Unit 3 Exam - Chapter 17

Spring and summer bring huge inputs of nutrients from the Mississippi River basin Explosive growth of phytoplankton that eventually die and are consumed by bacteria Depletes oxygen in the Gulf’s bottom layer of water Resulting dead zone contains little marine life Winter storms redistribute oxygen

chief causes: agriculture, industry, and untreated wastewater

Water pollution causes illness and death in humans and other species, and disrupts ecosystems

Change in water quality that can harm living organisms or make water unfit for human use

Discharge pollutants at specific locations Examples: factories, animal feedlots, underground mines, oil wells, and oil tankers

Broad, diffuse areas Rainfall or snowmelt washes pollutants from land into surface water Examples: runoff of fertilizers and pesticides from croplands, logged forests, lawns, and golf courses

Agricultural activities (Sediment eroded from the lands Fertilizers, pesticides, and bacteria from livestock and food) processing wastes Industrial facilities Mining Untreated human wastewater Plastic

Nutrients that cause oxygen depletion Mercury Pathogens from broken sewer pipes Sediment from land disturbance and erosion Metals

Contaminated drinking water An estimated 1.6 million people die every year

Many streams and rivers around the world are polluted —– Can cleanse themselves of biodegradable wastes if we do not overload them or reduce their flows Adding excessive nutrients to lakes from human activities can disrupt ecosystems Preventing pollution is more effective and less costly than cleaning it up

1970s: water pollution control laws

Cuyahoga River, Ohio, U.S. Driven by bottom-up pressure from citizens

EPA estimate: mining wastes pollute 40 percent of headwaters of western watersheds

Ohio River: most polluted river in the United States due to industrial wastes

Untreated sewage Industrial waste Nearly half of China’s rivers too toxic to touch or drink —- Liver and stomach cancer linked to water pollution among leading causes of death

Flowing rivers or streams can dilute organic pollutants and heated water unless overloaded Does not eliminate heavy metals or slowly degradable pollutants Oxygen sag curve is created when degradable pollutants are emitted and bacteria act to decompose the waste

Lakes and reservoirs are less effective at diluting pollutants than streams Stratified layers with little vertical mixing Little or no water flow Can take up to 100 years to flush and change the water in a lake Biological magnification of pollutants

Natural enrichment of a shallow lake, river mouth, or slow-moving stream Caused by runoff of plant nutrients such as nitrates and phosphates

Low nutrients Clear water

Nitrates and phosphates from human sources Farms, feedlots, streets, parking lots, lawns, mining sites, and sewage plants

Dense growths of algae and cyanobacteria Oxygen depleted by bacteria that decompose the algae

Remove nitrates and phosphates Recycle nutrients into the soil

Remove excess weeds Use herbicides and algaecides Pump in air Most lakes will recover if excessive input of nutrients is stopped

Level of nitrates discharged from Mississippi River into Gulf of Mexico tripled since 1950s Causes severe depletion of dissolved oxygen Food web disruption Many species cannot migrate away from area and die Causes deaths of seabird and marine mammal species that depend on dying fish and shellfish Human factors Dredging and straightening of rivers increases flow of nutrients Removal of wetlands that act as filters for pollutants