Impact of a mountain grassland fire on the concentration of aerosol black carbon and carbon monoxide near the surface at a remote coastal location

Abstract

A case study is presented on the impact of an extensive grassland fire, at a high altitude location in Western Ghats, on the aerosol black carbon (BC) mass concentration (M_B) and concentration (CO) of carbon monoxide measured at two remote, coastal, nearby locations. Observations revealed a substantial increase shortly after the outbreak of the fire at a high altitude location ( ~20 km away) in the concentrations of both species; while a two-fold increase occurred in the mass concentration of BC; the increase in CO though was less pronounced (by a factor of ~1.5). It is suggested that the sea-breeze circulation modified by the prevailing winds caused the transport of pollutants from the source region downwind to the coastal location. The impact persisted for one day after which it became insignificant. During the first maximum of these, the wind conditions were such that the pollutants emitted from the fire were transported offshore with the return flow of the sea breeze, they then sank along with the airmass and were again transported back to the coast via the sea breeze. During the second maximum (after sunset), the particles as well as the trace gases along with the airmass came directly to the regions of fire to the valley via katabatic flow and were again transported to the coast via the land breeze. This added with the nighttime confinement of pollutants near the surface caused the enhancement in nocturnal peak and it prevailed high until next day morning unlike normal days.