What are the sources of heavy metals in water?

• A. Human and Animal Wastes
• B. Unlined Landfills and Industrial Discharges
• C. Nitrates and Phosphates
• D. Thermal Pollution

Answer: (B)

Heavy metals in water mainly come from human activities that introduce metals directly or via waste streams. Unlined landfills allow leachate to percolate through waste and into groundwater or nearby surface waters, carrying metals such as lead, cadmium, mercury, and arsenic. Industrial discharges add metal pollutants straight into water bodies through effluents from processes like metal finishing, mining, smelting, and battery production. These are direct, persistent sources of heavy metals that contaminate water supplies and sediments.

Nitrates and phosphates are nutrients that drive eutrophication, not metal pollution. Thermal pollution changes water temperature, affecting ecosystems but not the presence of heavy metals. Wastes can contain metals too, but the combination of leachate from landfills and direct industrial discharges is the main pathway for heavy metals entering water.