06-06-2014, 04:26 PM
Environmental Geology-------Water Resources
1370248401-nov8powerpoint.ppt (Size: 1.9 MB / Downloads: 123)
Water Resources
Over the last century
Human population has increased 3x
Global water withdrawal has increased 7x
Per capita water withdrawal has increased 4x
About one-sixth of the world’s people don’t have easy access to safe water
Most water resources are owned by governments and are managed as publicly owned resources
Human water needs
A person needs about 1 gallon water/day for hydration
In the US each person uses about 188 gallons/day
An additional 657 gallons/person/day are used for irrigation, industrial use.
Total per capita use is about 2000 gal/person/day
If world’s water supply were 100 liters, the usable supply would be about 0.5 tsp
US has highest per capita water withdrawal, followed by Canada, Australia, Russia, Japan
Groundwater Pollution
70,000 chemicals are used not; effects of many are not known
Each year another 700-800 new chemicals are produced
55 million tons of hazardous chemical wastes are produced in the US each year
The 20 most abundant compounds in groundwater at industrial waste disposal sites include TCE, benzene, vinyl chloride…all are carcinogens, and also affect liver, brain, and nervous system
Inorganic Pollutants
3 groups
1) Produce no heavlth effects until a threshold concentration is exceeded—e.g., NO3 –ook at , 50mg/liter; at higher levels: methaemoglobinaemia
2) No threshold—e.g.—genotoxic substances: some natural and synthetic organic compounds, microorganic compunds, some pesticides, arsenic
3) Essential to diets: F, I, Se—absence causes problems, but too much also causes problems
Inorganic Trace Contaminants
Mercury—methyl Hg and dimethyl Hg in fish—probably most significant path to humans—Minamata Bay, Japan, 1950’s
Rhine River drains 185,000 sq km—heavily polluted by 1970’s
Lead—toxicity has been known for a long time
1859 book
Tetraethyl lead—anti-knowck additive for gas, 1930-1966
Radionuclides
Bikini Atoll in South Pacific: > 20 tests, 1946-1958
Inhabitants evacuated before 1946 tests; their descendents are still exiled
Atmospheric testing of nuclear weapons is now banned
National labs…now trying to clean up (Hanford)
Phosphates and Nitrates
Phosphates—mostly a result of sewage outflow and phosphate detergents
Additional phosphate grows excess algae…oxygen depletion, Lake Erie…1972 phosphate management plant…$7.6 billion
Nitrates—sewage and fertilizers
Dumping wastes in the oceans
Dumping industrial wastes off US coasts has stopped, but dredge products are legally dumped at 110 sites in Atlantic, Pacific, and Gulf Coasts
US has banned dumping sewage sludge in ocean since 1992
50 countries rep ~80% of world’s shipping fleet have agreed not to dump sewage and garbage
London Dumping Convention of 1972; 1994
Solutions Water Pollution
Prevent groundwater contamination
Greatly reduce nonpoint runoff
Reuse treated wastewater for irrigation
Find substitutes for toxic pollutants
Work with nature to treat sewage
Practice four R's of resource use (refuse, reduce, recycle, reuse)
Reduce resource waste
Reduce air pollution
Reduce poverty
Reduce birth rates