Aerosol particles below 3 nm can reach sizes having climatic impact

The Ministry of Science & Technology has said that aerosol particles below 3 nm which can reach sizes having climatic impact, formed frequently in urban locations in India as scientists tracing the concentration, size and evolution of aerosol particles smaller than 3 nanometres at an urban location in India have found frequent formation of sub-3nm aerosol particles in the atmosphere.

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

The formation of small molecular clusters of sub-3nm size is technically called aerosol nucleation, and subsequent growth of these newly formed clusters to the large sizes is called atmospheric new particle formation (NPF). The 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.

Scientists from the University of Hyderabad measured neutral sub-3nm particles for the first time at an urban location in India. Dr Vijay Kanawade and Mathew Sebastian used AIRMODUS nano Condensation Nucleus Counter (nCNC) to measure particle size distribution in the size range of 1 to 3 nm.

In the study supported by the Department of Science & Technology (DST) under the Climate Change Programme Division, they conducted continuous observations since January 2019 at the University of Hyderabad campus site and reported the formation rate of small molecular clusters in sub-3nm size regime, where aerosol nucleation triggers.

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

The research 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 scientists observed that only half of these events showed newly formed molecular clusters growing past 10 nm size. Thus particle size distributions display a conventional banana-shaped aerosol growth, which is indicative of a regional NPF event.

The team found a strong positive correlation between sub-3nm particle concentrations and sulphuric acid concentrations, confirming the potential role of sulfuric 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.

Moreover, these newly formed particles did not always grow to large sizes, and the team hypothesized that the particle growth was limited by lower concentrations of condensable vapours such as organic compounds. It called for research using state-of-the-art instrumentation to understand the mechanisms driving NPF in diverse environments across India.

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Arushi Sana is the Co Founder of NYK Daily. She was a Forensic Data Analyst previously employed with EY (Ernst & Young). She aims to develop a global community of knowledge and journalism par excellence through this News Platform. Arushi holds a degree in Computer Science Engineering. She is also a Mentor for women suffering from Mental Health, and helps them in becoming published authors. Helping and educating people always came naturally to Arushi. She is a writer, political researcher, a social worker and a singer with a flair for languages. Travel and nature are the biggest spiritual getaways for her. She believes Yoga and communication can make the world a better place, and is optimistic of a bright yet mysterious future!

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