Question

The ozone layer in the upper atmosphere a. is depleted when it interacts with chlorine atoms. b. is created by the accumulation of human-made pollutants. c. has been increasing in thickness since the 1960 s. d. is currently thickest over the Antarctic and thinnest over the equator:

Short answer

a. is depleted when it interacts with chlorine atoms.

Step-by-step solution

Understand the Ozone Layer Depletion

The ozone layer is essential for protecting life on Earth by blocking harmful ultraviolet (UV) radiation from the sun. It can be depleted by certain chemicals, especially those containing chlorine and bromine atoms. Focus on this point to determine if option (a) is correct.

Examine Human Impact on the Ozone Layer

Human activities have contributed to the depletion of the ozone layer through the emission of pollutants, particularly chlorofluorocarbons (CFCs). However, the ozone layer is not mainly created by these pollutants. Option (b) must be analyzed carefully to determine its accuracy.

Look at Historical Trends in Ozone Thickness

Since the 1960s, the ozone layer has not been increasing in thickness; instead, it has been depleting due to the effects of human-made chemicals. Consider this fact when determining if option (c) is correct.

Consider Ozone Layer Distribution

The distribution of the ozone layer varies with latitude. It is typically thickest over the poles and thinnest over the equator. Review this fact to assess the accuracy of option (d).

Key concepts

ultraviolet (UV) radiation

Ultraviolet (UV) radiation is a type of energy emitted by the sun. It is divided into three types based on wavelength: UV-A, UV-B, and UV-C.
UV-A has the longest wavelength and can penetrate deep into the skin, causing aging and potential damage over time.
UV-B has a shorter wavelength and is mostly absorbed by the ozone layer, but enough reaches the Earth's surface to cause sunburns and skin cancer.
UV-C has the shortest wavelength and is entirely absorbed by the ozone layer and the Earth's atmosphere, protecting life on Earth from its harmful effects.
The ozone layer's primary function is to absorb and block the majority of the sun's UV-B and UV-C radiation, allowing only a small amount to reach the Earth's surface. This protection is crucial, as excessive exposure to UV radiation can lead to various health issues in humans, including skin cancer, cataracts, and suppression of the immune system. It also negatively impacts marine ecosystems, especially phytoplankton, which form the basis of oceanic food chains.

chlorofluorocarbons (CFCs)

Chlorofluorocarbons (CFCs) are man-made chemical compounds that were once widely used in industries for refrigeration, air conditioning, and as propellants in aerosol sprays.
The structure of CFCs includes carbon, chlorine, and fluorine atoms. They are stable and non-toxic at Earth's surface, making them initially popular for various applications.
However, their stability allows them to rise and accumulate in the upper atmosphere, where they eventually break down under UV radiation.
When CFCs break down, they release chlorine atoms, which then participate in a series of reactions that lead to the destruction of ozone molecules. One single chlorine atom can destroy thousands of ozone molecules by converting them into ordinary oxygen, significantly depleting the ozone layer.
This process is particularly concerning because it disrupts the balance that naturally protects life on Earth from harmful ultraviolet (UV) radiation.

ozone distribution

Ozone distribution varies with latitude and altitude, and it undergoes seasonal fluctuations. The concentration of ozone is higher in the stratosphere, about 10 to 30 kilometers above the Earth's surface.
Usually, the highest concentrations of ozone are found between 15 to 35 kilometers, forming the ozone layer.
The distribution of this layer is not uniform; it tends to be thickest at the poles, especially during the spring and fall, and thinnest at the equator.
This pattern results from the dynamic nature of atmospheric circulation and the effects of temperature, sunlight, and wind patterns.
Over the polar regions, especially Antarctica, extreme depletion occurs, leading to what is commonly known as the ozone hole. This phenomenon is maximal during the southern hemisphere spring (September to November), as a result of unique meteorological and chemical conditions.
Understanding ozone distribution is critical for assessing the overall health of the ozone layer and for implementing policies aimed at reducing ozone-depleting substances, ensuring ongoing protection of life on Earth from UV radiation.