e2 acid deposition rain water
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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 originsTRANSCRIPT
E2 Acid Deposition Rain Water E2.1 State what is meant by Acid
deposition and Outline Its origins
E 2 Acid Deposition E2.1Statewhat is meant by Acid deposition and
Outline Its origins Acid Deposition: The Problem Continues What
Ever Happened to Acid Deposition?
In the 1980s, acid rain received a lot of media attention. 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
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 Carbonic Acid CO2 (g) H2O (l) H2CO3(aq) H2CO H+ (aq)+
HCO3-(aq) Acid Rain pH is a logarithmic scale
One pH unitcorrespond 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 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 ofS, N oxides Los
Angles 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 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
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 Formation Of Acid
Deposition
In the presence of moisture, Soxproduce Acids SO2(g) +H2O(l)
H2SO3(aq) Weak acid SO2(g) + O2(g) SO3(g) 2SO2(g) + O2(g)+ 2H2O(l)
H2SO4(aq) SO3(g) +H2O(l) H2SO4(aq) Strong acid 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 E 2.2 Environmental
Effects
Affects humans and aquatic life Dissolution of limestone Corrosion
of metals Deterioration of electrical equipment Vegetation, soil,
visibility 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 Effects on Humans due to acidic conditions
Alzheimer disease
Increased concentration of Al 3+ in water due to acidic conditions
Alzheimer disease 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
Effect on Aquatic life Eutrophication : Nitrates from acid
deposition Effect on materials Corrosion of basic materials,
limestone and dolomite CaCO3MgCO3 CaCO3(s) +H2SO4(aq) CaSO4(aq)
H2O(l) CO2(g) Sulfates can dissolve in water Structural damage /
stone leprosy Egin Egypt, Greece, Mexico, Turkey 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) Effect on materials
Deterioration of electrical equipment as a result of corrosion
Bleaching and weakening of paperfabric, leather Leach heavy metals
such as lead, cadmium and mercury in water system Environmental
Effects
Bleachingand weakening of fabric and leather Discoloration of paper
Acute and chronic effects on plants Significant decrease in crop
yields Material Damage carbon-steel, nickel, zinc, copper,
paint,
some plastics, paper, leather and textiles. Stainless steel and
aluminum are more resistant to acid rain. 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
Effect on Soil and Vegetation
Plants damage by acidconcentration Length of exposure Acute injury
due to short term exposure to high conc. Acid rain Attack on cells
producing dead leaves 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 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. Chlorophyll Mg 2+
chlorophylls : effective photoreceptors
contain a network of alternating single and double bonds, (
conjugated) Electron candelocalize 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. 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. atmospheric particles
enriched in sulfate (green) and methane sulfonate (blue) typical
for a marine environment Relative humidity 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 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) 2.Coal to SNG Conversion process allows removal of SO2
30 % energy required 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 ) 4.Post Combustion
Method
Lean burn engine Catalytic converter CO (g) NO(g) CO2(g) +N2 Using
Limestone fluidizedbeds Alkaline scrubbing 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 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 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 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 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 Ozone