Characterization of molecular markers in smoke from residential coal combustion in China

The organic constituents and distributions of molecular markers emitted from a residential coal-stove burning honeycomb coal briquettes were determined in this study. The major organic components emitted directly in smoke particles were polycyclic aromatic hydrocarbons (PAHs), with abundant hydroxy-polycyclic aromatic hydrocarbons (OH-PAHs), i.e., thermally altered derivative compounds from coal combustion, UCM (unresolved complex mixture of branched and cyclic compounds), n-alkanes and n-alkanoic acids. Other compounds present as minor components included n-alkenes, phenols, alkylbenzenes and n-alkanols. The distributions of the organic compounds in the coal smoke samples were highly variable and dependent on combustion temperature, flame aeration, fire duration, and coal rank. Coal smoke emissions may be identified by some indicators including: (1) presence of hydroxy-PAHs, (2) the decrease in carbon preference index (CPI) of n-alkanoic acids with increasing rank, (3) the decrease of the ratios of 17α(H),21β(H)-29-norhopane to 22R-17α(H),21β(H)-homohopane and 17α(H),21β(H)-29-norhopane to 17α(H),21β(H)-hopane with increasing rank, (4) the increases in the homohopane index [22S/(22S + 22R)] and the 17α(H),21β(H)-hopane to 17β(H), 21α(H)-hopane ratio with increasing rank, and (5) the increase of benzo[e]pyrene/(benzo[e]pyrene + benzo[a]pyrene) with increasing rank. In addition, the diagnostic ratios among PAHs and between PAHs and the corresponding hydroxy-PAHs, such as benz[a]anthracene/(benz[a]anthracene + chrysene), indeno[1,2,3-cd]pyrene/(indeno[1,2,3-cd]pyrene + benzo[ghi]perylene), pyrene/OH-pyrene, and chrysene/OH-chrysene can be used to distinguish bituminous from anthracite coal smoke emissions.