Air pollution disaster management
Air pollution is the introduction of
chemicals, particulate matter, or biological materials that cause harm or
discomfort to humans or other living organisms, or cause damage to the natural
environment or built environment, into the atmosphere.
Pollutants
Major
primary pollutants (directly emitted from a process) activity include:
·
Sulfur oxides (SOx) - SO2
is produced by volcanoes and in various industrial processes. Since coal and
petroleum often contain sulphur compounds, their combustion generates sulfur
dioxide.
·
Nitrogen oxides (NOx) -
Can be seen as the brown haze dome above or plume downwind of cities.
·
Carbon monoxide - is a colourless,
odorless, non-irritating but very poisonous gas. It is a product by incomplete
combustion of fuel such as natural gas, coal or wood. Vehicular exhaust is a
major source of carbon monoxide.
·
Carbon dioxide (CO2) - a
colourless, odorless, non-toxic greenhouse gas associated with ocean
acidification, emitted from sources such as combustion, cement production, and
respiration
·
Volatile organic compounds – (VOCs)
Methane (CH4) and non-methane (NMVOCs). Methane is an extremely
efficient greenhouse gas which contributes to enhanced global warming. Other
hydrocarbon VOCs are also significant greenhouse gases via their role in
creating ozone and in prolonging the life of methane in the atmosphere,
although the effect varies depending on local air quality. Within the NMVOCs,
the aromatic compounds benzene, toluene and xylene are suspected carcinogens
and may lead to leukemia through prolonged exposure. 1,3-butadiene is another
dangerous compound which is often associated with industrial uses.
·
Particulate matter - Particulates,
alternatively referred to as particulate matter (PM) or fine particles, are
tiny particles of solid or liquid suspended in a gas. Increased levels of fine
particles in the air are linked to health hazards such as heart disease,
altered lung function and lung cancer.
·
Persistent free radicals connected to
airborne fine particles could cause cardiopulmonary disease.
·
Toxic metals, such as lead, cadmium
and copper.
·
Chlorofluorocarbons
(CFCs) - harmful to the ozone
layer emitted from products currently
banned from use.
·
Ammonia
(NH3) - emitted from agricultural processes. Ammonia is a compound
with the formula NH3. It is normally encountered as a gas with a
characteristic pungent odor. Ammonia contributes significantly to the
nutritional needs of terrestrial organisms by serving as a precursor to
foodstuffs and fertilizers. Ammonia, either directly or indirectly, is also a
building block for the synthesis of many pharmaceuticals. Although in wide use,
ammonia is both caustic and hazardous.
·
Odors — such as from garbage,
sewage, and industrial processes
·
Radioactive pollutants - produced by
nuclear explosions, war explosives, and natural processes such as the
radioactive decay of radon.
Secondary
pollutants (Secondary pollutants are not
emitted directly. Rather, they form in the air when primary pollutants react or
interact) include:
·
Particulate matter formed from
gaseous primary pollutants and compounds in photochemical smog. Smog is a kind
of air pollution. Classic smog results from large amounts of coal burning in an
area caused by a mixture of smoke and sulfur dioxide. Modern smog does not
usually come from coal but from vehicular and industrial emissions that are
acted on in the atmosphere by ultraviolet light from the sun to form secondary
pollutants that also combine with the primary emissions to form photochemical
smog.
·
Ground level ozone (O3)
formed from NOx and VOCs. Ozone (O3) is a key constituent
of the troposphere. It is also an important constituent of certain regions of
the stratosphere commonly known as the Ozone layer. Photochemical and chemical
reactions involving it drive many of the chemical processes that occur in the
atmosphere by day and by night. At abnormally high concentrations brought about
by human activities (largely the combustion of fossil fuel), it is a pollutant,
and a constituent of smog.
·
Peroxyacetyl nitrate (PAN) -
similarly formed from NOx and VOCs.
·
Persistent organic pollutants (POPs)
are organic compounds that are resistant to environmental degradation through
chemical, biological, and photolytic processes. Because of this, they have been
observed to persist in the environment, to be capable of long-range transport,
bioaccumulate in human and animal tissue, biomagnify in food chains, and to
have potential significant impacts on human health and the environment.
Sources
Sources
of air pollution refer to the various locations, activities or factors which
are responsible for the releasing of pollutants into the atmosphere. These
sources can be classified into two major categories which are:
Anthropogenic
sources (human activity) mostly
related to burning different kinds of fuel
·
"Stationary Sources"
include smoke stacks of power plants, manufacturing facilities (factories) and
waste incinerators, as well as furnaces and other types of fuel-burning heating
devices
·
"Mobile Sources" include
motor vehicles, marine vessels, aircraft and the effect of sound etc.
·
Chemicals,
dust and controlled burn
practices in agriculture and forestry management. Controlled or prescribed
burning is a technique sometimes used in forest management, farming, prairie
restoration or greenhouse gas abatement. Fire is a natural part of both forest
and grassland ecology and controlled fire can be a tool for foresters.
Controlled burning stimulates the germination of some desirable forest trees,
thus renewing the forest.
