Ozone, a gas composed of three oxygen atoms (O₃), exists in two key layers of the Earth's atmosphere, each with vastly different effects on the environment and human health.
1. Stratospheric Ozone: The "Good" Ozone
The majority (about 90%) of ozone resides in the stratosphere, specifically a region between 15 and 30 kilometers above the Earth's surface. This is commonly known as the ozone layer. This stratospheric ozone is vital because it absorbs most of the sun's harmful ultraviolet-B (UV-B) radiation, protecting life on Earth. [Source: The ozone layer is the common term for the high concentration of ozone that is found in the stratosphere around 15–30km above the earth's surface. It covers the entire planet and protects life on earth by absorbing harmful ultraviolet-B (UV-B) radiation from the sun.]
- Location: 15-30 km above Earth's surface
- Role: Protects life by absorbing harmful UV-B radiation
- Impact: Essential for life on Earth.
2. Tropospheric Ozone: The "Bad" Ozone
The remaining 10% of ozone is found in the troposphere, the layer closest to the Earth's surface (extending from ground level up to the stratosphere). Unlike stratospheric ozone, tropospheric ozone, also called ground-level ozone, is a harmful air pollutant. It is not directly emitted but is formed through chemical reactions involving pollutants from vehicles, power plants, and industrial sources. [Source: Ground-Level Ozone is found at ground level (it is also called tropospheric ozone). It is not emitted directly into the air, but created by chemical reactions…The remaining 10 percent of atmospheric ozone is located in the troposphere, which extends from the surface of the Earth to the stratosphere.]
- Location: Ground level to the bottom of the stratosphere.
- Role: Harmful air pollutant.
- Impact: Damages human health and the environment.
In summary, ozone's location determines its impact: beneficial in the stratosphere, harmful at ground level.
