1.3b Causes of water pollution

atmospheric deposition

chemicals released by chimneys can enter the atmosphere and then fall back to earth as rain, entering water stores

GMO herbicide

when farmers use herbicides on fields, the chemicals used are gradually washed by the rain into the groundwater or surface waters nearby, causing contamination

sewage

sewage treatment systems release more than 850 billion gallons of untreated wastewater each year, carrying diseases

nutrients

nutrients in sewage and fertilisers( excess nitrogen and phosphorus in the water/ air) cause a massive increase the growth of algae, overwhelming huge areas of ocean, lakes, and rivers( eutrophication)

highway runoff

toxic pollution can enter waste water from highway runoff; highways are typically covered with many toxic materials, washed into drains and rivers when it rains

chemical waste

detergents, chemicals used in manufacturing units, heavy metals( e.g. lead, mercury, and cadmium) from gasoline and batteries

radioactive waste

generated by uranium mining, nuclear power plants, production and testing of military weapons, and universities/ hospitals using radioactive materials

oil pollution

12% of the oil entering oceans comes from tanker accidents, over 70% of oil pollution at sea comes from routine shipping and from drains on land; 500,000 tonnes of toil from land- based sources

plastics

washes up with waves, presents as a major hazards to seabirds, fish, and other marine creatures