Executive Summary : | Brown carbon (BrC), a light-absorbing fraction of organic carbon, significantly impacts climate change due to its light absorption characteristics. It affects atmospheric photochemistry and secondary organic aerosol formation processes, affecting regional air quality. However, the optical properties and formation mechanisms of BrC aerosols are poorly understood, especially as a function of aerosol size. The distribution of BrC and its constituents is influenced by factors like source origin, fuel type, combustion conditions, and atmospheric processing. In India, studies linking sources, atmospheric processing, molecular composition, and climate properties of BrC are limited. This work aims to collect size-segregated aerosol samples from two megacities, Delhi and Kolkata, to understand their BrC or HULIs profiles, primary emission vs secondary formation processes, chromophoric composition, and radiative forcing efficiency. |