What are aerosols?

Aerosols are an important factor to consider for monitoring climate, environment, and weather, as they can affect the functionality of equipment and components. They also play a significant role in air pollution and thus public health and environmental impact.

You cannot see them with the naked eye, but aerosols have a significant impact both positively and negatively on both health and the environment. In this article, you will gain insight into how aerosols are formed, what they are, and not least the impacts from them, as well as the challenges they can pose. Particularly anthropogenic aerosols, which are man-made, are a point of attention in the fight for a better climate and environment.

How do aerosols affect technical equipment?

When choosing professional technical equipment, it is essential to keep in mind that sensor-based applications have built-in properties that can handle the presence of aerosols, so the equipment’s functionality is maintained. If you are unsure about the impact of aerosols on your technical equipment, you can always seek technical advice from Hans Buch’s specialists.

Here are the key points to consider with technical equipment, which can, for example, affect meteorological tasks:

• Optical disturbances: Instruments such as radiometers and LIDAR use light and radiation. Aerosols can scatter or absorb light, which can affect the instruments’ ability to provide accurate measurements of cloud formation, radiation, and other optical properties.
• Reduced visibility: Particles such as dust, smoke, and fog reduce visibility for weather satellites and cameras that rely on clear visibility.
• Change in cloud formation and precipitation: Aerosols can attract water vapor, forming more small droplets. This can affect both cloud formation and cloud cover and lead to errors in measurements of both cloud types and precipitation amounts.
• Impact on temperature and humidity measurements: Aerosols can affect local temperatures as they can absorb or reflect sunlight, which can affect the accuracy of temperature and humidity measurements.
• Contamination of sensor surfaces: Aerosols in the form of particles from dust storms, volcanic ash, and man-made pollution sources can settle and, in the worst case, accumulate on the surfaces of sensors and cameras, thereby affecting performance and measurement accuracy.

What are aerosols? Origin and types

Aerosols are microscopic particles or droplets in the atmosphere. They can be both naturally occurring and man-made, and they play a significant role in terms of air quality, health, and climate.

Aerosols are defined as small solid or liquid particles in a gaseous substance such as air. The size varies significantly from particles that are only a few nanometers in size (less than a thousandth of a millimeter) to larger particles over 10 micrometers. These particles can come from many different sources and can consist of anything from dust and ash to organic compounds and heavy metals.

How are aerosols formed?

Aerosols can be formed through a range of processes, including:

• Mechanical dispersion: Mechanical forces, such as wind or sea spray, can cause particles from the ground or sea surface to be whirled up and become aerosols. Read more about mechanical solutions for many applications.
• Evaporation and condensation: Volatile liquids can evaporate and then condense again in the atmosphere, creating small droplets or particles.
• Combustion processes: When fossil fuels or biomass are burned, small particles such as soot or ash are released into the atmosphere.
• Chemical reactions: In the atmosphere, gaseous substances can react with each other and form new particles. This is often seen in the formation of sulfates and nitrates.

Types of aerosols

Aerosols can be divided into several categories based on their formation process, physical properties, and chemical composition. Here are the main types:

Primary aerosols

Primary aerosols are emitted directly from a source without any chemical transformations in the atmosphere. Examples of this include:

• Dust particles from desert areas, agriculture, or construction sites.
• Soot (black carbon), which occurs from incomplete combustion of fossil fuels and biomass.
• Sea salt formed from sea spray, where evaporation of seawater leaves small salt grains in the air.

Secondary aerosols

Secondary aerosols are formed through chemical reactions between gaseous substances in the atmosphere, often as a result of human activity. Some of the main examples include:

• Sulfate aerosols, which are formed when sulfur dioxide (SO2) reacts with water vapor and forms sulfuric acid.
• Nitrate aerosols, which occur from reactions between nitrogen oxides (NOx) and ammonia.
• Secondary organic aerosols (SOA), which are formed by the oxidation of organic compounds (VOCs).

Natural aerosols

These aerosols have a natural origin and are not directly the result of human activities. Examples are:

• Ash and gases from volcanic eruptions.
• Pollen and fungal spores from vegetation.
• Sea salt from wave spray and soil particles from wind.

Anthropogenic aerosols

Anthropogenic aerosols originate from human-made activities such as industry, agriculture, and transportation. Examples are:

• Particles from the combustion of fossil fuels (coal, oil) and biomass.
• Industrial emissions such as heavy metals and chemical vapors.
• Exhaust gases from cars and trucks.

Consequences and challenges of aerosols

Aerosols play a complex role in both the environment and health, and their presence in the atmosphere can have both positive and negative effects.

Environmental consequences

• Aerosols can alter the earth’s radiation balance by reflecting or absorbing sunlight, which can affect the global temperature.
• Some aerosols, such as sulfates, have a cooling effect as they reflect sunlight, while others, like black carbon, have a warming effect by absorbing heat.
• They can affect cloud formation, which can change precipitation patterns and thus have major consequences for the climate.

Health risks

• Smaller particles (under 2.5 micrometers, also known as PM2.5) can penetrate deep into the lungs and even reach the bloodstream, which can lead to serious health problems such as respiratory disorders, heart disease, and increased risk of cancer.
• Exposure to high concentrations of aerosols is associated with higher mortality and morbidity in urban areas with poor air quality.

Technological and scientific challenges

• It is difficult to measure and model aerosols accurately due to their large variation in size, shape, and chemical composition.
• There is a need for better monitoring techniques and more advanced models to understand their role in climate change and health impacts.

How aerosol pollution can be tackled

Aerosols are an important factor in both our climate and public health. Their complex nature makes them challenging to understand and control, but it is crucial to focus on reducing harmful emissions to ensure a healthier environment for the benefit of both public health and vegetation.

Managing aerosols requires a combination of regulation, technology, and international cooperation. Some of the key strategies include:

• Stricter regulation and legislation: Authorities can introduce stricter emission standards for industry, agriculture, and the transport sector to reduce the emission of harmful particles.
• International cooperation: Since aerosols can be transported over long distances, effective management of air pollution requires cooperation across national borders and international environmental agreements.
• Filtration and purification technologies: By implementing advanced filters and purification systems in power plants, vehicles, and industrial facilities, we can reduce the amount of aerosols in the air.
• Improved agricultural practices: Agriculture can contribute to less dust and ammonia emissions through better soil management and reduced burning of waste.

Sources

• UN’s Intergovernmental Panel on Climate Change (IPCC): IPCC AR6 Working Group I Report: The Physical Science Basis:
  https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/
• WHO: Global Air Quality Guidelines 2021:
  https://www.who.int/publications/i/item/9789240034228
• European Environment Agency (EEA): Europe’s air quality status 2024:
  https://www.eea.europa.eu/publications/europes-air-quality-status-2024