Heavy Metal Pollution Flashcards
Properties of heavy metals
Toxic, liposoluble, bioaccumulation, biomagnification, synergistic
Sources of Lead
Lead-acid batteries, Water pipes, petrol additives, lead-based paint, fishing weights, shotgun pellets.
Control of Lead
replacement of lead water pipes, replacement of lead as an anti-knocking agent in petrol with other chemicals such as benzine, replacement of lead solder with copper or tin, removal of lead from paints, tungsten fishing weights and shotgun pellets.
Effects of Lead
brain damage, paralysis, liver and kidney damage, death
Sources of Mercury
batteries, fluorescent lights, thermometers, production of chlorine (mercury electrodes), combustion of coal
Liquid, inorganic and organic mercury
Liquid mercury not easily absorbed, inorganic mercury absorbed in the gut, organic mercury easily absorbed via skin, gut and vapours
Effects of organic mercury
Organic mercury is liposoluble and therefore bioaccumulates and can biomagnify. Can pass through cell membranes and the blood-brain barrier and the placenta
What happened at Minamata?
1 A chemical factory released inorganic mercury in the bay
2 Sulphur loving anaerobic bacteria converted inorganic mercury to organic mercury
3 Organic mercury was taken up by algae and other organisms where it bioaccumulated and biomagnified in the food chain
4 Problems were first noticed in the “dancing cats” who ate fish
5 People suffered nervous system problems, birth defects, lowered IQ and death
Control of mercury
mercury thermometers replaced with alcohol or electronic thermometers, effluents containing mercury can be treated using reverse osmosis, activated carbon filters, ion exchange filters or disposed at high pH to reduce mercury solubility
Sources of Cadmium
nickel-cadmium batteries, incineration of plastics and paints, disposal of solar panels, drainage water from cadmium and zinc mines
Effects of Cadmium
brain damage, paralysis, lung cancer, kidney failure, decalcification of the skeleton
Control of Cadmium
Banning or restricting the use of cadmium, disposed of separately as hazardous waste, recycling of batteries
Sources of Tin
antifouling paint on boats (tributyltin, TBT)
Effects of Tin
TBT is an endocrine disruptor and alters the growth and reproductive organs of marine organisms and can be passed through the food chain through the consumption of shellfish.
Control of Tin
TBT is prohibited in antifouling paint, replaced with copper. Paint residues disposed of as chemical waste to landfill rather than the sea.
Sources of Iron
mining activities, iron ores such a hematite and magnetite, mine drainage, spoil heaps
Effects of Iron
not toxic but readily oxidies so lowers dissolved oxygen in water bodies killing aerobic organisms
Control of Iron
Managing spoil heap drainage water, water is passed over mesh screens where iron can oxidise and precipitate before release into rivers
