Topic 10:heavy Metals Flashcards
What affects heavy metal pollution?
Liposolubility
Synergism
Solubility
When are heavy metals most soluble?
At low PH
Sources of lead pollution
Car batteries,pipes,paint,solder,flashing for roofs and windows, anti-knock petrol additives
What uses of lead dont cause pollution?
Lead-acid batteries, lead flashing
Effects of lead pollution
Industrial workers may inhale lead dust or absorb it through skin if it dissolves in sweat
Acute exposure to large does can cause brain damage,paralysis and death
High does can cause liver and kidney failure
When are problems caused by lead most likely?
In industry accidents
How can industrial accidents be prevented so effects of lead are?
Wearing facemasks,water sprays, remote operations
6 uses of lead pollution that can be controlled
Water pipes, petrol additives,electrical solder,lead based paint,fishing weights,shotgun pellets
Use of lead for water pipes
Used this way for 4’500 years
Small amounts dissolve in water, those who drink it can suffer chronic exposure
How can lead pollution because of water pipes be controlled?
Most pipes were replaced with copper in 20th century, and the lead solder itch tin/zonc or copper
Areas of high risk (some old buildings still have lead pipes) phosphoric acid added to water supply
This produces an insoluble layer of lead phosphate in pipes so lead can’t dissolve into water
Use of lead in petrol additives and how this is a problem
Anti-knock agents added to petrol to smooth the explosion of combustion and reduce engine wear
However, they release lead particulates into the atmosphere, which is a threat to public health
How has lead pollution from petrol additives been controlled?
Been replaced since 1980s by chemicals like benzene
Use fuels that dont need lead additives e.g. diesel,hydrogen
Use of lead on electrical solder
Used in electrical connections, but tat isnt a public health threat
It is when it is melted during soldering or recycled after use-vapoursied and inhaled
Lead free solder is now widely used
Lead based paint and how it can be a problem
Lead added to accelerate drying and increase durability
Problem with old flaking paint-removal of old paint can be health hazard
Phased out since the 1980s and safer paint removal methods used e.g. chemical paint strippers
How can lead in fishing weights be an issue?
They might be lost or discarded,swallowed by waterfowl- then killed by lead poisoning
Control of lead in fishing weights
Phased out in the Uk, replaced with metals like tungsten which is less toxic
Lead in shotgu pellets
Problem when they miss target and land on the ground where birds feed so they could be poisoned
Some voluntary schemes use alternates
Ways that mercury can be released into the environment
Disposal of items with mercury in
Chemical plants the produce chlorine using mercury electrodes
Combustion of coal
Items contains mercury
Batteries,fluorescent light,thermometers
What does the chemical form of mercury determine?
Severity
Effects of liquid/elemental mercury
Not easily absorbed through skin or guts
But vapours may be absorbed in lungs if inhaled
Effects of inorganic mercury compounds
E.g. mercury oxide, absorbed moderately well in the gut
Effects of organic mercury compounds
E.g. methyl mercury
They are absorbed easily by skin,gut and in lungs
Also liposoluble so pass cell membrane easily, like the blood-brain barrier or placenta
Also causes kidney damage
How can low toxicity inorganic mercury become more dangerous?
If they enter anaerobic sediments in lakes or sea, they may be changes to organic by anaerobic microbes
How has mercury been controlled?
Mercury thermometers replaced by electric or alcohol
It can be removed from effluents by reverse osmosis or activated carbon filters
Sources of cadmium pollution
Disposal of old nickel-cadmium batteries
Incineration of waste containing cadmium pigments e.g.. paints and plastics
Drainage water from cadmium/zonc wastes
Name one new use of Cadmium
Cadmium-telluride photovoltaic solar panels
The manufacture and eventual disposal may cause pollution
Properties of cadmium
It is liposoluble and bioaccumulates
This can lead to toxic concentrations
It can biomagnify in food chains
Effects of cadmium
Brain damage7paralysis
Lung cancer
Kidney failure
Skeletal collapse due to bone decalcification
Control of cadmium
Restrictions/bans on use
Cadmium wast disposed in hazardous waste landfill sites
May be recycled
Uses of tin
Anti fouling paint on boats- toxic to marine organisms so growth is prevented
The active chemical is TBT
Effects of Tin
It was assumed the small amounts of TBT would disperse in the ocean and not cause an issue
But it is an endocrine disrupters that alters grown and reproduction of marine organisms
Can be passed to humans when shellfish eaten
How is tin controlled?
Prohibited from use in anti-fouling paint-less toxic metals like copper used
Some countries require that paint residues produced by boat cleaning is disposed of in chemical waste landfill
Effects of iron
Caused deoxygenation of water because it is oxidised
Causes death of aerobic organisms
Control of iron pollution
Spoil heap water is collected and passed over mesh screens
Iron is oxidised and deposited on the mesh so doesnt end up in rivers
Solid iron is periodically removed from the mesh
