1. E2 Acid Deposition
Rain Water

2. E2.1 State what is meant by Acid deposition and Outline It’s origins
E 2 Acid Deposition
E2.1 State what is meant by Acid deposition and
Outline It’s origins

3. Acid Deposition: The Problem Continues

4. What Ever Happened to Acid Deposition?
In the 1980’s, acid rain received a lot of media attention.

7. What is Acid Deposition? How Does it Form?
Acidic particles and gases that deposit on earth as precipitation by rain, fog, snow
Includes wet deposition of acidic gases
NOx and SOx
Dry deposition of acidic gases and particles in absence of rain

8. Acid Deposition
Precipitation with a pH lower than 5.6 is considered acidic
2.5 x mol dm-3 [H+] due to dissolved CO2 in water vapor

9. Carbonic Acid
CO2 (g) H2O (l) H2CO3(aq)
H2CO H+ (aq) + HCO3-(aq)

11. Acid Rain pH is a logarithmic scale
One pH unit correspond to factor of 10
Compare pH 5.6 and pH 4.2
pH 4.2 has 25 times more H ion concentration
Acid rain: pH 4 – 5 is common

12. Acid Rain in Los Angles pH = 1.7 1982 Dec
Oxides of N, S ( non-metals) /cause of acid deposition
Snow, fog, sleet, hail, drizzles become acidic in presence of S, N oxides

16. Los Angles

18. Acid Rain Dead Lakes in North America, China, Russia; pH 4.0
Kills fish
pH could be measured by pH paper, pH meter, universal indicator

19. Origin of Acid Rain from sulfur dioxide and nitrogen oxide particles
Once these particles are emitted into the air they form sulfate and nitrate particles
These particles can travel long distances on wind currents
By combining with water vapor, these particles form acids which fall to the earth as acid rain. : fog, sleets, hail, drizzles

20. Where do Sulfur Dioxide (SO2) and Nitrogen Oxide (NOx) Particles Come From?
Sulfur dioxide and nitrogen dioxide particles are emitted from utility plants, especially coal-fed electric plants
Automobiles also emit acid rain causing pollution

21. Formation Of Acid Deposition
In the presence of moisture, Sox produce
Acids
SO2(g) + H2O(l) H2SO3(aq)
Weak acid
SO2(g) + ½ O2(g) SO3(g)
2SO2(g) + O2(g) + 2H2O(l) H2SO4(aq)
SO3(g) + H2O(l) H2SO4(aq)
Strong acid

22. Acid Deposition : Nitrogen Oxides
NO2 gas: reddish-brown
Poisonous, highly reactive
4 NO2(g) + 2 H2O(l) + O HNO3(aq)
2 NO2(g) + H2O(l) HNO3(aq) HNO3(aq)
NO2(g) OH (g) HNO3 (aq)
Formed during photochemical smog

23. E 2.2 Environmental Effects
Affects humans and aquatic life
Dissolution of limestone
Corrosion of metals
Deterioration of electrical equipment
Vegetation, soil, visibility

24. 1. Effects of Acid Rain on Humans
Respiratory system irritation by breathing fine acid droplets
Severe eye irritation
Sulfate aerosol are powerful irritants
Penetrates lungs/ remain embedded and have severe asthmatic effect on young and elderly

25. Effects on Humans due to acidic conditions Alzheimer disease
Increased concentration of Al 3+ in water
due to acidic conditions
Alzheimer disease

26. Effect on Aquatic life Kills fish,
At pH 5, most fish eggs cannot hatch.
Salmon can not survive in pH ~ 5.5
Increase concentration of Al3+ ions affects the function of the gills.
Al3+ ions come from leaching of soil by acidic rain

27. Effect on Aquatic life
Eutrophication :
Nitrates from acid deposition

28. Effect on materials
Corrosion of basic materials, limestone and dolomite CaCO3 MgCO3
CaCO3(s) + H2SO4(aq)
CaSO4(aq) H2O(l) CO2(g)
Sulfates can dissolve in water
Structural damage / stone leprosy
Eg in Egypt, Greece, Mexico, Turkey

30. Effect on materials Corrosion of iron and steel promoted by acid rain
with increased
humidity,
high temperature,
presence of particulates
4 Fe(s) + x H2O(l) + 3O2(g)
2 Fe2O3.xH20(s)

31. Effect on materials
Deterioration of electrical equipment as a result of corrosion
Bleaching and weakening of paper fabric, leather
Leach heavy metals such as lead, cadmium and mercury in water system

32. Environmental Effects
Bleaching and weakening of fabric and leather
Discoloration of paper
Acute and chronic effects on plants
Significant decrease in crop yields

33. Material Damage carbon-steel, nickel, zinc, copper, paint,
some plastics,
paper, leather and textiles.
Stainless steel and aluminum are more resistant to acid rain.

