Anomalous Features of Black Carbon and Particulate Matter Observed Over Rural Station During Diwali Festival of 2015

Black carbon (BC) aerosol is the second most powerful climate forcing agent, ahead of methane, and second only to carbon dioxide, formed through the incomplete combustion of fossil fuels, bio-fuel and biomass, and is emitted in both anthropogenic and naturally occurring soot. In this communication, we present some interesting results of BC, particulate matter (PM), in conjunction with concurrent satellite and surface meteorological products, obtained during the recent Diwali festival episode of November 2015 over a rural station characterized by sparse population and complex terrain. This comprehensive study revealed (i) a clear diurnal variation of BC, PM1, PM2.5, and PM10 mass concentration with dual maxima (bimodal), one around early morning and the other around mid-night hours, due to emissions from traffic with minimum concentration around afternoon hours due to well-known planetary boundary-layer dynamics, (ii) the PM showed higher concentration (more than two-fold) during the festive period as compared to the pre- and post-festive periods, (iii) the aerosol optical depth (AOD) showed initially higher and subsequent dilution due to local meteorology, (iv) angstrom exponent (AE) showed larger values implying enhancement in fine-mode particles due to festive activity and (v) The NOAA-HYSPLIT air-mass back-trajectory analysis and CALIPSO satellite imageries portray contribution from the trans-boundary pollution through long-range transport mechanism. The results are explained by considering the terrain-induced meteorological conditions and local anthropogenic activities.