research interests

aerosol studies

An important gap in aerosol modeling, relates to near source aerosol dynamics, or how aerosol populations evolve a few milliseconds to minutes, on spatial scales of tens of metres, after emission. This is addressed by the development of theoretical models (analytical and numerical) to study the evolution of aerosol systems for atmospheric as well as indoor environments. Here, the novel element is introduction of the concept of number survival fraction of aerosols undergoing both coagulation and dispersion. These studies make it possible to predict the impact of emission sources on the persisting aerosol background in the atmosphere through parameterization, for example, explosive releases, geo-engineering problems, forest fires, etc. These contributions neatly bridge the gap between the sub-grid level near source processes and the large scale atmospheric transport processes described by global general circulation models.

In an application to indoor air pollution and health, a series of studies are conducted on dense aerosol releases in confined environments to target the understanding of ultrafine particle behavior in dense household smoke from solid-fuel combustion. Through a comprehensive numerical model it is shown that, counter intuitive to expectations, indoor ventilation could enhance concentration peaking effects. These studies have far reaching significance for exposure assessment to resident populations, as well as for estimating the global release of particles into outdoor atmosphere, from the indoor sources.

Further, as special application, the effect of coagulation on the evolution of activity size distributions of radioactive aerosols such as ²¹⁰Pb and ⁷Be are studied using the developed numerical models. These studies successfully predicted the shifting modes of the activity size distributions according to the life times of the species, and have considerable application to size-segregated atmospheric residence time estimation techniques.

A recent work on development of models for determining the lifetime of virus laden aerosols and quantifying their risk via airborne route is a very useful tool in the risk estimation of airborne virus laden droplets from COVID-19-infected subjects in indoor environments. By constructing a comprehensive model, this study demonstrates that the mean residence times of virusols, which are of relevance for disease control in indoor air and risk assessment, vary by nearly an order of magnitude depending upon the viral load in the biological fluid ejected from patients. Another study on estimation of size distribution of virus laden droplets from expiratory ejecta of infected subjects provides important information about the quantification of airborne virus in indoor environments. Due to Poissonian fluctuations, only a small fraction of droplets expirated from COVID-19-infected subjects would contain viruses. As a result, the size distribution metrics and residence time of those virus-laden droplets, called virusols, could be very different from those of total droplet populations.

Google Sites

Report abuse