Water covers over 70% of the Earth's surface and is a very important resource for people and the environment. Water pollution affects drinking water in groundwater, rivers and lakes all over the world. This consequently harms human health and the natural environment. Water pollution also harms marine ecology inc. fishstocks, sea-birds etc. http://www.water-pollution.org.uk/
Where does water pollution come from? Point source, directly into water, e.g. oil spill from a ship Nonpoint source, e.g. indirectly into water, e.g. fertiliser run-off from farms
Many activities result in water pollution Mining Agriculture – e.g. agro-chemicals; manure Household cleaning, e.g. phosphates Sediment, e.g. Land reclamation; erosion Industrial waste Oil spillage Dumping Sewage Air pollution settling in water, e.g. mercury (Hg) Radioactive pollution
Mining Exposes heavy metals and sulphur compounds which were previously locked underground Discharges contaminated effluent into water Relies on large quantities of water to process ore Seepage from waste – leaches aquifers, contaminating underground water Each tonne of copper extracted results in 99 tonnes of waste material
Exposure of sulphur in rocks reacts with water and oxygen to form sulphuric acid. Acid is carried off the mine-site by rainwater or surface drainage and deposited into nearby water bodies inc. groundwater. This severely degrades water quality, and can kill aquatic lifeand make water virtually unusable.
Heavy metals from industrial processes can accumulate in nearby lakes and rivers. These are toxic to marine life such as fish and shellfish, and subsequently to the humans who eat them. Heavy metals can slow development; result in birth defects and some are carcinogenic.
Agriculture Fertilisers used to increase plant growth contain nitrates and phosphates These nutrients end up in water, causing an overgrowth of algae. This is known as eutrophication or algal blooms. -Algae blocks light to deeper waters -As algae dies, its decomposition depletes oxygen from water -Reduces life in water (fish and plants)
The Salton Sea, California. Massive fish deaths are common here due to poor agricultural practices (supported by US legislation).
Household cleaners & personal products Wash down drain into water system Nonylphenol (in detergent) disrupts fish reproduction Phosphates cause eutrophication
Agriculture-pesticides Pesticides are another product resulting in water pollution Pesticides are designed to kill unwanted bugs and vermin They contain hazardous substances Pesticides in water end up in the human body Many pesticides are very long-living, and accumulate in the body Pesticides cause many health problems inc. hormone disruption, immuno-suppression, behavioural disorders, infertility, cancer
Sediment Soil, clay, sand, silt and dead organic (plant & animal) material can end up in water These particles make the water murky (unclear). This limits photosynthesis of water plants and makes it difficult for fish to find food. Sediment contaminates drinking water Sediment can carry nutrients thus causing algal blooms Sediment can kill fish (by blocking gills) and disrupt reproduction
What increases sediment in water? Land erosion (from deforestation) Construction activities Land reclamation Dredging Rain Stormwater Hosing of hard surfaces
Industrial processes By-products of industry such as radioactive waste, heavy metals, dyes Much hazardous waste is injected into deep bedrock (beneath water table). Some of these pollutants have found their way into the underground water Discharges (cooling waters) from power plants and factories warm the water, causing fish deaths & coral bleaching
Oil Oceans are polluted by oil on a daily basis from oil spills, routine shipping, run-offs and dumping. Oil spills make up about 12% of the oil that enters the ocean. The rest come from shipping travel, drains and dumping. An oil spill from a tanker is a severe problem because there is such a huge quantity of oil being spilt into one place. Oil spills cause a very localised problem but can be catastrophic to local marine wildlife such as fish, birds and sea otters. Oil cannot dissolve in water and forms a thick sludge in the water. This suffocates fish, gets caught in the feathers of marine birds stopping them from flying and blocks light from photosynthetic aquatic plants. Oil persists for a long time.
Dumping http://www.youtube.com/watch?v=8a4S23uXIcM Plastic soup - Moving up the food chain Animals mistake rubbish for food Marine animals often die after becoming entangled in fishing nets and other discarded rubbish Street litter often ends up in the ocean via stormwater drains
Dumping at sea Dumping of litter in the sea can cause huge problems. Plastic is eaten by marine animals and may result in death. Cardboard – Takes 2 weeks to degrade. Newspaper – Takes 6 weeks to degrade. Photodegradable packaging – Takes 6 weeks to degrade. Foam – Takes 50 years to degrade. Styrofoam – Takes 80 years to degrade. Aluminium – Takes 200 years to degrade. Plastic packaging – Takes 400 years to degrade. Glass – It takes so long to degrade that we don’t know the exact time.
Air pollution Airborne mercury (Hg) from fossil fuel burning and chlorine and cement industries settles in water This Hg accumulates in fish –the bigger the fish, the greater the amount Pregnant women and young children are most at risk from this
Radioactive pollution This is a hazardous material and all handling and disposal must be strictly compliant with government legislation Radioactive waste is very long-lived and needs “babysitting” for many millennia