Pollution can be monitored directly by measuring chemical indicators in soil, water, and air. Soil is monitored by measuring properties like texture, organic matter, and nutrient levels. Water is monitored by measuring concentrations of chemicals like nitrates, chlorine, and heavy metals. Air is monitored by measuring levels of pollutants like sulfur oxides, nitrogen oxides, and particulate matter. Pollution can also be monitored indirectly. Biochemical oxygen demand (BOD) measures how quickly microorganisms in water consume oxygen, indicating organic pollutants. A higher BOD means more pollution. While slower than chemical tests, BOD reflects biological impacts. Biotic indices use the diversity of indicator species to indirectly estimate pollution levels

1. Topic 5
Pollution Management
5.2 Detection and monitoring of pollution

2. Monitoring Pollution
• Soil
–
–
–
–
Texture
Density
Infiltration
Water retention
characteristics
– Organic matter
– Total
nitrogen, phosphor
us and potassium
(NPK)
– Microbial biomass
• Water
–
–
–
–
–
–
–
–
Nitrate concentration
Nitrite concentration
Free chlorine
Chloride
concentration
Hardness (mineral
content)
Heavy metals
BOD
COD
– Biological indicators
Direct
measuremen
t (chemical
indicators)
Indirect
measuremen
t

3. Monitoring Pollution
• Air
– SOx (sulphur oxides)
– NOx (nitrogen oxides)
– VOCs (volatile organic compounds)
– Concentration of particulate matter
– Concentration of heavy metals (esp. lead)
– Low level ozone
http://www.epa.gov/airquality/airdata/

4. Biochemical Oxygen Demand (BOD)
• The more respiring microorganisms in a sample of
water, the faster the oxygen in it will be consumed –
i.e. the higher its BOD
• You could also take a sample of water and seed it with
a known concentration of a known species of bacteria.
A measurement of how quickly the dissolved oxygen in
the water is consumed (in the dark) will then give an
indirect measurement the quantity of organic matter
(substrate) in the sample.
• Generally 3 day or 5 day BOD measurements are made
at 20oC in order to standardise the test (BOD3; BOD5)

5. Chemical Oxygen Demand (COD)
• An oxidising agent (usually potassium
dichromate, K2Cr2O7) is used to fully oxidise the organic
matter in a water sample to carbon dioxide. The
amount of oxygen used to achieve this is a
measurement of the COD (in mg/L)
• The COD test is faster than the BOD test, and does not
use bacteria which may be affected by pollutants in the
water sample
• However, since a researcher is interested in biological
systems rather than an indirect chemical test, the BOD
test is seen as being the more useful measurement

6. Indicator Species
• Certain species (usually invertebrates) are indicative of
water bodies of specific quality
• High biodiversity of such species is indicative of the
absence of organic pollutants
• Low biodiversity and a change to only specific tolerant
species is indicative of pollution
• There is usually a direct link between the BOD
concentration in a water body and the biodiversity of
indicator species
• It is a quick and direct method of estimating levels of
pollution

7. The Trent Biotic Index
• Turns your measurements of the biodiversity of indicator species
into a scale (1 – 10), using a chart:

8. Questions
1. Describe two direct methods used to monitor
pollution in air, water and soil
2. Define the term biochemical oxygen demand
and describe its advantages and
disadvantages
3. Describe the use of a biotic index to
indirectly monitor pollution