2. Research Background

The sources of black carbon (BC) in the atmosphere include wildfires, volcanoes eruption, energy-related combustion of fossil fuels and biofuels and some industrial activities (Penner et al. 1993; Streets et al. 2001; Bond et al. 2004). For the present-day, over two thirds of BC emissions are coming from anthropogenic sources due to a rapid increase of fossil fuel and biofuel consumptions by industry and by domestic activities (Bond et al. 2004). In addition, some natural processes also produce BC to the atmosphere, in particular from forest fires and savanna fires (Andreae and Merlet 2001). Based on past emission inventories of BC (Turco et al. 1983; Penner et al. 1993; Cooke and Wilson 1996; Liousse et al. 1996; Andreae and Merlet 2001; Novakov et al. 2003; Bond et al. 2004, 2007; Ito and Penner 2005; Dentener et al. 2006; Junker and Liousse 2008; Zhang et al. 2009; Lamarque et al. 2010; Granier et al. 2011; Lu et al. 2011; Diehl et al. 2012), the major emission sources of BC in the atmosphere include: (1) combustion of carbon-based fuels, including coal, oil, natural gas, crop residues and fuel wood by power plants, industrial sector, transportation and residential sector; (2) coke production, including the refining processes, the gas heating and the leakage processes; (3) brick production, including the material conveying processes, the product drying and fuel firing processes; (4) waste incineration, including combustion of municipal and industrial waste; (5) outdoor biomass burning, including the natural fires (forests fires, grassland fires, woodland fires and peat fires) and human-induced fires (deforestation and open burning of agricultural waste in the field). Previous studies show that domestic heating, residential cooking, on-road diesel vehicles, coke and brick production, and wildfires are the most important emission sources of BC in the atmosphere.