Polychlorinated biphenyls (PCBs) are one of the most widespread persistent organic pollutants, identified in every component of the global ecosystem. A production of approximately 2 * 10 9 Kg technical PCB occurred form 1930 to the late 1970 1 and the total amount released into the environment is estimated in 370. 000 2 tonnes. Twelve of the possible 209 PCBs are non- and mono-ortho substituted chlorinated biphenyls. They resemble 2,3,7,8-tetrachloro dibenzo-p-dioxin (TCDD) in their biological action, bio accumulating through the food chain and causing immuno-, reproductive and dermal toxicities. Therefore in 1997 the Word Health Organisation (WHO) extended the concept of toxic equivalency (TEQs) 3 also to these group of “dioxinlike” PCBs. At the moment a fraction of the produced PCBs is collected with the household waste and burned in incinerators. PCBs are evaporated during waste incineration and are partially destroyed during the incineration process, dependent on residence time/temperature. Catalytic dioxin destruction shall additionally reduce the emissions of PCBs. Anyway all PCBs left in the flue gas are emitted in the environment. Some publications present this as an additional source of PCBs 2,4,5,6. This work aims to investigate the congeners and homologous group distribution of PCBs in emission samples of municipal solid waste incinerators and to calculate the WHO-TEQPCB in relation to the WHO-TEQPCDD/F.
Materials and Methods
The evaluation was conducted on emissions of a municipal solid waste (MSW) incinerator with a total net capacity of 270 t/day, using roller type combustion grate and energy recovery (electricity and district heating). Flue gas cleaning is performed by a fabric filter and a wet scrubber, in line with a final SCR (Selective Catalytic Reduction) unit for NOx and PCDD/F conversion. Directly on the stack an automatic sampling system wasis installed , capable to perform isokinetic sampling of . PCDD/F for periods from 6 hours to 6 Weeks. This DioxinMonitoringSystem is using the dilution method which is described in the EN-1948 Part 1 7 and permits to collect the PCDD/F as well as PCB on a cartridge containing a dust filter and two dry poly urethane foams 8. At the end of sampling the cartridge was transferred to the lab. There the sample was extracted, cleaned and evaluated using the EN 1948 part 2 and 3. After soxhlet-extraction with toluene the sample extract was split in two parts:. One for PCDD/F and the other for PCB determination. After sulphuric acid (98%) pre-treatment an automatic multicolumn system (Dioxin PowerPrep, FMS) clean up has beenwas used for Dioxins and for PCBs. For PCB analysis carbon 13C12 labelled Standards (labeled “dioxinlike” congeners as well as labeled first and last eluting congener of each chlorination level) were added according EPA 1668A 9 after sampling. The HRGC- HRMS analysis has been was conducted on a Agilent 6890 gaschromatograph coupled on a Thermofinnigan MAT 95 XP operating at resolution 10.000. A HT-8 PCB 60 m, 0,25 mm column from SGE was used for PCB analysis.