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Fs atmospheric deposition fluxes and soil contamination close to a municipal solid waste incinerator
Chemosphere 83 (2011) 1366–1373
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PCDD/Fs atmospheric deposition fluxes and soil contamination close to a municipal solid waste incinerator Ivano Vassura a, Fabrizio Passarini a, Laura Ferroni b, Elena Bernardi a, Luciano Morselli a,⇑ a b
University of Bologna, Department of Industrial Chemistry and Materials, Viale Risorgimento 4, I-40146 Bologna, Italy University of Bologna, Rimini Branch, Via Angherà 22, I-47900 Rimini, Italy
a r t i c l e
i n f o
Article history: Received 23 August 2010 Received in revised form 25 January 2011 Accepted 27 February 2011 Available online 2 April 2011 Keywords: PCDD/Fs Monitoring Bulk deposition Atmospheric fallout Stack emissions Air pollution
a b s t r a c t Bulk depositions and surface soil were collected in a suburban area, near the Adriatic Sea, in order to assess the contribution of a municipal solid waste incinerator to the area’s total contamination with polychlorinated dibenzodioxins and polychlorinated dibenzofurans (PCDDs and PCDFs). Samples were collected at two sites, situated in the area most affected by plant emissions (according to the results of the Calpuff air dispersion model), and at an external site, considered as a reference. Results show that the studied area is subject to low contamination, as far as these compounds are concerned. Deposition fluxes range from 14.3 pg m 2 d 1 to 89.9 pg m 2 d 1 (0.75 pg-TEQ m 2 d 1 to 3.73 pg-TEQ m 2 d 1) and no significant flow differences are observed among the three monitored sites. Total soil concentration amounts to 93.8 ng kg 1 d.w. and 1.35 ng-TEQ kg 1 d.w, on average, and confirms a strong homogeneity in the studied area. Furthermore, from 2006 to 2009, no PCDD/Fs enrichment in the soil was noticed. Comparing the relative congener distributions in environmental samples with those found in stack emissions from the incineration plant, significant differences are observed in the PCDD:PCDF ratio and in the contribution of the most chlorinated congeners. From this study we can conclude that the incineration plant is not the main source of PCDD/Fs in the studied area, which is apparently characterized by a homogeneous and widespread contamination situation, typical of an urban area. Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction Incineration is an important process of municipal solid waste (MSW) treatment. In Europe-27, about 20% in weight of this kind of waste is incinerated (Eurostat, 2010). Up until the 1990s, many incinerators had considerable impact on the environment and health, because of their inefficient flue gas treatment, which entailed a high exposure of people to pollution agents (Italian Association of Epidemiology, 2008). Among these, there are major concerns over persistent organic pollutants (POPs), such as polychlorodibenzo-p-dioxins (PCDDs) and polychlorodibenzo furans (PDCFs). New generation plants, built after European Directive 2000/76/EC and the implementation of Best Available Techniques (according to IPPC Directive 96/61/EC), reduced the PCDD/Fs emissions by two or more orders of magnitude (Quaß et al., 2004). From a global perspective, the environmental release of these compounds showed a peak in the 1960s–1970s, then decreased continually (Hays and Aylward, 2003); in Europe today, stack emission fluxes are comparable to or lower than those of
⇑ Corresponding author. Tel./fax: +39 051 2093863. E-mail address: [email protected] (L. Morselli). 0045-6535/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2011.02.072
other sources, such as industries and vehicular traffic, as shown by various environmental studies (UNEP, 2001). PCDD/Fs are almost always formed as undesired by-products from all thermal processes when chlorine, oxygen, hydrogen and carbon are present (McKay, 2002; Stanmore, 2004; Altarawneh et al., 2009; Zhu et al., 2009). The main sources are combustion processes, taking place in incinerators, metallurgical industries and automobiles, but also other industrial activities (Brzuzy and Hites, 1996; Alcock et al., 2001; Ren et al., 2007). Even though PCDD/Fs undergo photolysis processes in the atmosphere, the main removal pathway is by wet and dry deposition (Horstmann and McLachlan, 1997; Schroder et al., 1997), resulting in a transportation of these compounds to soil and vegetation. In the soil, PCDD/Fs are strongly adsorbed on organic carbon and, due to the difficult degradation processes, their low mobility, and the high-persistency half-life of decades, they tend to accumulate (Sinkkonen and Paasivirta, 2000; Kapp, 2005). The main goal of this study is to assess the temporal trend of atmospheric depositions of PCDD/Fs in different environmental media, in the vicinity of a medium-sized incineration plant (according to Italian standards) located near Rimini, in the Emilia-Romagna Region (Northern Italy). In order to estimate the contribution of the incinerator with respect to other potential
I. Vassura et al. / Chemosphere 83 (2011) 1366–1373
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Fig. 1. Map of mean deposition fluxes of particulate from the incineration stack. The extent of deposition in the different areas is scaled according to a relative range (depending on the concentration of the studied pollutant in the emission). The three sampling sites are evidenced.
