Scientists tracing the concentration, size and evolution of aerosol particles smaller than 3 nanometers at an urban location in India have found the frequent formation of sub-3nm aerosol particles in the atmosphere.
What is Aerosol Nucleation?
- 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).
- 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.
What has the new research found?
- 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.
Role of Sulphur
- 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.
- 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.
