Emission characteristics and relationships among PCDD/Fs, chlorobenzenes, chlorophenols and PAHs in the stack gas from two municipal solid waste incinerators in China

An extensive investigation was conducted to understand polychlorinated dibenzo-p-dioxin and furan (PCDD/F) formation mechanisms and their relationships with chlorobenzenes (CBzs), chlorophenols (CPhs) and polycyclic aromatic hydrocarbons (PAHs) in the stack gas from two fluidized bed municipal solid waste incinerators in China. The toxic equivalent quantity (TEQ) value and the concentration of target compounds changed with the incinerator operating conditions. CPhs and PAHs were much more sensitive to operation conditions and were affected more easily by change. Only 2-monochlorophenol revealed a negative linear correlation (R-2 >= 0.7). More than half of the PAHs revealed an adequate correlation model with PCDD/F concentration (R-2 > 0.6), while CBzs showed almost perfect correlations with PCDD/Fs (R-2 >= 0.8, significance level a > 0.05). 123-Trichlorobenzene, 1234-tetrachlorobenzene and pentachlorobenzene revealed the best positive linear correlation (R-2 > 0.9). PCDFs were revealed to be the best target compounds for indication due to the similar formation variation trend to that of other precursors. Unary and multiple linear regression equations with high coefficients of determination between several CBz, PAHs and PCDD/Fs, TEQ and PCDFs were established. The detailed relationships among PCDD/F homologues, isomers and other compounds and their formation mechanism were also discussed.