sources, a comparison was performed with the concentration of the same compounds monitored in a control site.
2. Materials and methods 2.1. Sampling The incineration plant studied in this research has been in operation since 1976, and is situated in a suburban area, not far from a tourist town (Riccione), an important Italian highway (A14), and the Adriatic coast. This plant is authorized to burn 127 600 t per year of urban, hospital, and cemetery solid waste. Initially equipped with two separate incineration lines able to treat 120 t of municipal solid waste (MSW) per day each, plant capacity was increased of 200 t per day with a third line in 1992. From February 2008, the plant was revamped, with the construction of a new incineration line and the dismantling of the oldest ones; for this reason, the incinerator shut down its activity for about 6 months and while for another 6 months it operated at reduced capacity. Sampling net was drawn on the basis of the dispersion map calculated by the atmospheric dispersion model Calpuff, applied to incinerator emissions. This model has been officially suggested by US-EPA as a recommended model for long-range transportation in non-steady-state conditions. Calpuff simulates the effects of temporal and spatial variations in meteoclimatic conditions on pollutant transportation, transformation, and removal. Meteoclimatic conditions over a 3year period were provided by Regional Environmental Protection Agency, based on Calmet meteorological model (ARPA database, www.arpa.emr.it/sim/?osservazioni_e_dati/datiqaria). The three stacks of the considered incineration plant (point source) are 40 m high, have an inner diameter respectively of 1.1 m for the first two lines and 1.5 m for the third one. In each line the average linear emission velocity is of 15 m s 1 and the emission exit temperature of 433 K. The studied area, the dispersion model results and the monitoring sites are reported in Fig. 1.
The three sampling sites were located in zones affected by various deposition amounts, due to their different positions with respect to the incineration plant and main roads. In the area mostly influenced by the incineration plant (green1 area in Fig. 1), two sites were selected. The first site (site 1) was located on a 60 m asl hill ridge following the main wind axis between the incineration plant and the site itself. Moreover, it is placed in a suburban area approximately 2.5 km far from the plant and at about 600 m far from the A14 motorway, which runs roughly 30 m below; it receives pollutants coming from coastal urban area, incinerator and road traffic. The second site (site 2) was located about 7 km far from the shoreline, in a rural area 1.5 km far from the plant, pointed out by the dispersion model as the main incineration stack emission fallout zone. The third site (site 3) was located in an area of minimum plant emission deposition. This rural site is affected mainly by pollution from costal urban area. From 2006 to 2009, four surface soil samples from each monitoring site were collected yearly. Over the same period, a total of five campaigns for the collection of bulk atmospheric deposition samples, representative of summer and winter periods, were performed two by two (according to the scheme shown in Table 1). Results were compared with those sampled in a previous campaign (2001–2002).
2.1.1. Bulk deposition sampling Atmospheric depositions were collected by means of a bulk sampler consisting of a funnel directly connected to a collection bottle (10 L). The device is made of Pyrex glass and is placed in a polymer structure support hung from a pole 2 m from the ground. Before each sampling, the funnel and bottle are treated according to the following procedure: washing with HNO3 10% solution, then with bidistilled H2O, and lastly with acetone; this is followed by a silanization of the glass with dimethyldichlorosilane (5% in toluene) and subsequent rinse with toluene and then with methanol.
