Acid Deposition

1

Acid Deposition

• Brief History

• Acids and Bases

• Chemical Processes and Sources

• Deposition Processes

• Acid Deposition Distribution

• Environmental Effects

Health Effects

Lakes and Forests

• Abatement

2

Early History of Acid Deposition

• 1200s: Coal combustion produces SOx and NOx

• 1750s: Industrial Revolution expands use of coal-fired steam engines

• Early 1800s: Alkali factories producing compounds for soap release hydrochloric acid (HCl), some sulfuric acid (H2SO4) and NOx

• 1863 Alkali Act in the UK

3

pH

• pH: index of acidity or alkalinity of a solution

Negative logarithm of the H+ ion concentration

Ex. H2SO4 → 2H+ + SO42–

• Difference of 1.0 in pH equivalent to 10x difference in acidity

pH = 7.0: neutral

pH < 7.0: acidic

pH > 7.0: basic

4

Typical pH Values

1 2 3 4 5 6 7 8 9 10 11 12 13

Neutral

Distilled water LyeVinegar

Natural rain AmmoniaBattery

acidAcid rain

Tomato juice

Cola

beverage

Baking

soda

5

Sulfur ChemistryNatural SO2

SOx → … → SO3,g

Dissolve in

liquid water

Combustion

(oxidizes C, S,

N)

Fossil fuel

(C + S) Sulfuric acid

H2SO4,g/p

SO3,g + H2O,v

H2SO4,aq

SO2

6

Natural Sulfur Sources

Volcanoes

Organic Decay

SO2

H2S → … → SO2

7

Anthropogenic Sulfur

Fossil

Fuels

(C + S)

Coal

1–6% S

Oil

1–2% S

Gas

0.5% S60%

33%

7%

ElectricityIndustrialOther

8

Other Acids

Nitric acid (HNO3)

Organic acids

Hydrogen chloride (HCl)

NO2 + OH

Anthropogenic: Incineration of PVC plastic

Natural: Volcanic emission

Methyl chloride (CH3Cl) from ocean

9

Acid Deposition Processes

• Wet deposition

Acidicgases

Rain, snow scavenging

Runoff

Washout RainoutAcidic gases

Cloud or fog droplets

Acidic gasesWater

coating

10

• Dry deposition

Acidic gases

11

pH of Rain

CO2,g

SOx

H2CO3,aq

Unpolluted

rain

pH ~ 5.6

from carbonic acid

Acid rain

pH < 5

from sulfuric acidH2SO4,aq

12

Regional Transport of AcidsAdirondack Mts.

SW to

NE flow

SO2 source regions

SO2

receptor

region

Local

NOx in

So. Cal.

13

Precipitation pH

14

Precipitation pH

Hydrogen ion concentration as pH from measurements made at the Central Analytical Laboratory, 2009

National Atmospheric Deposition Program/National Trends Network http://nadp.sws.uiuc.edu

Lab pH

5.2 - 5.3 5.1 - 5.2 5.0 - 5.1 4.9 - 5.0 4.8 - 4.9 4.7 - 4.8 4.6 - 4.7 4.5 - 4.6 4.4 - 4.5 4.3 - 4.4 < 4.3

