Summary of topic 5.2
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
Summary of topic 5.2
- 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