Presentation Slides for
Air Pollution and Global Warming:
History, Science, and Solutions
Chapter 10: Acid Deposition
By Mark Z. Jacobson
Cambridge University Press (2012)
Last update: February 23, 2012
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internet and are provided to facilitate their display during course instruction.
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the textbook.
History of Acid Deposition
1200s. Coal used in lime kilns and forges produces sulfur and nitrogen
oxides that result in sulfuric and nitric acid deposition.
1750s. Expanded use of the steam engine at the beginning of the
Industrial Revolution increases sulfuric and nitric acid deposition.
1783. French Academy of Sciences offers a prize to a person who finds
the most efficient and economical method to produce soda ash
Na2CO3(aq), which along with animal fat, is used to make soap.
1789. Nicolas LeBlanc develops two-step soda ash process.
The Rise of Alkali Factories
Soda ash
+ Animal fat
=
Soap
www.nutritionfx.com
Img.alibaba.com
Keetsa.com
LeBlanc Process
High
temperature
2NaCl(s) + H2SO 4(aq)
Na2SO 4(aq) + 2HCl(g)
Sodium
Sulfuric
Sodium
Hydrochloric
chloride (salt)
acid
sulfate
acid
High
temperature
Na2SO 4(aq) + 2C + CaCO 3(s)
Na2CO3(aq) + CaS(s) + 2CO 2(g)
Sodium Carbon Calcium
Sodium
Calcium
Carbon
sulfate
from
carbonate
carbonate
sulfide
dioxide
charcoal from chalk
(10.1) - (10.2)
Sulfuric acid produced by burning sulfur and saltpeter in water
7S(s)+6KNO3(s)+4H2O(aq) --> 3K2S(s)+6NO(g)+4H2SO4(aq)
Byproducts of Leblanc Process
HCl(g)
evaporated H2SO4(g)
NO(g), which produces HNO3(g)
Soot (C)
CO2(g)
--> widespread acid deposition due mostly to HCl(g)
CaS(s), yellow-gray powder, forms hydrogen sulfide and gypsum
CaS(s) + H2O(aq) --> CaO(s) + H2S(g)
CaS(s) + O2(g) + 3H2O(aq) --> CaSO4-2H2O(s) + H2(g)
Piles of gypsum (galligu) still exist near old soda-ash factories.
Gypsum/Galligu Piles
Halton Borough Council, UK
Gypsum/Galligu Piles
www2.halton.gov.uk
The Rise of Alkali Factories
Widnes in Cheshire, 1800s, under cloud of LeBlanc Process
Halton Borough Council, UK
History of Acid Deposition
1791. LeBlanc patents technique
1793. Loses patent to the state during French Revolution
1806. LeBlanc commits suicide
1838. Liverpool landowner files complaint against an alkali
factory: destroyed crops and interfered with hunting.
Early 1860s. William Gossage, who built alkali factory in 1830,
develops scrubber for HCl(g) by converting a windmill into
a tower, filling tower with brushwood, and letting water
drip down the brush as smoke rose from the bottom.
HCl Scrubber Today
www.engpro.com
History of Acid Deposition
1861. Ernst Solvay (1838-1922) develops another way to form
soda ash, but it replaces Leblanc process only by 1880s.
1863. Due to devastation from Alkali factories and Gossage’s
scrubber, the 1863 Alkali Act passes in the U.K.
France. Regulation takes the form of planning laws controlling
location of alkali factories.
1866, 1868. Inventions allow chlorine to be recycled for
bleaching powder.
1881. U.K. Alkali Act is modified since significant pollution of
other chemicals from alkali factories still occurs.
Solvay Process
1861. Solvay rains a salt made of sodium chloride and
ammonium down a tower over an upcurrent of CO2(g). Only
inputs: limestone, salt. Only byproduct: calcium chloride.
