Characterisation of PCDD/F emissions from industrial sources. Influence of sampling methods on distribution profiles

Transcription

1 Characterisation of PCDD/F emissions from industrial sources. Influence of sampling methods on distribution profiles A. Sbrilli, M. Rotatori, E. Guerriero, M. Bianchini, P. F. Gigliucci & V. Colamonici CNR, Istituto sull inquinamento atmosferico, Via Salaria Km, 29, Monterotondo, Italy Abstract The aim of this paper is to present preliminary results on the characterisation of polychlorinated dibenzo-p dioxins and furans (PCDD/F) emission sources and to focus on the influence of sampling method on the distribution of these pollutants. The identification can be carried out by a comparison of 2,3,7,8 relative profiles or ITEQ values relative profiles and it is possible discriminate different industrial emission sources. Keywords: emission sources, PCDD/F, sampling method, relative distribution. 1 Introduction The profiles of the ten homologue groups is usually evaluated for the identification of PCDD/F emission sources. This kind of study provides different emission profiles, but they are hardly comparable with the same profiles from deposition, ground or air samples [1-3], since degradation reactions or distribution process in the environmental compartments can occur [4, 5]. For instance, the most volatile compounds undergo photochemical degradation and in the ground samples only the heaviest ones can be found. Another way is to compare the different pattern of all the congeners, considering the toxic and nottoxic ones, since some of them are often important for the characterisation of the process. Unfortunately in the routine analysis it is not possible to identify all the congeners.

2 552 Air Pollution XII Table 1: Relative distribution with a 100% recovery. congeners Recovery 100 Relative distribution ITEF quantity values % 2,3,7,8-TetraCDD ,2,3,7,8-PentaCDD ,2,3,4,7,8-HexaCDD ,2,3,6,7,8-HexaCDD ,2,3,7,8,9-HexaCDD ,2,3,4,6,7,8-HeptaCDD OctaCDD ,3,7,8-Tetra CDF ,2,3,7,8-PentaCDF ,3,4,7,8-Penta CDF ,2,3,4,7,8-HexaCDF ,2,3,6,7,8-HexaCDF ,3,4,6,7,8-HexaCDF ,2,3,7,8,9-HexaCDF ,2,3,4,6,7,8-HeptaCDF ,2,3,4,7,8,9-HeptaCDF Discussion OctaCDF TOTAL 288 Before choosing the distribution to evaluate, it is mandatory choosing a sampling method (for air samples or for stack emissions) that provides a representative sample, in order to quantify the real distribution of PCDD/F congeners. As far as air samples are concerned, there is no European standard. For this reason many errors can occur, and the best experimental methods include the use of different filtration devices (filter and PU foam, for instance) and of labelled standards adsorbed onto them, in order to quantify the more volatile and the less volatile compounds. As far as stack emissions samplings are concerned, the EN 1948 method is specific for PCDD/F determination. It includes sampling methods (part 1), sample treatment and analytical determination. In spite of the efforts for the harmonisation of the previous methods, some critical points still remain, especially regarding the first part. It provides three different methods (filter/condensation, dilution and cooled probe), and let the operator the freedom

3 Air Pollution XII 553 to use one of them. In our opinion the filter/condensation and the dilution methods avoid condensation process in the filtration and adsorbing steps that could negatively influence the recovery of compounds. On the contrary, in the cooled probe method the micropollutants can disperse in whole sampling device, with losses and contamination of the following samples. Table 2: Relative distribution with a 50% recovery. Recovery 50 Relative distribution Congeners ITEF quantity values % 2,3,7,8-TetraCDD ,2,3,7,8-PentaCDD ,2,3,4,7,8-HexaCDD ,2,3,6,7,8-HexaCDD ,2,3,7,8,9-HexaCDD ,2,3,4,6,7,8-HeptaCDD OctaCDD ,3,7,8-Tetra CDF ,2,3,7,8-PentaCDF ,3,4,7,8-Penta CDF ,2,3,4,7,8-HexaCDF ,2,3,6,7,8-HexaCDF ,3,4,6,7,8-HexaCDF ,2,3,7,8,9-HexaCDF ,2,3,4,6,7,8-HeptaCDF ,2,3,4,7,8,9-HeptaCDF OctaCDF TOTAL 144 Independently from the sampling method, The EN 1948 provides quality controls by using 13 C 12 labelled standard in all the steps of the determination (sampling, extraction and instrumental analysis). In our opinion it is not enough sufficient. Firstly, in the very first step, three Furans are placed onto the filtration device, in order to monitor possible losses, but Dioxins are not mentioned. Secondly, since the standard are placed only onto the filter, the more volatile congeners in vapour phase could be underestimated. Finally, the sampling standard recovery rate needs to be higher than 50 %, but it is not used for the last quantification step. Just the extraction recovery rates are used and obviously this

