Chromium Contamination of Groundwater

Context: The National Green Tribunal has instructed the Central Ground Water Board (CGWB) to investigate chromium contamination in the groundwater of Sukinda Valley, Odisha.

Key Details:

  • Location: Sukinda Valley in Odisha is home to 97% of India’s chromite ore deposits.
  • Chromium Characteristics: Chromium is a shiny, hard, brittle metal with a silver-grey color, found naturally in rocks, plants, soil, volcanic dust, and animals, but not in its free metal form. It is primarily extracted as the mineral chromite.
  • Common Forms in Water:
    • Trivalent Chromium (Cr III): A necessary dietary element found in many foods like vegetables, fruits, meats, grains, and yeast.
    • Hexavalent Chromium (Cr VI): Toxic and classified by the WHO as carcinogenic, it can cause severe health issues including stomach ulcers, cancers, and significant damage to the kidneys and liver.

Properties:

  • Oxidation: Chromium does not tarnish in air and forms a protective green chromic oxide layer when heated.
  • Stability: In oxygen, it forms a thin oxide layer that protects the underlying metal.

Applications:

  • Aesthetics and Protection: Used for its shiny appearance to coat cars, stoves, and other appliances, protecting them from corrosion.
  • Industrial Uses: Its high melting point and stability make it valuable in the textile and refractory industries.
  • Alloys and Plating: Integral in stainless steel production, chrome plating, and metal ceramics.
  • Catalytic Uses: Employed as a catalyst in dyeing, leather tanning, and making molds for brick firing.
  • Magnetic Tape Production: Chromium (IV) oxide (CrO2) is used in manufacturing magnetic tape.

Chromium Pollution:

  • Permissible Limits:
    • Indian Standards: The maximum permissible concentration of hexavalent chromium (Cr VI) in drinking water is 50 micrograms per liter.
    • US EPA Standards: The recommended permissible concentration is lower, at 10 micrograms per liter.

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