Organic Species Emitted as a Part of Combustion Residue: Fate and Transformation in the Ambient Air

Abstract

Organic species emitted as a part of combustion residue are one of the major components of both gaseous and particulate emission. These species gets diluted and transformed when they come in contact with the atmospheric gases. The gas to particulate conversion of SVOC (semi volatile organic compound) leads to the formation of SOA (secondary organic aerosol). Gas to particle conversion is very sensitive to the level of dilution. Combustion generated particulates are formed as a result of a complex process. The precise mechanism of SOA formation is still not completely understood but it is largely attributed to oxidation of reactive organic gases (ROGs) and gas to particle phase conversion. Polycyclic aromatic hydrocarbons (PAHs) present in the combustion products may also get transformed upon dilution and oxidation when emitted in the ambient atmosphere. PAHs and their derivatives are formed by the incomplete combustion of organic materials arising from combustion and due to anthropogenic emissions. The PAH concentration varies significantly in various rural and urban environments and their concentration are mainly influenced by the level of vehicular and domestic emissions. Diagnostic ratio (DR) approaches allow either individual PAHs or their combination to be used for identifying their origin sources. This paper discusses the fate and transformation of SOA and Polycyclic aromatic hydrocarbons (PAHs) largely emitted from combustion sources. The effect of temperature and relative humidity on the formation of SOA and a brief discussion on its measurement and analysis has also been described in this study. Finally, a brief discussion on various health effects attributed to combustion generated species has been provided.