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Groundwater Nitrate Contamination
Context:
India’s groundwater is grappling with rising levels of chemical contamination, with excessive nitrates, fluoride, and uranium posing significant health and environmental challenges. According to the Central Groundwater Board (CGWB), the number of districts with excessive nitrate levels surged from 359 in 2017 to 440 in 2023, marking a worrying seven-year high.
Reasons for Nitrate Accumulation:
- The excessive use of nitrogenous synthetic fertilizers, largely driven by subsidies, is the primary contributor to rising nitrate levels.
- These fertilizers leach into groundwater, particularly in agricultural zones where irrigation practices rely heavily on groundwater extraction.
- Poor regulation of fertilizer application and inefficient irrigation systems further aggravate the problem.
State of Excess Nitrates in Groundwater:
- The presence of nitrates in groundwater exceeding the safe limit of 45 mg/litre has reached alarming levels.
- In 2023, 56% of India’s districts recorded excessive nitrate contamination, based on an analysis of 15,239 groundwater samples, with 19.8% of samples surpassing safe nitrate limits.
- While this proportion is slightly lower than the 21.6% in 2017, the total number of affected districts has significantly increased, highlighting a growing regional disparity.
Sources of Excess Nitrate Accumulation in Groundwater:
- Synthetic Fertilizers: Overuse in agriculture leads to nitrate leaching into groundwater.
- Improper Waste Disposal: Unregulated disposal of sewage and industrial waste contributes to nitrate buildup.
- Livestock Farming: Animal waste and manure are significant sources of nitrates in groundwater.
Distribution of Nitrate Contamination Across India:
Nitrate contamination is more pronounced in certain states, with regional hotspots revealing worrisome trends:
- Rajasthan: 49% of tested samples exceeded safe limits.
- Karnataka: 48% of tested samples were contaminated.
- Tamil Nadu: 37% of samples showed excessive nitrate levels.
States in central and southern India are experiencing rising contamination:
- Maharashtra: 35.74% of tested samples.
- Telangana: 27.48%.
- Andhra Pradesh: 23.5%.
- Madhya Pradesh: 22.58%.
Other Contaminations: Fluoride and Uranium
Beyond nitrates, groundwater contamination by fluoride and uranium is another critical concern:
- Fluoride contamination is severe in Rajasthan, Haryana, Karnataka, Andhra Pradesh, and Telangana, posing long-term health risks like dental and skeletal fluorosis.
- Uranium contamination has crossed unsafe levels (30 ppb) in Rajasthan, Gujarat, Haryana, Punjab, Tamil Nadu, Andhra Pradesh, and Karnataka. The highest concentrations are reported in Rajasthan and Punjab, exacerbated by overexploitation of groundwater resources.
Seasonal variations are notable, with nitrate contamination rising post-monsoon (32.66%) compared to pre-monsoon levels (30.77%).
Impact of Excess Nitrate, Fluoride, and Uranium Contamination:
- Health Risks:
- Excess nitrates can lead to methemoglobinemia (blue baby syndrome) in young children, a condition that reduces the blood’s oxygen-carrying capacity.
- Fluoride exposure causes skeletal and dental fluorosis.
- Prolonged uranium ingestion can result in kidney damage and potential carcinogenic effects.
- Environmental Consequences:
- Nitrate accumulation in water bodies leads to eutrophication, disrupting aquatic ecosystems.
- Chemical contaminants degrade soil and water quality, impacting agriculture and biodiversity.
What Should Be Done:
- Fertilizer Regulation:Promote the use of biofertilizers and organic farming practices to reduce dependence on nitrogenous synthetic fertilizers.
- Groundwater Management:
- Develop and enforce policies for sustainable groundwater extraction.
- Invest in artificial groundwater recharge techniques to dilute contaminants.
- Monitoring and Awareness:
- Expand the scope of groundwater quality monitoring to ensure timely detection of contaminants.
- Raise public awareness about the health risks associated with nitrate, fluoride, and uranium contamination.