·
Fumes from paint, hair spray,
varnish, aerosol sprays and other solvents
·
Waste deposition in landfills, which
generate methane. Methane is not toxic; however, it is highly flammable and may
form explosive mixtures with air. Methane is also an asphyxiant and may
displace oxygen in an enclosed space. Asphyxia or suffocation may result if the
oxygen concentration is reduced to below 19.5% by displacement
·
Military, such as nuclear weapons,
toxic gases, germ warfare and rocketry
Natural
sources
·
Dust from natural sources, usually
large areas of land with little or no vegetation
·
Methane, emitted by the digestion of
food by animals, for example cattle
·
Radon gas from radioactive decay
within the Earth's crust. Radon is a colorless, odorless, naturally occurring,
radioactive noble gas that is formed from the decay of radium. It is considered
to be a health hazard. Radon gas from natural sources can accumulate in
buildings, especially in confined areas such as the basement and it is the
second most frequent cause of lung cancer, after cigarette smoking
·
Smoke and carbon monoxide from wildfires
·
Vegetation, in some regions, emits
environmentally significant amounts of VOCs on warmer days. These VOCs react
with primary anthropogenic pollutants—specifically, NOx, SO2,
and anthropogenic organic carbon compounds—to produce a seasonal haze of
secondary pollutants.
·
Volcanic activity, which produce
sulfur, chlorine, and ash particulates
Health
effects
The World Health Organization states
that 2.4 million people die each year from causes directly attributable to air
pollution, with 1.5 million of these deaths attributable to indoor air
pollution. "Epidemiological studies suggest that more than 500,000
Americans die each year from cardiopulmonary disease linked to breathing fine
particle air pollution. " A study by the University of Birmingham has
shown a strong correlation between pneumonia related deaths and air pollution
from motor vehicles. Worldwide more deaths per year are linked to air pollution
than to automobile accidents. Published in 2005 suggests that 310,000 Europeans
die from air pollution annually. Causes of deaths include aggravated asthma,
emphysema, lung and heart diseases, and respiratory allergies. The US EPA
estimates that a proposed set of changes in diesel engine technology (Tier 2)
could result in 12,000 fewer premature mortalities, 15,000 fewer heart
attacks, 6,000 fewer emergency room visits by children with asthma, and 8,900
fewer respiratory-related hospital admissions each year in the United States.
Air pollution is also emerging as a risk factor for stroke, particularly in
developing countries where pollutant levels are highest.
The worst short term civilian
pollution crisis in India was the 1984 Bhopal Disaster. Leaked industrial
vapours from the Union Carbide factory, belonging to Union Carbide, Inc.,
U.S.A., killed more than 25,000 people outright and injured anywhere from
150,000 to 600,000. The United Kingdom suffered its worst air pollution event
when the December 4 Great Smog of 1952 formed over London. In six days more
than 4,000 died, and 8,000 more died within the following months. An accidental
leak of anthrax spores from a biological warfare laboratory in the former USSR
in 1979 near Sverdlovsk is believed to have been the cause of hundreds of
civilian deaths. The worst single incident of air pollution to occur in the
United States of America occurred in Donora, Pennsylvania in late October,
1948, when 20 people died and over 7,000 were injured.
The health effects caused by air
pollution may include difficulty in breathing, wheezing, coughing and aggravation
of existing respiratory and cardiac conditions. These effects can result in
increased medication use, increased doctor or emergency room visits, more
hospital admissions and premature death. The human health effects of poor air
quality are far reaching, but principally affect the body's respiratory system
and the cardiovascular system.
A new economic study of the health
impacts and associated costs of air pollution in the Los Angeles Basin and San
Joaquin Valley of Southern California shows that more than 3800 people die
prematurely (approximately 14 years earlier than normal) each year because air
pollution levels violate federal standards. The number of annual premature
deaths is considerably higher than the fatalities related to auto collisions in
the same area, which average fewer than 2,000 per year.
Diesel exhaust (DE) is a major
contributor to combustion derived particulate matter air pollution. In several
human experimental studies, using a well validated exposure chamber setup, DE
has been linked to acute vascular dysfunction and increased thrombus formation.
This serves as a plausible mechanistic link between the previously described
association between particulate matter air pollution and increased
cardiovascular morbidity and mortality. Chronic obstructive pulmonary disease
(COPD) includes diseases such as chronic bronchitis, emphysema, and some forms
of asthma.
Particulates
pollution
Particulates
– also known as particulate matter (PM), fine particles, and soot – are tiny
subdivisions of solid matter suspended in a gas or liquid. In contrast, aerosol
refers to particles and/or liquid droplets and the gas together. A particle
with an aerodynamic diameter of 10 micrometers moves in a gas like a sphere of unit density (1 gram
per cubic centimeter) with a diameter of 10 micrometers. PM diameters range
from less than 10 nanometers
to more than 10 micrometers.
The
notation PM10 is used to describe particles of 10 micrometers or
less and PM2.5 represents particles less than 2.5 micrometers in
aerodynamic diameter.
