Propreties Of Pollutants 2 Flashcards
What does persistence mean?
It is a measure of how long it takes for a pollutant to chemically break down. So it is a measure of the length of time that a pollutant remains in the environment and can therefore cause harm.
On which kind of substances the term persistence is usually applied
The term persistence is usually only applied to substances that will eventually break down p, so it is not used for elements that cannot break down or compounds that are stable (described as being degradable)
Name examples of persistent pollutants
CFC
DDT
Heavy metals such as lead and mercury
Explain the persistence of CFC
Chemically stable, break down slowly, they may remain in the atmosphere for many decades
Explain the persistence of DDT
DDTis stable, although it does gradually break down, although it has not been used in the yuk for 30 years some is still present in wildlife and humans
Explain the persistence of heavy metals
Heavy metals such as lead and mercury are elements and do not break down at all
Example of non persistent pollutants
Sewage breaks down rapidly as long as the conditions are right for the bacterias that cause decomposition(warm, plenty of O2)
Pyrethroid insecticides break down rapidly compared to organochlorines such as DDT
What does degradation mean
Degradation is the process of chemical breakdown
What is meant by biodegradation
Biodegradation is the process of being broken down by biological processes, especially the action of decomposers such as bacteria and fungi.
What affect the rate of biodegradation or biodegradability
It is affected by environmental factors such as temperature and oxygen availability
What does include biodegradable pollutants
Sewage, paper and cardboard
Name some less biodegradable pollutants
Plastics and DDT
What is meant by Mobility
Mobility is a measure of how easily a material moves in the environment, Pollutants that are mobile are likely to travel longer distances and therefore cause problems over larger areas, although they may also become diluted and less locally harmful
What can you say about the mobility CFC
CFC are persistent gases which are not very soluble in water and are therefore not removed by rain. So they can travel long distances in the atmosphere.
what can you say about mobility of sulfur dioxide gas
Because sulfur dioxide is a gas, it can be carried long distances before it causes acid rain, but because it is washed out of the atmosphere when it dissolves in rain, it usually travels a maximum of few hundred miles
