Understanding the Chemistry of the Atmosphere

The Earth's Early Atmosphere

The Earth's primordial atmosphere, formed around 4.5 billion years ago, consisted mainly of hydrogen, helium, and other light gases. Over billions of years, volcanic activity and the release of gases from the planet's interior led to the formation of a secondary atmosphere rich in water vapor, carbon dioxide, nitrogen, and other compounds.

Evolution of the Modern Atmosphere

The modern atmosphere we know today is the result of a complex series of chemical and biological processes that occurred over time:

• Photosynthesis by early life forms consumed carbon dioxide and released oxygen, gradually increasing oxygen levels and decreasing carbon dioxide.
• Nitrogen-fixing bacteria helped increase nitrogen levels in the atmosphere.
• Ongoing volcanic outgassing and other geological processes continued to release gases into the atmosphere.

The Greenhouse Effect and Climate Change

The greenhouse effect is a natural process that traps some of the Sun's heat within the Earth's atmosphere, making the planet warm enough to sustain life. Greenhouse gases like carbon dioxide, methane, and water vapor absorb and re-emit infrared radiation, preventing it from escaping into space.

However, human activities such as burning fossil fuels, deforestation, and agriculture have significantly increased the levels of greenhouse gases in the atmosphere, leading to an enhanced greenhouse effect and global climate change. The resulting increase in average global temperatures has far-reaching consequences, including rising sea levels, more extreme weather events, and disruptions to ecosystems.

Atmospheric Pollutants and Their Impact

The combustion of fossil fuels in vehicles, power plants, and industrial processes releases various pollutants into the atmosphere:

• Carbon monoxide (CO): Produced by incomplete combustion, it reduces the oxygen-carrying capacity of blood and can be fatal at high concentrations.
• Sulfur dioxide (SO2): Released from burning coal and oil, it contributes to acid rain and respiratory problems.
• Nitrogen oxides (NOx): Formed during high-temperature combustion, they contribute to smog, acid rain, and respiratory issues.
• Particulates: Fine particles from industry, vehicles, and fires can penetrate deep into the lungs, causing respiratory and cardiovascular problems.

These pollutants not only harm human health but also damage ecosystems, buildings, and cultural heritage sites. Efforts to reduce emissions and transition to cleaner energy sources are crucial for mitigating these environmental and health impacts.

Worked Example: Calculating Carbon Footprint

Problem: A family of four produces an average of 12 tonnes of carbon dioxide (CO2) per year from their household activities and transportation. If the average carbon footprint per person in their country is 8 tonnes of CO2 per year, how much above or below the national average is their household carbon footprint?

Solution:

1. Calculate the total carbon footprint for the family: 12 tonnes of CO2 per year
2. Calculate the expected carbon footprint for a family of four based on the national average: 4 people × 8 tonnes of CO2 per person = 32 tonnes of CO2 per year
3. Subtract the family's carbon footprint from the expected value: 32 tonnes - 12 tonnes = 20 tonnes of CO2 per year
4. Therefore, the family's carbon footprint is 20 tonnes of CO2 per year below the national average.