GGH2604_ ASSIGNMENT 2 2020.

GGH2604 - People And The Environment. As humans have colonised and modified the Earth’s surface, they have developed progressively more sophisticated tools and technologies. These tools have resulted in ozone depletion, acid rain, climate change, photochemical smog and a change in climate in Africa. 1. CAUSES OF OZONE DEPLETION There are two different types of ozone depletion, both are very similar. The first one has been a slow, but steady ozone depletion of 4% per decade of the earth’s stratosphere (ozone layer). This has been happening constantly since the 1970’s. The other is a much larger, although seasonal loss of ozone over the polar regions. This yearly occurrence is called the ozone hole. There are many causes for ozone depletion, but the most important process in both trends is catalytic destruction of ozone by atomic chlorine and bromine. Both come from the breaking down of chlorofluorocarbons (freons) by photons in the atmosphere (Engler, 2017). Ozone layer is a deep layer in earth’s atmosphere that contain ozone which is a naturally occurring molecule containing three oxygen atoms. These ozone molecules form a gaseous layer in the Earth’s upper atmosphere called stratosphere. This lower region of stratosphere containing relatively higher concentration of ozone is called Ozonosphere. The Ozonosphere is found 15-35 km (9 to 22 miles) above the surface of the earth. Credible scientific studies have substantiated that the cause of ozone layer depletion is human activity, specifically, human-made chemicals that contain chlorine or bromine. These chemicals are widely known as ODS, an acronym for Ozone-Depleting Substances. The scientists have observed reduction in stratospheric ozone since early 1970’s. It is found to be more prominent in Polar Regions. Ozone-Depleting Substances have been proven to be eco-friendly, very stable and nontoxic in the atmosphere below. This is why they have gained popularity over the years. However, their stability comes at a price; they are able to float and remain static high up in 4 the stratosphere. When up there, ODS are comfortably broken down by the strong UV light and the resultant chemical is chlorine and bromine. Chlorine and bromine are known to deplete the ozone layer at supersonic speeds. They do this by simply stripping off an atom from the ozone molecule. One chlorine molecule has the capability to break down thousands of ozone molecules (Proshad ram, 2018). Ozone-depleting substances have stayed and will continue to stay in the atmosphere for many years. This, essentially, implies that a lot of the ozone-depleting substances human have allowed to go into the atmosphere for the previous 90 years are still on their journey to the atmosphere, which is why they will contribute to ozone depletion. The chief ozone-depleting substances include chlorofluorocarbons (CFCs), carbon tetrachloride, hydrochlorofluorocarbons (HCFCs) and methyl chloroform. Halons, sometimes known as brominated fluorocarbons, also contribute mightily to ozone depletion. However, their application is greatly restricted since they are utilized in specific fire extinguishers. The downside to halons is they are so potent that they are able to deplete the ozone layer 10 times more than ozone-depleting substances. MAIN OZONE DEPLETING SUBSTANCES Chlorofluorocarbons (CFCs) - It’s billed as the most extensively utilized ozone-depleting substance because it attributes to more than 80% of overall ozone depletion. It was utilized as a coolant in home appliances like freezers, refrigerators and air conditioners in both buildings and cars that were manufactured prior to 1995. This substance is usually contained in dry cleaning agents, hospital sterilants, and industrial solvents. The substance is also utilized in foam products like mattresses and cushions and home insulation. Hydrofluorocarbons (HCFCs) - Hydrofluorocarbons have over the years served in place of Chlorofluorocarbons. They are not as harmful as CFCs to ozone layer. Halons - It’s especially used in selected fire extinguishers in scenarios where the equipment or material could be devastated by water or extinguisher chemicals. Carbon Tetrachloride -Also used in selected fire extinguishers and solvents. 5 Methyl Chloroform - Commonly utilized in industries for cold cleaning, vapour degreasing, chemical processing, adhesives and some aerosols (Jan Zalasiewicz, 2014). SERIOUS EFFECTS OF OZONE DEPLETION. 1. Damage to human health - If the ozone layer is depleted, it means humans will be overly exposed to strong UV light. Overexposure to strong UV light causes skin cancer, cataracts, sunburns, weakening of immune system and quick aging. 2. Devastation to environment - Many crops species are vulnerable to strong UV light and overexposure may well lead to minimal growth, photosynthesis and flowering. Some of the crop species vulnerable to UV light include barley, wheat, corn, oats, rice, broccoli, tomatoes, cauliflower just to name a few. Forests equally bear the brunt of ozone depletion. 3. Threat to marine life - Certain marine life, especially planktons, is greatly impacted by exposure to strong ultraviolet rays. In the aquatic food chain, planktons appear high up. If planktons decrease in number due to ozone layer destruction, the marine food chain would be disrupted in many ways. Also, overexposure of sun rays could reduce the fortunes of fishers. On top of that, certain species of marine life have been greatly affected by overexposure to ultraviolet radiation at their early stage. 