chlorofluorocarbons
(CFCs)
A hydrocarbon in which all the hydrogen atoms have been replaced by
chlorine and fluorine. Fluorocarbons are used as a feedstock, as a
refrigerant in refrigerators and air conditioners, as a solvent and as a
blowing agent of plastic foam, as propellant for households (aerosol
sprays) and in some asthma inhalers. Because CFCs are not destroyed in
the lower atmosphere (troposphere) they drift into the upper atmosphere
(stratosphere). Here CFCs undergo photodissociation promoted by UV light,
and chlorine atoms are formed which are responsible of destructive
effects on the ozone layer (ozone depletion). Their use has been
generally prohibited by the Montreal Protocol (1987), and
hydrochlorofluorocarbons are now used as CFC substitutes.
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composting
Is the controlled biological decomposition of organic material
in the presence of air to form a humus-like material. Compost is the
relatively stable humus material that is produced from a composting
process in which bacteria in soil mixed with garbage and degradable trash
break down the mixture into organic fertilizer.
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ecosystem
Is a naturally occurring assemblage of organisms
(plant, animal and other living organisms—also referred to as a biotic
community or biocoenosis)
living together with their environment (or biotope),
functioning as a unit of sorts. The term ecosystem first appeared in a
1935 publication by the British ecologist Arthur Tansley,
and includes the physical and biological components of an environment
considered in relation to each other as a unit. An ecosystem is a dynamic
and complex whole, interacting as an ecological unit, a structured
functional unit in equilibrium, characterized by energy
and matter
flows between the different elements that compose it.
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Environmental Chemistry
Is the study of the sources, reactions, transport, effects, and fates of
chemical species in water, soil, air, and living environments (biogeochemical
cycles, etc) and of the effects of anthropic activity and
technology on them (pollutant emission, etc.).
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externalities
An externality occurs in economics when a decision (for example, to pollute the atmosphere)
causes costs or benefits to individuals or groups other than the person
making the decision. Pollution by a firm in the course of its production
which causes nuisance or harm to others, is an example of a negative
externality, external cost, or external diseconomy.
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food chain
A graphical representation of the sequence of organisms, each of which
uses the next, lower member of the sequence, as a food source. The chain
starts with plants or other autotrophs (an organism that satisfies its
need for organic food molecules by using the energy of the sun, or of the
oxidation of inorganic substances, to convert inorganic molecules into
organic molecules. Green plants are autotrophs),
which are eaten by herbivores. The
herbivores are eaten by carnivores. These are eaten by other carnivores.
When any organism dies, it is eaten by tiny microbes (detrivores) and the
exchange of energy continues.
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food web
The complex and interconnected web of feeding relationships by which
energy and nutrients are transferred from one species to another in an
ecosystem.
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Green Chemistry (Sustainable
Chemistry)
Green Chemistry means chemistry for the environment, a fundamental new
philosophy of thinking that can help chemists in research and production
to develop more eco-friendly and efficient products and processes. Green
chemistry is the attempt to prevent pollution, to reduce or eliminate
the use and generation of hazardous substances and to design chemical
products and processes to reduce the harm they cause to
ecosystems.
Thus, environmental chemistry is necessary for green chemistry to be
possible, since how different chemicals behave in the environment to be
able to make things better, must be known. Thanks to the 1990 US
Pollution Prevention Act, and the 1995 Presidential Green Chemistry
Challenge Grants, there are now many examples of innovative and
economically competitive Green Chemistry technologies in the chemical
industry.
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hazardous substances
Any material that poses a
threat to human health and/or the environment. Typical hazardous
substances are toxic, corrosive, ignitable, explosive, or chemically
reactive. Hazard refers to a condition
or physical situation (for instance the exposure to a hazardous substance)
with a potential for an undesirable consequence, such as harm to life or
environment. Risk, on the other hand, is a
measure of the probability that damage to life, health, or the environment
will occur as a result of a given hazard. Risk is the product of the
hazard multiplied by dose. Dose is the actual quantity
of a hazardous substance to which an organism has been exposed.
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landfill
Sanitary landfills are disposal sites for non-hazardous solid wastes
spread in layers, compacted to the smallest practical volume, and
covered by material applied at the end of each operating day. Secure
chemical landfills are disposal sites for hazardous waste, selected and
designed to minimize the chance of release of hazardous substances into
the environment.
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methylmercury
A neurotoxin deriving from the microbiological methylation of mercuric
ions, it may be found in high concentrations in the biota of aquatic ecosystems.
Here methylmercury undergoes biomagnification along the food chain.
Seafood consumption is the
main way methylmercury is taken up by humans.
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nitrogen oxides
NOx is the generic term for nitrogen oxides, a group of highly reactive
gases, all of which contain nitrogen and oxygen in varying amounts. The
most important are nitrogen monoxide NO (colourless and odourless),
nitrogen dioxide NO2 (reddish-brown, pungent odour) with minor amounts of NO3 and N2O4.
It forms by direct combination of oxygen and nitrogen under electric
discharge (lightening) or when fuel is
burned at high temperatures, as in a combustion process. The primary
sources of NOx are motor vehicles, electric utilities, and other
industrial, commercial, and residential sources that burn fuels.