The composition of aerosols and
particles depends on their source. Wind-blown mineral dust tends to be made of
mineral oxides and other material blown from the Earth's crust; this
particulate is light-absorbing. Sea salt is considered the second-largest
contributor in the global aerosol budget, and consists mainly of sodium
chloride originated from sea spray; other constituents of atmospheric sea salt
reflect the composition of sea water, and thus include magnesium, sulfate,
calcium, potassium, etc. In addition, sea spray aerosols may contain organic
compounds, which influence their chemistry. Sea salt does not absorb.
Secondary particles derive from the
oxidation of primary gases such as sulfur and nitrogen oxides into sulfuric
acid (liquid) and nitric acid (gaseous). The precursors for these aerosols—i.e.
the gases from which they originate—may have an anthropogenic origin (from
fossil fuel or coal combustion) and a natural biogenic origin. In the presence
of ammonia, secondary aerosols often take the form of ammonium salts; i.e.
ammonium sulfate and ammonium nitrate (both can be dry or in aqueous solution);
in the absence of ammonia, secondary compounds take an acidic form as sulfuric
acid (liquid aerosol droplets) and nitric acid (atmospheric gas). Secondary
sulfate and nitrate aerosols are strong light-scatterers. This is mainly because
the presence of sulfate and nitrate causes the aerosols to increase to a size
that scatters light effectively.
Organic matter (OM) can be either
primary or secondary, the latter part deriving from the oxidation of VOCs;
organic material in the atmosphere may either be biogenic or anthropogenic.
Organic matter influences the atmospheric radiation field by both scattering
and absorption. Another important aerosol type is constitute of elemental
carbon (EC, also known as black carbon, BC): this aerosol type includes
strongly light-absorbing material and is thought to yield large positive
radiative forcing. Organic matter and elemental carbon together constitute the
carbonaceous fraction of aerosols.
The composition of particulate matter
that generally causes visual effects such as smog consists of sulphur dioxide,
nitrogen oxides, carbon monoxide, mineral dust, organic matter, and elemental
carbon also known as black carbon or soot. The particles are hydroscopic due to
the presence of sulphur, and SO2 is converted to sulphate when high
humidity and low temperatures are present. This causes the reduced visibility
and yellow color
Sources
Natural:-
volcanoes, dust storms, forest and grassland fires, living vegetation, and sea
spray.
Man made:- ,
Burning of fossil fuels in vehicles, power plants and various industrial
processes.
Effects
Effects
on vegetation:-Particulate matter
can clog stomatal openings of plants and interfere with photosynthesis
functions. In this manner high particulate matter concencentrations in the
atmosphere can lead to growth stunting or mortality in some plant species.
Climate
effects: Climate effects
can be extremely catastrophic; sulfur dioxide ejected from the eruption of
Huaynaputina probably caused the Russian famine of 1601 - 1603, leading to the
deaths of two million.
Particles can affect the climate in
two different ways. The "direct effect" is caused by the fact that
the particles scatter and absorb solar and infrared radiation in the atmosphere
called Global dimming, a gradual reduction in the amount of global direct
irradiance at the Earth's surface, has partially counteracted global warming
from 1960 to the present
The addition of PM into the
atmosphere causes the water to condense on to the particles. This results in
more, but smaller droplets in the clouds, which increases the cloud albedo. In
addition to increasing the albedo, this effect tends to decrease the chance of
precipitation. If precipitation is suppressed, this results in excess water
remaining in the atmosphere. Atmospheric soot directly absorb solar radiation,
which heats the atmosphere and cools the surface.
The primary concern for climate
effects of particulate air pollution is an increase in global average
temperatures. Urbanization and industrialization is the main cause of airborn
particulate matter, and so it follows that air pollution is a more serious
threat in densely populated areas. Electricity and heat produced by antiquated
methods such as wood burning and coal combustion is still the primary method
for sustaining everyday life in developing countries. Climate effects
inevitably lead to health effects, which are listed above, but consist mainly
of respiratory problems, cardiovascular disease, and premature death
Acid rain
Acid rain is a rain or any other form
of precipitation that is unusually acidic, meaning that it possesses elevated
levels of hydrogen ions (low pH). It can have harmful effects on plants,
aquatic animals, and infrastructure. Acid rain is caused by emissions of carbon
dioxide, sulfur dioxide and nitrogen oxides which react with the water
molecules in the atmosphere to produce acids. Governments have made efforts
since the 1970s to reduce the release of sulfur dioxide into the atmosphere
with positive results. Nitrogen oxides can also be produced naturally by
lightning strikes and sulfur dioxide is produced by volcanic eruptions. The
chemicals found in acid rain can cause paint to peel, corrosion of steel
structures like bridges and stone statues to begin to appear old and worn down,
which reduces their value and beauty.
Definition
"Acid
rain" is a popular term referring to the deposition of wet (rain, snow,
sleet, fog, cloudwater, and dew) and dry (acidifying particles and gases)
acidic components. Distilled water, once carbon dioxide is removed, has a
neutral pH of 7. Liquids with a pH less than 7 are acidic, and those with a pH
greater than 7 are alkaline. “Clean” or unpolluted rain has a slightly acidic
pH of over 5.7, because carbon dioxide and water in the air react together to
form carbonic acid, but unpolluted rain also contains other chemicals. A common
example is nitric acid produced by electric discharge in the atmosphere such as
lightning. Carbonic acid is formed by the reaction
Carbonic acid then can ionize in water forming low
concentrations of hydronium and carbonate ions:
H2O (l) + H2CO3 (aq) 
HCO3− (aq) + H3O+ (aq)
Acid deposition as an environmental issue would include
additional acids to H2CO3.
