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Lecture 3

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Environmental Science
Jovan Stefanovic

LECTURE 3 (JANUARY 25, 2012): WATERBORNE HAZARDS AND HUMAN HEALTH Liquid natural capitol  The Earth is water planet  Water covers 71% of Earth surface  Mostly salty water  No species can do without water  Sculpting the Earth’s surface  Moderating climate  Removing and diluting wastes and pollutants World’s Problems  Quantity of water  Quality of water  Withdrawal- total amount of water removed from a river, lake or aquifer for any purpose.  Some may be returned to the source for reuse  Use about 54 % of the world's reliable runoff of surface water and could be using 70-90% by 2025 Quantity of water: How much fresh water is available? Stress on the world’s major river basins World’s Problems  Some areas have lots of water but the largest rivers are far from agricultural and population centers – since water is not near agricultural places, the water must be transported which costs money.  Lots of precipitation arrives during short period but cannot be collected and stored  Lakes and rivers shrinks How do we use the world’s fresh water?  In Canada we mostly use water for power plant cooling  Agriculture is most responsible for water use Average water use in Canadian homes (Environment Canada, 2005)  Toilet flushing is second most use of water  Shower and bath is first Hydrological poverty  One out of six people do not have regular access to clean water  Diarrheal deaths kill over 2 million children annually  Hydrological poverty – not enough water is available  Many people do not have access to clean water or need to go to far places to get clean water – Africa  Diarrhea – microbes are the problem Water and Your health  Drinking water  Swimming water DRINKING WATER  Annual reports on local drinking water quality  Tap water & bottled water  Naturally pure water & distilled water  Natural content of minerals in water  Surface water - In urban areas  rivers  lakes  springs  cisterns  Ground water- In rural areas  wells  We drink water from Lake Ontario – not from the shore. We have one of the safest drinking water in the world.  Water without cells is called distilled water – you don’t want to drink distilled water because your body needs calcium, magnesium, etc.  Main sources of drinking water is surface water and ground water  Ground water mostly used in rural areas  Two different kinds of ground water – one is unconfined ground water and the other is confined aquifers  Confined aquifer is better How development change the natural flow of water  Quality of Water  Agriculture – pesticides might reach the ground water  Storage tanks (storage of organic solvents, etc) might leak and contaminate the ground water  Septic tank from houses or farms – if not properly secured might reach ground water  Landfills Quality of water  Water pH – good ph is 7, if higher than 7 then some cells may precipitate and you can get solid with water, if below 7, acidic water dissolves metals. pH of water affects our health  Hardness – total amount of cells mostly calcium, magnesium in the water. If water is soft there is not enough cells, if hard there is too much cells. You don’t want soft water because it can dissolve lead.  Color – you don’t want colour. If there is colour, it is an indication of chemicals like copper, or organic matter  Turbidity – if water turbid it does not necessary mean it’s contaminated.
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