Uranium Contamination in Ground Water

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    In News

    • Recently, a report titled “Groundwater yearbook 2021-2022” was released on the state of groundwater released by the Central Ground Water Board (CGWB).

    Key Findings

    • Twelve Indian states have uranium levels beyond permissible limits in their groundwater.
    • Punjab is the worst-affected state in terms of the percentage of wells found to have uranium concentration of more than 30 ppb. 
    • Haryana is the second state in terms of uranium prevalence in groundwater.
    • 9.2 percent of the samples from Uttar Pradesh had a high concentration of uranium.
    • Uranium concentration is found to be within safe limits in 13 states.
      • The safe levels prescribed by the Bureau of Indian Standards (BIS) and the World Health Organization (WHO) is 30 ppb.

    State

    Maximum value of Uranium observed 

    (in ppb)

    Percentage of samples beyond permissible limit of BIS 

    (U >30 ppb)

    Punjab

    532

    29

    Haryana

    518

    14.4

    Uttar Pradesh

    239

    9.2

    Rajasthan

    186

    8.6

    Tamil Nadu

    159

    3.4

    Madhya Pradesh

    149

    1.3

    Odisha

    61.4

    0.69

    Delhi

    58.3

    3.9

    Telangana

    36.1

    1.43

    Chhattisgarh

    32

    0.12

    Bihar

    31.4

    0.36

    Source: Groundwater yearbook 2021-22

     

    Causes of contamination

    • Geogenic processes are responsible for uranium contamination.
    • High levels of uranium are largely due to natural uranium content in aquifer rocks, oxidation state and groundwater chemistry.
      • Overexploitation of groundwater has been observed in all types of aquifers in the country, confirmed in another 2021 study by researchers from Bhabha Atomic Research Centre (BARC) and Homi Bhabha National Institute.
    • Extreme bicarbonate levels were also found at the sites with high uranium levels. 
      • Bicarbonates help to bring the uranium out of the source rocks and is a reason for the high occurrence of the element. 
      • The interaction of the extracted uranium with other chemicals in the groundwater, such as bicarbonate, which can further enhance its solubility.
    • Water-rock interactions that cause the uranium to be extracted from those rocks.
    • Oxidation conditions that enhance the extracted uranium’s solubility in water.
    • The human-made causes too are behind this:
      • Over-exploitation of groundwater from irrigation further exacerbates uranium mobilisation. 
      • It is likely to be one of the reasons for uranium and other geogenic contaminants, including arsenic and fluoride.
      • Nitrate pollution. 
      • Groundwater table decline

    What is Uranium?

    • As an element: 
      • It is a naturally occurring element found in low levels within all rock, soil, and water.
      • Uranium is a weak radioactive substance because of its long physical half-life.
      • It is the highest-numbered element to be found naturally in significant quantities on earth. 
    • Groundwater: 
      • Uranium is a nephrotoxic element and can have an adverse impact at very high concentrations. 
      • This means that people dependent on groundwater containing the element are at a higher risk of impaired renal function and kidney disease. Exposure to uranium may also lead to other adverse health impacts, including bone toxicity.

    Threat to Groundwater

    • Degradation from human activities, often associated with poor land, agricultural, and waste management threatens:
      • Current uses of groundwater and 
      • Human and ecosystem health 
      • Limits benefits of future generations
    • The problem is more pronounced in South Asia because much of the groundwater is heterogenous. Some 70 percent of groundwater is hosted only in 30 percent of land cover in south Asia and the rest is hosted in areas covered by Himalayan rivers.
    • Water pollution is another issue as much of the groundwater is polluted by contaminants like arsenic and Fluoride. More than 400 million people are exposed to these pollutants. So, it is not just a quantity issue but also a water quality issue in India.

    Health Impact

    • Exposure to uranium may lead to numerous adverse health impacts including bone toxicity and impaired renal function.
    • Exposure to uranium could also cause cancer.

    Significance of Groundwater

    • Ground water has become an increasingly important natural resource catering to the fresh water requirements of various sectors in India. 
    • Ground water has steadily emerged as the backbone of India’s agriculture and drinking water security.
    • About 90% of this was used for irrigation, the rest went to towns and villages.
    • Groundwater is the principal water source for a fourth of the world’s population. India is the world’s largest groundwater user; nearly 250 cubic kilometres was taken out in 2017. 

    Way Ahead

    • There is a need for an urgent response from all stakeholders. Protection of groundwater must be guaranteed across all sectors including agriculture.
    • Governance, actions and investments on groundwater should be prioritized in vulnerable and climate change / hazard-exposed regions, including sub-Saharan Africa, Small Island Developing States and coastal zones, areas with no or slowly renewable and vulnerable aquifers, and aquifers with naturally occurring but hazardous contaminants, like arsenic
    • Reverse osmosis (RO) is one of the latest membrane-based technologies used in water purification systems to remove uranium. 
    • More studies and Research is needed on the removal of uranium from drinking water using a hybrid membrane technique. 

    Source: DTE