Last modified on 17 February 2012, at 22:39

IB Environmental Systems and Societies/Detection and monitoring of pollution

5.2 Detection and Monitoring of PollutionEdit


5.2.1 Describe two direct methods of monitoring pollution.

-air pollution-

  • measure the acidity of rain water to determine levels of
  • measure CO2, CO, or NOx levels in the atmosphere using a gas sensor
  • measure particulate matter suspended in the atmosphere

-soil pollution-

  • conduct tests for nitrates and phosphates according to the test manufacturer’s instructions
  • measure the level of organic matter in the soil

-water pollution-

  • nitrate and phosphate tests
  • fecal coliform tests
  • tests for heavy metals

5.2.2 Define the term biochemical oxygen demand (BOD) and explain how this indirect method is used to assess pollution levels in water.

  • Biochemical Oxygen Demand: A measure of the amount of dissolved oxygen required to break down the organic material in a given volume of water through aerobic biological activity.
 high BOD indicates there are many organisms using oxygen for respiration
 low BOD indicates relatively few organisms needing oxygen for respiration
 high BOD = low DO levels = high pollutant levels, especially nitrate & phosphate
 low BOD = high DO levels = low pollutant levels

5.2.3 Describe and explain an indirect method of measuring pollution levels using a biotic index.

  • We can measure pollution levels 2 different ways: we can measure the pollution itself

directly, or we can use some other factor that is correlated to pollution levels as an indirect indicator of those pollution levels.

  • the Trent Biotic Index uses the presence or absence of 6 key organisms(plecopteran larvae, ephemeropteran larvae, trichopteran larvae, Gammarus, Asellus and tubificids plus red chironomid larvae) to indicate the relative level of pollution in a stream.
 Advantage: Easy to use, especially for moderately or heavily polluted sites.
 Disadvantages: not specific enough, doesn’t fully account for habitat quality
  • We can also use “abiotic factors that change as a result of the pollutant” to indirectly test the pollution levels such as dissolved oxygen (DO) or BOD levels of the water
 Indicator species are those species that are present either only in polluted areas or only in unpolluted areas. 
 For example… 
 o freshwater shrimp, 
 o freshwater mussels,
 o stonefly nymphs, 
 o caddisfly larvae, 
 o rat-tailed maggot    
 o sludge worms in polluted water, 
 o peppered moth wing color (predominantly black indicates high levels of soot and particulate matter in the air; predominantly light grey indicates relatively particulate-free air), 
 o Gammarus - small crustaceans that are sensitive to different salinity levels, 
 o Asellus - another small freshwater crustacean, which is relatively tolerant of pollution, and therefore an indicator of polluted sites