Levels, profiles, and emission characteristics of chlorobenzenes in ash samples from some industrial thermal facilities in northern Vietnam.

Chlorobenzenes (CBzs) are unintentionally produced organic contaminants from different thermal industrial processes, which have been scarcely surveyed in Asian developing countries including Vietnam. In this study, residue concentrations, profiles, emission factors, and annual emissions of seven chlorobenzene compounds were investigated in fly ash and bottom ash samples of some industrial facilities including brick making plant, steel and zinc production plants, and industrial and municipal waste incinerators in northern Vietnam. Total concentrations of seven CBzs in the ash samples were generally decreased in the order: industrial waste incinerator > municipal waste incinerator > steel-making plant > brick making plant. Emission pattern of CBzs varied considerably among different industrial plants, with 1,2- and 1,3-dichloro-, 1,2,3,4-tetrachloro-, and hexachlorobenzene as predominant compounds in the industrial waste incinerators and steel-making plants. Emission factors of CBzs estimated for the fly ash and bottom ash samples were in the range of 118-2020 and 5.3-22,600 μg ton, respectively. Average annual emissions (AEs) of total seven CBzs estimated for fly ash and bottom ash in the investigated plants were in the range of 154-54,300 and 20,160-161,400 mg year, respectively. The AEs of CBzs estimated for fly ash in the steel-making plant were higher than those in the waste incinerators. Meanwhile, CBz emissions for bottom ash were the highest in the steel-making plant, followed by the industrial and municipal waste incinerators. This is among the first studies on the emission characteristics of both low and highly chlorinated benzenes from industrial activities in Vietnam.