Isotopic compositions of elemental carbon in smoke and ash derived from crop straw combustion

Six cultivars of straw for rice, maize and wheat, respectively, were burned under flaming and smoldering conditions, and carbon isotopic ratio values of elemental carbon (EC) in smoke and ash determined. The results showed that mean carbon isotopic fractionation (Δ13C) between EC in flaming and smoldering smoke from rice straw, and the starting material was −2.7‰ and −3.0‰, respectively. Moreover, the corresponding Δ13C values for EC in flaming and smoldering smoke from wheat straw were −0.1‰ and +0.4‰, respectively. Δ13C for EC in the two types of smoke from maize straw were −3.4‰ and +0.2‰, respectively. Δ13C for EC in flaming and smoldering ash from rice straw were −1.8‰ and −1.6‰ in turn. Δ13C for EC in flaming and smoldering ash from wheat straw were +0.9‰ and +2.4‰, respectively. Additionally, the ones for EC in the two types of ash from maize straw were −1.2‰ and −1.0‰, respectively. If δ13CEC values for pollutants, such as straw smoke, soot from coal and diesel-powered vehicles, and ambient PM2.5 in a region, are determined in summer and autumn, the contribution of straw burning to ambient EC is likely to be estimated with the approach of carbon isotopic mass balance.