History
The corrosive effect of polluted,
acidic city air on limestone and marble was noted in the 17th century by John
Evelyn, who remarked upon the poor condition of the Arundel marbles. Since the
Industrial Revolution, emissions of sulfur dioxide and nitrogen oxides to the
atmosphere have increased. In 1852, Robert Angus Smith was the first to show
the relationship between acid rain and atmospheric pollution in Manchester,
England. Though acidic rain was discovered in 1852, it was not until the late
1960s that scientists began widely observing and studying the phenomenon. The
term "acid rain" was coined in 1872 by Robert Angus Smith. Canadian
Harold Harvey was among the first to research a "dead" lake. Public
awareness of acid rain in the U.S increased in the 1970s after The New York
Times promulgated reports from the Hubbard Brook Experimental Forest in New
Hampshire of the myriad deleterious environmental effects demonstrated to
result from it.
Occasional pH readings in rain and
fog water of well below 2.4 have been reported in industrialized areas.
Industrial acid rain is a substantial problem in China and Russia and areas
down-wind from them. These areas all burn sulfur-containing coal to generate
heat and electricity. The problem of acid rain not only has increased with
population and industrial growth, but has become more widespread. The use of
tall smokestacks to reduce local pollution has contributed to the spread of
acid rain by releasing gases into regional atmospheric circulation. Often
deposition occurs a considerable distance downwind of the emissions, with
mountainous regions tending to receive the greatest deposition (simply because
of their higher rainfall). An example of this effect is the low pH of rain
(compared to the local emissions) which falls in Scandinavia.
History of acid rain in the United States
Since
1998, Harvard University wraps some of the bronze and marble statues on its
campus, such as this "Chinese stele", with waterproof covers every
winter, in order to protect them from erosion caused by acid rain (or,
actually, acid snow)
In 1980, the U.S. Congress passed an
Acid Deposition Act. This Act established a 18-year research program under the
direction of the National Acidic Precipitation Assessment Program (NAPAP).
NAPAP looked at the entire problem. It enlarged a network of monitoring sites
to determine how acidic the precipitation actually was, and to determine long
term trends, and established a network for dry deposition. It looked at the
effects of acid rain and funded research on the effects of acid precipitation
on freshwater and terrestrial ecosystems, historical buildings, monuments, and
building materials. It also funded extensive studies on atmospheric processes
and potential control programs.
In 1991, DENR provided its first
assessment of acid rain in the United States. It reported that 5% of New
England Lakes were acidic, with sulfates being the most common problem. They
noted that 2% of the lakes could no longer support Brook Trout, and 6% of the
lakes were unsuitable for the survival of many species of minnow. Subsequent
Reports to Congress have documented chemical changes in soil and freshwater
ecosystems, nitrogen saturation, decreases in amounts of nutrients in soil,
episodic acidification, regional haze, and damage to historical monuments.
Meanwhile, in 1989, the US Congress
passed a series of amendments to the Clean Air Act. Title IV of these
amendments established the Acid Rain Program, a cap and trade system designed
to control emissions of sulfur dioxide and nitrogen oxides. Title IV called for
a total reduction of about 10 million tons of SO2 emissions from power plants.
It was implemented in two phases. Phase I began in 1995, and limited sulfur
dioxide emissions from 110 of the largest power plants to a combined total of
8.7 million tons of sulfur dioxide. One power plant in New England (Merrimack)
was in Phase I. Four other plants (Newington, Mount Tom, Brayton Point, and
Salem Harbor) were added under other provisions of the program. Phase II began
in 2000, and affects most of the power plants in the country.
During the 1990s, research continued.
On March 10, 2005, EPA issued the Clean Air Interstate Rule (CAIR). This rule
provides states with a solution to the problem of power plant pollution that
drifts from one state to another. CAIR will permanently cap emissions of SO2
and NOx in the eastern United States. When fully implemented, CAIR will reduce
SO2 emissions in 28 eastern states and the District of Columbia by over 70
percent and NOx emissions by over 60 percent from 2003 levels.
Overall, the Program's cap and trade
program has been successful in achieving its goals. Since the 1990s, SO2
emissions have dropped 40%, and according to the Pacific Research Institute,
acid rain levels have dropped 65% since 1976. However, this was significantly
less successful than conventional regulation in the European Union, which saw a
decrease of over 70% in SO2 emissions during the same time period.
In 2007, total SO2
emissions were 8.9 million tons, achieving the program's long term goal ahead
of the 2010 statutory deadline.
The EPA estimates that by 2010, the
overall costs of complying with the program for businesses and consumers will
be $1 billion to $2 billion a year, only one fourth of what was originally
predicted.
