ap environmental science

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AP Environmental ScienceAP Environmental Science

Acid Acid RainRain

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This is the Island known as Earth

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Background Background InformationInformation

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AtmosphereAtmosphere

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Earth’s AtmosphereEarth’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

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If theIf the EarthEarth is is compared to thiscompared to this

OrangeOrange

the Earth’s the Earth’s atmosphere atmosphere would be would be

thinner than the thinner than the layer of layer of

pesticide onpesticide on this this Orange’s Orange’s surfacesurface

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Two Atmosphere Two Atmosphere LayersLayers

• Stratosphere is above Stratosphere is above Troposphere Troposphere –Ozone Layer blocks UV radiation Ozone Layer blocks UV radiation

• Troposphere is where we liveTroposphere is where we live–Weather occurs hereWeather occurs here

• 72% of all air is below the 72% of all air is below the cruising altitude of commercial cruising altitude of commercial airliners (33000 ft)airliners (33000 ft)

Measuring Acid RainMeasuring 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…Two Forms…

Wet

Refers to acid rain, fog, sleet,

cloud vapor and snow.

• Dry

Refers to acidic gases and particles.

CompoundsCompounds

Two main contributers to acid deposition:

• Sulfur Dioxide (SO2)

• Nitrogen Oxides (NOx)

* 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.

CO2 + H2O H2CO3 (carbonic acid)

SO2 + H2O H2SO3 (sulphorous acid)

NO2 + H2O HNO2 (nitrous acid) + HNO3 (nitric acid)

Fossil fuelsPower plants

Industrial emissions

Auto emissions

Primary PollutantsSO2

NO2

Secondary Pollutants

H2SO4 HNO2

sulfuric acid nitric acid

soilsleaching of minerals

vegetationdirect toxicity

indirect health effects

water

sedimentsleaching

aluminum

acidic precipitation

Wind

Transformation tosulfuric acid (H2SO4)

and nitric acid (HNO3)

Nitric oxide (NO)

Acid fog

Ocean

Sulfur dioxide (SO2)and NO

Windborne ammonia gasand particles of cultivated soilpartially neutralize acids and

form dry sulfate and nitrate salts

Dry aciddeposition

(sulfur dioxidegas and particles

of sulfate andnitrate salts)

Farm

Lakes indeep soil

high in limestoneare buffered

Lakes in shallowsoil low inlimestonebecomeacidic

Wet acid deposition(droplets of H2SO4 andHNO3 dissolved in rain

and snow)

AcidicAcidicPrecipitationPrecipitation

““Wet” Acid Wet” Acid RainRain

Acidic water flows over and

through the ground, it affects

a variety of plants and animals.

““Dry” Acid RainDry” Acid Rain

• Dry deposition refers to acidic gases and particles.

• About half of the acidity in theatmosphere 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 RainEffects 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

NutrientsNutrients• 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 Effects on WildlifeWildlife• 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 Effects on WildlifeWildlife

• 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 Acid Rain and ForestsForests

• 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.

GermanyGermanyMongoliaMongolia

Great Smoky Mountains, NC

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Sulfate Ion Concentrations1985-2004

198519861984

http://nadp.sws.uiuc.edu/amaps2/

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198619871985

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198719881986

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198819891987

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198919901988

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199019911989

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199119921990

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199219931991

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199319941992

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199819991997

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199920001998

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200420052003

Sulfate Ion Concentrations1985-2004