Glossary - Global Environmental Issues - page 194

latent heat The quantity of heat absorbed or released
by a substance during a change of state. Latent
heat of fusion is involved in the transformation of
a solid into a liquid (or liquid into a solid) as in
the ice-water-ice transformation. Latent heat of
vaporization is the equivalent in changes
involving liquids and gases, such as water and
water vapour.
leaching The removal of soluble minerals from soil by
percolating water. Leaching is commonly
accelerated in soils subject to acid precipitation.
leguminous plants A group of pod (or legume) bearing
plants of the pea family. Nodules on the roots of
leguminous plants contain nitrogen-fixing bacteria
which have an important role in the earth/
atmosphere nitrogen cycle.
lime injection multi-stage burning (LIMB) A technique
developed to reduce acid gas emissions from coal
burning furnaces. Fine lime is injected into the
combustion chamber where it fixes the sulphur
released from the burning coal, thus reducing
sulphur dioxide emissions by 35-50 per cent.
limestone A sedimentary rock consisting mainly of
calcium carbonate. When limestone is heated,
carbon dioxide is driven off and calcium oxide or
lime is left. Lime has been used for centuries to
sweeten acid soils, and as an alkali it is widely used
to neutralize the acid gas emissions responsible for
acid rain .
liquid phase reaction The conversion of acid gases into
liquid acids, the reactions taking place in solution.
(See also gas phase reaction .)
Little Ice Age A period of global cooling lasting for
about 400 years from the mid-fourteenth to the
mid-eighteenth century.
Live Aid An organization set up in 1985 to help the
victims of drought and famine in Ethiopia. It raised
money through two major concerts in England and
the United States at which the leading popular
entertainers of the day performed.
London Smog (1952) A major pollution event in
London, England caused by a combination of
meteorological conditions (low temperatures, high
pressure, poor ventilation) and energy use (the
burning of high-sulphur coal). An estimated 4,000
deaths were attributed to the smog.
Long Range Transportation of Air Pollution (LRTAP)
The transportation of air pollution over great
distances—usually in excess of 500 km—by the
prevailing winds in the atmosphere. Aggravated by
the introduction of the tall stacks policy, which

increased the height of emissions, encouraged
LRTAP and contributed to the spread of acid rain
damage.
long-wave radiation Relatively low energy radiation
from the infrared sector of the electromagnetic
spectrum. Terrestrial radiation is long-wave.

M
malnutrition A result of the consumption of essential
nutrients at levels inadequate to maintain good
health.
maritime tropical air mass (mT) An air mass
originating over the oceans in tropical latitudes,
and therefore hot and moist. mT air is also
inherently unstable and capable of producing large
amounts of precipitation.
melanoma A malignant, normally fatal form of skin
cancer, associated with over-exposure to ultraviolet-
B radiation. (See also skin cancer .)
mesopause The boundary between the mesosphere and
thermosphere lying some 80 km above the earth's
surface.
mesosphere The layer of the atmosphere lying above
the stratosphere. In it temperatures decline with
increasing altitude from close to 0°C at the
stratopause to-80°C at the mesopause .
methane A simple hydrocarbon gas produced
during the decomposition of organic material
under anaerobic conditions. It is a powerful
greenhouse gas, being about twenty-one times
more effective than carbon dioxide, molecule
for molecule, and increasing more rapidly.
methane sulphonic acid (MSA) a gas produced by the
oxidization of dimethyl sulphide (DMS) released
by phytoplankton during their seasonal bloom.
MSA is ultimately converted into sulphate in the
atmosphere, therefore adding to natural
atmospheric acidity.
methyl bromide A fumigant which may be responsible
for as much as 10 per cent of existing ozone
depletion. It is used to kill pests in the fruit and
vegetable industry.
mid-latitude frontal model A model of mid-latitude
cyclonic circulation developed between 1915 and
1920 by Norwegian weather forecasters. It
identified the interactions between the air masses
in a mid-latitude cyclone and explained the
resulting weather patterns. It remained an
important forecasting tool in mid-latitudes for at