5 Earth’s Atmosphere Compared to the size of the Earth (12000 km) The atmosphere is very thin (120 km) http://www.gsfc.nasa.gov/gsfc/earth/pinatuboimages.htm
6 If the Earth is compared to this Orange the Earth’s atmosphere would be thinner than the layer of pesticide on this Orange’s surface
7 Two Atmosphere Layers Stratosphere is above TroposphereStratosphere is above Troposphere – Ozone Layer blocks UV radiation Troposphere is where we liveTroposphere is where we live – Weather occurs here 72% of all air is below the cruising altitude of commercial airliners (33000 ft)72% of all air is below the cruising altitude of commercial airliners (33000 ft)
Measuring Acid Rain Acid rain is measured using a "pH" scale. – The lower a substance's pH, it is more acidic Pure water has a pH of 7.0 – Normal rain is slightly acidic and has a pH of about 5.6 Any rainfall has a pH value less than 5.6 is defined as acid rain As of the year 2000, the most acidic rain falling in the US has a pH of about 4.3.
Two Forms… Wet Refers to acid rain, fog, sleet, cloud vapor and snow. Dry Refers to acidic gases and particles.
Compounds Two main contributers to acid deposition: Sulfur Dioxide (SO 2 ) Nitrogen Oxides (NO x ) * 66% of all sulfur dioxides and 25% of all nitrogen oxides comes from electric power generation that produces energy by burning fossil fuels.
When gas pollutants e.g. sulfur dioxide, nitrogen dioxide dissolve in rain water, various acids are formed. CO 2 + H 2 O H 2 CO 3 (carbonic acid) SO 2 + H 2 O H 2 SO 3 (sulphorous acid) NO 2 + H 2 O HNO 2 (nitrous acid) + HNO 3 (nitric acid)
Fossil fuels Power plants Industrial emissions Auto emissions Primary Pollutants SO 2 NO 2 Secondary Pollutants H 2 SO 4 HNO 2 sulfuric acidnitric acid soils leaching of minerals vegetation direct toxicity indirect health effects water sediments leaching aluminum acidic precipitation
Wind Transformation to sulfuric acid (H 2 SO 4 ) and nitric acid (HNO 3 ) Nitric oxide (NO) Acid fog Ocean Sulfur dioxide (SO 2 ) and NO Windborne ammonia gas and particles of cultivated soil partially neutralize acids and form dry sulfate and nitrate salts Dry acid deposition (sulfur dioxide gas and particles of sulfate and nitrate salts) Farm Lakes in deep soil high in limestone are buffered Lakes in shallow soil low in limestone become acidic Wet acid deposition (droplets of H 2 SO 4 and HNO 3 dissolved in rain and snow) AcidicPrecipitation
“ Wet” Acid Rain Acidic water flows over and through the ground, it affects a variety of plants and animals.
“Dry” Acid Rain Dry deposition refers to acidic gases and particles. About half of the acidity in the atmosphere falls back to earth through dry deposition. The wind blows these acidic particles and gases onto buildings, cars, homes, and trees. http://svr1-pek.unep.net/soechina/images/acid.jpg
Effects of Acid Rain Has a variety of effects, including damage to forests and soils, fish and other living things, materials, and human health. Also reduces how far and how clearly we can see through the air, an effect called visibility reduction. Effects of acid rain are most clearly seen in the aquatic environments Most lakes and streams have a pH between 6 and 8 http://cica.indiana.edu/projects/Biology/movies.html
In areas where buffering capacity is low, acid rain also releases aluminum from soils into lakes and streams Aluminum is highly toxic to many species of aquatic organisms. http://home.earthlink.net/~photofish/fish_photos/sw10_thumb.jpg
Nutrients Acidic water – dissolves the nutrients and helpful minerals in the soil – washes them away before trees and other plants can use them to grow. Acid rain also causes the release of substances that are toxic to trees and plants, such as aluminum, into the soil.
Effects on Wildlife Generally, the young of most species are more sensitive to environmental conditions than adults. At pH 5, most fish eggs cannot hatch. At lower pH levels, some adult fish die. Some acid lakes have no fish.
Effects on Wildlife Both low pH and increased aluminum levels are directly toxic to fish. In addition, low pH and increased aluminum levels cause chronic stress that may not kill individual fish, but leads to lower body weight and smaller size and makes fish less able to compete for food and habitat.
Acid Rain and Forests Acid rain does not usually kill trees directly. Instead, it is more likely to weaken trees – Damaging their leaves – Limiting the nutrients available to them – Exposing them to toxic substances slowly released from the soil.