Question

Which of the following is responsible for depletion of the ozone layer in the upper strata of the atmosphere? (a) freons (b) ferrocene (c) fullerenes (d) polyhalogens

Short answer

(a) Freons are responsible for ozone layer depletion.

Step-by-step solution

Problem Understanding

We need to identify which of the given options is responsible for the depletion of the ozone layer in the Earth's upper atmosphere.

Ozone Layer Depletion Explanation

The depletion of the ozone layer is primarily caused by chemicals that release chlorine or bromine when they are broken down by ultraviolet (UV) radiation, which occur in the upper atmosphere. These chemicals include chlorofluorocarbons (CFCs).

Identification of Compounds

The options given are evaluated: (a) Freons are a group of chlorofluorocarbons (CFCs), widely known for their role in ozone layer depletion. (b) Ferrocene is an organometallic compound and not related to ozone depletion. (c) Fullerenes are carbon structures with no known impact on ozone depletion. (d) Polyhalogens are compounds containing multiple halogen elements, but they are not specifically known for ozone depletion like CFCs are.

Correct Option

Freons (option a) are responsible for the depletion of the ozone layer, as they are chlorofluorocarbons that breakdown in the atmosphere releasing chlorine atoms which then deplete the ozone layer.

Key concepts

Freons

Freons are a category of chemicals mostly known as refrigerants that have become synonymous with ozone layer depletion. These compounds are part of a larger group called chlorofluorocarbons (CFCs). Initially, Freons were highly valued because they are non-flammable and non-toxic, making them perfect for use in air conditioning, refrigerators, and aerosol sprays.

However, the downside to using Freons came into light when it was discovered that they contribute significantly to the destruction of the ozone layer. When Freons are released into the atmosphere, they eventually reach the stratosphere. Here they are broken down by ultraviolet (UV) radiation.

This breakdown releases chlorine atoms, which are the main culprits in ozone depletion. A single chlorine atom can destroy many ozone molecules, thus creating what’s commonly known as the ozone "hole." The realization of Freons' environmental impact has led to international agreements and regulations to phase them out, aiming to heal the ozone layer over time.

Chlorofluorocarbons (CFCs)

Chlorofluorocarbons (CFCs) are a group of synthetic compounds made up primarily of carbon, chlorine, and fluorine. These were invented in the early-to-mid 20th century and found widespread use in various industrial applications, most notably as refrigerants and in aerosol propellants.

The issue with CFCs became evident as they confessed their darker side. CFCs are stable chemicals, a trait that made them so useful initially. But the same stability means they linger in the upper atmosphere where they are eventually broken apart by UV radiation.

This breakdown releases chlorine atoms, a type of atom that acts as a catalyst in the destruction of ozone molecules. Due to the long life of CFCs, the damaging effects are persistent, even years after the CFCs have been banned from most uses. Efforts like the Montreal Protocol, an international treaty signed in 1987, aim to reduce and eventually eliminate the use of substances, including CFCs, harmful to the ozone layer.

Ultraviolet (UV) Radiation Impact

Ultraviolet (UV) radiation is a form of energy emitted by the sun and is invisible to the human eye. While essential for processes like vitamin D production in humans, it can have detrimental effects on living organisms if not regulated properly by the Earth's atmosphere.

The ozone layer plays a crucial role here, as it absorbs a significant amount of incoming UV radiation. This absorption shields the Earth's surface from the more harmful types of UV radiation, namely UVB and UVC, which can cause skin cancer and cataracts in humans, and damage to sensitive ecosystems.

However, when ozone layer depletion occurs, this protective shield is compromised, allowing more UV radiation to reach the Earth’s surface. This increase in UV exposure poses risks not only to human health but also to wildlife and plant life, disrupting natural processes and ecosystems.

Understanding the interplay between UV radiation and the ozone layer has been vital for both environmental science and public health, driving initiatives to protect and restore our atmospheric shield.