Emissions of polycyclic aromatic hydrocarbons from coking industries in China

This study set out to assess the characteristics of polycyclic aromatic hydrocarbon (PAH) emission from coking industries, with field samplings conducted at four typical coke plants. For each selected plant, stack flue gas samples were collected during processes that included charging coal into the ovens (CC), pushing coke (PC) and the combustion of coke-oven gas (CG). Sixteen individual PAHs on the US EPA priority list were analyzed by gas chromatography/mass spectrometry (GC/MS). Results showed that the total PAH concentrations in the flue gas ranged from 45.776 to 414.874 mu g/m(3), with the highest emission level for CC (359.545 mu g/m(3)). The concentration of PAH emitted from the CC process in CP1 (stamp charging) was lower than that from CP3 and CP4 (top charging). Low-molecular-weight PAHs (i.e., two- to three-ring PAHs) were predominant contributors to the total PAH contents, and Nap, AcPy, Flu, PhA, and AnT were found to be the most abundant ones. Total BaPeq concentrations for CC (2.248 mu g/m(3)) were higher than those for PC (1.838 mu g/m(3)) and CG (1.082 mu g/m(3)), and DbA was an important contributor to carcinogenic risk as BaP in emissions from coking processes. Particulate PAH accounted for more than 20% of the total BaPeq concentrations, which were significantly higher than the corresponding contributions to the total PAH mass concentration (5%). Both particulate and gaseous PAH should be taken into consideration when the potential toxicity risk of PAH pollution during coking processes is assessed. The mean total-PAH emission factors were 346.132 and 93.173 mu g/kg for CC and PC, respectively.