By Sohni Zahid Atmosphere and Environment

Copyright © Marshall Cavendish International (Singapore) Pte. Ltd. The Carbon Cycle If the atmosphere is to maintain a constant amount of carbon dioxide, the rate of removal of atmospheric carbon dioxide must be balanced by the rate of return of the gas. The mechanism that maintains the level of carbon dioxide in the atmosphere is called the carbon cycle.

Copyright © Marshall Cavendish International (Singapore) Pte. Ltd. What processes produce carbon dioxide? 1. Respiration During respiration, carbon and hydrogen compounds in food are converted into carbon dioxide and water. C 6 H 12 O 6 (aq) + 6O 2 (g)  6CO 2 (g) + 6H 2 O(l) + energy 2. Combustion of fuels An example of such fuel is methane. CH 4 (g) + 2O 2 (g)  CO 2 (g) + 2H 2 O(l) + energy

Copyright © Marshall Cavendish International (Singapore) Pte. Ltd. What processes remove carbon dioxide? 1. Photosynthesis During photosynthesis, green plants convert carbon dioxide and water into glucose and oxygen (Fig. 20.7) in the presence of sunlight. 6CO 2 (g) + 6H 2 O(l)  C 6 H 12 O 6 (aq) + 6O 2 (g)

Copyright © Marshall Cavendish International (Singapore) Pte. Ltd. The Greenhouse Effect Carbon dioxide is not the only greenhouse gas. Other gases, such as methane (CH 4 ) and nitrous oxide (N 2 O), are even stronger infrared absorbers. The natural greenhouse effect is crucial for maintaining the proper temperature needed to sustain life on Earth. Without these greenhouse gases, Earth’s surface temperature would be –40 °C and it would be permanently covered with ice.

Infra red radiation partly trapped inside the green house. Same effect is observed in atmosphere due to high production of green house gases. What could be the results of it??

Floods Melting of Ice Death of Animals Drought

Copyright © Marshall Cavendish International (Singapore) Pte. Ltd. Human activities like the burning of fossil fuels and large scale cutting down of forests are causing some greenhouse gases, especially carbon dioxide, to build up rapidly in the atmosphere. This means that carbon dioxide is being added to the atmosphere at a higher rate than photosynthesis can remove the excess gas. The effect of carbon dioxide build-up is an increase in the Earth’s average temperature. Global Warming

Copyright © Marshall Cavendish International (Singapore) Pte. Ltd. a decrease in crop yields world-wide because the areas that are currently covered by vegetation may become deserts, the melting of large quantities of ice in the North Pole and South Pole. This will cause the levels of oceans to rise and flood low-lying countries such as the Netherlands. Animals are dying having hazardous affect on ecosystem. the rapid evaporation of water from the Earth’s surface. When this happens, carbon dioxide dissolved in the oceans will be driven out into the atmosphere. This adds further to the greenhouse effect. Consequences of Global Warming

Stop Global Warming

Sources of Water Supply Rivers (water from rainfall) Ground Waters ( Held in rock structure called aquifers) Drinkable water from sea after desalination (removal of Salts from Sea Water).

Natural substances in water Oxygen (Essential for fish and Life) Dissolved minerals ( Fe, Mg, Ca, K, Zn, nitrate and sulfate ions) Organic Matter ( from decay of dead plants and animals by bacteria) Bacteria (mostly harmless) ( For details refer to p.g 218 Fundamental Chemistry ) Metals Non-metals

Pollutants from Human Activity Rivers passing from farmland, Industrial Area and Seas get polluted with following: Waste from mines (Hg, As, Pb) Factory waste ( Liquid or Effluent) Fertilizers (Nitrates (NO 3 ) -1 and Phosphates (PO 4 ) -3 flourish Algae) Animal Waste and Sewage (containing Nitrates and Phosphates, harmful microbes such as Virus, Bacteria, Parasite) Water from Sewage Works.

Eutrophication Eutrophication is when the environment becomes enriched with nutrients. This can be a problem in marine habitats such as lakes as it can cause algal blooms. Fertilizers are often used in farming, sometimes these fertilizers run-off into nearby water causing an increase in nutrient levels. This causes phytoplankton to grow and reproduce more rapidly, resulting in algal blooms. This bloom of algae disrupts normal ecosystem functioning and causes many problems. The algae may use up all the oxygen in the water, leaving none for other marine life. This results in the death of many aquatic organisms such as fish, which need the oxygen in the water to live. The bloom of algae may also block sunlight from photosynthetic marine plants under the water surface. Some algae even produce toxins that are harmful to higher forms of life. This can cause problems along the food chain and affect any animal that feeds on them.

Treatment of Water in Plant Step 1: Screening ( Remove Large Particles Such as Twigs) Step 2: Coagulation ( Suspended Particles settle down. Remove Such as Fe Sulfate) Step 3: Floatation ( Coagulated Particles Float and Skimmed Off) Step 4: Filtration ( By using Bed of Fine Sand) Step 5: Charcoal Filtration ( To remove Bad Taste and Smell) Step 6 : Chlorination (To kill Microbes) Step 7: Addition of Fluoride (Fight Tooth Decay, used in some treatment Plants ) Step 8: Storage in Reservoirs.

Also Refer Your Text Books: Fundamental Chemistry Chemistry Matters