Research Projects

Hydroxyl radical (•OH) is known as the detergent of the earth’s atmosphere, and in the daytime more than 60% of the troposphere’s •OH is produced by photodissociation of atmospheric nitrous acid (HONO). It is believed that the main atmospheric source of HONO is the heterogeneous nighttime reactions of NO2, produced primarily via different anthropogenic activities, on wet surfaces. However, recent atmospheric modeling studies predict that there are missing sources of atmospheric HONO. Under the scope of this project, two new atmospheric production channels for HONO have been identified through laboratory investigations. Those are the reactions of gaseous NO2 with hydroxyacetone and glycolaldehyde, where both the latter two belong to the category of atmospherically significant volatile organic compound. The accumulated experimental data indicate that these reactions occur in the gas phase only, and not via heterogeneous surface reactions. In addition, under the project’s scope. a new gas phase reaction channel for the production of atmospheric nitric acid has been found where NO2 reacts with phenol, and the implication of the reaction has been analyzed thoroughly. A mobile quantum cascade laser-based spectrometer has been developed for the direct estimation of the atmospheric abundances of HONO. It is aimed that the spectrometer will be deployed at a suitable location in the near future. An alternative long path optical wave guide type apparatus has been developed, and which has been used to measure the atmospheric abundances of HONO in the premises of the Indian Association for the Cultivation of Science in the rainy season of 2019. The measured data is consistent with the reports of investigations carried out in the other parts of the world.