Emissions
of chemicals leading to acidification
The most important gas which leads to
acidification is sulfur dioxide. Emissions of nitrogen oxides which are
oxidized to form nitric acid are of increasing importance due to stricter
controls on emissions of sulfur containing compounds. 70 Tg(S) per year in the
form of SO2 comes from fossil fuel combustion and industry, 2.8
Tg(S) from wildfires and 7-8 Tg(S) per year from volcanoes.
Natural phenomena
The principal natural phenomena that
contribute acid-producing gases to the atmosphere are emissions from volcanoes.
Thus, for example, fumaroles from Laguna Caliente crater of Poás Volcano create
extremely high amounts of acid rain and fog with acidity 2 of pH, clearing an
area of any vegetation and frequently causing irritation to the eyes and lungs
of inhabitants in nearby settlements. Acid-producing gasses are created also by
biological processes that occur on the land, in wetlands, and in the oceans.
The major biological source of sulfur containing compounds is dimethyl sulfide.
Nitric acid in rainwater is an
important source of fixed nitrogen for plant life, and is also produced by
electrical activity in the atmosphere such as lightning.
Acidic deposits have been detected in
glacial ice thousands of years old in remote parts of the globe.
Soils of Coniferous forests are
naturally very acidic due to the shedding of needles and this phenomenon should
not be confused with acid rain.
Human activity
The
principal cause of acid rain is sulfur and nitrogen compounds from human
sources, such as electricity generation, factories, and motor vehicles. Coal
power plants are one of the most polluting. The gases can be carried hundreds
of kilometers in the atmosphere before they are converted to acids and
deposited. In the past, factories had short funnels to let out smoke but this
caused many problems locally; thus, factories now have taller smoke funnels.
However, dispersal from these taller stacks causes pollutants to be carried
farther, causing widespread ecological damage
Chemical
processes
Combustion of fuels creates sulfur
dioxide and nitric oxides. They are converted into sulfuric acid and nitric
acid
Gas phase chemistry
In the gas phase sulfur dioxide is
oxidized by reaction with the hydroxyl radical via an intermolecular reaction:
SO2
+ OH· → HOSO2·
which is followed by:
HOSO2·
+ O2 → HO2· + SO3
In the presence of water, sulfur
trioxide (SO3) is converted rapidly to sulfuric acid:
SO3
(g) + H2O (l) → H2SO4 (l)
Nitrogen dioxide reacts with OH to
form nitric acid:
NO2
+ OH· → HNO3
Chemistry in cloud droplets
When clouds are present, the loss
rate of SO2 is faster than can be explained by gas phase chemistry
alone. This is due to reactions in the liquid water droplets.
Hydrolysis
Sulfur
dioxide dissolves in water and then, like carbon dioxide, hydrolyses in a
series of equilibrium reactions:
SO2
(g) + H2O SO2·H2O
SO2·H2O
H+
+ HSO3−
HSO3−
H+
+ SO32−
Oxidation
There
are a large number of aqueous reactions that oxidize sulfur from S(IV) to
S(VI), leading to the formation of sulfuric acid. The most important oxidation
reactions are with ozone, hydrogen peroxide and oxygen (reactions with oxygen
are catalyzed by iron and manganese in the cloud droplets).
Acid deposition
Wet deposition
Wet
deposition of acids occurs when any form of precipitation (rain, snow, and so
on.) removes acids from the atmosphere and delivers it to the Earth's surface.
This can result from the deposition of acids produced in the raindrops (see
aqueous phase chemistry above) or by the precipitation removing the acids
either in clouds or below clouds. Wet removal of both gases and aerosols are
both of importance for wet deposition.
Dry deposition
Acid
deposition also occurs via dry deposition in the absence of precipitation. This
can be responsible for as much as 20 to 60% of total acid deposition. This
occurs when particles and gases stick to the ground, plants or other surfaces.
Adverse effects
Acid rain has been shown to have
adverse impacts on forests, freshwaters and soils, killing insect and aquatic
life-forms as well as causing damage to buildings and having impacts on human
health.
Surface waters and aquatic animals
Both the lower pH and higher
aluminium concentrations in surface water that occur as a result of acid rain
can cause damage to fish and other aquatic animals. At pHs lower than 5 most
fish eggs will not hatch and lower pHs can kill adult fish. As lakes and rivers
become more acidic biodiversity is reduced. Acid rain has eliminated insect
life and some fish species, including the brook trout in some lakes, streams,
and creeks in geographically sensitive areas, such as the Adirondack Mountains
of the United States. However, the extent to which acid rain contributes
directly or indirectly via runoff from the catchment to lake and river acidity
(i.e., depending on characteristics of the surrounding watershed) is variable.
The United States Environmental Protection Agency's (EPA) website states:
"Of the lakes and streams surveyed, acid rain caused acidity in 75 percent
of the acidic lakes and about 50 percent of the acidic streams".
Soils
Soil biology and chemistry can be
seriously damaged by acid rain. Some microbes are unable to tolerate changes to
low pHs and are killed. The enzymes of these microbes are denatured (changed in
shape so they no longer function) by the acid. The hydronium ions of acid rain
also mobilize toxins such as aluminium, and leach away essential nutrients and
minerals such as magnesium.