1 For interpretation of color in Fig. 1, the reader is referred to the web version of this article.
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I. Vassura et al. / Chemosphere 83 (2011) 1366–1373
Table 1 Periods and sites of atmospheric deposition sampling during the different campaigns. Sampling period
Sample Id.
Exposure time (d)
26/10/2001–7/12/2001 11/12/2001–16/1/2002 02/08/2006–21/09/2006 2/01/2007–01/03/2007 10/08/2007–10/09/2007 25/03/2008–04/05/2008 24/01/2009–12/03/2009
2001-I 2001-II 2006-I 2007-I 2007-II 2008-I 2009-I
43 47 50 37 31 41 48
Site 1
X X X X X
Site 2
Site 3
X X
X X X X X X
X
2.1.2. Soil sampling Soil sampling is carried out for each site, using a statistical approach: the selected area is approximately delimited by a circumference with a radius of 30 m, centered on the point in which the sampler is placed. At least nine samples of surface soil (0–15 cm), about 250 g each, are collected within this area using a stainless steel manual auger. Afterwards, samples are manually cleared of vegetation and combined in a single sample of about 2–2.5 kg. In the laboratory,
Table 2 PCDD/Fs deposition flows (pg m Average temperature (°C)
2,3,7,8-TCDD 1,2,3,7,8-PeCDD 1,2,3,6,7,8-HxCDD 1,2,3,4,7,8-HxCDD 1,2,3,7,8,9-HxCDD 1,2,3,4,6,7,8-HpCDD 1,2,3,4,6,7,8,9-OCDD 2,3,7,8-TCDF 1,2,3,7,8-PeCDF 2,3,4,7,8-PeCDF 1,2,3,4,7,8-HxCDF 1,2,3,6,7,8-HxCDF 2,3,4,6,7,8-HxCDF 1,2,3,7,8,9-HxCDF 1,2,3,4,6,7,8-HpCDF 1,2,3,4,7,8,9-HpCDF 1,2,3,4,6,7,8,9-OCDF Total EPCDDb Total EPCDFb Tot PCDD-PCDFb PCDD/PCDF ratio a b
2
d
1
and pg m
2
d
samples are dried at room temperature in a laminar flow hood. Then they are manually ground, sieved through a 2 mm square mesh screen and, lastly, homogenized. The resulting sample is kept in a glass container at 4 °C until the analytical stage.
2.2. PCDD/Fs determination The PCDDs and PCDFs studied are the ‘‘dirty 17’’ with the highest toxicity equivalent factors. The specific congeners are listed in Table 2 and in Table 3. The sample extraction, purification, and analysis of PCDD/Fs were performed following the EPA 1613B method, developed for isomerspecific determination of the 2,3,7,8-substituted, dibenzo-p-dioxins and dibenzofurans in aqueous, solid, and tissue matrices by isotope dilution, high resolution capillary column gas chromatography (HRGC)/high resolution mass spectrometry (HRMS). The analyses were performed at the Interuniversity Consortium ‘‘Chemistry for the Environment’’ (INCA). QC/QA of the analysis was guarantee by the SINAL (now ACCREDIA) laboratory accreditation procedures for the PCDD/F analysis, in conformity to the UNI CEI EN ISO/IEC 17025:2005. This National System operates within the EA (European
1
TEQ) during all sampling campaigns.
