Chapter 44 Human Effects on the Biosphere (Sections 44.4 - 44.7)

44.4 Acid Rain Pollutants disrupt physiological processes of organisms Sulfur dioxides from coal-burning power plants, and nitrogen oxides from burning gas and oil, are common air pollutants pollutant Substance that is released into the environment by human activities and interferes with the function of organisms that evolved in the absence of the substance or with lower levels

Acid Rain (cont.) Dry acid deposition occurs when dry dust particles coated with airborne sulfur and nitrogen fall to the ground Wet acid deposition (acid rain) occurs when pollutants combine with water and fall as acidic precipitation acid rain Low pH rain that forms when sulfur dioxide and nitrogen oxides mix with water vapor in the atmosphere

Acid Rain (cont.) Acid rain in aquatic habitats prevents fish eggs from developing and kills adult fish Acid rain in forests burns tree leaves, and makes trees more susceptible to insects and pathogens Acid rain alters composition of soils Positive hydrogen ions displace positive nutrient ions such as calcium, causing nutrient loss Acidity causes soil particles to release metals such as aluminum that harm plants

Average Precipitation Acidities Figure 44.5 Acid rain.

Effects of Acid Rain

ANIMATION: Acid deposition To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

44.5 Biological Effects of Chemical Pollutants Chemicals released by human activities can accumulate in the bodies of organisms and interfere with metabolism bioaccumulation An organism accumulates increasing amounts of a chemical pollutant in its tissues over the course of its lifetime

Accumulation and Magnification In animals, hydrophobic chemical pollutants ingested or absorbed across the skin accumulate in fatty tissues Pollutant concentration in tissues increases with age, and with trophic level (biological magnification) biological magnification A chemical pollutant becomes increasingly concentrated as it moves up through food chains

Biological Magnification of DDT As a result of bioaccumulation and biological magnification, even seemingly low environmental concentrations of pollutants can have major detrimental effects on a species During the 1960s, ospreys were driven toward extinction by widespread use of DDT, because this chemical interferes with their egg shell formation

Biological Magnification of DDT Concentration of DDT in osprey tissues was 276,000 times higher than that in the water Figure 44.6 Biological magnification in an estuary on Long Island, New York, as reported in 1967 by George Woodwell, Charles Wurster, and Peter Isaacson. The upper photo shows an osprey, a top predator in this ecosystem.

Biological Magnification of DDT Figure 44.6 Biological magnification in an estuary on Long Island, New York, as reported in 1967 by George Woodwell, Charles Wurster, and Peter Isaacson. The upper photo shows an osprey, a top predator in this ecosystem.

Point and Nonpoint Sources Pollutants that come from a few easily identifiable sites (point sources) – such as a factory – are the easiest to control Pollution from widespread release of a pollutant (nonpoint sources) – such as oil that drips from vehicles – is more difficult to control

ABC Video: Pharmaceuticals in Water Supplies

BBC Video: Pesticides: Will More Restrictions Help or Hinder?

44.6 The Trouble With Trash Trash buried in the ground (such as lead from batteries) can contaminate groundwater Trash dumped at sea (such as plastics) harms marine life Plastic and other garbage that enters our coastal waters persists for many years To reduce the impact of plastic trash, avoid buying plastics, or be sure to recycle or dispose of them properly

Effects of Discarded Plastics Seabirds often mistake floating bits of plastic for food, and feed them to their chicks, with deadly results This Laysan albatross chick was fed more than 300 pieces of plastic by its parents Figure 44.7 One effect of discarded plastic in a marine environment. A Recently deceased Laysan albatross chick, dissected to reveal the contents of its gut. B Scientists found more than 300 pieces of plastic inside the bird. One of the pieces had punctured its gut wall, resulting in its death. The chick was fed the plastic by its parents, who gathered the material from the ocean surface, mistaking it for food.

BBC Video: Plastic Bag Charge Debated

44.7 Ozone Depletion and Pollution Ozone is said to be “good up high, but bad nearby” In the upper atmosphere, ozone absorbs most incoming ultraviolet (UV) radiation that damages DNA and causes mutations – but near the ground, it is a harmful pollutant ozone layer High atmospheric layer with a high concentration of ozone (O3) that prevents much ultraviolet radiation from reaching Earth’s surface

Depletion of the Ozone Layer In the mid-1970s, scientists noticed that Earth’s ozone layer (10.5 to 17 miles above sea level) was thinning, particularly over Antarctica (the “ozone hole”) In 1987, countries worldwide agreed to phase out production of chlorofluorocarbons (CFCs) and other ozone-destroying chemicals – but existing CFCs break down very slowly

The Ozone Hole Ozone levels in the upper atmosphere in September 2007 Check the ozone hole’s current status at: http://ozonewatch.gsfc.nasa.gov/ Figure 44.8 Ozone and CFCs.

Concentration of CFCs in the Upper Atmosphere Figure 44.8 Ozone and CFCs.

Near-Ground Ozone Pollution Near the ground, ozone irritates eyes and respiratory tracts of humans and wildlife, and interferes with plant growth Ground-level ozone forms when nitrogen oxides and volatile organic compounds released by burning or evaporating fossil fuels are exposed to sunlight Warm temperatures speed the reaction

ANIMATION: How CFCs destroy ozone To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

ANIMATION: The GreenHouse Effect To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

BBC Video: Who Pays the Price for Technology?