FESEM Analysis showing evidence of aerosol Mixing over Indo-Gangetic Plains

Kanpur AERONET deployed in January 2001 has provided a long-term dataset which has been used to understand the aerosol properties and aerosol long term trend in the Indo-Gangetic Plains (IGP). Recent studies have revealed higher black carbon (BC) mass concentrations in the IGP, home to 900 million people. We present analysis of black carbon mass concentrations obtained from several locations in the IGP - namely Varanasi, Lucknow, Kanpur, Greater Noida and Delhi. Measurements show significant diurnal variation with higher BC concentrations in the morning hours and low concentrations during afternoon and evening time. Seasonally, BC concentrations are generally found to be higher during winter months compared to spring and summer monsoon season showing high seasonal variability. The higher winter-time BC is associated with a stable and shallow boundary layer which favors accumulation of pollutants over the IGP, resulting in dense haze conditions. Filter-based analysis, obtained from samples used in Aethalometer and high vacuum sampler, were analyzed to study aerosol surface characteristics and size of particles. Additionally, FESEM (Field Emission Scanning Electron Microscope) analysis show many dust minerals (Na, Al, Si, K, Fe), biogenic substances, fly ash of varying sizes 15 nanometer to 5 micron. The SEM imagery also show heterogeneous aerosol particles, sometimes these mineral grains are seen separately and sometime coating of fly ash and mineral particles are clearly seen. Similarly, Kanpur AERONET data is analyzed during winter and pre-monsoon season, contrasting aerosol properties (SSA, Refractive index and Size distribution) are found that are associated with large aerosol mixing, also supported from the FESEM analysis.