title: [Carbon isotopic compositions of n-alkanes and n-alkanoic acids in the smoke from combustion of rice straw].
abstract: In order to investigate the carbon isotopic fractionation in n-alkanes and n-alkanoic acids in smoke from rice straw combustion, six types of rice straw were burned in laboratory under flaming and smoldering conditions, and the compound specific isotopic compositions for the two classes of biomarkers in the smoke were determined. The results showed that the delta13C values of individual n-alkanes and n-alkanoic acids released from flaming burns of all the rice species ranged from -28.6 per thousand to -38.8 per thousand and from -29.6 per thousand to -41.9per thousand, respectively, and that the mean delta13C values for the two compound classes in the flaming smoke for the six types of rice straw were in the range of -32.6 per thousand to -36. 4per thousand and -34.0 per thousand to -36.2 per thousand, respectively. Moreover, the n-alkanes in the smoke from the most straws were more depleted in 13C in general than the identical substances with equal carbon number in corresponding unburned biomass. The magnitude of the isotopic discrimination (delta) was up to 4.1per thousand. Conversely, the n-alkanoic acids in the smoke tended to be more enriched in 13C than the corresponding biomarkers in the unburned straw for all of the species, and the delta was up to 6.3 per thousand. The delta13C values of the individual n-alkanes and n-alkanoic acids in the smoke from smoldering burns of the six species varied between -31.7 per thousand and -39.0 per thousand and between -31.3 per thousand and -38.8 per thousand, respectively. The average values for the two compound classes in the smoke for a species were in the range of -35.1 per thousand to -36.4 per thousand and -34.4 per thousand to -35.6 per thousand, respectively. The compound specific delta13C values of the n-alkanes in the smoke for most species were smaller than those of the same substances in the corresponding rice straw, and the greatest delta was 6.1 per thousand. However, the delta13C values of n-alkanoic acids in the smoke were greater than those in the rice straw, and the delta was up to 8.4 per thousand. The n-alkanes from the smoldering burn were more depleted in 13C than those from the flaming burn of the identical rice species, whereas the n-alkanoic acids (> or = C19) more enriched in 13C. These results suggest that there is significant difference in the carbon isotopic composition of individual n-alkanes or n-alkanoic acids in the smoke derived from rice straw combustion and the unburned biomass, and that converse carbon isotopic fractionation occurs in the two compound classes in the smoke relative to those in the rice straw.
authors: School of Environmental Science and Engineering, Nanjing University of Information Science & Technology, Nanjing 210044, China. liugang650104@sina.com
authors: Gang
authors: G
authors: Liu
authors: Li-Na
authors: LN
authors: Sun
authors: Jiu-Hai
authors: JH
authors: Li
authors: Hui
authors: H
authors: Xu
mesh_terms: D000473:Alkanes / Q000032:analysis / Q000737:chemistry*; D002087:Butyrates / Q000032:analysis / Q000737:chemistry; D002210:Caprylates / Q000032:analysis / Q000737:chemistry; D002247:Carbon Isotopes / Q000032:analysis*; D002681:China; D005227:Fatty Acids / Q000032:analysis / Q000737:chemistry*; D017745:Incineration; D012275:Oryza / Q000737:chemistry*; D018547:Plant Stems / Q000737:chemistry; D012906:Smoke / Q000032:analysis*
chemical_list: D000473:Alkanes; D002087:Butyrates; D002210:Caprylates; D002247:Carbon Isotopes; D005227:Fatty Acids; D012906:Smoke