mercury and heavy metal pollution
TRANSCRIPT
- 1.Mercury and other heavy metals
VCE Environmental Science: Unit 4
Area of Study 1: Pollution
2. Definition of Heavy Metals
Noun (Music) Very loud, brash rock music, often with shouted,
violent lyrics.;)
"Heavy metals" is an inexact term used to describe more than a
dozen elements that are metals or metalloids.
Examples of heavy metals include chromium, arsenic, cadmium, lead,
mercury and manganese.
A metal of relatively high density, or of high relative atomic
weight.
3. 4. Sources of heavy metals
Heavy metals occur naturally in the ecosystem with large variations
in concentration.
The primary anthropogenic sources of heavy metals are point sources
such as mines, foundries, smelters, and coal-burning power plants,
as well as diffuse sources such as combustion by-products and
vehicle emissions.
Waste-derived fuels are especially prone to contain heavy metals,
so heavy metals are a concern in consideration of waste as
fuel.
Electronic waste is also a significant source of heavy metal
contaminants.
5. 6. Persistence
Because they cannot be degraded or destroyed, heavy metals are
persistent in all parts of the environment.
Human activity affects the natural geological and biological
redistribution of heavy metals through pollution of the air, water,
and soil.
Humans also affect the natural geological and biological
redistribution of heavy metals by altering the chemical form of
heavy metals released to the environment. Such alterations often
affect a heavy metal's toxicity by allowing it to bioaccumulate in
plants and animals, biomagnify in the food chain, or attack
specific organs of the body.
They are often stored as fat-soluble compounds in the body.
7. 8. Exposure
Heavy metals are associated with myriad adverse health effects,
including
allergic reactions (e.g., beryllium, chromium),
neurotoxicity affects nervous system(e.g., lead),
nephrotoxicity affects kidneys(e.g., mercuric chloride, cadmium
chloride), and
cancer (e.g., arsenic, hexavalent chromium).
Humans are often exposed to heavy metals in various waysmainly
through the inhalation of metals in the workplace or polluted air,
or through the ingestion of food (particularly seafood) that
contains high levels of heavy metals or paint chips that contain
lead.
9. Biomagnification
10. Toxicity of heavy metals
Living organisms require varying amounts of "heavy metals."
Iron, cobalt, copper, manganese, molybdenum and zinc are required
by humans. Excessive levels can be damaging to the organism.
11. Toxicity of Heavy Metals
Other heavy metals such as mercury, plutonium, and lead are toxic
metals that have no known vital or beneficial effect on organisms,
and their accumulation over time in the bodies of animals can cause
serious illness.
Certain elements that are normally toxic are, for certain organisms
or under certain conditions, beneficial. Examples include vanadium,
tungsten, and even cadmium.
12. Example: Cadmium
Cadmium has many commercial applications, including electroplating
and the manufacture of batteries.
Exposure to cadmium can occur in the workplace or from contaminated
foodstuffs and can result in emphysema, renal failure,
cardiovascular disease, and perhaps cancer.
13. 14. Example: Lead
Humans discovered lead more than 8,500 years ago, and over time
have used lead in artwork, plumbing, gasoline, batteries, and
paint. Modern-day exposure to lead occurs in the workplace or
through the ingestion of lead-contaminated items such as paint
chips. The primary adverse health effect from exposure to lead is
permanent neurological impairment (particularly in children). Other
adverse health effects associated with lead include sterility in
males and nephrotoxicity.
15. 16. 17. Case Study: Mercury
Mercury, or quicksilver, was known in ancient times as hydrargyros,
hence its chemical symbol Hg.
Mercury is the only metal that is liquid at room temperature and
pressure.
Mercury is an extremely rare element, but occurs in deposits
throughout the world mostly as cinnabar (or mercuric
sulphide).
18. More about Mercury
Like water, mercury can evaporate and become airborne.
Because it is an element, mercury does not break down into less
toxic substances.
Once mercury escapes to the environment, it circulates in and out
of the atmosphere until it ends up in the bottoms of lakes and
oceans.
Mercury can be found as the elemental metal or in a wide variety of
organic and inorganic compounds.
Depending on its chemical form, mercury may travel long distances
before it falls to earth with precipitation or dust.
19. Uses of Mercury
Felting and Hat-making
Fluorescent lamps
Mercury batteries
Thermometers and thermostats
Vacuum pumps,
Barometers,
Electric rectifiers and switches
Printer and photocopy toners.
Mercury-vapor lamps (for sterilizing water and instead of steam in
boilers
of some turbine engines.)
Amalgamation (to dissolve silver or gold to form an amalgam, as in
tooth fillings) This process has been largely supplanted by the
cyanide process, in which gold or silver is dissolved in solutions
of sodium or potassium cyanide.
20. Sources of Mercury
Non-ferrous metal manufacturing, mining and alumina production are
the largest sources of mercury emissions in Australia.
Precious metal mining (which can emit mercury to water or
land),
Cement manufacturing (which may emit mercury into the air)
and
Chemical manufacturing, which can emit of mercury to land and into
water.
Fossil fuel power plants may also emit mercury into the air by
burning fuels such as coal, oil, and petrol.
Our landfills and sewage also contribute to mercury being released
into our soil and water.
Small amounts of mercury can be released into the air in the
exhaust fumes of cars, buses and motorbikes.
21. 22. Transport of Mercury
Mercury chloride will act as a particle, following wind patterns,
and being deposited by rain.
Elemental mercury may be a gas in the atmosphere.
Emissions of mercury and or mercury compounds can produce elevated,
but still low-level concentrations in the atmosphere around the
source.
Elemental mercury can evaporate from both soil and water into the
atmosphere.
23. 24. Sinks for Mercury
When mercury enters the environment from emissions in the air,
water or soil, it oxidises into other compounds of mercury.
These other forms of mercury form methyl mercury, through either
chemical or biological (bacteria) processes.
Methyl mercury builds up in the tissues of fish and shellfish. In
areas of mercury contamination, larger and older fish tend to have
higher levels of mercury.
25. Exposure to Mercury
Eating fish or shellfish which have been exposed to mercury.
Drinking water or eating foods that contain traces of
mercury.
Being exposed to mercury from dental work and medical
treatments.
Breathing contaminated air.
Working at, or living near, factories where mercury is produced or
used, such as fossil fuel plants or cement manufacturers.
26. Effects on Humans
Depending on its chemical form (elemental, inorganic or organic)
mercury is able to cause a myriad of adverse health effects
including :
neurotoxicity (elemental mercury, methyl-mercury),
nephrotoxicity (elemental mercury, mercuric salts such as mercuric
chloride),
teratogenicity(methyl-mercury) abnormalities in physiological
development, including birth defects
death (elemental mercury, methyl-mercury).
27. Environmental Health Effects
Aquatic life the fish, shellfish and other creatures in our rivers,
lakes and oceans are likely to be exposed to mercury as it is often
found in water. It can make them very sick, and may even kill
them.
Mercury can build up in the tissues of fish and shellfish and be
harmful to people and to other animals that eat them.
Once mercury is released into the environment it will remain there
for many years.
28. 29. 30. 31. 32. 33. References
Encyclopaedia of Public Health
http://www.npi.gov.au/students/mercury.html
http://www.npi.gov.au/substances/mercury/index.html
http://en.wikipedia.org/wiki/Mercury_(element)
http://www.mercuryinschools.uwex.edu/curriculum/hg_in_env.htm