Acid Deposition - class.atmos.ucla.educlass.atmos.ucla.edu/AS2/scrns/web notes (turco...
Transcript of Acid Deposition - class.atmos.ucla.educlass.atmos.ucla.edu/AS2/scrns/web notes (turco...
Acid Deposition
• Acids and Bases
• Chemical Processes and Sources
• Deposition Processes
• Acid Deposition Distribution
• Environmental Effects➔ Health Effects
➔ Lakes and Forests
• Abatement
Depositionprocesses Sulfur
sources
Anthropogenic Natural/Biogenic
Rainacidity
pH
Distribution
Threats
Lakes
Forests
Urbaninfrastructure
Studies andpolitics
People
Abatement
Alt. fuels
Alt. energygeneration
Acidchemicalprocesses
Acid Deposition
Reduceemissions
pH• Solution: substance dissolved in water
• p H: index of acidity or alkalinity of asolution
• pH difference of 1.0 is 10· difference inacidity
pH = 7.0: neutral
pH < 7.0: acidic
pH > 7.0: basic or alkaline
Typical pH Values
1 2 3 4 5 6 7 8 9 10 11 12 13
Batteryacid
Colabeverage
Tomato juiceAcid rain
Natural rain
Bakingsoda
Ammonia
Lye
A C I D B A S ENeutral
Vinegar Distilled water
Sulfur Chemistry
Fossil fuel(C + S)
Natural SOX
Combustion(adds O to C
and S)
SOX fi … fi SO3,g
Dissolve inliquid water
H SO2 4,aq
Sulfuric acid
SO3,g H O,2 v+
H SO2 4,g/p
Natural Sulfur Sources
Volcanoes SO2
Organic Decay H S fi … fi SO2 2
Anthropogenic Sulfur
FossilFuels(C+S)
Coal1–6% S
Oil1–2% S
Gas0.5% S
• Electricity• Industrial
• Other
61.70%
31.60%6.70%
Other Acidic SpeciesNO + H O2 2
Nitric acid (HNO )3
Organic acids
Hydrogen chloride (HCl)
Natural
Anthropogenic Incineration ofPVC plastics
Volcanic HCl
Methyl chloride (CH Cl)from ocean
3
Acid Deposition Processes• Wet deposition: liquid water removes
acidic species from atmos.
Acidgases
(Runoff)
Rain, snow scavenging Acid gases
Cloud, fog droplets
Washout
Rainout
Watercoat
Acid
. .
. . . .
. ..
.. .
.. . . . . .
Acid
• Dry deposition: no liquid waterinvolved
pH of Rain
Unpollutedrain
CO2,g
H CO2 3,aq(Carbonic acid)
pH ~ 5.6
SOX
H SO2 4,aq
Acid rain
pH < 5;typ. 4 to 4.5
(Sulfuric acid)
Regional Transport of Acids
SO source regions2
SW to NEflow
SO receptorregion
2
Adirondack Mts.
LocalNOx inSo. Cal.
2
Precipitation pH, 1996
SO Health Effects
• Effect of SO gas on respiratorysystem (ch. 7)
2
➔ Taste
➔ Odor
➔ Slight Bronchial constriction
➔ Inflammation of mucous membranes
• SO + aerosol particles worsethan SO alone
22
X
High-altitudelakes
Low-altitudelakes
Water sourcefilters thru
soil; buffered
Little orno soi l
buffering
Water source =direct precip.
and runoff
West: alkalinelimestone soi l
East: acidicgranite soi l
Freshwater Acidification
Feedback
• Effects
➔ Aquatic plants and fish stunted,reproduction impaired
➔ Metallic ions (e.g., aluminum,copper, lead) leach from soils intolakes
Growth/reproduction ratesuppression ordeath of trees
Susceptible regions?
Downwindof sulfursources
Highelevation
Eastern regionsof continents(west-to-eastprevail ing wind)
Long-term contactwith acidifiedclouds/fog
Thinner soils,less buffering
E. Europe, NE U.S., SE Canada
Forest Decline
Abatement
Dispersion
Locatedownwind, notupwind ofsensitive areas
Tal ler stacks
Abatement
Low-sulfur fuel
Oil, gasLow-sulfurcoal
Solvent-refined coal
Coal gassification
Abatement
Reduce emissions
Modifiedcombustion
Scrubbers
Abatement
Lake andsoil buffers
Clean-up