Chapter 10 - Heavy Metals

Question 1

What are some examples of heavy metals

Answer 1

1) lead
2) mercury
3) cadmium
4) tin
5) iron

Question 2

What are the sources of lead pollution

Answer 2

1) lead acid batteries
2) lead flashing used in building construction

Question 3

What are the effects of lead pollution

Answer 3

1)industrial workers may inhale less dust or absorb it through the skin if dissolved in sweat causing acute issues such as brain damage and paralysis
2)rainwater flowing over lead roof flashing may inhibit the growth of moss and lichens

Question 4

How can lead pollution be controlled

Answer 4

1) water pipes = all lead water pipes have been replaced preventing chronic exposure, lead solder has also now been replaced
2) petrol additives = lead replaced with chemicals such as benzene
3)fishing weights = replaced with less toxic metals

Question 5

What are the sources of mercury pollution

Answer 5

1) disposal of items containing mercury, for example batteries or thermometers
2) chemical plants that produce chlorine using mercury electrodes
3) combustion of coal

Question 6

What are the effects of the chemical form on the toxicity of mercury

Answer 6

1) liquid mercury is not easily absorbed through the skin or gut although vapours may be absorbed in the lungs if inhaled
2) inorganic mercury such as mercury oxide is absorbed well in the gut
3) organic mercury is absorbed easily through the skin and the gut and inhalation. Causes issues such as kidney and brain damage

Question 7

How can mercury pollution be controlled

Answer 7

1) replace mercury thermometers with alcohol or electronic ones
2) remove mercury from effluents by reverse osmosis or activated carbon filters
3) ion exchange filters
4) dispose at high pH to reduce solubility

Question 8

What are the effects of iron pollution

Answer 8

1) causes deoxygenating when it’s oxidised in water - leads to death of aerobic organisms
2) iron is soluble and may be leached into a river by water drainage through a spoil heap

Question 9

How can iron pollutants be controlled

Answer 9

1) mesh screen = spoil heap drainage water is collected and passed over mesh screens where the iron becomes oxidised and is deposited on the mesh so when the water flows into the river there is no longer a risk of deoxygenating