ACID
PRECIPITATION
Introduction
Acid precipitation is
any form of precipitation (rain, snow, hail or fog) whose acidity has been
increased through the intake of acid pollutants from the air.
Acid rain is the term
used to describe polluted rainfall (acid
pollution)
acid rain is the
directly linked air pollution. acid rain is becoming a global environmental
problems. it is the transboundary
pollution.
Background:
In 1872,Rober Angus
Smith coined the term 'acid rain' in his book 'air and rain:the beginning of a chemical climatology'.
Smith first found
acid rain in heavily industrialized Manchester ,England in 1852.
He proved that acid rain has connection to pollution in atmosphere.
Driving forces of
acid rain:
1)
Natural
causation of acid rain
a.
Volcanic
Eruption
b.
lightning
c.
Emission
from the vegitatives
2) Artificial cause
a.
Factories
b.
Motor
vehicles and automobiles exhaust
c.
Coal
based power plant
1. Natural causes
a. Volcanic eruption
v olcanic eruptions release water vapor
and gases such as carbon dioxide and monoxide, sulfur dioxide, hydrogen
chloride, hydrogen sulfide, hydrogen fluoride, ammonia, methane and silicon
tetrafluoride. These gases react with water vapor to precipitate as acid rain.
Hydrochloric and hydrofluoric acids, together with other fluoride and chloride
compounds, which build up in large concentrations in the vicinity of the
eruption area, are poisonous to plants and animals, cause skin and eye
irritations and can damage machinery. Sulfur dioxide from a volcano, together
with aerosols, can rise 19 to 32 kilometers (12 to 20 miles) into the
atmosphere and cause a global cooling effect by blocking solar radiation.
b, lightning
Lightning is one of the major sources of localized
atmospheric nitrogen, sulfur and carbon oxides. Lightning bolts reach
temperatures of about 30,000 degrees Celsius (54,000 degrees Fahrenheit) and
can transmit a current of up to 20,000 amps. This is powerful enough to cause
nitrogen and oxygen in the atmosphere to react and create nitrogen oxide and
nitrogen dioxide. The latter dissolves in water vapor to precipitate as weak
nitric acid. Lightning also triggers wildfires that emit carbon and sulfur
oxides into the atmosphere that in turn dissolve in water vapor and precipitate
as carbonic and sulfuric acids.
c. Emissions
from Vegetation
Terrestrial
vegetation produces carbon dioxide as part of the transpiration process and
when rotting on the ground. Aquatic plants and bacteria that exist in anaerobic
-- oxygen-free -- conditions emit methane. Tropical and temperate forests emit
isoprene, a biogenic volatile organic compound. Isoprene is oxidized in the
troposphere and reacts with nitrogen oxides to produce ozone, organic nitrates
and organic acids such as methacrylic and acrylic acids. These acids contribute
to the acidification of rainwater.
2.Artificial causes:
a. Factories
Power
plants release the majority of sulfur dioxide and much of the nitrogen oxides
when they burn fossil fuels, such as coal, to produce electricity. In addition,
the exhaust from cars, trucks, and buses releases nitrogen oxides and sulfur
dioxide into the air. These pollutants cause acid rain
b. Motor vehicles and automobiles exhaust
The emissions of pollutants from vehicles are generally low but
the numbers of vehicles increasing on the road therefore the environmental
pollutions are also increases. About 35% of CO, 30% of HC and 25% percent of
NOx produced into the atmosphere is from the transportation sector.
c. Coal based power plant
The
coal-fired power plants produce smoke that contains harmful gases such as
carbon dioxide and sulfur oxide. From the experiment you should understand that
coal impurities such as sulfur, producing gas sulfur oxide reacts with water in
the atmosphere and come down Earth as acid rain.
Forms
of Acid Deposition
Wet
Deposition
Wet deposition is what we most commonly think of
as acid
rain. The sulfuric and nitric acids formed in the atmosphere
fall to the ground mixed with rain, snow, fog, or hail.
Dry
Deposition
Acidic particles and gases can also deposit from the
atmosphere in the absence of moisture as dry
deposition. The acidic particles and gases may deposit to
surfaces (water bodies, vegetation, buildings) quickly or may react during
atmospheric transport to form larger particles that can be harmful to human
health. When the accumulated acids are washed off a surface by the next rain,
this acidic water flows over and through the ground, and can harm plants and
wildlife, such as insects and fish.
The amount of acidity in the atmosphere that
deposits to earth through dry deposition depends on the amount of rainfall an
area receives. For example, in desert areas the ratio of dry to wet
deposition is higher than an area that receives several inches of rain each
year
pressure of acid
precipitation in the environment
•
Loss
of biodiversity
•
Impact
on ecosystem
•
Pressure
on production or consumption processes.
1.loss of biodiversity
Organisms
vary in their tolerance of acid rain, with some species unable to survive in
water with a pH less than 6.0. ... Acid rain causes a cascade of
effects that harm or kill individual fish, reduce population numbers,
completely eliminate species from a lake, and decrease biodiversity.