Production of carbon dioxide
CaCO3(s) + heat --> CaO(s) + CO2(g)
Production of sodium bicarbonate
NaCl(s)+NH3(g)+CO2(g)+H2O(aq)-->NaHCO3(aq)+NH4Cl(s)
Production of sodium carbonate, recycling of carbon dioxide
2NaHCO3(aq) + heat --> Na2CO3(aq) + H2O(aq) + CO2(g)
Recycling of ammonia
2NH4Cl(s) + CaO(s) --> 2NH3(g) + CaCl2(s) + H2O(aq)
Robert Angus Smith (1817-1884)
Library and Information Centre, Royal Society of Chemistry
Acidity
Measure of the concentration of hydrogen ions (H+) in solution
pH = -log10[H+]
[H+] = molarity (M, moles of H+ per liter of solution)
Higher [H+] --> lower pH --> more acidic solution
(10.3)
Acidity
In dilute water, the only source of H+ is
H2O(aq)
Liquid
water
H+ + OHHydrogen Hydroxide
ion
ion
[H+][OH-] = 10-14 M2 --> [H+]=[OH-]=10-7 M
--> pH = -log10[10-7M] = 7
(10.4)
Acid/Base
Acid
Substance that, when added to a solution, dissociates,
increasing [H+], decreasing pH
Strong acid: Substances that dissociate readily
(e.g., H2SO4, HCl, HNO3)
Weak acids: Substances that dissociate less readily
(e.g., H2CO3)
Base (alkalis)
Substances that, when added to a solution, reduce [H+],
increasing pH. (e.g., NH3(aq), Ca(OH)2(aq))
pH Scale
Acid
rain, fog
(2-5.6)
pH
0
1
2
Battery Lemon
acid
juice
(1.0)
(2.2)
3
Natural
rainwater
(5-5.6)
4
Apples
(3.1)
Vinegar
CH3COOH(aq)
(2.8)
More acidic
5
6
Sea
water
(7.8-8.3)
7
8
9
10
Distilled
water
(7.0)
Milk
(6.6)
Baking
soda
NaHCO3(aq)
(8.2)
11
12
13
14
Ammonium
Lye
hydroxide
NaOH(aq)
NH4OH(aq)
(13.0)
(11.1)
Slaked lime
Ca(OH)2(aq)
(12.4)
More basic or alkaline
Figure 10.3
pH of Food
Lime
Lemon
Apple
Apple juice
Tomato juice
Buttermilk
Banana
Cheddar cheese
Beef
Cabbage
Asparagus
Milk
Crab
Egg white
1.9
2.1-2.2
2.9-3.3
4.0
4.4
4.5
4.6
5.3
5.5
5.7
5.9
6.4-6.6
7.0
8.0
Acid Dissociation
Addition of acid to solution increases [H+], decreasing pH
Carbonic acid
CO2(aq) + H2O(aq)
Dissolved Liquid
carbon dioxide water
H2CO3(aq)
Dissolved
carbonic acid
H+ + HCO32H+ + CO32Hydrogen Bicarbonate Hydrogen Carbonate
ion
ion
ion
ion
Sulfuric acid
H2SO4(g)
Sulfuric
acid gas
H2SO4(aq)
Dissolved
sulfuric acid
H+ + HSO4Hydrogen Bisulfate
ion
ion
2H+ + SO42Hydrogen Sulfate
ion
ion
(10.5) - (10.6)
Acid Dissociation
Hydrochloric acid
HCl(g)
HCl(aq)
H+ + ClHydrogen Chloride
Hydrochloric
Dissolved
ion
ion
acid gas
hydrochloric acid
Nitric acid
HNO3(g)
Nitric
acid gas
HNO3(aq)
Dissolved
nitric acid
H+ + NO3Hydrogen Nitrate
ion
ion
(10.7) - (10.8)
S(IV) and S(VI) Families
S(IV) Family
Sulfur dioxide
SO2(g,aq)
S(VI) Family
S
O
O
O
O
Sulfurous acid
H2SO3(aq)
S
HO
OH
O
Bisulfite ion
HSO3-
S
HO
Sulfite ion
SO32-
Table 10.1
O
O
S
O
O
Sulfuric acid
H2SO4(g,aq)
O
Bisulfate ion
HSO4-
O
Sulfate ion
SO42-
S
OH
OH
O
S
O
OH
O
O
S
O
O
Mechanisms of Converting
S(IV) to S(VI)
Why is converting to S(VI) important?
It allows sulfuric acid to enter or form within cloud drops
and aerosol particles, increasing their acidity
Mechanisms
1. Gas-phase oxidation of SO2(g) to H2SO4(g) followed by
condensation of H2SO4(g)
2. Dissolution of SO2(g) into liquid water to form
H2SO3(aq) and its dissociation products, which convert
chemically to H2SO4(aq) and its dissociation products.
