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September 09, 2011
E8 Waste
E7 Soil
E6 Water treatment
E5 Dissolved oxygen in water
E4 Ozone depletion
E3 Greenhouse effect
E2 Acid deposition
E1 Air pollution
Option E: Environmental chemistry
TODAY!
September 09, 2011
September 09, 2011
Sun light coming in: Visible light Sun reflected out: IR
Equilibrium: light coming in = light going out
Therefore, the temperature on earth stays the same.
However, the greenhouse gases allows the visible light to come in, but absorb the IR light going out and reradiate back on the earth.
This way, light coming in > light going out.Therefore, the temperature on Earth is increasing gradually.
September 09, 2011
CH4: Anaerobic decay of organic matter caused by intensive farming
H2O: Evaporation of oceans and lakes
CO2: Combustion of fossil fuels and biomass
N2O: Artificial fertilizers and combustion of biomass
CFCs: Refrigerants, propellants, foaming agents, solvents
Heat trapping effectiveness
not very effective
not very effective
effective
very effective
the most effective
September 09, 2011
September 09, 2011
Good ozone found in stratosphere. It protects us from UV light.Bad ozone found at ground level and formed from sun and VOC's. Results in smog
FREE RADICAL = VERY REACTIVE
September 09, 2011
CFCs:
The most common CFC is CFC-12 : dichlorodifluoromethane CCl2F2
Also known as freon, used for refrigerants propellants for aerosols, foaming agents for expanding plastics, and cleaning solvents.
Oxides of nitrogen (NOx): formed from internal combustion engines, power stations, and jet aeroplanes.
September 09, 2011
CFCs destroy the ozone layer because the UV light breaks the relatively weak C-Cl bond.This allows the formation of Chlorine radicals which reacts with the ozone molecules.
Alternatives must have similar chemical properties but not contain a bond that can be broken by UV to form radicals.
The properties required are: low reactivity, low toxicity, and low inflammability, as well as no weak C-Cl bonds. They should not absorb IR radiation as well, or they will act as greenhouse gases.
The alternatives are: hydrocarbons, fluorocarbons, and HFCs.
September 09, 2011
September 09, 2011
Try some problems!
September 09, 2011
BOD is a measure of the dissolved oxygen (in ppm) required to decompose the organic matter in water biologically (in a certain volume of water, at a certain temperature).
Water that has a high BOD without the means of replenishing oxygen will rapidly not sustain aquatic life.
Usually you need about 5 ppm to support life, but it varies.
September 09, 2011
If sufficient oxygen is present, organic material will decay aerobically, and oxides and oxyanions are produced.
Anaerobic decay involves organisms that do not require oxygen. The products are in reduced form, and are often foul smelling and toxic.
September 09, 2011
Nitrates, and phosphates (waste from intensive farming, artificial fertilizers, detergents) accumulate in lakes. They act as nutrients and rapidly increase the growth of algae and plants, called an algae bloom.
--- Lots of detergents are now being pitched as "eco friendly" since they are phosphate free and don't contribute to this problem.
Normally, when plants and algae die they decomposes aerobically to form CO2 and water. However, if the growth is excess, then anaerobic decomposition will occur due to the lack of oxygen in water. The products not only smells bad but also poisons the water. As a results, more species with die, and more anaerobic decomposition will happen, and the lake is devoid of life.
September 09, 2011
Thermal pollution - a change in temperature of an environment due to anthropogenic means.
The solubility of oxygen in water is temperature dependent. As the temperature is increased, the solubility drops. At the same time the metabolic rate of fish and other organisms increases, so the demand for oxygen also increases.
Same problem is caused by people cutting down too many trees near a lake, so that the shade is reduced and the temperature increases.
Many industrials use water a coolant (cheap) and they just discharge the heated water back to the sea/ocean. If the water is too cool, fish also may die off.
September 09, 2011
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