Heavy metal contamination in Delhi's groundwater
Why in news?
A recent CPCB report highlights severe heavy metal contamination in Delhi's groundwater
Key Contaminants and Rankings
- Uranium: 13 of 83 samples above limits; part of northwestern hotspot including Delhi.
- Lead: Tops national list at 9.3% exceedance.
- Nitrate and Fluoride: Driven by human activities and natural rock interactions.
- Salinity Issues: Sodium Adsorption Ratio (SAR) up to 179.8 (34.8% exceedance); Residual Sodium Carbonate (RSC) worst nationally at 51.11%.
Reasons for the contaminants
- Overuse of groundwater: Too many borewells and handpumps suck up water faster than it refills, letting dirty stuff build up deep underground.
- Farming chemicals: Fertilizers and pesticides wash from fields into water, spiking nitrate levels.
- Bad waste dumping: Sewage, trash, and factory leaks seep into the ground, adding lead and other metals.
- Natural rock leaks: Rocks like granite release uranium and fluoride as water flows through them.
- Old landfills: Leaky garbage sites let metals like lead and cadmium mix into nearby water.
Health and Usage Impacts
- High uranium links to kidney issues and carcinogenicity, while lead acts as a neurotoxin. Elevated SAR and RSC render water unsuitable even for irrigation or industry.
- Delhi Jal Board supplies over 450 million liters daily of minimally treated groundwater, prompting demands for public testing data from all 5,500 tubewells.
CPCB Recommendations
The board urges source protection, better fertilizer use, effluent regulations, targeted treatments, and hydrogeochemical mapping for hotspots like Delhi. Monsoon recharge often fails to dilute contaminants due to local factors.
Download Pdf
