Fix Ozone Layer Depletion

Over two billion years ago, blue-green algae, early aquatic organisms, began using energy from the sun to convert molecules of water and carbon di-oxide and recombine them into organic com-pounds and molecular oxygen. This has resulted in increase of oxygen and decrease of carbon dioxide in the atmosphere. In the atmosphere, some oxy-gen molecules absorb energy from the sun’s ultra-violet (UV) rays and split to form single oxygen atoms. These atoms combined with molecular oxygen (O2) to form ozone (O3) molecules, which are very effective in absorbing ultraviolet rays.

Ozone was discovered in 1785 by Dutch physicist, MV Marum, but it was only in 1840 that the Ger-man chemist CF Schenbein could synthesise it.

Ozone layer is not really a layer, but has become known as such because most ozone particles are scattered between 19 and 30 km up in the strato-sphere in the form of thick sheet, called ozono-sphere. Ozone also occurs in very small amounts in the lowest few kilometres of stratosphere i.e., the troposphere. The ozone layer has the capability to absorb almost 97-99 per cent of harmful ultra-violet radiations, that sun emits, which can produce long-term devastating effects on human be-ings as well as plants and animals.

Different Layers

There are two layers of ozone in the atmosphere; from ground-level up to 10 km, bad ozone exists in the troposphere, and is harmful to breathe. After 10 km stratosphere starts, the good ozone layer ex-tends upward up to 30 km and protects life on Earth from the sun’s harmful UV rays.

Bad ozone layer is created by chemical reactions between oxides of Nitrogen and volatile organic compounds (VOC) in the presence of sunlight. Ground-level ozone is a harmful pollutant.

Good ozone layer is produced naturally in the stratosphere by UV rays reacting with oxygen. But this good ozone has gradually been destroyed by human-made chemicals referred as ozone-depleting substances (ODS), including Chloro-fluorocarbons (CFCs), Hydrochlorofluocarbans (HCFCs), halons, methyl bromide, carbon tetra-chloride and methyl chloroform. These substances were being used in coolants, foaming agents, fire extinguishers, solvents, pesticides and aerosol pro-pellants. They are broken down by sun’s UV rays and release chlorine and bromine molecules, which destroy the good ozone. Scientists estimate that one chlorine atom can destroy 100,000 ozone molecules.

Ozone Hole

It is an area in the stratosphere where ozone deple-tion is so severe that levels fall below 200 Dobson Unit (DU) - the traditional measure of stratospheric ozone. Normal ozone concentration is about 300-350 DU. Scientists came to know that Ozone Destroying Substances (ODS) - mostly chlorine and bromine from CFC’s and halon were responsi-ble for ozone depletion, to the extent of 1 percent per day.

The satellite data from NASA confirmed that the hole covered the entire Antarctic Continent. Formation of ozone holes is irregular over the entire earth. For instance, the stratospheric circulation is much irregular in Arctic region and Arctic ozone layer is not normally cold as that of Antarctic, hence deep ozone hole is unlikely over North Pole.

Ozone Depletion

Over India

According to the head of the National Ozone Cen-tre in New Delhi, there is no trend to show total ozone depletion in the stratosphere over India. However, the Centre for Science and Environment, New Delhi, revealed a disturbing trend in ground-level ozone pollution rise across India’s major cit-ies like Delhi, Bangalore, Jaipur, Kolkata, etc.

Effects of Ozone

Depletion

1. Human and Animal Health: Exposure of Ul-traviolet radiation (UVR) to skin causes sun-burn, skin cancer- also in animals and to eyes causes damage to cornea and cataract.

2. Terrestrial Ecosystems: In forests and grass-lands, UVR exposure results mutation thus al-tering the biodiversity in different ecosystems.

3. Aquatic Ecosystems: The coastal zones are more sensitive to the UVR than those living in offshore, that are adapted to higher levels of radiation. The UVR can cause damage to early development stages of fish, shrimp, crab, am-phibians and other animals, the worst effect being decreased reproductive capacity and im-paired larval development.

4. Effect on Materials: Increased levels in UVR have adverse effects on synthetic polymers, naturally occurring biopolymers and some other materials of commercial interest.

Montreal Protocol

In a bid to contain the Ozone depletion, a land-mark multilateral environmental agreement was formulated that regulates the production and con-sumption of ODS. ODS when released into the at-mosphere, change the stratospheric ozone layer - Earth’s protective shield that protects humans and the environment from harmful levels of UV radiation from sun. Adopted on 16 September, 1987 and celebrated as International Day for Preserva-tion of Ozone layer, Montreal Protocol is a rare treaty to achieve universal ratification. The parties to this reached an agreement on 15 October 2016 in Kigali, Rwanda, to phase down HFCs.

The Montreal Protocol is saving about two million people each year by 2030 from skin cancer. The parties to the protocol have phased out 98 per cent of ODS globally compared to 1990 levels. Under Kigali Amendment, use of HFCs is expected to prevent the emissions up to 105 billion tonnes of carbon dioxide equivalent to GHGs, helping to avoid up to 0.5 degrees Celsius of global tempera-ture by 2100.

Solutions and Recovery

The entire planet is vulnerable to effects and con-sequences due to ozone depletion. The solutions are; 1. ODS like CFC’s, halons should be avoided to use. 2. Eco-friendly pesticides should be used for pest control. 3. Use of nitrous oxide should be prohibited. 4. Natural and eco-friendly cleaning products should be used in the household. Non-toxic products like vinegar and bicarbonate should be put to use.

Recovery

As per the guidelines of Montreal Protocol and subsequent amendments the consumption of ODS has fallen by 90-95 percent till 2005. The size of Antarctic Ozone hole reached 29.9 million square kilometres in 2000. By 2021 the area shrank to 24.8 million square kilometres. A few years back, United Nations report estimated that Antarctic ozone hole would close slowly and stratospheric ozone concentrations would return to 1980 values by 2060 and that of Arctic, ozone levels are ex-pected to return to 1980 values by mid-2030s.

Ensuring protection of ozone layer must be our long-term commitment and responsibility.

The whole humanity around the world and each gener-ation must take up the baton to ensure the contin-ued survival of our planet’s protective shield. Teaching the next generation about the Montreal Protocol empowers them with the knowledge that environmental challenges can be overcome if we listen to the science and work together.

(Writer is a retired IFS officer)