4. Effect on animals - In domesticated animals, too much Ultraviolet radiation could also lead to skin and eye cancer. 5. Impacts certain materials - Materials like plastics, wood, fabrics, rubber are massively degraded by too much ultraviolet radiation (Reiny, 2018). Solutions to Ozone Depletion 1. Desist from using pesticides - Pesticides are great chemicals to rid your farm of pests and weeds, but they contribute enormously to ozone layer depletion. The sure-fire solution to get rid of pests and weeds is to apply natural methods. Just weed your farm manually and use alternative eco-friendly chemicals to alleviate pests. 6 2. Discourage driving of private vehicles - The easiest technique to minimize ozone depletion is to limit the number of vehicles on the road. These vehicles emit a lot of greenhouse gases that eventually form smog, a catalyst in the depletion of ozone layer. 3. Utilize environmentally friendly cleaning products - Most household cleaning products are loaded with harsh chemicals that find way to the atmosphere, eventually contributing to degradation of the ozone layer. Use natural and environmentally friendly cleaning products to arrest this situation. 4. Prohibit the use of harmful nitrous oxide - The Montreal Protocol formed in 1989 helped a lot in the limitation of Chlorofluorocarbons (CFCs). However, the protocol never covered nitrous oxide, which is a known harmful chemical that can destroy the ozone layer. Nitrous oxide is still in use today. Governments must take action now and outlaw nitrous oxide use to reduce (Proshad ram, 2018) 2. PHOTOCHEMICAL SMOG Air pollution is the excessive concentration of foreign matter in the air, which adversely affects the well-being of an individual or causes damage to property. Photochemical air pollution due to formation of photochemical smog is restricted to highly motorised areas in metropolitan cities like Los Angeles. It occurs under adverse meteorological conditions, when the air movement is restricted. Photochemical smog is a complex mixture of several compounds. It has been found that at the time of photochemical smog formation, there is a considerable increase in the amount of ozone and oxidant material. The ozone is not found in appreciable amounts at night, but only during the day. These facts clearly indicate that photochemical formation of ozone or oxidant from impurities, takes place due to the action of sunlight (Bhartendu, 2013). Effects of photochemical smog The effects of photochemical smog on human beings, plants and materials have been studied where it usually occurs. Additional information has also been obtained by stimulating photochemical smog in environmental chambers. Following are the important 7 effects of photochemical smog : (i) Eye irritation: Probably, the compounds responsible for eye irritation are formaldehyde, acrolein, PAN and peroxy benzoyl nitrate. (ii) Vegetation damage: The effects observed are silvering and bronzing of underside of leaves followed by collapse of cells, and necrosis. Growth retardation has also been reported. The three principal phytoxicants are ozone, nitrogen dioxide and PAN. This has resulted in economic loss. (iii) Visibility reduction: This is perhaps the most commonly observed effect of photochemical smog. The aerosol particles causing the photochemical smog contain compounds of carbon, oxygen, hydrogen, nitrogen, sulphur, and halides. (iv) Cracking of rubber: This is primarily due to the ozone constituents of photochemical smog. An important economic effect of smog is deterioration of the side walls of automobiletyres. To overcome this problem, an antiozonant is being used (Bhartendu, 2013). (v) Fading of dyes: This is another important economic effect of photochemical smog. Photochemical smog is a complex mixture of several compounds. Among its various constituents, ozone and PAN (peroxy acetyl nitrate) are significant. Photochemical air pollution occurs predominantly in highly motorised areas and where inversion conditions prevail in the atmosphere. The size of the particles is about 0.3 µ. The liquid phase is largely made up of organic matter. Photochemical air pollution is caused due to photochemical oxidation of hydrocarbons and nitrogen oxides. It has been found that at time of photochemical smog formation, there is a considerable increase in the amount of ozone and oxidant material. Facts clearly indicate that photochemical formation of ozone or oxidant from impurities, takes place due to the action of sunlight. The nature of the photochemical reactions that takes place in the atmosphere depends on a number of factors like light intensity, hydrocarbon reactivity, ratio of hydrocarbons to nitric oxide, presence of light absorbers, and metrological 8 variables. Photochemical air pollution shows its effects like eye irritation, vegetation damage, visibility reduction, cracking of rubber and fading of dyes (Borwer, 1956). 