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5. Activity: Contamination of Water; Cradle to Grave.
From the time water falls to the ground until the time it is turned once again into vapor it is continually absorbing and transporting other compounds. Some, such as carbon dioxide, dissolve into water vapor as it rises to its condensation point and on its gravity precipitated fall, while others are added to the mix on the ground. These contaminants of water fall into two categories; desirable and undesirable. The former are solutes such as minerals which can, at certain concentrations, give water a pleasant taste and be beneficial while the latter are collectively known as Pollutants. Water pollutants fall into two broad categories as well; those which are added to the water system at easily identifiable locations, such as an outflow from a sewage treatment facility, known collectively as Point Sources, and those from Non-Point Sources whose sources are less readily identified, such as pesticides and herbicides from a golf course or agricultural application.
Water pollutants can be divided into the following categories:
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disease-causing agents: viruses,
bacteria and other parasites.
• inorganic chemicals: toxic metals, salts and acids.
• synthetic organic compounds: detergents, oil, industrial wastes, pesticides and
solvents.
• fertilizers: plant nutrients, mostly nitrates and phosphates.
• sediments: soil, silt and clay from land erosion.
• oxygen-demanding wastes: sewage, animal manure, and some industrial wastes.
• radioactive materials: effluents from mining, research facilities or natural sources.
• thermal pollution: heat from industrial and electric power plants.
Water Quality is based on the presence or absence of these water pollutants. In much of the industrialized world water may contain one or more of these compounds and still be considered acceptable as drinking water. Threshold limits are determined through experimentation, usually on animals, and values are then extrapolated for human consumption.
The water quality of aquatic ecosystems can be rated by examination of three indicators: the concentration of dissolved oxygen (DO), the biological oxygen demand (BOD), and the coliform bacteria count. Because aerobic respiration is a pathway for energy derivation for most aquatic organisms, oxygen is required. Measurement of DO allows estimation of a water body’s ability to support life. BOD is a measure of an aquatic ecosystem’s rate of consumption of oxygen. If oxygen is consumed too rapidly DO may drop to levels low enough to threaten organisms requiring larger concentrations. Measurement of coliform bacteria is used as an indicator of animal related disease-causing agents in an aquatic system.
Research a pollutant and create a poster which shows:
1. Chemical or Biological nature of the pollutant.
2. Identify the Land Use(s) which can give rise to this pollutant.
3. A diagram showing the entry point of a pollutant, how it travels through and is
removed from or is stored by an aquatic system.
4. What the possible effects are of the pollutant on aquatic and terrestrial life forms.
5. An example of contamination by this pollutant and its effects on life forms.