pib releases 02-08-2021

Paper	Topics	Subject
PT Pickups	Aerosol and Climate Change	Biodiversity & Environment

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Scientists tracing the concentration, size and evolution of aerosol particles smaller than 3 nanometres at an urban location in India have found the 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 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 the subsequent growth of these newly formed clusters to 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 approaches, 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.
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 regional NPF event.

Relation with Sulphuric acid concentrations

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, calling for research using state-of-the-art instrumentation to understand the mechanisms driving NPF in diverse environments across India.