Science

Aerosol particles below 3nm can reach sizes that can have climatic impacts: Study

Our Bureau Hyderabad June 15 | Updated on June 15, 2021

These are formed frequently in urban locations

Aerosol particles below 3 nanometres, which can reach sizes with climatic impacts, are formed frequently in urban locations in India, finds a study by researchers at University of Hyderabad.

Aerosols are tiny solid or liquid particles suspended in the atmosphere. Scientists, characterising the concentration, size and evolution of aerosols smaller than 3nm at an urban location in Hyderabad, have found frequent formation of sub-3nm neutral aerosols in the atmosphere.

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This has critical importance as a major fraction of these newly-formed particles can reach sizes of cloud condensation nuclei where they have climatic impacts.

The formation of small molecular clusters of sub-3nm and their subsequent growth to the large sizes is called atmospheric new particle formation (NPF). NPF occurs everywhere in the terrestrial troposphere, and therefore, it is a large source of aerosol numbers to the atmosphere. Though extensively studied globally using field observations, laboratory experiments and modelling approach, it is largely unexplored in India.

Dr Vijay Kanawade and Mathew Sebastian from the Aerosol Physics Laboratory, University of Hyderabad, measured neutral sub-3nm particle concentrations at an urban location in India and reported the formation rate of small molecular clusters, for the first time, in sub-3nm size regime, where aerosol nucleation triggers. The researchers have used AIRMODUS nano Condensation Nucleus Counter (nCNC) to measure particle size distribution in the size range of 1 to 3 nm diameter since January 2019 at the University of Hyderabad campus site. Dr Jeff Pierce from Colorado State University, US was also part of this study.

Their findings published in the journal ‘Atmospheric Environment’ showed that a pool of sub-3nm particles is often present in the atmosphere, but how fast these clusters grow depends on various factors.

The team found a strong positive correlation between sub-3nm particle concentrations and sulphuric acid concentrations, confirming the potential role of sulphuric acid in the formation of sub-3nm particles. While NPF often starts with sulphuric acid in the atmosphere, sulphuric acid alone fails to explain observed particle formation and growth rates in the atmosphere. Other vapours such as ammonia, amines and organics play a crucial role in the growth of newly-formed particles.

This work has been recently published in the ELSEVIER journal “Atmospheric Environment.”

Published on June 15, 2021

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