2
H+ (aq) + Mg2+ (clay) 2 H+
(clay) + Mg2+ (aq)
Soil
chemistry can be dramatically changed when base cations, such as calcium and
magnesium, are leached by acid rain thereby affecting sensitive species, such
as sugar maple (Acer saccharum).
Forests and other vegetation
Adverse effects may be indirectly
related to acid rain, like the acid's effects on soil or high concentration of
gaseous precursors to acid rain. High altitude forests are especially
vulnerable as they are often surrounded by clouds and fog which are more acidic
than rain.
Other plants can also be damaged by
acid rain, but the effect on food crops is minimized by the application of lime
and fertilizers to replace lost nutrients. In cultivated areas, limestone may
also be added to increase the ability of the soil to keep the pH stable, but
this tactic is largely unusable in the case of wilderness lands. When calcium
is leached from the needles of red spruce, these trees become less cold
tolerant and exhibit winter injury and even death.
Human health effects
Acid
rain does not directly affect human health. The acid in the rainwater is too
dilute to have direct adverse effects. However, the particulates responsible
for acid rain (sulfur dioxide and nitrogen oxides) do have an adverse effect.
Increased amounts of fine particulate matter in the air do contribute to heart
and lung problems including asthma and bronchitis.
Other adverse effects
Acid
rain can also damage buildings and historic monuments, especially those made of
rocks such as limestone and marble containing large amounts of calcium
carbonate. Acids in the rain react with the calcium compounds in the stones to
create gypsum, which then flakes off.
CaCO3
(s) + H2SO4 (aq) CaSO4
(aq) + CO2 (g) + H2O (l)
The effects of this are commonly seen on old gravestones,
where acid rain can cause the inscriptions to become completely illegible. Acid
rain also increases the corrosion rate of metals, in particular iron, steel,
copper and bronze.
Affected
areas
Places with significant impact by
acid rain around the globe include most of eastern Europe from Poland northward
into Scandinavia, the eastern third of the United States, and southeastern
Canada. Other affected areas include the southeastern coast of China and Taiwan.
Prevention
methods
Technical solutions
Many coal-burning power plants use
Flue gas desulfurization (FGD) to remove sulfur-containing gases from their
stack gases. For a typical coal-fired power station, FGD will remove 95 percent
or more of the SO2 in the flue gases. An example of FGD is the wet scrubber
which is commonly used. A wet scrubber is basically a reaction tower equipped
with a fan that extracts hot smoke stack gases from a power plant into the
tower. Lime or limestone in slurry form is also injected into the tower to mix
with the stack gases and combine with the sulfur dioxide present. The calcium
carbonate of the limestone produces pH-neutral calcium sulfate that is
physically removed from the scrubber. That is, the scrubber turns sulfur pollution
into industrial sulfates.
In some areas the sulfates are sold
to chemical companies as gypsum when the purity of calcium sulfate is high. In
others, they are placed in landfill. However, the effects of acid rain can last
for generations, as the effects of pH level change can stimulate the continued
leaching of undesirable chemicals into otherwise pristine water sources,
killing off vulnerable insect and fish species and blocking efforts to restore
native life.
Vehicle emissions control reduces emissions
of nitrogen oxides from motor vehicles.
International treaties
A number of international treaties on
the long range transport of atmospheric pollutants have been agreed for
example, Sulphur Emissions Reduction Protocol under the Convention on Long-Range
Transboundary Air Pollution. Canada and the US signed the Air Quality Agreement
in 1991. Most European countries and Canada have signed the treaties.
Emissions trading
In this regulatory scheme, every
current polluting facility is given or may purchase on an open market an
emissions allowance for each unit of a designated pollutant it emits. Operators
can then install pollution control equipment, and sell portions of their
emissions allowances they no longer need for their own operations, thereby recovering
some of the capital cost of their investment in such equipment. The intention
is to give operators economic incentives to install pollution controls.
The first emissions trading market
was established in the United States by enactment of the Clean Air Act
Amendments of 1990. The overall goal of the Acid Rain Program established by
the Act is to achieve significant environmental and public health benefits
through reductions in emissions of sulfur dioxide (SO2) and nitrogen
oxides (NOx), the primary causes of acid rain. To achieve this goal
at the lowest cost to society, the program employs both regulatory and market
based approaches for controlling air pollution.
Water
pollution - Types, sources, effects and control measures
Sources of surface water pollution
are generally grouped into two categories based on their origin.
Point sources:- (contaminants that
enter a waterway from a single, identifiable source, such as a pipe or ditch) . Ex. discharge from a sewage treatment
plant, a factory, or a city storm drain.
Non–point sources (NPS) :-
(diffuse contamination that does not originate from a single discrete source).
NPS pollution is often the cumulative effect of small amounts of contaminants
gathered from a large area. Ex. leaching out of N compounds from fertilized
agricultural lands. Contaminated storm water washed off of parking lots, roads
and highways, called urban runoff.
