The conversion of energy from one form to another
often affects the environment and the air we breath
in many ways. Each liter of gasoline burned by a vehicle
produces about 2.5 kg of CO2
An average car driven about 13,500 miles a year and
consumes about 600 US gallons (1680 kg; 1 US gallon is
3.78541178 litres while an imperial gallon is 4.546092 litres)
of gasoline emits about 12,000 lbm of CO2
to the atmosphere
a year, which is about four times the weight of a typical car.Global climate change is due to the excessive use of fossil fuels
(e.g., coal, petroleum products, and natural gas in electric power
generation, transportation, buildings, and manufacturing), and it
has been a concern in recent decades. Under normal conditions,
vegetation consumes CO2 and releases O2 during
photosynthesis, thus keeps the CO2 concentration in the
atmosphere in check. A mature, growing tree consumes about
12 kg of CO2 a year and exhales enough oxygen to support a
family of four. However, deforestation and the huge increase in
CO2 production in recent decades has disturbed this balance. In a 1995 report, the earth world's leading climate scientists
concluded that the earth has already warmed about 0.5?C
during the last century, and they estimate that the earth's
temperature will rise another 2?C by the year 2100. A rise of this magnitude can cause severe changes in weather
patterns with storms and heavy rains and flooding at some parts
and drought in others, major floods due to the melting of ice at
the poles, loss of wetlands and coastal areas due to rising sea
levels, variations in water supply, changes in the ecosystem due
to the inability of some animal and plant species to adjust to the
changes, increases in epidemic diseases due to the warmer
temperatures, and adverse side effects on human health and
socioeconomic conditions in some areas. The seriousness of these threats has moved the United Nations
to establish a committee on climate change. A world summit in
1992 in Rio de Janeiro, Brazil, attracted world attention to the
problem. 162 nations signed an agreement prepared by the
committee in 1992 to control greenhouse gas emissions. In December 2011, countries agreed in Durban, South
Africa, to forge a new deal forcing the biggest polluting
countries to limit greenhouse gas emissions. The Kyoto
Protocol was extended to allow five more years to finalize a
wider agreement. The goal was complete producing a new,
legally binding accord to cut greenhouse gas emissions by
2015 that would come into force by 2020. The conference included
participants from 196 nations. The main result of the conference was the establishment of a
goal to limit global warming to less than 2?C compared to
preindustrial times. According to the agreement, human-made
greenhouse emissions should be eliminated during the second
half of the 21st century. Greenhouse gas emissions can be reduced by increasing
conservation efforts, improving conversion efficiencies, and meet
new energy demands by using renewable energy (e.g.,
hydroelectric, solar, wind, and geothermal energy) rather than
fossil fuels.Smog is made-up mostly of
ground-level ozone O3
, but also contains numerous other
chemicals including carbon monoxide CO, particulate matter
such as soot and dust, volatile organic compounds VOCs
such as benzene, butane, and other hydrocarbons
Unlike the useful ozone layer high in the
stratosphere that protects the earth from the sun's
harmful ultraviolet rays, ozone at ground level is a
pollutant with several adverse health effects.A significant
portion of the VOC or HC emissions is caused by the
evaporation of fuels during refuelling or spillage during spit
back or evaporation from gas tanks with faulty caps that do
not close tightly
Ozone and Smog
Smog is the dark yellow or brown haze that builds up in a
large, stagnant air mass and hangs over the populated areas
on calm, hot summer days. Ground-level smog and ozone form
in urban areas with heavy traffic or industry, but the
prevailing winds can transport them several hundred
miles to other cities (i.e., pollution knows no
boundaries, it is a global problem)
Ozone irritates eyes and damages the air sacs in the lungs
where oxygen and carbon dioxide are exchanged, causing
eventual hardening of this soft and spongy tissue. Smog also contains suspended particulate matter (e.g., dust
and soot emitted by vehicles and industrial facilities), which
irritate the eyes and the lungs since they may carry acids and
metals compounds such as acids and metals
Acid Rain
Fossil fuels are mixtures of various chemicals, including
small amounts of sulfur.The Greenhouse Effect: Global Warming and Climate
Change
Glass at thicknesses encountered in practice transmits over
90 percent of radiation in the visible range and is practically
opaque (non-transparent) to radiation in the longer
wavelength infrared regions (i.e., allows the solar radiation to
enter freely but blocks the infrared radiation emitted by the
interior surfaces). The surface of the earth, which warms up during the day
as it absorbs solar energy, cools down at night by radiating part
of its energy into deep space as infrared radiation
Carbon dioxide (CO2
), water vapour, and trace
amounts of some other gases (e.g., methane
and nitrogen oxides) act like a blanket and
keep the earth warm at night by blocking the
heat radiated from the earth, Fig. Many people die each year due to heart and lung
diseases related to air pollution
Hundreds of elements and compounds (e.g.,
benzene and formaldehyde are emitted during the
combustion of coal, oil, natural gas, and wood in
electric power plants, vehicles engines, furnaces,
and even fireplaces).Some compounds are added
to liquid fuels for various reasons (e.g., Methyl
tertiary-butyl ether (MTBE) is added to raise the
octane number of the fuel and to oxygenate the
fuel in winter months to reduce urban smog).The
largest source of air pollution is motor vehicles
The pollutants released by vehicles are usually grouped as
hydrocarbons (HC), nitrogen oxides (NOx), and carbon
monoxide (CO).Volcanic eruptions and hot springs also
release sulphur oxides (the cause of the rotten egg smell)
The sulphur oxides and nitric oxides react with
water vapour and other chemicals high in the
atmosphere in the presence of sunlight to form
sulfuric and nitric acids (Fig.2.62).2.65).2.66).