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Lecture 3

EESA10H3 Lecture Notes - Lecture 3: Novella, Methyl Tert-Butyl Ether, Chlordane

Environmental Science
Course Code
Jovan Stefanovic

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Week 3 Lecture 3
Water Hazards and Human Health
Liquid Capitol
- The earth is composed of 71% water mostly saltwater
- Moderates climate, dilutes and removes pollutants and wastes
- Every living creature needs water Human body is 60% water
World’s Water Problem
- Withdrawal the amount of water removed from a river, lake, or aquifer.
- Some may be returned to the source for reuse
- Fresh water = 2.6% of all water available
o Mostly in glaciers, ice caps, and groundwater
o Readily accessible freshwater can be found in lakes, rivers, soil moisture
- Stress on the World’s river basins?
o Water stress = <1700 cubic meters/year/person
o Water Scarcity = <1000 cubic meters/year/person
- Some areas have lots of water some are too far from population and agriculture not
distributed to key areas properly
- Precipitation cannot be collected and stored effectively
- As a result, lakes and rivers shrink eg. Aral Sea
- How do we use water?
o 85% is used for irrigation and not returned to the water basin
o Canada = mainly used to cool power plants
In homes = showering, toiler, laundry, drinking, cleaning
o China = agriculture
o USA = both
o All = mainly delivered to the public and industries
- Hydrological Poverty not enough water eg. Asia/Africa (1 out of 6 don’t have access to
clean water)
o People in these areas need to walk and get water = increased chances of contracting
diseases/death eg. Diarrhea kills 2 million children annually (dehydration)
o Bad hygiene at home and body = host to diseases and parasites
- Water and your health
o Drinking water
Let the water system go for a few minutes in the morning because the water in
the system has been idle overnight and might have higher traces of minerals
and chemicals
Annual reports of water quality
Tap water checked everyday
o Hot water accumulates more lead
o Acidic waters dissolves more metal and lead
o Soft water attracts more metals

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o Surface water mostly in urban areas come from lakes,
basins, rivers
o Ground water mostly in rural areas come from wells,
Bottled water - not checked everyday
o Plastic use may be a danger strip some essential minerals eg.
Calcium and Magnesium
Mineral water higher salt level
o Sources of water
Runoff from the mountain reaches the soil and lakes
Ground water is naturally purified in rocks and sand
Unconfined aquifer
Easier to contaminate
Less often used
Confined Aquifer
Cleaner and harder to get
Need to drill to get access
o Effects of Urbanization
Surface runoff is smaller in urbanized areas because of concrete
In rural areas, there is more soil = more ground water, runoff is also slow due
to vegetation
How is drinking water treated?
- Water from rivers, lakes, streams
o In settling tanks treated with coagulants so dirt and contaminants settle at the
bottom of the tank.
o It is then filtered and particles are removed
o Chemical filtration reverse osmosis, chlorination, resins, charcoal
Chlorination important in the process as it makes the water safe for
drinking prolonged effect of disinfection
- Groundwater
o Naturally filtered through rocks, sand
o Has less organic matter and is fine without any treatment
o Problem arises when there is contamination of the soil as it can leak to these sources
Contaminants in drinking water
- Pesticides and fertilizers
o Used in agriculture
o Produced nitrates and contaminates water can be washed off by runoffs and be fed
into streams/rivers/lakes
- Underground storage tanks
o Age of these tanks old tank can start leaking chemicals and contaminate ground
water eg. Septic tanks
o Sewers and lagoons can leak nitrogen
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