Case Studies

Question 1

Camelford UK

Answer 1

• Episodic pollution
• Aluminium sulphate coagulant in drinking water treatment used to removed suspended matter
• July 1988 20 tonnes discharged into wrong tank, contaminated water entered distribution system and local rivers
• pH 3.9-5 acid leaching plumbing metals 620mg (Pb,Cu,Zn)
• Caused fish death, galvanised/dissolved tanks and pipes and possible cerebral dysfunction in local population

Question 2

River Thames UK

Answer 2

• Chronic
• 13-15th century - Important for transport and food
• 16th century - shipyards established East london
• 18-19th century more docks and industry brought extensive pollution
• 1830s - outbreak of cholera
• 1840s - O2 disappeared, fish stocks died out
• 1880s - new sewage to divert sewage downstream
• Water declared ‘dead’ in 1957
• 1960s - docks closed and major clean-ups were done
• 1974 - Salmon return with upper reaches showing 20 species of freshwater fish and 14 species of euryhaline fish and lower reaches showing 80+ species marine fish

Question 3

Lake Kariba Zimbabwe

Answer 3

• Point
• Build across the Zambezi river 1958 for hydro-electric power
• Diverse aquatic ecosystem
• Pesticides widely used in zimbabwe in 1960 (DTT)
• Sprayed over 100 tons around lake Kariba in 1980s to removed mosquito and tsetse fly
• Short heavy storms caused high erosive run-off
• Biomagnification occurs up the food chain so crocodile has high DDT conc in them
• DDT banned and use of pyrethroids and other less effective methods

Question 4

Minamata Japan

Answer 4

• Diffuse
• Use of acetaldehyde for production, requires mercuric sulphate and mercuric oxide
• Compounds where being converted into organic mercury (poisonous)
• 1950s - unknown neurological disease affecting children and adults
• Causes birth defects, severe cerebral palsy, blindness and mental retardation
• Bay had to be dredged at vast expensive, adult victims survived
• Outbreak reoccured in Niigata and in amazon basin

Question 5

Lake Erie, Canada

Answer 5

• Nitrogen levels in lakes very reasonable ~3
• Phosphorus levels in Lake Erie is very high, due to having more urban runoff than other lakes
• 1950s - change in fish stocks (sturgeon, herring and trout lost)
• 1970s - Developed anoxia, collapse of benthic organisms

Question 6

Black sea, Europe

Answer 6

-Deep inland sea which has only 200m of oxygenated water
-Below 200m water is anoxiated as it contains H2S, P and N
-Europe and USSR injected a lot of industrial, agricultural material and sewage
-Early 1980s - pollution killed algal meadows, marine ecosystem disappears
-Mid 1980s - Alien jellyfish species introduced, fish stocks collapse
-1990s - Mnemiopsis population estimated at
900 million tonnes (500 m-3
)
10 times annual global fish catch