Researchers at the University of Hyderabad (UoH) have found a frequent formation of sub-3 nanometers neutral aerosols in the city atmosphere that in a way indicate the quality of air is affected.
Vijay Kanawade and Mathew Sebastian from UoH measured neutral sub-3nm particle concentrations in Hyderabad city and reported the formation rate of small molecular clusters, for the first time, in sub-3nm size regime, where aerosol nucleation triggers, according to their study published in Elsevier journal, Atmospheric Environment.
Elsevier is a Netherlands-based publishing company specialising in scientific, technical, and medical content, and publishes more than five lakh articles annually in 2,500 journals.
The researchers 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 on the UoH campus site. Jeff Pierce from Colorado State University, USA, was also part of this study.
Aerosols are tiny solid or liquid particles suspended in the atmosphere. 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, 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.
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 hypothesised 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.
Speaking to The Hindu , Mr Kanawade said the study is of critical importance as a major fraction of these newly formed particles can reach sizes of cloud condensation nuclei where they have climatic impacts. Aerosols can suppress or enhance rainfall as well depending on their chemical composition.
He observed that the presence of aerosols in the atmosphere was common but their presence in urban areas means, over a period of time, the city may have to face haze and air quality may also get affected in the process. He says the study of aerosols is not prolific in India and a lot of research needs to be done before coming to a total conclusion on these aerosols affecting the urban atmosphere badly.