2.impact on
ecosystem
Dead or dying trees are a common sight in areas effected by
acid rain. Acid rain leaches aluminum from the soil. That aluminum may be
harmful to plants as well as animals. Acid rain also removes minerals and
nutrients from the soil that trees need to grow
3.pressure on production and
consumption processes.
The
acidic nature of acid rain leaches plant nutrients out of the soil and
can make it less productive for agriculture. ... When the plants absorb water
that normally contains the minerals, they get hydrogen instead and can't grow
as large or as quickly as before. In severe cases, this lack of minerals can
kill the plants.
STATES
Acid Monsoonal Rains in Nepal in August 2008
•
PH of rain between 4.1
and 4.8 (American Geophysical Union)
impact of acid precipitation
1.empact on the
soil
Acid
rain leaches aluminum from the soil. That aluminum may be harmful
to plants as well as animals. Acid rain also removes minerals and nutrients
from the soil that trees need to grow. ... The trees are then less able to
absorb sunlight, which makes them weak and less able to withstand freezing
temperatures.
2.surface water
and acquatic animals
The ecological effects of acid rain
are most clearly seen in the aquatic, or water, environments, such as streams,
lakes, and marshes. Acid rain flows into streams, lakes, and marshes after
falling on forests, fields, buildings, and roads. Acid rain also falls directly
on aquatic habitats. Most lakes and streams have a pH between 6 and 8, although
some lakes are naturally acidic even without the effects of acid rain.
3. effect of Acid rain on Forest,Vegetation
Acid
rain can be extremely harmful to forests. Acid rain that seeps into
the ground can dissolve nutrients, such as magnesium and calcium, that trees
need to be healthy. Acid rain also causes aluminum to be released into the
soil, which makes it difficult for trees to take up water.
4.building and statues
When
acid rain and dry acidic particles fall to earth, the nitric and sulfuric acid
that make the particles acidic can land on statues, buildings, and other
manmade structures, and damage their surfaces. The acidic
particles corrode metal and cause paint and stone to deteriorate more quickly.
5.Empact on the human health
Acid Rain Can
Cause Health Problems in People
Air pollution like sulfur dioxide and nitrogen
oxides can cause respiratory diseases, or can make these diseases worse.
Respiratory diseases like asthma or
chronic bronchitis make it hard for people to breathe. The pollution
that causes acid rain can also create tiny particles. When these particles get
into people’s lungs, they can cause health problems, or can make existing
health problems worse. Also, nitrogen oxides cause ground-level ozone.
This ground-level ozone causes respiratory problems, like pneumonia and bronchitis, and can even cause permanent lung damage. The health
effects that people have to worry about are not caused by the acid rain, but
are caused when people breathe in these tiny particles or ozone. Swimming in an
acidic lake or walking in an acidic puddle is no more harmful to people than
swimming or walking in clean water.
Prevention of acid precipitations
1. Reduce amount of sulphur dioxide and oxides
of nitrogen released into the atmosphere
i.
Use less energy (hence less fuel burnt)
ii.
Use cleaner fuels
iii.
Remove oxides of sulphur and oxides of nitrogen before releasing
(a)
Flue gas desulphurization
(b)
Catalytic Converters
2. Use cleaner fuels
i.
Coal that contains less sulphur
ii.
“Washing” the coal to reduce sulphur content
iii.
Natural Gas
3. Flue Gas Desulphurisation (FGD)
i.
Removes sulphur dioxide from flue gas (waste gases)
ii.
Consists of a wet scrubber and a reaction tower equipped with a fan that
extracts hot smoky stack gases from a power plant into the tower
iii.
Lime or limestone (calcium carbonate) in slurry form is injected into the tower
to mix with the stack gases and reacts with the sulphur dioxide present
iv.
Produces pH-neutral calcium sulphate that is physically removed from the
scrubber
iv.
Sulphates can be used for industrial purposes
4. Use other sources of electricity (i.e.
nuclear power, hydro-electricity, wind energy, geothermal energy, and solar
energy)
i.
Issue of cost
5. Reducing the effects of Acid Rain by Liming
i.
Powdered limestone/limewater added to water and soil to neutralize acid
ii.
Used extensively in Norway and Sweden
iii.
Expensive, short-term remedy
Responces
1.
Cleaning
up Exhaust Pipes and Smokestacks
(Catalytic converters are fixed on the
exhaust pipe system to reduce NOx emission. )
2. Restoring Damaged Environments
3. Alternative energy sourses
4. Individual, National/State, and International
Actions
•
Individual (Uses public transport)
•
National level
A)Legislation
•
Industrial enterprise act (1990)
•
Vehicle and Transport act (1993)
•
Environment protection act (1996)
B) Policies
•
Nepal environmental policy and plan action
(1993) (NEPAP)
International level
•
New England Governors/Eastern Canadian Premiers
Acid Rain Action Plan
1998