5.3

Sites not pictured:AK01 5.1 AK03 5.1 PR20 5.1 VI01 5.1

#

#

#

#

#

#

#

#

#

#

# #

#

#

#

#

#

#

#

#

#

#

#

# #

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

# #

#

#

#

#

# #

#

# #

#

#

#

##

# #

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

# #

#

#

#

#

#

#

#

# #

# #

# #

##

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

##

# #

#

#

#

#

#

# #

#

#

#

#

#

#

#

#

#

# #

#

#

#

#

#

#

# #

#

##

#

#

# #

#

#

# #

#

# #

#

#

# #

# #

#

#

#

#

#

# #

#

#

# #

#

# #

#

#

# #

5.7

5.0

5.9

5.5

5.45.6

5.3 5.3

5.4 5.5

5.6

5.3 5.0

4.9

4.8

4.9

4.8

4.9

4.7

5.6

4.84.7 5.9

4.7

4.8

5.65.4

5.4 5.5

5.4

5.7

5.3 5.4

4.9

5.7

5.0 4.9

5.0

4.9

5.0

4.8

5.3

5.1

5.5

4.8

4.7

4.9

6.3 5.8

5.3

5.1

5.4

5.4 5.6

5.3

4.8

5.0 5.4

5.0

4.9

4.9

5.4

5.0

4.7

6.1

6.0

5.0

4.9

5.1

5.8

4.8

4.9

5.0

4.8

5.7

5.0

5.7

5.4

5.0

5.1

5.4

5.5

5.3

5.3

5.7

5.45.4

4.8

4.9

5.0

4.9

4.8

4.7

4.9

4.8

5.1

5.4

5.4

5.5

5.8

5.5

5.4

5.4

5.2

6.0

5.2

4.9

4.9

5.1

5.0

5.0

4.8

4.9

5.0 5.1

5.0

5.6

5.7 4.9

5.1

5.0

5.0

5.5 4.9 4.9

4.9

5.4 5.6

4.9 4.9

4.8

5.1 5.1

5.05.0

4.9

5.5

5.25.4

5.7

6.0

5.5

5.1

5.1

5.0

5.3

5.3

5.4

5.6

4.9

5.0

5.0 4.8

5.6

5.86.1

4.8

4.7

5.4

6.0

4.8 4.8

4.8 4.8

4.9

4.8

4.7

4.7 4.6

4.8

5.4

5.5

6.1

5.3

5.4 5.4 5.5

4.7 4.74.6

4.7

4.7

5.8

6.1

4.9

5.0 5.0

5.0

5.5 5.0 5.4

5.4

4.8

5.0

5.0

4.9

4.9

5.2

5.6

5.1 5.2

5.3

5.2

5.4

5.3 5.1

#

#

#

#

#

15

SOx Health Effects

• Effect of SO2 gas on respiratory system (ch. 7)

Taste

Odor

Slight bronchial constriction

Inflammation of mucous membranes

• SO2 + aerosol particles is worse than SO2 alone

16

Freshwater Acidification

High-altitude

Lakes

Low-altitude

Lakes

Water source =

direct precip.

and runoff

Little or

no soil

buffering

East: acidic

granite soil

West: alkaline

limestone soil

Water source

filters through

soil—buffered

17

Freshwater Acidification

High-altitude

Lakes

Low-altitude

Lakes

Water source =

direct precip.

and runoff

Little or

no soil

buffering

East: acidic

granite soil

West: alkaline

limestone soil

Water source

filters through

soil—buffered

18

Effects

19

Effects

20

Effects

21

Effects

• Aquatic plants and fish are stunted, reproduction impaired

• Metallic ions (e.g., aluminum, copper, lead) mobilize and leach from soils into nearby lakes

22

Forest Decline

• Definition: suppression of growth/reproduction rates and death of trees

• Susceptible regions:

Downwind of sulfur sources

• Eastern regions of continents, due to west-to-east prevailing winds

High elevation

• Long-term contact with acidified clouds and fog

• Thinner soils, less buffering

Eastern Europe, Northeastern

U.S., Southeastern Canada

23

24

Recent Regulatory Action

• Clean Air Act Amendments of 1970 (US)

• 1977: National Atmospheric Deposition Program (NADP, US)

• 1979: Geneva Convention ln Long-range Transboundary Air Pollution

1985: Sulfur Protocol

1988: Nitrogen Oxide Protocol

1994: Second Sulfur Protocol

• Clean Air Act Amendments of 1990 (US)

25

AbatementLocate acid

sources downwind

of sensitive areas

26

Abatement

DispersionTaller stacks

27

Abatement

Use low-

sulfur fuels

Oil, gas

Low-sulfur coal

Coal gassification

Solvent-refined coal

Reduce emissions

Scrubbers

Modified

combustion

28

Abatement

Clean-up

Lake and soil buffers

29