Environmental Science / Unit 6: Water Resources and Pollution
6.3 Types of Water Pollution
Notes
Water pollution is any change to water that harms organisms or limits its use.
- Point source pollution comes from one identifiable place, such as a factory pipe or sewage treatment outfall. It is easier to monitor and regulate.
- Nonpoint source pollution comes from many diffuse sources, such as fertilizer and pesticide runoff from farms and lawns, oil from roads, and sediment. It is harder to control.
- Common pollutants: pathogens (from sewage), nutrients (nitrogen and phosphorus), sediment, toxic chemicals, heavy metals (lead, mercury), oil, and thermal pollution (hot water from power plants, which holds less dissolved oxygen).
- Dissolved oxygen (DO) is a key measure of water health. Biochemical oxygen demand (BOD) is the oxygen microbes need to break down organic matter; high BOD means low DO.
- Bioaccumulation is the buildup of a toxin in an organism; biomagnification is the increase in toxin concentration at higher trophic levels (mercury in large fish).
- Example: a pipe discharging factory waste into a river is a point source; runoff from a thousand lawns is nonpoint.
Practice
Which is an example of point source pollution?
A point source has one identifiable discharge location.
A power plant releases warm water into a river. Why does this harm fish?
Gas solubility decreases as temperature increases.
Mercury becomes more concentrated in each higher level of the food chain, so large predator fish have the highest levels. This process is called:
Biomagnification is the increase in concentration up trophic levels.
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