Chapter 21 By: Vanessa LaTorre

The pH of Precipitation  Precipitation is naturally acidic – pH 5.2 to 5.6 Due to carbon dioxide in atmosphere Dissolves in water and forms carbonic acid  pH scale measures acidity or alkalinity Scale from 0 to 14 pH 7 neutral, 7 alkaline  Acid precipitation if pH level 5.0 or less

Formation of Acid Precipitation  Volcanic eruptions emit sulfur dioxide With moisture in air forms sulfuric acid  Forest fires/lightning lower pH of precipitation Release nitrogen oxide compounds Mix with moisture in air Forms nitric acid

Anthropogenic Gases  Combustion of fossil fuels: Gasoline, coal, natural gas Adds nitrogen oxides and sulfur dioxide to atmosphere Trucks and automobiles get power from hydrocarbons Gasoline mixes with air and is ignited Burning of a substance is called combustion Forms nitrogen oxide compounds

Anthropogenic Gases (continued)  Coal is burned for energy Contains sulfur Combines with oxygen to form sulfur dioxide  Nitrogen oxides and sulfur dioxide- anthropogenic gases Means human created Rise into atmosphere and combine with water form nitric and sulfuric acids

Anthropogenic Gases (continued)  Acid deposition is different than acid precipitation When dry, nitrogen and sulfur deposited directly Causes a reaction with surrounding environment Leads to the formation of strong acids Also caused by anthropogenic gases

Long-Distance Transport of Acid-Causing Pollutants  Majority of sulfur dioxide comes from the Midwest  90% of all acid precipitation and deposition From sulfur dioxide  Because of prevailing winds west-east Northeast receives greatest amount of acid precipitation

Long-Distance Transport of Acid- Causing Pollutants (continued)  When produced west of Appalachian Mountains Nitrogen oxides/sulfur dioxide rise into atm. Mix with atmospheric moisture (water vapor) Forms acid precipitation By time reaches Appalachian Mountains pH is 4.3 to 4.5

Long-Distance Transport of Acid- Causing Pollutants (continued)  Called long-distance transport of acid precipitation  Similar process in Europe Western Europe creates pollutants Causes precipitation Falls on eastern Europe

Effects of Acid Deposition on Aquatic Ecosystems  Unpolluted ecosystems pH is 6.0 to 8.0  Lakes and ponds exposed experience decreasing pH  Aquatic organisms die at pH 4.0 or lower  Acids that collect also leach heavy metals Mercury, aluminum, and calcium Absorbed by tissues of organisms Cause adverse health effects

Effects of Acid Deposition on Aquatic Ecosystems (continued)  Humans who eat these organisms are also affected Toxic metals build up in human tissue Cause health problems  Worst effect in winter Acidic snow accumulates Spring thaw releases large amounts of acidic water

Effects of Acid Deposition on Aquatic Ecosystems (continued)  Acidic water enters nearby lakes and streams Causes acid shock Acidic water rapidly entering aquatic ecosystem Most adult organisms can survive Younger organisms and eggs are usually killed Natural limestone rock outcrops buffer the acids

Effects of Acid Precipitation on Terrestrial Ecosystems  Many plants and trees are stressed Caused from acids burning leaves and stems Leaves and stems exposed to disease Causes them to loose water  Acids can leach important plant nutrients Potassium, calcium, and magnesium Other nutrients can be released causing damage

Effects of Acid Precipitation on Terrestrial Ecosystems (continued)  Acid precipitation can kill off beneficial organisms Bacteria and fungi that add soil fertility Can also inhibit germination of plant seeds Directly affects agricultural production

Effects of Acid Deposition on Humans  Humans affected by acid precipitation and deposition Consume fish that live in acidic waters May intake toxic heavy metals Affects food production and forest products Timber pulp, and maple sugar Can also cause respiratory illness Irritation of eyes, nose, and throat

Effects of Acid Deposition on Building Materials  Structures and building materials damaged Weathering of concrete and stone is enhanced Bridges, buildings, and concrete structures Slowly dissolved and weakened Stone and brick broken down over time Steel, iron, and copper are corroded Paints, varnish, rubber, and ceramics damaged