|Scientific Information on Ozone Layer Depletion
What is Ozone (O3)?
Ozone (O3) is a naturally occurring gas made of a triple form of oxygen and more than 90% of it is found in the Stratosphere 10 to 50 km above the earth’s surface. This region where Ozone is concentrated in the Stratosphere is commonly known as the Ozone Layer. This ozone layer acts as a protective shield, which filters the harmful Ultraviolet rays.
Mechanism of Ozone Layer Depletion.
In 1980s it was discovered that the most commonly used ozone depleting substances (ODS) are Chlorofluorocarbons (CFCs), which is used in the Refrigeration industry. When CFCs are released to the atmosphere they reach the stratosphere and are split by Ultra violet B radiation. This process sets highly reactive Chlorine atoms free. Bromine atoms were also released in a similar manner from substances like Halon and Methyl Bromide. These Chlorine and Bromine atoms acts as a destroying agent of ozone molecules i.e. ozone is broken in to Oxygen and forms Chlorine Monoxide and a free high-energy oxygen atom. By this way a single Chlorine atom can destroy up to 100,000 ozone molecules. Bromine compounds also play a key role in destroying the ozone layer. Some chemical compounds like Nitrous Oxide and other Nitrogen compounds also have a damaging affect on the ozone layer.
- Step 01- CFCs are broken down in to Chlorine and Dichlorofluoromethane by the UV rays.
- Step 02- Ozone molecules are broken down in to oxygen (O2) and Chlorine monoxide (ClO) by these Chlorine atoms. This process reduces the Ozone (O3) in the stratosphere.
- Step 03- a free oxygen atom reacts with chlorine monoxide and a chlorine atom is set free. Repetition of this process gradually thins out the Ozone layer.
Effects of Ozone Layer Depletion
The direct result of the ozone layer depletion will be an increase of the amount of UV radiation that will reach the earth’s surface. These Ultra violet rays have a destructive effect on humans, marine life, crops and other living creatures.
Impact on human life:
According to studies ozone depletion will lead to human skin cancer, eye cataracts and also it will affect the capacity of the human immune system resulting in decline in the immunization process and increase in the occurrence of infections diseases.
Impact on the ecological system and sea life:
Ultra violet rays have an adverse effect on plant and marine life. Seeds of plants and larvae of sea creatures that are exposed to the sun will be seriously damaged thereby breaking the natural life system and food production. Growth of plants and crops will also be restricted. In a developing country like Sri Lanka effects of these changes will be aggravated by the poor health condition, undeveloped agricultural methods and other economical set backs.
Impact on the global climate:
Ozone depletion and release of CFCs will also have an adverse affects on the global climate, Changes in temperature profile, cloud formation and weather processes are also predicted by the scientists.
Depletion ofthe Ozone layer will result in UV radiation filtering through the Troposphere. This UV radiation will react with Oxygen (O2 ) and create Ozone (O3) at the Troposphere where it is harmful to humans, crops and other living creatures.
Therefore a lot is at stake for the survival of the human race. To protect the earth and its inhabitants the task ahead should not be prolonged or taken lightly. The world community has not yet felt the full impact of ozone depletion. Therefore it is important to take preventive action before we experience the full impact of ozone depletion.
Industries using ODS in Sri Lanka.
The prominent use of ODS in Sri Lanka can be monitored in the refrigerant and air conditioning sector. Refrigerants are the working materials in refrigeration plants. Accordingly CFC11 (R11), CFC12 (R12), CFC113 (R113), CFC114 (R114) and CFC115 (R115) are the most commonly used ODS. Among these gases CFC-12 (R12) has the widest usage in Sri Lanka. ODS is also used in the garment manufacturing industry in a very small scale as a solvent, and is also used for dry-cleaning textiles.
The most Commonly used Halons are Halon 1211,1301, and 2402.These contain Bromine compounds and has a high ozone depleting potential (ODP). Helons are used in fire extinguishing equipments .No virgin Halon is being imported to the country now, however there is a possibility of the use of already installed systems being used in case of a fire, because no steps have been taken to install the prevailing systems with alternative systems.
Sri Lanka does not export ODS /ODS containing equipment nor does it produce ODS /ODS containing equipment. However there were three refrigeration factories using CFCs, these factories were converted to non-CFC technology with the grants of the Multilateral Fund. Therefore Sri Lanka’s ODS consumption is involved only, where imports of these equipments and substances are concerned. These imported substances are mainly used for repairing and servicing of refrigerators, air conditioners…etc.
Commonly used ODS in Sri Lanka.
• CFC11 (R11) is used in Air conditioners with turbo compressors, flashing agents for cleaning refrigerating systems. It is been used as a foaming agent for hard foam insulation (Polyurethane).
• CFC12 (R12) is normally used in household refrigerators, cooling and air-conditioning for the transport sector i.e. car air conditioners etc. and Commercial scale refrigerating plants. CFC 12 is also imported as a substance to Sri Lanka for the purpose of servicing and maintenance of the above equipments. This was also used as a propelling agent of spray cans in the Aerosol industry.
• CFC115 (R115) Pure substance is not imported in Sri Lanka but it is being imported as a blend of CFC115 and HCFC-22. This chemical is used in commercial and industrial refrigeration, transport sector air conditioning, cold storage and food processing industry.
• CFC216 (R216) is used in Sri Lanka in the solvent sector and a process agent. e.g. to manufacture activated carbon .
• Methyl Bromide CH3Br is imported as a pre shipment fumigant and to control a wide range of pests. It is used as a soil treatment to control soil pests such as Nematodes, Seeds fungi, bacteria and other parasite plants. In Sri Lanka Methyl Bromide is commonly used in the Tea plantation sector.
• Carbon tetrachloride is being imported by the activated carbon industry to check the absorption quality of the activated carbon. It is also being used as a cleaning agent in the garment industry.
• Trichloroethane is also used as a solvent for cleaning metals.
Since Sri Lanka is not producing any of the ODSs, consumption is based on imports. Data on consumption was extracted from the records at the National Ozone Unit. The control of CFC is determined by using the average consumption during 1995-1997 which is considered as the Base value for a country. The base value for the total CFC consumption for Sri Lanka was 449.54 MT. Annual consumption of all CFCs are given in table 1.
Table 1.CFC consumption in Sri Lanka in MT
||Consumption in Metric tones
| Baseline (1995-97Aver.)
| CFC 11
| Total CFC
The other ODSs, Carbon Tetra Chloride (CTC), Methyl Chloroform (MCF), Methyl Bromide (MeBr) and Hydro chlorofluorocarbon (HCFC) are other ODS consumed in Sri Lanka are given in table 2.
Table 2: ODS Consumption (other than CFC) in Sri Lanka
||ODS Consumption in Metric Tones
| Base Line
| Total (Including CFC)