a
Bulk deposition flux site 1 pg m 2 d 1 (pg-TEQ m 2 d 1)
Bulk deposition flux site 2a pg m 2 d 1(pg-TEQ m 2 d 1)
Bulk deposition flux site 3a pg m 2 d 1(pg-TEQ m 2 d 1) 2001-I 12
2001-II 2
2006-I 22
2007-I 9
2007-II 22
2008-I 13
0.32 (0.32) 0.32 (0.16) 0.64 (0.064) 0.77 (0.077) 0.64 (0.064) 9.0 (0.090) 48 (0.048) 0.83 (0.083) 0.77 (0.039) 1.5 (0.77)
0.37 (0.37) 0.74 (0.37) 0.74 (0.074) 1.3 (0.13)
0.28 (0.28) 0.28 (0.14) 0.55 (0.055) 0.55 (0.055) 0.55 (0.055) 1.5 (0.015) 6.7 (0.0067) 0.33 (0.033) 0.28 (0.014) 0.33 (0.17) 0.55 (0.055) 0.55 (0.055) 0.55 (0.055) 0.55 (0.055) 1.3 (0.013) 0.83 (0.0083) 1.4 (0.0014)
0.37 (0.37) 0.37 (0.19) 0.74 (0.074) 0.74 (0.074) 0.74 (0.074) 4.6 (0.046) 15 (0.015) 0.60 (0.060) 0.60 (0.030) 0.86 (0.43) 0.77 (0.077) 0.74 (0.074) 0.78 (0.078) 0.74 (0.074) 2.7 (0.027) 1.1 (0.011) 2.2 (0.0022)
0.44 (0.44) 0.44 (0.22) 0.89 (0.089) 0.89 (0.089) 0.89 (0.089) 3.9 (0.039) 17 (0.017) 0.53 (0.053) 0.44 (0.022) 0.80 (0.40) 0.89 (0.089) 0.89 (0.089) 0.89 (0.089) 0.89 (0.089) 3.5 (0.035) 1.3 (0.013) 3.0 (0.0030)
0.34 (0.34) 0.34 (0.17) 0.67 (0.067) 0.67 (0.067) 0.67 (0.067) 3.1 (0.031) 15 (0.015) 0.54 (0.054) 0.67 (0.034) 0.81 (0.40) 0.74 (0.074) 0.74 (0.074) 0.74 (0.074) 0.67 (0.067) 2.1 (0.021) 1.0 (0.010) 1.8 (0.0018)
2006-I 22
2007-I 9
2007-II 22
2008-I 13
2009-I 7
2001-I 12
2001-II 2
0.28 (0.28) 0.28 (0.14) 0.55 (0.055) 0.55 (0.055) 0.55 (0.055) 2.0 (0.020) 14 (0.014) 0.33 (0.033) 0.28 (0.14) 0.39 (0.19) 0.55 (0.055) 0.55 (0.055) 0.55 (0.055) 0.55 (0.055) 1.3 (0.013) 0.83 (0.008) 1.7 (0.0017)
0.37 (0.37) 0.37 (0.19) 0.74 (0.074) 0.74 (0.074) 0.74 (0.074) 4.7 (0.047) 30 (0.030) 0.57 (0.057) 0.63 (0.031) 0.80 (0.40) 0.77 (0.077) 0.74 (0.074) 0.80 (0.080) 0.74 (0.074) 2.7 (0.027) 1.1 (0.011) 1.9 (0.0019)
0.44 (0.44) 0.44 (0.22) 0.89 (0.089) 0.89 (0.089) 0.89 (0.089) 4.3 (0.043) 12 (0.012) 0.53 (0.053) 0.53 (0.027) 0.80 (0.40) 0.98 (0.098) 0.89 (0.089) 1.2 (0.12) 0.89 (0.089) 6.1 (0.061) 1.3 (0.013) 3.0 (0.0030)
0.34 (0.34) 0.34 (0.17) 0.67 (0.067) 0.67 (0.067) 0.67 (0.067) 2.6 (0.026) 13 (0.013) 0.47 (0.047) 0.47 (0.024) 0.60 (0.30) 0.67 (0.067) 0.67 (0.067) 0.74 (0.074) 0.67 (0.067) 2.2 (0.022) 1.0 (0.010) 1.7 (0.0017)
0.14 (0.14) 0.36 (0.18) 0.67 (0.067) 0.69 (0.069) 0.57 (0.057) 6.0 (0.060) 17 (0.017) 1.2 (0.12)
