5.2 Detection and Monitoring of Pollution

5.2.1 Describe two direct methods of monitoring pollution.

Aspect Monitored
pH meter/probe of universal indicator kit
Ph 8-11= alkaline
Ph7= neutral
Ph1-6= acidic
Nitrate testing kit
4-5 mgdm^2=clean water
5-15mgdm^2=polluted water
Carbon monoxide
Carbon monoxide monitor
10-200 ppb= natural level
200-500 ppb=polluted

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 is a measure of the total demand for oxygen by living and chemical components in a water body
  • Measuring BOD is a very useful when examining the health of water ways e.g. stream, rivers and lakes
  • BOD is essentially the amount of dissolved oxygen required to break down organic materials in a given volume of water through aerobic activity
  • Essentially it is a measure of oxygen uptake in water
Calculating BOD
  • The BOD in a given body of water is determined by the number of aerobic organisms and their rate of respiration
  • The greater the amount of organic pollutant in the water the more microbes are required to break it down. Hence, there is a positive relationships between pollutant level and BOD

How to measure BOD?
  • Take a sample of water at measure volume
  • Measure the oxygen level
  • More the sample in a dark place at 20 degree for five days
  • After five days re-measure the oxygen level
  • BOD is the difference between the two measurement

What does this mean?
  • 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.

Biotic Indexes
-Indicator species
  • The health of an ecosystem can often be measured by indicator species e.g. frog
  • More of less of these species can indicate whether an ecosystem is polluted
  • Species have a sensitive level (tolerance towards pollution)

(Further Reading, just scroll down to 5.2.3)