4 554 Air Pollution XII matter implies an expected error in quantification (up to 100 % of uncertainty). Unfortunately, this problem has a deep effect on the relative PCDD/F distribution profiles, especially in charge of the most volatile congeners and in emissions with a low particulate concentration. In fact, if we compare two different sampling with a recovery of 100 % (at best of hypothesis) and 50 % (at worst of hypothesis) (table 1-2), we obtain the same relative distribution and completely different recovered amounts. But if we consider a real case (table 3), when the volatile congeners get lost in a higher extent, the relative distribution can undergoe high variations. In Italy, in case of values lower than the detection limit (LOD), it was proposed to consider in the ITEQ sum half of this LOD. In facilities with a low PCDD/F emission this factor can dramatically influence the characterisation of the emission and the real relative distribution. Table 3: Variation in the relative distribution with a real recovery. Congeners ITEF recovery? ITEQ Distribution Variation quantity values % % 2,3,7,8-TetraCDD ,2,3,7,8-PentaCDD ,2,3,4,7,8-HexaCDD ,2,3,6,7,8-HexaCDD ,2,3,7,8,9-HexaCDD ,2,3,4,6,7,8-HeptaCDD OctaCDD ,3,7,8-Tetra CDF ,2,3,7,8-PentaCDF ,3,4,7,8-Penta CDF ,2,3,4,7,8-HexaCDF ,2,3,6,7,8-HexaCDF ,3,4,6,7,8-HexaCDF ,2,3,7,8,9-HexaCDF ,2,3,4,6,7,8-HeptaCDF ,2,3,4,7,8,9-HeptaCDF OctaCDF Total 180.7

5 Air Pollution XII Figure 1: %ITEQ Municipal waste incinerator Figure 2: Hospital waste incinerators Figure 3: Sewage sludge incinerators. 3 Results and discussion In our sampling campaigns we use the filtration/dilution method. The filtration temperature is kept lower than 125 C and higher than the condensation

6 556 Air Pollution XII temperature of the compounds object of study. Vapours are condensed after the filter and then adorbed on a XAD-2 trap. Othewise, a reverse configuration can be used, and the micropollutants in vapour phase and on the particulate matter ca adsorb directly on the trap. This configuration allow to avoid the liquid-liquid extraction. We decided to evaluate the profiles of the relative distributions of 2,3,7,8 PCDD/F and the relative distribution of the ITEQ values, rather than the homologue distribution or single congener pattern. The behaviour of dioxins and furans strictly depends on the physico-chemical properties of the homologue group with the same chlorination degree and their concentration changes follow the same tendency. So the relative distribution should be influenced by concentration change in a lesser extent. The emission profiles of municipal, sewage sludge and hospital waste incinerators, cement industry, thermoelectric power plant fuelled with Heavy fuel oils and Orimulsion have been evaluated (Figure 1-7). 2 1 Figure 4: Cement plant fuelled with Coal and heavy oil Figure 5: Cement plant fuelled with Coal and polymers.

7 Air Pollution XII Figure 6: Power plant fuelled with HFO Figure 7: Power plant fuelled with Orimulsion. The 2,3,7,8, relative profiles show that it is possibile to focus on different types of industrial sources. The incineration of municipal, and hospital wastes is characterised by a high emission of Hexa and Hepta Furans, whereas the incineration of sludges is very different. The combustion of coal and heavy oils leads to a higher presence of the less volatile congeners. We decided to evaluate the ITEQ relative distributions, by applying the ITEF to the obtained values, in order to compare the importance of the different groups to the total emitted toxicity. The results show that two main profiles can be found. The relative profile of incinerators and cement fuelled with coal and polimers are very similar, and the highest contribution to the ITEQ emission come from Penta and Hexa Furans, whereas for other fuels as heavy oils and emulsions the contribution of Tetra and Penta Dioxins becomes relevant. In conclusion, the evaluation of the relative profiles of 2,3,7,8 congeners and of their ITEQ values can lead to a characterisation of the industrial emission sources. The main problem remains the comparison of profiles obtained with different methods, because the EN 1948 does not assure a complete homogenisation of data.

8 558 Air Pollution XII References [1] K. Everaert and J. Baeyens. The formation and emission of dioxins in large scale thermal processes. Chemosphere [2] R. E. Alcock, A.J. Sweetman, K. C. Jones. A congener-specific PCDD/F emissions inventory for the UK: do current estimates account for the measured atmospheric burden? Chemosphere [3] H. Hagenmaier, C. lindig and J. She. Correlation of environmental occurrence of polychlorinated dibenzo-p-dioxins and dibenzofurans with possible sources. Chemosphere [4] K. Lohman and C. Seigneur. Atmospheric fate and transport of dioxins: local impacts. Chemosphere [5] I.Ogura, S. Masunaga and J. Nakanishi. Congener-specific characterization of PCDDs/PCDFs in atmospheric deposition: comparison of profiles among deposition, source and environmental sink. Chemosphere [6] W. W. Brubaker and R. A. Hites. Polychlorinated dibenzo-p-dioxins and dibenzofurans: gas-phase hydroxyl radical reactions and related atmospheric removal. Environmental Science and Technology