34. Material Damage Structural damage to underground pipes, cables
and foundations submerged in acid waters can also occur,
in addition to damage to buildings, bridges and vehicles above ground

35. Effect on Soil and Vegetation
Plants damage by acid concentration
Length of exposure
Acute injury due to short term exposure to high conc. Acid rain
Attack on cells producing dead leaves

36. Effects on Vegetation Chronic injury
Long term exposure to even low acid concentration
Disrupts chlorophyll synthesis
Yellowing of leaves due to acid entering stomata of leaves
Bleached spots, suppression of plant growth, reduction in yield

37. Effects on Vegetation Removes important nutrient from soil Eg. Mg 2+
It is an essential mineral nutrient for life[1][2][3] and is present in every cell type in every organism.

39. Chlorophyll
Mg 2+

41. chlorophylls : effective photoreceptors
contain a network of alternating single and double bonds, ( conjugated)
Electron can delocalize stabilizing the structure.
Such delocalized poly-enes have very strong absorption bands in the visible regions of the spectrum,
allowing the plant to absorb the energy from sunlight.

42. Effects on visibility
Mist of sulfuric acid and sulfate aerosol cause great loss of visibility
Curtail air flights
Aerosol particles modify Earth's radiation budget. They are also linked to adverse health effects.

44. atmospheric particles enriched in sulfate (green) and methane sulfonate (blue) typical for a marine environment

45. Relative humidity

47. Controlling Acid Deposition
Reduction of SOX and NOX
Reduction of SO2 emission: E1.2
Use of catalytic convertor
Lean burn engines
. use of low –sulfur, cleaner burning coal
Anthracite / high heat content

48. Coal
low grade( sub bituminous) coal and lignite of low sulfur content does not produce much heat
due to lower carbon content ( ~ more of coal needs to burn)

49. 2.Coal to SNG Conversion process allows removal of SO2
30 % energy required

50. Cleaning Coal Before combustion / pre combustion
Coal is finely ground and washed with water
Iron pyrite settles down because of higher density
Organic sulfur can not be removed
Process is expensive (50 % S removal )

51. 4.Post Combustion Method
Lean burn engine
Catalytic converter
CO (g) NO(g) CO2(g) + N2
Using Limestone fluidized beds
Alkaline scrubbing

52. Promoting use of alternative energy sources
Solar,
wind,
fuel cells,
hybrid automobiles
Increased public transportation
Addition of lime to soil and lakes to neutralize acidity

53. Can We Do Anything About Acid Rain?
YES! We can all take small actions to help solve the problem
We can help by:
using our cars less
conserving electricity
choosing electricity providers that emit lower amounts of air pollution emissions

58. How Does Acid Rain Effect Our Lives?
Poor forest health due to acidification of soil: acid rain can kill nutrient-producing microorganisms
Acidification of lakes and streams can lead to the death of aquatic life, such as trout and bass
Acidity can leach mercury out of the soil, causing toxic levels to build up in the fish we eat
Acid rain can erode buildings and monuments and destroy paint finishes

59. What else needs to be done about Acid Rain ?
In 1990, an amendment to the Clean Air Act called for reductions in sulfur emissions
This proved to be less effective than hoped, as acid rain still persists today
This is largely due to 2 reasons:
1) reductions in sulfur emissions were not great enough and
2) there were no reductions in nitrogen emissions which are also implicated in forming acid rain

60. What is Being Done About Acid Rain?
An International Acid Rain Steering Committee was formed and is currently discussing joint action to further reduce sulfur emissions by 50% and
reduce nitrogen emissions by 30% by the year 2010

66. Ozone