PCDD/F and “Dioxin-like” PCB emissions from iron ore sintering plants in the UK

Abstract

Investigations have been carried out at the three Corus UK sinter plants over the period 2002–2004 to characterise the emissions of both 2,3,7,8-PCDD/Fs and WHO-12 PCBs, to estimate annual mass releases of these organic micro-pollutants using the I-TEF and WHO-TEF schemes, and to investigate the formation of PCBs in the iron ore sintering process. Results showed that the sintering of iron ore produces a characteristic WHO-12 PCB and PCDD/F congener pattern that is substantially the same for all UK sinter plants. With regard to WHO-12 PCBs, the most abundant congeners were typically PCBs 118 (6–9 ng N m −3), 105 (2–4 ng N m −3) and 77 (2–3 ng N m −3). All other WHO-12 PCBs were also detected at concentrations around 1 ng N m −3. All sinter plants investigated exhibited very similar TEQ concentrations. WHO-12 PCB emissions were in the range 0.042–0.111 ng WHO-TEQ N m −3, whereas PCDD/F emissions ranged from 0.39 to 1.62 ng WHO-TEQ N m −3. PCDF congeners were the main contributors to the overall TEQ in sintering emissions (ca. 85%). Amongst WHO-12 PCBs, PCB 126 was the only noteworthy contributor to total TEQ (ca. 5–7%), a similar contribution to that from PCDDs. Based on the measurements that Corus UK has undertaken at these three sinter plants, annual mass releases of WHO-12 PCBs and PCDD/Fs have been calculated. For UK sinter plants, a total mass release of 29.5 g WHO-TEQ per annum [WHO-12 PCBs + PCDD/Fs] has been estimated, representing 9% of the total PCDD/F emissions to the UK atmosphere. Measurements were also carried out at a UK sinter plant to determine the windleg emission profile of WHO-12 PCBs. Results showed that WHO-12 PCBs were formed in the same regions of the sinter strand as 2,3,7,8-PCDD/Fs, indicating that there was a strong correlation between the formation of WHO-12 PCBs and PCDD/Fs in the iron ore sintering process.