Unit C Section 3.2
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Techniques that can change the concentration of pollutants:
• dispersion, • dilution, • biodegradation, • phytoremediation, • photolysis.
What is Dispersion?
Dispersion is the scattering of a substance away from its source.
What is Dilution?
Dilution reduces the concentration of a pollutant by mixing the polluting substance with large quantities of air or water.
What is biodegradation?
• “Bio” refers to living things and “degrade” means to break up. • Living things break down chemicals -Organisms such as earthworms, bacteria, and fungi help the biodegradation of most organic substances, including many pollutants.
Which organisms are the most important in biodegradation?
• Micro-organisms • Many different types of micro-organisms live in soil and water. • Algae, bacteria, fungi, and protozoa are common.
What is aerobic(air) biodegradation:
Bacteria using oxygen for biodegration -These bacteria can only grow and reproduce with oxygen.
What does anaerobic mean:
Bacteria that do need do not need an environment with oxygen. -for example, deep within landfill sites.
What are PCBs?
-PCBs (polychlorinated biphenyls) are human-made oils used in electrical equipment.
How are anaerobic bacteria helpful?
Some types of anaerobic bacteria remove chlorine from harmful chlorine-containing compounds such as PCBs. • These bacteria are able to remove chlorine atoms from the pollutant’s molecules and replace them with hydrogen atoms. • The molecules can then be used as food for the bacteria
What are the factors that affect the rate of biodegradation?
• Temperature (little bacteria growth in the cold which causes biodegradation. • soil moisture, • pH, • oxygen supply, • nutrient availability
What are bioreactors?
-Bioreactors are designed to speed up the decomposition of organic wastes such as food and paper in municipal landfills.
Why are liquids added to landfills?
-Liquids are added to the landfill to create ideal conditions for micro-organisms that decompose organic waste
What are methods that speed up biotechnology?
• Bioreactors • Adding Liquid to landfills • planting vegetation
How does planting vegetation help speed up biodegradation?
-Bacteria and fungi occur in larger numbers in soil that contains plants than they do in soil without plants. -The bacteria and fungi live around the roots of the plants.
What is Phytoremediation?
-Phytoremediation is a technique that can be used to reduce the concentration of harmful chemicals in soil or groundwater. -“Phyto” means plant and “remediation” means correction or cure.
How does phytoremediation reduce harmful chemicals?
-Some plants can absorb and accumulate (build-up) unusually large amounts of metals from the soil.
What happens to plants after they reduce harmful chemicals in phytoremediation
• The plants are allowed to grow for some time and then harvested and burned or composted. • In some cases, the metal can be recycled. • Once the plants used for phytoremediation have “cleaned” the soil, other plants can be planted there.
What is Photolysis?
-Photolysis is the breakdown (lysis) of compounds by sunlight (photo).
What is an example of photolysis?
• An example of photolysis is the formation of ozone. • Nitrogen dioxide in the presence of light breaks down to form nitrogen monoxide and an oxygen atom. • The oxygen atom then combines with an oxygen molecule to form ozone.
Photolysis with ozone stages:
nitrogen dioxide ➝ nitrogen monoxide + oxygen atom oxygen atom + oxygen molecule ➝ ozone
another example of photolysis?
Photodegradable plastic is made of chemicals that react when exposed to sunlight. After about three months, these reactions have changed the plastic to a fine powder that is easier to dispose of than the original plastic objects. The problem with photodegradable plastic is that it will not decompose if it’s buried or placed anywhere else that sunlight cannot reach it.