Gas-Phase Oxidation of S(IV) to
S(VI)
+ OH(g), M
SO 2(g)
HSO3(g)
Sulfur
dioxide
Bisulfite
+ O2(g)
HO2(g)
+ H2O(g)
SO 3(g)
H2SO 4(g)
Sulfur
trioxide
Sulfuric
acid
(10.9)
Aqueous-Phase Oxidation of S(IV)
Step 1. S(IV) dissolution and dissociation
SO2(g)
SO2(aq)
Sulfur
dioxide
gas
Dissolved
sulfur
dioxide
SO 2(aq) + H2O(aq)
H2SO 3(aq)
Dissolved Liquid
sulfur
water
dioxide
Sulfurous
acid
H+ + HSO3Hydrogen Bisulfite
ion
ion
2H+ + SO32Hydrogen Sulfite
ion
ion
(10.10) - (10.11)
Aqueous-Phase Oxidation of S(IV)
Step 2. S(IV) oxidation by hydrogen peroxide in solution
HSO3- + H2O2(aq) + H+
Bisulfite Dissolved
ion
Hydrogen
peroxide
SO42- + H2O(aq) + 2H+
Sulfate
ion
Alternate Step 2. S(IV) oxidation by ozone in solution
SO 32- + O3(aq)
Sulfite
ion
Dissolved
ozone
SO 42- + O2(aq)
Sulfate Dissolved
ion
oxygen
(10.12) - (10.13)
Production of Nitric Acid Gas
M
OH(g) + NO2(g)
Hydroxyl Nitrogen
radical
dioxide
HNO3(g)
Nitric
acid
(10.14)
Effects of Acid Deposition
Lakes and streams
Lake pH decreased 1 pH unit between the 1950s and 1960s
in Scandinavia. 25,000 out of 90,000 lakes in Sweden were
acidified in the 1970s. 17,000 of these were due to
anthropogenic pollution.
Fish and microorganisms are sensitive to pH.
Plants
Acids damage trees at their roots and erodes cuticle wax.
Acidified water carries away minerals.
Acids release metals Al3+, Fe3+ from the minerals
Al(OH)3(s), Fe(OH)3(s). Metals are toxic to roots.
Prunerov Power Plant, Sulfur
Triangle, 2005
www.chmi.cz
Dead Norway Spruce, Bohemian
Forest, Czech Republic, 2005
www.chmi.cz
Dead Norway Spruce, Nacetin
Forest, Czech Republic, 1995
www.chmi.cz
Dead Spruce, Mt. Mumlava,
Czech Republic
www.chmi.cz
Acidified forest near Most,
Czechoslovakia (1987)
Owen Bricker, United States Geological Survey
Acidified Forest, Oberwiesenthal,
Germany (1991)
Stefan Rosengren/Naturbild
Acidified Creek, New South
Wales, 2007
www.ramsar.org
Neutralizing Acids
Add ammonium hydroxide to a lake
NH4OH(aq) + H+
Ammonium Hydrogen
hydroxide
ion
NH4+ + H2O(aq)
Ammonium Liquid
ion
water
Add slaked lime to a lake
Ca(OH)2(aq) + 2H+
Calcium Hydrogen
hydroxide
ion
Ca2+ + 2H2O(aq)
Calcium Liquid
ion
water
Calcium carbonate is a natural neutralizing agent in soil
CaCO3(s) + 2H+
Calcium Hydrogen
carbonate
ion
Ca2+ + CO2(g) + H2O(aq)
Calcium Carbon
Liquid
ion
dioxide
water
gas
(10.15) - (10.17)
Liming of a Lake in Sweden
Tero Niemi / Naturbild
Neutralizing Acids
Sea salt is a natural neutralizing agent near the coast
NaCl(s) + H+
Sodium Hydrogen
chloride
ion
Na+ + HCl(g)
Sodium Hydrochloric
ion
acid
Ammonia is a neutralizing agent
NH3(aq) + H+
Dissolved Hydrogen
ammonia
ion
NH4+
Ammonium
ion
(10.19) - (10.20)
Visibility Trend Sulfur Triangle
Stjern et al. (2011)
1994
U.S.
Rainwater
pH
2009
U.S. National Atmospheric Deposition Program/National Trends Network
Effects of Acid Deposition
Materials
The addition of sulfuric acid to marble or limestone
produces gypsum, which forms a crust that creates pits
when rain loosens the crust.
Crusting of marble and limestone
CaCO3(s) + 2H+
Ca2+ + CO2(g) + H2O(aq)
Calcium Hydrogen
Calcium Carbon
Liquid
carbonate
ion
ion
dioxide
water
gas
CaSO 4-2H2O(s)
Ca2+ + SO42- + 2H2O(aq)
Calcium Sulfate
Liquid
Calcium sulfate
ion
ion
water
dihydrate (gypsum)
(10.17) - (10.18)
Cathedral of Learning,
Pittsburgh, 1930 and 1934
University Archives, University of Pittsburgh
Sandstone Figure in 1908 and
1968, Westphalia, Germany
Herr Schmidt-Thomsen
Recent Regulation of Acid Deposition
1970. U.S. Clean Air Act Amendments
1977. U.S. National Atmospheric Deposition Program
1979. Geneva Convention on Long-Range Transboundary Air
Pollution
1985. Sulfur Protocol
1988. Nitrogen Oxide Protocol
1990. U.S. Clean Air Act Amendments
1994. Second Sulfur Protocol
Methods of Controlling Emission
Use of low-sulfur coal
Remove sulfur from high-sulfur coal
Advanced scrubbers (e.g., flue-gas desulfurization)