Sources of Carbon Dioxide & Particulates (College Board AP® Environmental Science): Study Guide

CO₂ appears naturally in the atmosphere from sources such as respiration, decomposition, and volcanic eruptions

It is a greenhouse gas that, when in the atmosphere, holds heat from the sun and warms the Earth's surface, creating the natural greenhouse effect

Natural sources of CO₂ include:

• Large-scale volcanic eruptions discharge dissolved CO₂ in magma into the atmosphere

• A large amount of CO₂ is released as a by-product of respiration, which converts food into energy they can utilize

• Aerobic decomposition is where microorganisms, such as bacteria and fungi, break down organic matter in the presence of oxygen and release CO₂

• Anaerobic decomposition is where microorganisms, such as bacteria, break down organic matter without oxygen and release both CO₂ and methane

PM₁₀ particles like dust, pollen, ash or mold are too small to be filtered out by nose hairs or trachea cilia and are a respiratory irritant

PM_2.5 particles travel deep into the lungs and are linked to chronic bronchitis and increased risk of lung cancer

There are a variety of natural sources of particulate matter, including:

Dust storms throw massive volumes of dust and sand into the air, causing PM

• Desert and semi-arid dust storms can travel great distances and disrupt air quality across huge areas

Volcanic eruptions: large volumes of ash and other volcanic debris can increase PM levels

• Buildings, automobiles, and infrastructure can be damaged by volcanic ash

Smoke and ash from wildfires release high levels of PM

• Wildfires can be caused by lightning, accident, or arson

Coastal sea spray can disperse salt particles and other contaminants into the air

Biological processes: plant spores can increase PM levels in the air

Radiation from rocks and minerals like uranium and radon can increase PM levels