Lecture 17 Natural Groundwater Contaminants by bIU33417


									Water Use, Overuse, and Natural Contamination
 Water Mining
Over-exploitation of renewable     India
and non-renewable aquifers         Iran
Withdrawals exceed recharge
creating deficits in the aquifer
Lack of contemporary recharge      Morocco
                                   Saudi Arabia
                                   South Korea
                                   United States
                            The Middle East

                              . (Mm3/yr)
             COUNTRY             Total use   % Non-renewable
             Saudi Arabia         21,000          84%

               Bahrain             258            35%

                Egypt             4,850           18%

               Jordan              486            35%

                Libya             4,280           70%

               Yemen              2,200           32%

Saudi Arabia and Libya, use 77% of the estimated total world extraction
of non-renewable groundwater for urban supply and irrigated agriculture.
Falls in the water table between 1982 and
   2000 range from 3 to 6 feet per year

Within 15 years Quetta will run out of water
if the current consumption rate continues
                  Iran: Water Refugees

                                             Villages Abandoned

over pumping by an average of 5 billion tons (3.7 Ma-f)of water per year
             Equivalent to 1/3 Iran’s annual grain harvest

                 Water table falling by 8.5 feet per year
                            Qa-Disi Aquifer

                            35,000 years old

                            Saudi farmers are now
                            pumping water from wells
                            that are 4,000 feet deep

71 percent drop in wheat harvest from a high of 4.1
  million tons in 1992 to 1.2 million tons in 2005,
        water extraction exceeds the
        annual recharge by a factor
        of five,

        Water table dropping
        6 meters (18 ft) per year

          pumped dry by 2010

        relocate the capital
   Other Large Deficits

  India        ½ the world’s
               total use of
  China        groundwater           1 foot
  Pakistan 1 acre agriculture
      Area =   for

Pumping: 325 million acre feet

Recharge: 205 million acre feet

Deficit: 120 million acre feet

     1 acre-foot = 325,851 gallons
                                                       Shallow , unconfined
                                                       aquifer depleted

               Deficit feeds 100 million people

Level of the deep aquifer is dropping nearly 3 meters (10 feet) per year

 Deep wells must reach more than half a mile to tap fresh water

 Deficit of 80 million acre-feet

   Deficit feeds 200 million

      Failure of 246 surface
      irrigation projects

       21 million wells

    $600 electric pumps
      (1% of GDP)
                                          95 %
water table falling by 20 feet per year
  5 acres of land
 Pumps 3200 gallons/hr

 Irrigates alfalfa for 64 hours

 24 times per year

4.9 million gallons water/yr
Yield: 6.5 gallons milk/day

4.9 million gallons => 2400 gallons milk
  (2000 gallons water/ gallon milk)
United States
                 United States
 1/3 of irrigation water comes from groundwater

The 3 largest aquifers are in arid/semi-arid regions
  Ogallala Aquifer         Midwest
  Central Valley Aquifer   California
  Southwest Aquifer System Arizona, Utah, Nevada
    Deficit of 30 million acre-feet

      High Plains Aquifer (Ogallala)
 ¼ gone in areas of Texas, Oklahoma, Kansas
Water table declines up to 100 feet in some areas

    Central Valley Aquifer (California)
   Pumping 15% more water than is replaced
  Water storage capacity has declined by 50%

Southwest Aquifer (Utah, Nevada, Arizona)
   Pumping 50% more water than is replaced
Phoenix Arizona   Growing 2 acres/hr
                  Among the highest water users

tripled in population over the last 40 years
 Central Arizona Project

Canal 335 miles long

44 billion gallons/yr

7% lost to evaporation
Use, Overuse, Quality
Septic systems
Urban Runoff
Natural Groundwater Contaminants

       21 million wells

    Tapping water as
   deep as 1,000 meters

water table falling by 20 feet per year
Deeper Wells and Fluoride

       Naturally occurring element in Granite
       which dissolves into the groundwater

    Water near the surface is generally unaffected

    Lowering water tables = deeper wells

    Deep groundwater contains high fluoride levels

    fluoride in water can be a cumulative poison
Intentional Fluoridation of Water in the U.S.

Fluoridation became an official policy of the U.S.
Public Health Service in 1951.

