Effects of pH on Ecosystems
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Transcript of Effects of pH on Ecosystems
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Effects of pH on EcosystemsEffects of pH on Ecosystems
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Acids and BasesAcids and Bases
• Acids release a hydrogen ion into water (aqueous) solution• Acids neutralize bases in a neutralization reaction
– An acid and a base combine to make a salt and water• Acids corrode active metals • Acids taste sour
– Stomach acid is hydrochloric acid – Acetic acid is the acid ingredient
in vinegar– Citrus fruits such as lemons,
grapefruit, oranges, and limes have citric acid in the juice
– Sour milk, sour cream, yogurt, and cottage cheese have lactic acid from the fermentation of the sugar lactose
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Acids and BasesAcids and Bases
• Bases release a hydroxide ion into water solution • Bases neutralize acids in a neutralization reaction
– Acid plus base makes water plus a salt• Bases denature protein
– Bases are slippery to the touch– Strong bases are very
dangerous because a great amount of the material of humans is made of protein
• Bases taste bitter– There are very few food
materials that are alkaline, but those that are taste bitter
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Acids and Bases Are Measured By pHAcids and Bases Are Measured By pH
• Acids have a low pH (less than 7)
• Bases have a high pH (greater than 7, up to 14)
• Neutral solutions have a pH of approximately 7
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pH Shows the Concentration of HpH Shows the Concentration of H++ Ions Ions
• [H+] is the concentration of hydrogen ions in a solution
• Lots of hydrogen ions = a strong acid
• Very few hydrogen ions = a strong base
Pure water is neutral – the number of H+ ions equals number of OH- ions
Now the solution is acidic – the number of H+ ions is greater than the number of OH- ions
Now, let’s add a strong acid, such as HCl:HCl
H+ Cl-
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pH Shows the Concentration of HpH Shows the Concentration of H++ Ions Ions
• [H+] is the concentration of hydrogen ions in a solution
• Lots of hydrogen ions = a strong acid
• Very few hydrogen ions = a strong base
Pure water is neutral – the number of H+ ions equals number of OH- ions
Now the solution is basic – the number of H+ ions is less than the number of OH- ions
Now, let’s add a strong base, such as NaOH:NaOH
Na+ OH-
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pH Shows the Concentration of HpH Shows the Concentration of H++ Ions Ions
• [H+] is the concentration of hydrogen ions in a solution
• Lots of hydrogen ions = a strong acid– Gastric juice has an H+
concentration of 1 x 10-1, or .1
• Very few hydrogen ions = a strong base– Ammonia has an H+
concentration of 1 x 10-12, or .000000000001
• pH is the negative log of [H+]– As pH gets lower, the [H+]
number gets higher
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Practice Calculating pHPractice Calculating pH
• Determine the pH of a 0.0034 M solution of HNO3
pH = -log[H+] = -log(0.0034) = 2.47
• Determine the pH of a 0.001 M solution of HCl
pH = -log[H+] = -log(0.001) = 3
• Determine the pH of a 0.09 M solution of HBr
pH = -log[H+] = -log(0.09) = 1.05
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Acid RainAcid Rain• Deposited material from the
atmosphere containing higher than normal amounts of nitric and sulfuric acids
• Acid rain formation results from both natural sources and man- made sources – Natural: Volcanoes and
decaying vegetation– Man-made: Emissions of
sulfur dioxide (SO2) and nitrogen oxides (NOx) resulting from fossil fuel combustion
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Acid Rain FormationAcid Rain Formation• Sulfur dioxide and nitrogen oxides are released
when fossil fuels are burned (such as coal)
• SO2 and NOx molecules react in sunlight to create sulfuric acid and nitric acid
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Acid Rain FormationAcid Rain Formation• Some of these particles fall down to the ground as
dry deposition• Other particles mix with water in the clouds, and
the resulting rain has a high acidity due to release of H+ ions
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Major Power Plants Major Power Plants Sources of NOx Emissions and Acid rain
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Nitrogen deposition 1989 - 1991 Nitrogen deposition 1995 - 1998
Nitrogen DepositionNitrogen Deposition
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ION CONCENTRATION ION CONCENTRATION MEASUREMENTS IN RAINMEASUREMENTS IN RAIN
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Affected AreasAffected Areas• Acid rain is a problem in Eastern Canada and the
Northeastern USA• Large smelters in western Ontario and steel processing
plants in Indiana, Ohio use coal as a source of fuel • Acid rain from power plants in the Midwest harms the
forests of upstate New York and New England• The sulfur dioxide is carried eastward by the jet stream
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Sensitive SoilSensitive Soil• If a body of water is surrounded by limestone, that
can act as a buffer to the acid• In many areas water and soil systems lack natural
alkalinity like limestone and cannot neutralize acid
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Surface water sensitivity to Acid DepositionSurface water sensitivity to Acid Deposition
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Acid Rain Kills FishAcid Rain Kills Fish• Acid rain runoff through soil mobilizes metals• Acid reacts with metals such as aluminum
– Normally aluminum is immobile– below pH 5 - mobile aluminum
• Water with mobile aluminum runs off into lakes and streams
• Fish breath in the water, and aluminum clogs gills causing suffocation
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Acid Rain Kills FishAcid Rain Kills Fish
• Fish eggs often will not hatch water with a pH of 5 or less
• Young fish are more sensitive to water acidity than adult fish
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SourcesSources• http://www.chemtutor.com/acid.htm • http://water.me.vccs.edu/courses/env211/lesson7.htm• http://lincoln.pps.k12.or.us/lscheffler/AcidRain.ppt• http://academic.engr.arizona.edu/HWR/Brooks/NATS101sec48/lectures/4-22-
2003.ppt• http://www.nicholas.duke.edu/downloads/psk9/teaching/env279/topic9.ppt• http://www.epa.gov/airtrends/aqtrnd95/no2.html• http://www.epa.gov/acidrain/index.html • http://misterguch.brinkster.net/WKS001_017_424346.pdf • http://misterguch.brinkster.net/PRA027.pdf