Occurrence of polycyclic aromatic hydrocarbons (PAHs) during the coking process has been widely recognized. The formation of polychlorinated naphthalenes (PCNs) from PAHs during some thermal related processes has been confirmed in many studies. Thus, the coking process is assumed to be a potential source of PCNs. However, intensive investigations on PCN emissions during the coking process are lacking. In order to evaluate PCN emissions from the coking process, an intensive study comprising 11 typical coke plants was undertaken. PCNs were qualified and quantified by isotope dilution HRGC/HRMS techniques. The concentrations of PCNs in stack gas samples collected from the investigated coke plants were in the range of 1.6-91.8 ng Nm -3 (0.08-4.23 pg TEQ Nm -3 ). The emission factors of PCNs were found to be in the range of 0.77-1.24 ng TEQ per ton of coke production. The estimated annual toxic emissions of PCNs from the global coking industry vary from 430 to 692 mg TEQs. Characteristics of the PCN profiles were dominated by the lower chlorinated homologues, with mono-CN being the most abundant homologue. According to the PCN distribution and correlations of PCN homologues, it was speculated that chlorination is possibly the dominant pathway of PCN formation during the coking process.

The coking process is considered to be a potential source of unintentionally produced persistent organic pollutants (UP-POPs). However, intensive studies on the emission of UP-POPs from the coking industry are still very scarce. Emission of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs), dioxin-like polychlorinated biphenyls (dl-PCBs), hexachlorobenzene (HxCBz), and pentachlorobenzene (PeCBz) covered under the Stockholm Convention were investigated for the coking process in this study. Stack gases from some typical coke plants in China were collected and analyzed to estimate the emission of UP-POPs from the coking industry. Emission factors of 28.9 ng WHO-TEQ tonne -1 for PCDD/Fs, 1.7 ng WHO-TEQ tonne -1 for dlPCBs, 596 ng tonne -1 for HxCBz, and 680 ng tonne -1 for PeCBz were derived based on the investigated data. The annual emissions from the global coking industry were estimated to be 15.8 g WHO-TEQ for PCDD/Fs, 0.93 g WHO-TEQ for dl-PCBs, 333 g for HxCBz, and 379 g for PeCBz, respectively (reference year 2007). According to the distribution of PCDD/Fs, we argued for the de novo synthesis to be the major pathway of PCDD/F formation. With regard to the characteristics of dl-PCBs, the most abundant congener was CB-118, and the most dominant contributor to the total WHO-TEQ of dl-PCBs was CB-126. IntroductionPersistent organic pollutants (POPs) are extremely harmful to human health and the environment because of their high toxicity, persistence in the environment, and bioaccumulation through the food web. Once released into the environment, they can be transported and distributed on a global scale by the grasshopper effect and global fractionation (1,2). Minimizing environmental exposure to POPs is an important public goal for environmental protection, also with respect to sustainable development. As it is very difficult to eliminate POPs by photodegradation, chemical degradation, or biodegradation under environmental conditions due to their high stability and persistence (3), controlling and regulating the emission of unintentionally produced POPs (UP-POPs) from key sources is one of the most effective measures for protecting our environment and human health from .Evaluating the emissions of UP-POPs from sources is important for applying the best available technology/best environmental practice (BAT/BEP) to priority sources and developing a POP inventory. Many sources for the emission of UP-POPs have been identified and quantified (7,8), and the effects of various parameters on the formation of UPPOPs have been demonstrated in many studies (9-13). Sources of POPs and their relative importance have changed substantially over the past several decades. Municipal waste incineration was previously a major contributor of UP-POPs to the environment, but following the implementation of various regulations, and improvements in combustion technology and emission cleaning techniques, this is now generally considered to have a lower contribution to the total emissions to air. Thus, some other potential sources ...

No abstract