By 1960 water fluoridation had become widely used
in the U.S. reaching about 50 million people.

By 2006, 69.2% of the U.S. population on public water
systems were receiving fluoridated water.
              How does it work?

Tooth enamel is made of a mineral called hydroxyapatite


        Bacteria in the mouth create acids (H+)

Hydroxyapatite is subject to dissolution by acids (H+)

    Fluoridation changes the chemical composition of
 hydroxyapatite to a crystal less subject to acid dissolution
         Sodium fluorosilicate (Na2SiF6)
            Sodium fluoride (NaF)
              NaF           Na+ + F-

        Ingestion of fluoridated water increases
             the F- concentration in saliva

 F- replaces OH in hydroxyapatite making fluoroapatite


                 Ca5(PO4)3 OH
Fluoroapatite is less soluble in acid than hydroxyapatite
Fluoride concentrations
In U.S. tap water

   0.6 – 1.1 mg/L

        Lower values in warm climates
        Fluoride levels > 1.5 mg/L

  Dental Fluorosis
                                  1.6 to 6.6 mg/day

                             Colorado Brown Stain

  Permissible fluoride limit in India is 1.2 mg/L

Fluoride levels between 5-25 mg/L have been found
 Fluoride levels > 10 mg/L

             Skeletal Fluorosis

                              9 mg/day to 12 mg/day

Fluorosis has risen from 1 million to 25 million
and now to 60 million people in India.
Groundwater and Arsenic
           Arsenic is Naturally Occurring

             occurs primarily in association
             with sulfur-containing minerals

  mean values of arsenic content in soils, the earth’s
  crust, and sediments are between 1.5, and 7.7 mg/kg

Natural waters, in general, contain low levels of total arsenic

    Mobilization of arsenic in the environment arises from
anthropogenic activities related to mining and ore processing,
  metallurgy, agriculture, wood preservation, and industry.
 Inorganic Forms of Arsenic

             AsO3-3                      AsO4-3
             Arsenite                    Arsenate

         Low Oxygen                  High Oxygen

  Arsenite is more toxic than arsenate, interfering with
  enzyme activities which catalyze metabolic reactions

Arsenite compounds are also more mobile in the environment
  due to higher solubility compared to arsenate compounds

    Both arsenate and arsenite are chronic accumulative toxins
“The World’s Largest Mass Poisoning”
      Bangladesh and W. India

ranked among the world's
10 poorest countries
 Floodplain and Delta of the
 Ganges and Brahmaputra

Floodplain: area paralleling a
river that is periodically inundated
                                         Ganges-Brahmaputra Delta
Deltas are formed from the deposition
of sediment carried by the river as
the flow leaves the mouth of the river

    Accumulation of
    thick muds
    in the floodplains
    and deltas
Prior to 1970s

One of the highest infant mortality rates in the world
Principally due to waterborne disease.

      Ineffective water and sewage systems
      Periodic monsoons and floods

                    water-borne pathogens
                       cholera, dysentery

Deaths Due to Surface water contamination: 250,000/yr
Deaths Due to Surface water contamination: 250,000/yr

  The Solution: Tap groundwater resources

              • easy
              • inexpensive

    First 1 million were sunk with aid from
             World Governments
                   World Bank
      12 million hand-operated tube wells
      deliver water to over 80% of the
      rural village population

Infant mortality and diarrheal illness reduced by 50%
 Wells in Floodplain
 and Delta Sediments

 Natural erosion of
 arsenic to water-
 bearing units.

Well depths between 20m and 100 m

               Water Bearing Muds
                                     WHO/U.S limit: 10 ppb
                                     Bangladesh limit: 50 ppb

Majority of wells > 50 ppb arsenic    Some wells contain 500 - 1000 ppb
Exposure Estimates

     Above 50 ppb:         35 million

     Above 10 ppb:         57 million

         Early Symptoms:

         Skin lesions and thickening
         Strong skin pigmentation
2003 Studies
               83 million people

Bihar: 40% wells contaminated
Red River Delta

11 million people

First wells sunk
7 years ago
End Lecture 17
Next: Florida’s Aquifers
   Sea Levels

Temporary reestablishment
of carbonate deposition

    One gallon of gasoline can
    contaminate 1 million gallons
    of drinking water

         1 ppm

To top