Black Carbon: A threat for earth’s Ozone layer

Context:

• Black carbon (BC) is a new concern for the climate researchers.
• Aeroplanes may be ejecting significant amounts of Black Carbon (BC) — a pollutant known to aggravate breathing disorders, upset the monsoon and quicken glacier melt and may be depleting the ozone layer.

Explanation:

The 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. 

• The stratosphere extends anywhere from 4 to 12 miles (6 to 20 km) above Earth’s surface up to 31 miles (50 km). This is the layer where most commercial airliners fly and weather balloons travel to.
• With due course of time, aviation has experienced rapid expansion as the world economy has grown. But along with the expansion the total aviation emissions have increased, because increased demand for air transport has outpaced the reductions in specific emissions from the continuing improvements in technology and operational procedures.

Emissions of aircraft:

• The principal emissions of aircraft include the greenhouse gases carbon dioxide and water vapor (H₂O).
• Other major emissions are nitric oxide (NO) and nitrogen dioxide (NO₂) (which together are termed NO_x), sulfur oxides (SO_xO), and soot.

 How Do Aircraft Affect Climate and Ozone?

• Aircraft emit gases and particles directly into the upper troposphere and lower stratosphere where they have an impact on atmospheric composition. Their immediate adverse affects are as follows:

1. These gases and particles alter the concentration of atmospheric greenhouse gases, including carbon dioxide CO₂), ozone (O₃), and methane (CH₄)
2. Trigger formation of condensation trails (contrails)
3. These gases may increase cirrus cloudiness-all of which contribute to climate change.
4. Aeroplanes may be ejecting significant amounts of Black Carbon (BC) — a pollutant which may be a contribute in depleting the ozone layer, according to a study by climate researchers from multiple institutions in the country.

• Though airborne, BC is known to dissipate and settle down in a few months under the influence of rain and wind and is unlikely to travel upward of 4 km, but these black carbon particles can linger long enough to provide a fertile ground for other chemical reactions that can deplete the ozone layer.
• Because BC particles strongly absorb solar and terrestrial radiation and heats up the atmosphere it can upset the monsoon system.
• If deposited on snow, it could accelerate the heating of snow and quicken the melting of glaciers.

Other reasons of Ozone depletion:

Man-made reasons:

• In the 1970s, scientists discovered that human activities were the greatest cause of upsetting this delicate balance of production and destruction of ozone.
• It was found that the layer was being attacked by releasing Ozone Depleting Substances (ODS) like chlorofluorocarbons or CFCs coming from air conditioners, cleaning solvents, aerosol sprays and refrigerators.
• The problem with ODS is that they are not washed back in the form of rain on the earth and in-fact remain in the atmosphere for quite a long time.
• With so much stability, they are transported into the stratosphere. The emission of ODS account for roughly 90% of total depletion of ozone layer in stratosphere. These gases are carried to the stratosphere layer of atmosphere where ultraviolet radiations from the sun break them to release chlorine (from CFCs) and bromine (from methyl bromide and halons).
• The chlorine and bromine free radicals react with ozone molecule and destroy their molecular structure, thus depleting the ozone layer.

Natural reasons:

• Ozone layer has been found to be affected by certain natural phenomena such as Sun-spots and stratospheric winds. But this has been found to cause not more than 1-2% depletion of the ozone layer and the effects are also thought to be only temporary.

Consequences:

The consequences of the depletion of the ozone layer are dramatic.

1. Increased ultraviolet radiation leads to a growing number of skin cancers and cataracts and also reduces the ability of people’s immune systems to respond to infection.
2. UV radiations also affect plants by increasing germination that reduces crop yield.
3. It causes severe damage in the early development stage of shrimps, crabs and amphibians.
4. Additionally, the growth rates of the world’s oceanic plankton, the base of most marine food chains, have been negatively affected, leading to increased atmospheric carbon dioxide and thus to global warming.
5. Materials like plastics, wood, fabrics, rubber are massively degraded by too much ultraviolet radiation.

Solutions to Ozone Depletion:

Restrict usage of pesticides:

• Pesticides are great chemicals to rid your farm of pests and weeds, but they contribute enormously to ozone layer depletion.
• The best solution to get rid of pests and weeds is to apply natural methods.

Minimize Private vehicles:

• The easiest technique to minimize ozone depletion is to minimize 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.

Environmental 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.
• Thus, using natural and environmentally friendly cleaning products is the best way to arrest this situation.

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.

Governments must take action now and outlaw nitrous oxide use to reduce the rate of ozone depletion