- Organic
Organic pollutants contain the element Carbon given the symbol C
sometimes seen as C12. Compounds containing hydrogen
and carbon alone
are known as hydrocarbons. Thousands of organic chemicals are now used
in industry, agriculture and other activities. Examples of organic
pollutants include:- organic solvents, e.g. Trichloroethylene (used
to de-grease components prior to various manufacturing processes),
Polychlorinated bi-phenyls, (used to cool coils in
large transformers), Benzo-a-pyrene (found in cigarette smoke),
Alcohols, such as phenol which is among the top 50 chemicals produced,
(used in the manufacture of resins), Acrylonitrile used in the
manufacture of rubber, pesticides, polyphosphate and alkyl sulphonate
detergents, plastics, oil, etc etc. All of these compounds contain
carbon and some contain inorganic elements, e.g., sulphur, phosphorus,
oxygen, chlorine, fluorine, nitrogen and cyanide.
- Organometallic
These pollutants essentially contain both a metal and organic group.
Examples are less common than for organic material but include
compounds such as Tetra-ethyl-lead, di-benzene chromium, ethyl
mercuric chloride and tri-butyl-tin. Tin has in fact the greatest
number of organometallic compounds in commercial use. The main use of
these types of compound have been as, fungicides, disinfectants, and
general pesticides. In addition some organo-metallic materials are
produced as a result of the addition of metals into the environment
which are then acted upon by various processes and organisms.
- Inorganic
This category covers those chemicals that do not generally contain
carbon. Inorganic compounds are widespread in the natural environment
and include, acids, bases, metals, salts/minerals. Inorganic
pollutants include, Sulphur dioxide a gas produced in the burning of
fossil fuels, metals and minerals as bi-products and products of
mining activity, e.g. lead, arsenic, cadmium, sulphides, and
compounds such as sodium hydroxide, and nitric acid.
- Physical/Particulate
Physical pollutants may contain one or all of the three groups
discussed above. Examples of this group are soils/clays
entering rivers, soot particles in the atmosphere and heat generated
by various industrial processes, including power generation. In
waters particulates are described by the term "suspended solids" and
there are tests available to assess their concentration.
- Radiological
This group covers those materials classed as radioactive. Atoms of
individual elements are made up of very small "subatomic" particles.
Protons and neutrons occupy the center or nucleus of the atom, whilst
electrons move in orbits around the nucleus. Atoms of the same
element whose nuclei contain different numbers of neutrons are called
isotopes, e.g., H11, H21,
H31 are
three forms of hydrogen all contain 1 proton but 0, 1, and 2 neutrons
respectively. Some isotopes,(also known as nuclides), spontaneously
disintegrate to form other elements and during this process emit
alpha and/or beta particles and/or gamma rays, it is these isotopes
that are classed as radioactive. Naturally occurring "radioisotopes"
include the potassium element with atomic mass number 40
(40K), and the Radon element with atomic mass number
222 (222R). Other radioisotopes of concern are,
3H (hydrogen), 14C (carbon), 32P
(phosphorus), 90Sr(strontium), 238U (uranium),
129I (iodine).
- Biological
With this pollutant group the main concerns tend to be associated
with public health and drinking water. Biological pollutants
generally termed pathogens include bacteria, parasites and viruses.
Typical examples are the Bacteria:- salmonella typhi, shigella
dysenteriae, vibrio cholerae, the viruses:- poliovirus,
cytomegalovirus, and parasites:- entamoeba histolytica,
cryptosporidium parvum.
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