Types
Oxygen-depleting
substances
Oxygen-depleting substances may be
natural materials, such as plant matter (e.g. leaves and grass) as well as
man-made chemicals. Other natural and anthropogenic substances may cause
turbidity (cloudiness) which blocks light and disrupts plant growth, and clogs
the gills of some fish species.
Many of the chemical substances are
toxic. Pathogens can produce waterborne diseases in either human or animal
hosts. Alteration of water's physical chemistry includes acidity (change in
pH), electrical conductivity, temperature, and eutrophication. Eutrophication
is an increase in the concentration of chemical nutrients in an ecosystem to an
extent that increases in the primary productivity of the ecosystem. Depending
on the degree of eutrophication, subsequent negative environmental effects such
as anoxia (oxygen depletion) and severe reductions in water quality may occur,
affecting fish and other animal populations.
Pathogens
Coliform bacteria are a commonly used
bacterial indicator of water pollution, although not an actual cause of
disease. Other microorganisms sometimes found in surface waters which have
caused human health problems include Burkholderia pseudomallei, Cryptosporidium
parvum, Giardia lamblia,Salmonella ,Novovirus
and other viruses, Parasitic worms (helminths).
High levels of pathogens may result
from inadequately treated sewage discharges. This can be caused by a sewage
plant designed with less than secondary treatment (more typical in
less-developed countries). In developed countries, older cities with aging
infrastructure may have leaky sewage collection systems (pipes, pumps, valves),
which can cause sanitary sewer overflows. Some cities also have combined
sewers, which may discharge untreated sewage during rain storms. Pathogen
discharges may also be caused by poorly managed livestock operations.
Chemical and other
contaminants
Contaminants
may include organic and inorganic substances.
Organic
water pollutants include:
·
Detergents
·
Disinfection by-products found in
chemically disinfected drinking water, such as chloroform
·
Food processing waste, which can
include oxygen-demanding substances, fats and grease
·
Insecticides and herbicides, a huge
range of organohalides and other chemical compounds
·
Petroleum hydrocarbons, including
fuels (gasoline, diesel fuel, jet fuels, and fuel oil) and lubricants (motor
oil), and fuel combustion byproducts, from stormwater
runoff
·
Tree and bush debris from logging
operations
·
Volatile organic
compounds (VOCs), such as industrial solvents,
from improper storage.
·
Chlorinated solvents, which are dense
non-aqueous phase liquids (DNAPLs), may fall to the bottom of reservoirs, since
they don't mix well with water and are denser.
o
Polychlorinated biphenyl (PCBs)
o
Trichloroethylene
·
Various chemical compounds found in
personal hygiene and cosmetic products
Inorganic
water pollutants include:
·
Acidity caused by industrial
discharges (especially sulfur dioxide from power plants)
·
Ammonia from food processing waste
·
Chemical waste as industrial
by-products
·
Fertilizers containing
nutrients--nitrates and phosphates--which are found in stormwater runoff from agriculture,
as well as commercial and residential use
·
Heavy metals from motor vehicles (via
urban stormwater runoff) and acid mine drainage
·
Silt (sediment) in runoff from
construction sites, logging, slash and burn practices or land clearing sites
Macroscopic
pollution—large visible items polluting the water—may be termed
"floatables" in an urban stormwater context, or marine debris when
found on the open seas, and can include such items as:
·
Trash or garbage (e.g. paper,
plastic, or food waste) discarded by people on the ground, along with
accidental or intentional dumping of rubbish, that are washed by rainfall into
storm drains and eventually discharged into surface waters
·
Nurdles, small ubiquitous waterborne
plastic pellets
·
Shipwrecks, large derelict ships
Thermal pollution
Thermal pollution is the rise or fall
in the temperature of a natural body of water caused by human influence.
Thermal pollution, unlike chemical pollution, results in a change in the
physical properties of water. A common cause of thermal pollution is the use of
water as a coolant by power plants and industrial manufacturers. Elevated water
temperatures decreases oxygen levels (which can kill fish) and affects
ecosystem composition, such as invasion by new thermophilic species. Urban
runoff may also elevate temperature in surface waters.
Thermal
pollution can also be caused by the release of very cold water from the base of
reservoirs into warmer rivers.
Effects
Water pollution affects our, rivers,
lakes, oceans and drinking water. Some water pollution effects show up
immediately where as others don’t show up for months or years. The water
pollution has damaged the food chain and is very important for the food
preparation of plants through photosynthesis. When Filth is thrown in water the
toxins travel from the water and when the animals drink that water they get
contaminated and when humans tend to eat the meat of the animals is infected by
toxins it causes further damage to the humans. Infectious diseases such as
cholera and typhoid can be contracted from drinking contaminated water. Our
whole body system can have a lot of harm if polluted water is consumed
regularly. Other health problems associated with polluted water are poor blood
pressure, vomiting, skin lesions and damage to the nervous system. In fact the
evil effects of water pollution are said to be the leading cause of death of
humans across the globe. Pollutants in the water alter the overall chemistry of
water, causing a lot of changes in temperature. These factors overall have had
an adverse effect on marine life and pollutes and kills marine life. Marine
life gets affected by the ecological balance in bodies of water, especially the
rivers and the lakes.
