Heavy Metal Pollution in the Cauvery River
Study Overview
Sites covered:
18 sediment sites, 10 fish sampling sites along the Cauvery River.
Analyzed metals: Chromium (Cr), Cadmium (Cd), Copper (Cu), Lead (Pb), and Zinc (Zn).
Purpose: Assess ecological and human health risks due to heavy metal contamination in sediments and fish.
Key Findings
1. Contamination Pattern
Heavy metal accumulation in fish tissues varied by species.
Cadmium (Cd) and Lead (Pb) exceeded safe threshold limits for:
Non-carcinogenic (organ damage)
Carcinogenic (cancer-causing) risks.
2. Pollution Indices Used
Igeo (Geoaccumulation Index): To determine heavy metal pollution in sediments
Contamination Factor (CF): Degree of contamination per metal.
Pollution Load Index (PLI): Overall site pollution.
Potential Ecological Risk Index (PERI): Evaluates environmental hazard.
3. Major Sources
Source Type | Example |
Industrial Effluents | Textile & electroplating units (Erode region) |
Agricultural Runoff | Fertilizers & pesticides |
Urban Wastewater | Untreated municipal sewage |
Natural Sources | Mineralized zones upstream – mainly iron |
4. Spatial Variation
Significant variation between sampling sites due to differing human pressures.
Public Health Implications
Health Risks:
Cadmium and Lead pose both cancerous and non-cancerous risks.
Prolonged consumption → bioaccumulation in humans.
Safe Limit:
Fish consumption up to 250 g twice a week considered safe.
Risks depend on age, amount, and frequency of intake.
EPA Findings (VIT study):
Target Hazard Quotient (THQ) for several metals > 1 → real human health risk.
Scientific & Environmental Significance
Reveals ecological stress in Cauvery due to industrialization and urbanization.
Confirms biomagnification of heavy metals up the food chain.
Highlights gaps in environmental management and regulatory enforcement.
Provides scientific basis for policymaking and local interventions.
Recommendations
Continuous monitoring of sediments, water, and aquatic species.
Stricter effluent regulations for industrial discharge.
Public awareness campaigns on safe fish consumption.
Policy intervention to manage land-use and emission sources.
Long-term studies to track heavy metal trends and health outcomes.
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Bioaccumulation (within one organism) ·
It means the gradual buildup of a toxic
substance (like mercury, lead, or pesticides) inside the body of a single
organism over time. ·
The rate at which the substance enters the
body is faster than the rate at which it is removed. ·
Example: A fish
living in polluted water absorbs cadmium through its gills and food. Over
time, the metal builds up in its tissues. Biomagnification (across the food chain) ·
It means the increase in the
concentration of a toxic substance as it moves up the food chain. ·
Each predator eats many contaminated prey,
so the pollutant becomes more concentrated at higher levels. ·
Example: Small
fish absorb mercury → big fish eat many small fish → birds or humans eat the
big fish and get even more mercury.
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Prelims Practice MCQs
Q. Which of the following heavy metals were identified as major contaminants in the Cauvery River ?
Cadmium
Lead
Zinc
Mercury
Select the correct answer:
(a) 1 and 2 only
(b) 1, 2 and 3
(c) 2 and 4 only
(d) 1, 2, 3 and 4
✅ Answer: (b)
Explanation: The study focused on Cd, Pb, Zn, Cu, and Cr. Mercury was not part of the analysis.
Q. The “Geoaccumulation Index (Igeo)” is used to:
(a) Assess water pH variation
(b) Measure organic waste in rivers
(c) Quantify heavy metal pollution in sediments
(d) Estimate biodiversity index
✅ Answer: (c)
Explanation: Igeo compares current metal concentrations with pre-industrial background levels to assess pollution.
The Geoaccumulation Index (𝐼𝑔𝑒𝑜) is a tool used to assess the contamination level of heavy metals in soil and sediment. It compares the concentration of a metal in a sample to its natural background concentration, and the resulting value indicates the level of pollution, ranging from unpolluted to extremely polluted. This index helps researchers identify and quantify pollution from human activities like mining, industry, and agriculture.
Q. Consider the following statements:
Cadmium and Lead pose both carcinogenic and non-carcinogenic risks to humans.
The main source of these metals in the Cauvery is geological.
Safe consumption limit estimated: 250 g of fish twice a week.
Which of the above is/are correct?
(a) 1 and 3 only
(b) 2 and 3 only
(c) 1 and 2 only
(d) All three
✅ Answer: (a)
Explanation: Industrial and urban effluents are the main sources (not natural). Cadmium and lead are toxic even at low doses.
Q. The “Pollution Load Index (PLI)” gives an idea about:
(a) Level of biodiversity in polluted zones
(b) Overall degree of heavy metal contamination in an area
(c) Organic waste accumulation
(d) Sediment grain size distribution
✅ Answer: (b)
Explanation: The Pollution Load Index (PLI) evaluates soil contamination by heavy metals.
