What are Aerosols?

• Aerosols are defined as a combination of liquid or solid particles suspended in a gaseous or liquid environment.
• In the atmosphere, these particles are mainly situated in the low layers of the atmosphere (< 1.5 km) since aerosol sources are located on the terrestrial surface.
• Aerosols can be tiny droplets, dust particles, bits of fine black carbon, and other things, and as they float through the atmosphere they change the whole energy balance of the planet.

Types of Aerosols

“Primary” aerosols, like dust, soot, or sea salt, come directly from the planet’s surface. They get lifted into the atmosphere by gusty winds, shot high into the air by exploding volcanoes, or they waft away from smokestacks or flames. 

“Secondary” aerosols form when different things floating in the atmosphere—like organic compounds released by plants, liquid acid droplets, or other materials—crash together, culminating in a chemical or physical reaction.

Origin of Aerosols

• Natural sources of aerosols include sea salt generated from breaking waves, mineral dust blown from the surface by wind, and volcanoes.
• Anthropogenic aerosols include sulfate, nitrate, and carbonaceous aerosols, and are mainly from fossil fuel combustion sources.

Why in News?

Scientists have found that aerosols like black carbon and dust, which makes the Indo-Gangetic Plain one of the most polluted regions of the world, have led to increased incidents of high rainfall events in the foothills of the Himalayan Region.

Aerosols on climate

• Aerosols influence climate in two primary ways: by changing the amount of heat that gets in or out of the atmosphere, or by affecting the way clouds form.
• Some aerosols, like many kinds of dust from ground-up rocks, are light-colored and even a little bit reflective. When the sun’s rays beam down on them, they bounce the rays back out of the atmosphere, preventing that heat from ever reaching Earth’s surface-cooling of the atmosphere.
• But other aerosols, like black carbon from burned coal or wood, do the opposite, absorbing heat from the sun as it beats down. That ends up warming the atmosphere.

Other effects of Aerosols

• They affect the atmospheric chemical composition.
• They can reduce visibility.
• They have important impacts on air quality and human health (e.g. aerosols can cause damage to heart and lungs).
• They serve as nuclei for cloud droplets or ice crystals in ice clouds.
• In addition to scattering or absorbing radiation, aerosols can alter the reflectivity, or albedo, of the planet.
• In the Arctic, aerosols from wildfires and industrial pollution are likely hastening the melting of ice.
• As an indirect effect, aerosols in the lower atmosphere can modify the size of cloud particles, changing how the clouds reflect and absorb sunlight, thereby affecting the Earth’s energy budget.

References:

1. https://www.pib.gov.in/PressReleasePage.aspx?PRID=1679743
2. https://www.nationalgeographic.com/environment/global-warming/aerosols
3. http://ozone.meteo.be/meteo/view/en/19016929-What+are+the+effects+of+aerosols.html