Heavy Metal Pollution and Eutrophication

Monitoring and Management‎ > ‎5. Water‎ > ‎

Gather, process and present information on the range and chemistry of the tests used to:

  • identify heavy metal pollution of water
  • monitor possible eutrophication of waterways
  • Heavy Metal: A metal with a relative density of 5.0 or higher.
  • Heavy metals, such as mercury and lead, can cause various health problems.
  • The heavy metal pollution of water can be tested using:
    • Atomic absorption spectroscopy, using a light source specific to the heavy metal being tested.
    • Flame tests.
    • Sodium sulfide solution, which can be added to a highly concentrated acidified or basified water sample (heavy metal ions react with sulfide ions to form sulfide precipitates):
  • If a precipitate is formed when the sample is acidified, then one or more of the following is present: lead, silver, mercury, copper, cadmium, arsenic.
  • If a precipitate is formed when the sample is basified, then one or more of the following is present: chromium, zinc, iron (III), nickel, cobalt, manganese, aluminium.
  • Eutrophication: The abundant growth of aquatic plants due to nutrient-enriched conditions, in particular, nitrate and phosphate enriched conditions.
  • The aquatic plants that grow abundantly in eutrophication eventually use up all of the available nutrients that they require and die.
  • The plants decompose, and in doing so, use up all dissolved oxygen.
  • After using all oxygen, they decay anaerobically, resulting in chemicals that kill all remaining life.
  • The decay causes sediment at the bottom of the water body.
  • The mains sources of nutrients that cause eutrophication are:
    • Sewerage.
    • Fertiliser.
  • Nitrate and phosphate are monitored in waterways vulnerable to eutrophication.
  • The nitrogen-phosphorus ratio of waterways is often monitored, with the EPA recommending a ratio of less that 10:1.