Topics Covered:
Conservation, environmental pollution and degradation, environmental impact assessment
Heavy metals contaminating rivers
What to study?
For Prelims: What are heavy metals?
For Mains: Key findings, contamination and concerns.
Context: Central Water Commission (CWC) has released a report on heavy metals contaminating Indian rivers.
Background:
The exercise was limited to surface water and did not cover groundwater contamination.
Value addition for Mains:
Key findings:
- Samples from two-thirds of the water quality stations spanning India’s major rivers are contaminated by one or more heavy metals, exceeding safe limits set by the Bureau of Indian Standards.
- Ironemerged as the most common contaminant.
- Arsenic and zinc are the two toxic metals whose concentration is always found within the limits.
- Other major contaminants found in the samples were lead, nickel, chromium, cadmium and copper.
- The contamination of water sites depends on the season- varied presence of contaminants is found in different seasons.
- Metals found in Non-Monsoon Period: Lead, cadmium, nickel, chromium and copper.
- Monsoon Period:Iron, lead, chromium and copper exceeded ‘tolerance limits’ in this period most of the time.
- The main sources of heavy metal pollution are mining, milling, plating and surface finishing industries that discharge a variety of toxic metals into the environment.
- The population growth and rise in agricultural and industrial activities are also responsible for contamination of surface water.
What’s the concern?
The presence of metals in drinking water to some extent is unavoidable and certain metals, in trace amounts, are required for good health. However, when present above safe limits, they are associated with a range of disorders.
Long-term exposure to the heavy metals may result in physical, muscular, and neurological degenerative processes that mimic Alzheimer’s disease, Parkinson’s disease, muscular dystrophy and multiple sclerosis.
For Prelims:
What are heavy metals?
Metals with relatively high densities, atomic weights, or atomic numbers.
A density of more than 5 g/cm3 is sometimes quoted as a commonly used criterion.
Sources: the Hindu.
