive amounts of suspended soil particles Originates from erosion of agricultural lands, forest soils exposed by logging, degraded stream banks, overgrazed rangelands, strip mines, and construction Problems Limits light penetration Covers aquatic animals and plants Brings insoluble toxins into waterways

Sediment Pollution Makes water turbid (cloudy) Extreme turbidity Reduces number of photosynthetic algae and plants that require light for photosynthesis Decreases number of aquatic organisms that feed on producers Sediments can form layer over coral reefs or shellfish beds that can clog gills and feeding structures of aquatic animals

Sediment Pollution Particles can also carry toxic chemicals (inorganic and organic) into water Can also transport disease-causing agents

Sediment Pollution 1998 EPA study – sediments in 7% of watersheds are so seriously contaminated with toxic pollutants that eating fishes from those waterways would threaten human health Sediments can fill in waterways – problem in lakes and channels through which ships have to pass

Inorganic Plant and Algal Nutrients Chemicals such as nitrogen and phosphorus that stimulate the growth of plants and algae Essential for normal functioning of healthy ecosystem Harmful in large concentrations Sources: Human and animal wastes, plant residues, atmospheric deposition, and fertilizer runoff Causes: Enrichment, bad odors, and a high BOD

Mississippi Dead Zone

Mississippi Dead Zone Fertilizer runoff from midwestern fields, manure runoff from livestock operations 1998 Senate Agriculture Hearings -- US livestock produce 20 times the feces and urine that humans do Not covered by water quality laws Do not go to wastewater treatment plants

Mississippi Dead Zone Dead zone extends from sea floor up into water column to within several meters from surface Floods and droughts change its size Persists from March/April to September Most severe in June, July, August 2002 – more than 22,000 km2 – size of Massachusetts

Mississippi Dead Zone No life other than anaerobic bacteria Active swimmers avoid area Bottom dwellers suffocate Hypoxia affects more than 146 coastal areas in world

Organic Compounds Chemicals that contain carbon atoms Natural examples: sugars, amino acids, and oils Human-made examples: pesticides, solvents, industrial chemicals, and plastics

Organic Compounds 2002 USGS Study of 139 streams in 30 states: Tested for 95 organic compounds Found low concentrations of 82 compounds One found in 80% of streams More than 1/3 contained traces of 10 or more Effects on human health largely unknown

Inorganic Chemicals Contaminants that contain elements other than carbon Examples: acids, salts, and heavy metals Do not degrade easily

Lead Found in old paint, industrial pollutants, leaded gasoline 1978 – lead paint banned 1986 – leaded gasoline outlawed Dust released into atmosphere, contaminates soil, especially inner cities near highways Contaminates soil, surface water, and groundwater when incinerator ash dumped in landfills Pesticides, fertilizers Food cans and certain types of dinnerware

Mercury Vaporizes at room temperature Coal-fired power plants release 40% of mercury in environment Fluorescent lights and thermostats Also released during metal smelting Mercury bioaccumulates in the muscles of top predators of the open ocean Human exposure primarily due to eating fishes and marine mammals

Radioactive Substances Contain atoms of unstable isotopes that spontaneously emit radiation Sources Mining Processing radioactive materials Nuclear power plants Natural sources

Thermal Pollution Occurs when heated water produced during industrial processes is released into waterways Organisms affected Temperature affects reproductive cycles, digestion rates, and respiration rates Warm water holds less DO than cold water