Fish and shellfish kills have been
reported, because toxins climb the food chain after small fish consume
copepods, then large fish eat smaller fish, etc. Each successive step up the
food chain causes a stepwise concentration of pollutants such as heavy metals
(e.g. mercury) and persistent organic pollutants such as DDT. This is known as
biomagnification, which is occasionally used interchangeably with
bioaccumulation.
Large gyres (vortexes) in the oceans
trap floating plastic debris. The North Pacific Gyre for example has collected
the so-called "Great Pacific Garbage Patch" that is now estimated at
100 times the size of Texas. Many of these long-lasting pieces wind up in the
stomachs of marine birds and animals. This results in obstruction of digestive
pathways which leads to reduced appetite or even starvation.
Control
Domestic sewage
In urban areas, domestic sewage is
typically treated by centralized sewage treatment plants. In the U.S., most of
these plants are operated by local government agencies, frequently referred to
as publicly owned treatment works (POTW). Municipal treatment plants are designed
to control conventional pollutants: BOD and suspended solids. Well-designed and
operated systems (i.e., secondary treatment or better) can remove 90 percent or
more of these pollutants. Some plants have additional sub-systems to treat
nutrients and pathogens.
A household or business not served by
a municipal treatment plant may have an individual septic tank, which treats
the wastewater on site and discharges into the soil. Alternatively, domestic
wastewater may be sent to a nearby privately owned treatment system (e.g. in a
rural community).
Industrial wastewater
Some industrial facilities generate
ordinary domestic sewage that can be treated by municipal facilities.
Industries that generate wastewater with high concentrations of conventional
pollutants (e.g. oil and grease), toxic pollutants (e.g. heavy metals, volatile
organic compounds) or other nonconventional pollutants such as ammonia, need
specialized treatment systems. Some of these facilities can install a
pre-treatment system to remove the toxic components, and then send the
partially-treated wastewater to the municipal system. Industries generating
large volumes of wastewater typically operate their own complete on-site
treatment systems.
Some industries have been successful
at redesigning their manufacturing processes to reduce or eliminate pollutants,
through a process called pollution prevention.
Heated water generated by power
plants or manufacturing plants may be controlled with:
·
cooling ponds, man-made bodies of
water designed for cooling by evaporation, convection, and radiation
·
cooling towers, which transfer waste
heat to the atmosphere through evaporation and/or heat transfer
·
cogeneration, a process where waste
heat is recycled for domestic and/or industrial heating purposes.
Agricultural wastewater
Nonpoint source controls
Sediment (loose soil) washed off
fields is the largest source of agricultural pollution in the United States.
Farmers may utilize erosion controls to reduce runoff flows and retain soil on
their fields. Common techniques include contour plowing, crop mulching, crop
rotation, planting perennial crops and installing riparian buffers.
Nutrients (nitrogen and phosphorus)
are typically applied to farmland as commercial fertilizer; animal manure; or
spraying of municipal or industrial wastewater (effluent) or sludge. Nutrients
may also enter runoff from crop residues, irrigation water, wildlife, and
atmospheric deposition. Farmers can develop and implement nutrient
management plans to reduce excess application of nutrients.
To minimize pesticide impacts,
farmers may use Integrated Pest Management (IPM) techniques (which can
include biological pest control) to maintain control over pests, reduce
reliance on chemical pesticides, and protect water quality.
Point source wastewater treatment
Farms with large livestock and
poultry operations, such as factory farms, are called concentrated animal
feeding operations or confined animal feeding operations in the U.S. and are
being subject to increasing Government regulation. Animal slurries are usually
treated by containment in lagoons before disposal by spray or trickle
application to grassland. Constructed wetlands are sometimes used to facilitate
treatment of animal wastes, as are anaerobic lagoons. Some animal slurries are
treated by mixing with straw and composted at high temperature to produce a
bacteriologically sterile and friable manure for soil improvement.
Construction site stormwater
Sediment from construction sites is
managed by installation of:
·
erosion controls, such as mulching
and hydroseeding, and
·
sediment controls, such as sediment
basins and silt fences.
Discharge of toxic chemicals such as
motor fuels and concrete washout is prevented by use of:
·
spill prevention and control plans,
and
·
specially designed containers (e.g.
for concrete washout) and structures such as overflow controls and diversion
beams.
Urban runoff (storm
water)
Effective control of urban runoff
involves reducing the velocity and flow of storm water, as well as reducing
pollutant discharges. Local Governments use a variety of stormwater management
techniques to reduce the effects of urban runoff.
Pollution prevention practices
include low impact development techniques, installation of green roofs and
improved chemical handling (e.g. management of motor fuels & oil,
fertilizers and pesticides). Runoff mitigation systems include infiltration
basins, bioretention systems, constructed wetlands, retention basins and
similar devices.
Thermal pollution from runoff can be
controlled by stormwater management facilities that absorb the runoff or direct
it into groundwater, such as bioretention systems and infiltration basins.
Retention basins tend to be less effective at reducing temperature, as the
water may be heated by the sun before being discharged to a receiving stream.
posted by Dr.C.Prabakaran @ 8:22 PM
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