Flashcards in Spring 2013 past papa Deck (12):
Four intrinsic properties of pollutants that determine their impact to the environment
Short and long term toxicity
Chemical reactions the compound undergoes
Tendency to bio-accumulate
Ease of control
What is meant by the term pollutant linkage
A pollutant linkage represents the presence of a source of contamination which has the potential to impact on a receptor by means of a pathway.
How does the grain size of a sediment sample influence its elemental concentration and why might this be particularly important in the study of estuarine pollution?
There is a strong correlation between grain size and elemental concentration. As grain size decreases surface area to volume ration increases for so absorption and other processes small particles dominate. Fine sediments located in estuaries so active sedimentation of pollutants sorbed onto particles deposited locally.
What is a VOC and list the main sources of VOC's to the environment and their recent trends.
Volatile organic compound. Solvent use - petrol distribution and handling - motor use. 1990-2006 fell by 62%
How have lead inputs into the EU changed over the last 200 years and how might these be reflected in the composition of steadily accumulating lake sediments?
Lead inputs have decreased.
With examples, differentiate between chronic and acute pollution.
Acute pollution is the release of a pollutant not normally for longer than a day - short term event. E.g Piper alpha
Chronic pollution is the release of a pollutant of a high/low concentration over a prolonged period of time. Power stations etc
Explain the main function of the primary treatment stage of sewage discharges
The main function is to remove suspended solids. Sludge settles and oil and grease rises.
Explain what is meant by median effective concentration and median effective time?
Average time for 50% of the population to receive a sub-lethal effect following acute administration of a chemical at a concentration.
Median effective time is when 50% of the population have sub-lethal effects within a specific time normally 48-96 hours.
Briefly explain how the chemical structure of a hydrocarbon influences its degradation after an oil spill
Straight small branched chains = rapid
Cyclic compounds degrade slower
If it has a higher molecular weight it biodegrades slower.
Briefly outline what is meant by bio-accumulation of pollutants.
Chemical concentration in an organism that exceeds that of the surrounding medium. Encompasses all routes of exposure dietary absorption, respiration and skin absorption.
With reference to specific examples explain the environmental factors which may influence the toxicity of potential pollutants? (big question)
So organo complexes form. For example methylmercury. Inorganic mercury (from storm runoff/rainfall) is transformed by natural sulfate reducing bacteria into methyl mercury. This is can cause birth defects, disorders of the brain and effect the immune system. It is taken up very quickly by organisms but is hard to excrete or get rid of. Recognized as an amino acids so freely transported throughout the body.
Salinity may also effect the toxicity of potential pollutants. Increased salinity means organisms use alot of energy on ionic pumps or cell volume regulation so increased susceptibility to toxic stress. Salinity effects the larvae of fiddler crabs.
Alexandrium tamarense a dinoflagellate which can cause paralytic shellfish which directly effects humans. The growth rate decreases with the decrease of water temp and light intensity.
Also pH effects.
Interaction with other toxins. e.g cu with cl = synergism combines effect of the two higher the the sum of each individual value.
Mb molybdenum more mobile in alkaline conditions.