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ozone
Ozone in the upper atmosphere (stratosphere) is able to absorb the major
part of the sun's ultraviolet radiation and therefore prevent this
dangerous radiation from reaching the surface. Without a protective
ozone layer in the atmosphere, animals and plants could not exist. A
drastic depletion of the ozone layer over the Antarctic, the "ozone
hole", was noticed in the 70s, and depletion was found to be caused
chiefly by ozone reacting chemically with chlorine released from chlorofluorocarbons (CFCs).
The effects on the ozone layer, if human use of
CFC gases was to continue at an unaltered rate, were reckoned
and, in 1998, the Montreal Protocol banned the production of
CFCs.
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particulate
matter, (fine particles, aerosol)
Particles coming from natural (volcanic eruptions, forest fires) or
anthropic sources (combustion-based processes), such as carbon and ash,
which gradually fall from the smoke plume downwind from the source.
Aerosol can be sampled on the basis of the average aerodynamic diameter
(dM): we often refer to PM10 (dM
< 10 x 10-6 m) e
PM2.5 (dM <
2.5 x 10-6 m).
Epidemiological studies unambiguously pointed out the role of
PM2.5 annual mean concentrations
in enhancing inflammatory and allergic responses in the respiratory
system.
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photochemical smog
Under adverse weather conditions and/or in the presence of air pollution conditions, volatile organic compounds (VOCs) and
nitrogen oxides interact under the action of sunlight to produce a plethora of secondary pollutants,
part of which (for instance ozone) are toxic to vegetal and animal life. Smog forms a
brownish-yellow haze primarily over urban areas, and is most prevalent in the summer months,
when there is the most sunlight and temperatures are the highest.
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pollutant
Contaminant that adversely alters the physical, chemical, or biological
properties of the environment. The term includes nutrients, pathogens,
toxic metals, carcinogens, etc. Pollutants are classified as either
Primary or Secondary. For example, a primary air pollutant is one that
is added directly to the air from a given source. An example of a
primary air pollutant would be carbon monoxide
because it is added to the air as a by-product of combustion.
A secondary air pollutant is formed in the atmosphere through chemical reactions.
An example of a secondary air pollutant would be the formation of ozone
in photochemical smog.
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pollution
Contamination of the environment as a result of human activities. The
term pollution refers primarily to the fouling of air, water, and
land by wastes (air pollution, water pollution, solid waste).
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radon
A colourless, naturally occurring, radioactive, inert gas formed by
radioactive decay of radium atoms in soil, rocks and uranium ores. Being
a gas, it can enter buildings through openings or cracks in the
foundation. The radon gas itself decays into radioactive solids, called
radon daughters. The radon radioactive daughters (polonium, lead,
bismuth) attach to dust particles in the air, and can be inhaled. The
inhalation of radon daughters has been linked to lung cancer.
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reclamation of contaminated sites
Contaminated land is defined
as land "where there is a serious threat or risk to health, flora and/or
fauna", and is generally reserved for areas where the pollutant or
harmful substance is man-made or is put there by humans. Besides
posing a potential hazard to human
health, and threatening the
environment (natural and built), it
is a risk to investment and regeneration and limits land development -
particularly in urban areas.
There are more than 10,000 identified contaminated sites in Italy.
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sustainability,
sustainable development
Meeting the needs of the
present generation without compromising the ability of future generations
to meet their own needs or the health of the planet. Essentially it is
about living, working and ordering society in ways which
are environmentally "sustainable", encouraging reduction of pollution,
re-use of resources, promoting biodiversity etc. The term originally
applied to the exploitation of natural resources, where the focus was long-term. Today, it applies to many
disciplines, including economic development, environment, food production,
energy and lifestyle.
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thalidomide
An
emblematic example of a chemical applied to health. Its use in treating
sickness during pregnancy in the 1960s resulted in birth defects. The
birth defects were caused because thalidomide changes the growth and
development of new blood vessels (angiogenesis) in the developing babies.
Forty years later, researchers are hoping to use thalidomide to stop
cancers from developing new blood vessels. This should reduce the
cancer's supply of oxygen and nutrients, which, it is hoped, will cause
the tumour to shrink, or at least to stop growing. It is most commonly
used to treat a type of cancer known as
myeloma.
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thermal inversion
In meteorology,
an atmospheric condition in which the air temperature rises with
increasing altitude, holding surface air down and preventing dispersion
of pollutants.
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validation
The process by which the integrity, correctness and fulfilment to
precisely defined criteria (for example addressed by statistics) of
series of analytical data are established. In environmental modelling
(for example climate modelling), the most obvious way to validate a
climate model is to use it to analyze past events, and then see whether
its simulated prediction 'came true,' or how close it was to being
correct.
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volatile organic compounds (VOCs)
This class of chemicals includes a plethora of organic molecules,
aliphatic and aromatic hydrocarbons, halogen-containing compounds, etc.
They are released into the atmosphere by natural processes (terpenes from
vegetation) or anthropic activities (accidental spillouts from chemical
plants, or during transport, storage or use of low-boiling organic
products). They are co-responsible for the formation of photochemical smog.
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