Topic 10:heavy Metals

Question 1

What affects heavy metal pollution?

Answer 1

Liposolubility
Synergism
Solubility

Question 2

When are heavy metals most soluble?

Answer 2

At low PH

Question 3

Sources of lead pollution

Answer 3

Car batteries,pipes,paint,solder,flashing for roofs and windows, anti-knock petrol additives

Question 4

What uses of lead dont cause pollution?

Answer 4

Lead-acid batteries, lead flashing

Question 5

Effects of lead pollution

Answer 5

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

Question 6

When are problems caused by lead most likely?

Answer 6

In industry accidents

Question 7

How can industrial accidents be prevented so effects of lead are?

Answer 7

Wearing facemasks,water sprays, remote operations

Question 8

6 uses of lead pollution that can be controlled

Answer 8

Water pipes, petrol additives,electrical solder,lead based paint,fishing weights,shotgun pellets

Question 9

Use of lead for water pipes

Answer 9

Used this way for 4’500 years
Small amounts dissolve in water, those who drink it can suffer chronic exposure

Question 10

How can lead pollution because of water pipes be controlled?

Answer 10

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

Question 11

Use of lead in petrol additives and how this is a problem

Answer 11

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

Question 12

How has lead pollution from petrol additives been controlled?

Answer 12

Been replaced since 1980s by chemicals like benzene
Use fuels that dont need lead additives e.g. diesel,hydrogen

Question 13

Use of lead on electrical solder

Answer 13

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

Question 14

Lead based paint and how it can be a problem

Answer 14

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

Question 15

How can lead in fishing weights be an issue?

Answer 15

They might be lost or discarded,swallowed by waterfowl- then killed by lead poisoning

Question 16

Control of lead in fishing weights

Answer 16

Phased out in the Uk, replaced with metals like tungsten which is less toxic

Question 17

Lead in shotgu pellets

Answer 17

Problem when they miss target and land on the ground where birds feed so they could be poisoned
Some voluntary schemes use alternates

Question 18

Ways that mercury can be released into the environment

Answer 18

Disposal of items with mercury in
Chemical plants the produce chlorine using mercury electrodes
Combustion of coal

Question 19

Items contains mercury

Answer 19

Batteries,fluorescent light,thermometers

Question 20

What does the chemical form of mercury determine?

Answer 20

Severity

Question 21

Effects of liquid/elemental mercury

Answer 21

Not easily absorbed through skin or guts
But vapours may be absorbed in lungs if inhaled

Question 22

Effects of inorganic mercury compounds

Answer 22

E.g. mercury oxide, absorbed moderately well in the gut

Question 23

Effects of organic mercury compounds

Answer 23

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

Question 24

How can low toxicity inorganic mercury become more dangerous?

Answer 24

If they enter anaerobic sediments in lakes or sea, they may be changes to organic by anaerobic microbes

Question 25

How has mercury been controlled?

Answer 25

Mercury thermometers replaced by electric or alcohol
It can be removed from effluents by reverse osmosis or activated carbon filters

Question 26

Sources of cadmium pollution

Answer 26

Disposal of old nickel-cadmium batteries
Incineration of waste containing cadmium pigments e.g.. paints and plastics
Drainage water from cadmium/zonc wastes

Question 27

Name one new use of Cadmium

Answer 27

Cadmium-telluride photovoltaic solar panels
The manufacture and eventual disposal may cause pollution

Question 28

Properties of cadmium

Answer 28

It is liposoluble and bioaccumulates
This can lead to toxic concentrations
It can biomagnify in food chains

Question 29

Effects of cadmium

Answer 29

Brain damage7paralysis
Lung cancer
Kidney failure
Skeletal collapse due to bone decalcification

Question 30

Control of cadmium

Answer 30

Restrictions/bans on use
Cadmium wast disposed in hazardous waste landfill sites
May be recycled

Question 31

Uses of tin

Answer 31

Anti fouling paint on boats- toxic to marine organisms so growth is prevented
The active chemical is TBT

Question 32

Effects of Tin

Answer 32

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

Question 33

How is tin controlled?

Answer 33

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

Question 34

Effects of iron

Answer 34

Caused deoxygenation of water because it is oxidised
Causes death of aerobic organisms

Question 35

Control of iron pollution

Answer 35

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