3. ACID RAIN The effect of acidification has been sighted all over the world such as deleterious ecological effects such as reduced reproduction of aquatic fish species, dieback and stunted growth in plants, accumulation of toxic aluminium and heavy metals in soil and water bodies, biodiversity loss including corals and shellfish, degrade to the manmade structures made up of marble and stone and corrosion of metal structures. According to 2012 progress report of US EPA (2013), The Impacts of major global environmental problems such as acid rain, acid deposition, depletion of ozone layer and health and environmental effects of particle matter are declining. Acid rain caused by emission of SO2 and NOX from various sources to the atmosphere and they dissolve in atmospheric water and produce acids in the rain water. Effects on surface waters Acid rain releases aluminium from the soil into lakes and streams which is toxic to many aquatic organisms. According to natural surface effects of deposition about 75% of the lakes and about 50% of the streams in U.S are acidified as the pH falls below 5. Similarly, in eastern Canada about 14,000 lakes were reported as acidic. Soft waters with low alkaline metal ions are more susceptible to acidification. Acidification effects shell forming mollusks, shell fish, coral reefs, sea grass beds and juvenile stages of aquatic organisms. In case of shell fish and corals their calcareous shell or skeleton get dissolved in acidic environment. Reduced pH encourages the growth of acid tolerant forms such as some bacteria and protozoa. Acid rain is not the sole cause of acidification, some swamps, bogs and marshes naturally have low level of pH (Taffel, 2016). Effects on forest Acid precipitation on vegetation reduces the photosynthesis and growth also increase the susceptibility to draught and disease, process called ‘dieback’ it causes browning of leaf 9 and fall off, in addition, effects such as thinning of annual growth ring and reduction in biomass (due to reduced growth), it also damages the fine root system, affect root mycorrhiza (due to increase in Al and acidity) and decrease the lichens, reduction of soil fertility as potassium leached out of the soil, phosphorus is also reduced this reduces the fruit production, toxic metals such as zinc and aluminium accumulates, aluminium toxicity retard root growth and causes loss of chlorophyll. Young seed lings are more susceptible than older plants. Soil acidity can be overcome by addition of lime, whereas alkalinity of limestone neutralizes the negative ions in acid (Kumar, 2017). Effects to manmade structures Nitric acid, sulphurus and sulphuric acid concentrated in dew or rain deposited on automotive coating causes fading of the paint, thus the modern vehicle manufactures are coating with acid resistant top paint and modern buildings are painted with acid resistant exterior wall paints. Metal such as bronze and alloy structures get corrode, acid also degrade marble (limestone) architectures. Visibility impairment Acid fog particularly particles of suphur dioxide and sulphur trioxide reduces the visibility by 50-70% in eastern U.S.A. Health effects The causing agents of acid rain SO2, SO3 and NOx may affect the health particularly SO2 & SO3 effect on asthma and emphysema patients and increase the incidence (Umhlathuze, 2018/19) Particulate deposition of particles less than PM 2.5 can even reach the blood stream via lungs and cause harmful effects such as lung cancer. Acid rain is one of the world’s major environmental problems since 19th century. Coal burning is the major cause of SO2 production and also vehicle emission and various fossil fuel based power generation emits NOx. Both SO2 and NOx produces sulphuric and nitric 10 acid respectively by reacting with atmospheric water vapour and precipitate as wet deposition such as rain, snow, sleet and fog and dry deposition including hazardous particles of PM 2.5. Acid rain affects forest trees cause yellowing and leaf fall, acidified rivers and lakes causes fish death, loss of calcareous shell forming species (mollusks), it also affects soil microorganisms causes increased nitrification which also leads to eutrophication in water bodies and changes in the biodiversity. Acid rain also destroys the coral reefs. It causes leaching of metal ions including toxic Aluminium and heavy metals such as chromium, cadmium and nickel, which adversely affects the soil micro flora and aquatic biota. Acid rain deteriorates the marble, stone monuments and architectures, corrode metal structures and fading paints. Liming is used to neutralize the acidity in soil and aquatic bodies. 4. CLIMATE CHANGE AND ITS IMPACTS IN AFRICAN CONTINENT The global temperature and precipitation have changed rapidly over the last century due to anthropogenic increases of greenhouse gases (GHGs) in the atmosphere, for example, burning of fossil fuels, like coal, petroleum and natural gasses and widespread deforestation. The Intergovernmental Panel on Climate Change (IPCC) has predicts that the global surface temperature will increase by 1.4 - 5.8°C by 2100 years due to increasing concentration of GHGs specifically carbon dioxide. Temperature across African continent are predicted to rise by 2 - 6°C over the next 100 years and rainfall variability is predicted to increase, resulting in frequent flooding and drought. According to IPCC report on Regional Climate projections of 2007, by 2050 the average temperatures in Africa are predicted to increase by 1.5 - 3°C, and the warming of Africa continent is very likely to be larger than the globe (Hulme, 2001).