Earth's Atmosphere: Layers and Environmental Challenges

Atmospheric Layers and Dynamics

Within the Earth's atmosphere, there are distinct characteristics of air movement. For instance, some layers exhibit horizontal air movement but not significant vertical movement.

Mesosphere: Temperature and Phenomena

The mesosphere extends from the stratopause up to 80 km, reaching the mesopause. In this layer, the temperature significantly decreases to a minimum of about -80°C. It is also the layer where phenomena like shooting stars (meteors) are commonly observed as they burn up upon entry.

Thermosphere and Ionosphere: Ionization and Heat

The thermosphere and ionosphere extend from the mesopause to over 500 km. In this layer, molecules of different gases are ionized by the action of high-energy solar radiation (such as gamma rays, ultraviolet, and short X-rays). As a consequence of this ionization, the temperature rises dramatically, reaching between 1000°C and 1500°C.

Regional Environmental Problems

This section addresses environmental problems whose effects manifest at greater distances from their origin, such as acid rain and pollution from ionizing radiation.

Acid Rain: Causes and Effects

Acid deposition is primarily caused by the emission of sulfur oxides (SOx) and nitrogen oxides (NOx). These pollutants are largely produced by burning fossil fuels in power stations and motor vehicles, especially in urban areas. These products react with water vapor, light, and hydroxyl radicals, forming acidic compounds.

These secondary contaminants can be deposited in two ways:

• Dry deposition: Occurs in gaseous form or as aerosols, typically close to the emission source.
• Wet deposition: Happens when contaminants mix with water and become part of precipitation, allowing them to be transported over greater distances.

The overall effect of acid rain is the acidification of the environment, impacting soil, water bodies, and forests. It also leads to the corrosion of metals and carbonates in buildings and historical monuments.

Pollution from Ionizing Radiation

Ionizing radiation consists of electromagnetic waves with sufficient energy to ionize atoms or molecules of the matter they interact with, thereby altering its structure and function.

Its origin is varied, stemming from sources such as nuclear power plants, medical activities, laboratories, research centers, industrial plants, and nuclear explosions. Radiation with more penetrating power includes X-rays and gamma rays, while alpha and beta radiation have less penetrating power.

Global Environmental Issues

These are problems that affect the entire planet, including global warming, climate change, and the destruction of the ozone layer. Global atmospheric dynamics mean that problems caused by emissions are not evenly distributed across different continents.

Greenhouse Effect and Climate Change

The greenhouse effect is the natural increase of global temperature due to the effect of certain molecules in the atmosphere. These molecules allow the passage of short-wavelength radiation (visible light, short-wave infrared) but trap the long-wave infrared radiation emitted by the Earth's surface, leading to warming.

Ozone Layer Depletion

The stratospheric ozone layer absorbs harmful ultraviolet (UV) radiation through continuous reactions of formation and destruction, which are normally in dynamic equilibrium.

Between 1977 and 1984, it was revealed that the amount of ozone had decreased by 40% during the Antarctic spring. It was found that this ozone depletion is primarily due to the action of active chlorine in the stratosphere. The main origin of this element is chlorofluorocarbons (CFCs), which are chlorinated and fluorinated derivatives of hydrocarbons.