0.32 (0.32) 0.51 (0.26) 0.67 (0.067) 1.2 (0.12) 0.96 (0.096) 13 (0.13)
0.37 (0.37) 0.60 (0.30) 0.67 (0.067) 1.1 (0.11)
17 (0.32) 5.4 (0.37) 22 (0.69) 3.1
36 (0.47) 8.5 (0.75) 45 (1.2) 4.2
18 (0.52) 17 (0.39) 15 (0.86) 7.2 (0.61) 33 (1.4) 24 (1.0) 1.2 2.4
2009-I 7
0.14 (0.14) 0.42 (0.21) 0.32 (0.032) 0.90 (0.090) 1.0 (0.10) 0.61 (0.061) 11 (0.11) 7.3 (0.073) 25 21 (0.025) (0.021) 2.3 (0.23) 1.4 (0.14)
37 (0.037) 1.7 (0.17) 1.0 1.4 1.8 (0.052) (0.071) (0.090) 1.8 (0.92) 2.6 (1.3) 3.4 (1.7)
1.3 (0.065) 2.2 (1.1)
1.4 (0.14) 2.2 (0.22) 1.3 (0.13) 2.1 (0.21) 1.6 (0.16) 2.8 (0.28) 0.67 0.67 (0.067) (0.067) 4.5 7.3 (0.045) (0.073) 0.63 1.0 (0.0063) (0.010) 5.1 5.7 (0.0051) (0.0057)
0.29 (0.029) 5.53 (0.053) 0.82 (0.0082) 6.6 (0.0066)
0.74 (0.074) 13 (0.13) 46 (0.046) 1.9 (0.19) 1.8 (0.089) 3.0 (1.5)
2.5 (0.25) 1.9 (0.19) 1.1 (0.11) 2.3 (0.23) 2.2 (0.22) 1.6 (0.16) 0.96 2.0 (0.20) (0.096) 2.8 (0.28) 2.0 (0.20) 1.3 (0.13) 2.8 (0.28) 0.67 (0.067) 6.9 (0.069) 0.89 (0.0089) 5.6 (0.0056)
0.64 (0.064) 3.6 (0.036) 0.64 (0.0064) 3.6 (0.0036)
0.74 (0.074) 7.0 (0.070) 0.97 (0.0097) 6.0 (0.0060)
25 (0.47) 52 (0.82) 39 (0.87) 30 (0.56) 58 (0.44) 62 (0.95) 9.4 (0.31) 21 (0.45) 19 (1.6) 27 (2.4) 29 (2.9) 23 (1.9) 14 (1.3) 28 (2.6) 5.0 (0.33) 9.8 (0.78) 44 (2.1) 79 (3.2) 68 (3.7) 54 (2.5) 73 (1.7) 90 (3.5) 14 (0.65) 31 (1.2) 1.4 1.9 1.4 1.3 4.1 2.2 1.9 2.2
Numbers in italics correspond to sample below the limit of quantification (LOQ). The flux has been calculated using the LOQ. For the calculation of PCDDs flux, PCDFs flux and total flux, the congener flux below LOQ was included using half of the LOQ.
22 (0.52) 20 (0.40) 11 (0.70) 9.0 (0.78) 33 (1.2) 29 (1.2) 2.1 2.2
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I. Vassura et al. / Chemosphere 83 (2011) 1366–1373 Table 3 Concentration (ng kg
1
d.w.) of PCDD/Fs in the different soil samples. Soil concentration site 1a ng kg 1 d.w. (ng-TEQ kg 1 d.w.) 2006
2,3,7,8-TCDD 1,2,3,7,8-PeCDD 1,2,3,4,7,8-HxCDD 1,2,3,6,7,8-HxCDD 1,2,3,7,8,9-HxCDD 1,2,3,4,6,7,8-HpCDD
0.2 (0.2) 0.3 (0.15) 0.4 (0.04) 0.6 (0.06) 0.8 (0.08) 9.5 (0.095) 1,2,3,4,6,7,8,9-OCDD 81 (0.081) 2,3,7,8-TCDF 1,2,3,7,8-PeCDF 2,3,4,7,8-PeCDF 1,2,3,4,7,8-HxCDF 1,2,3,6,7,8-HxCDF 2,3,4,6,7,8-HxCDF 1,2,3,7,8,9-HxCDF 1,2,3,4,6,7,8-HpCDF
0.6 (0.06) 0.5 (0.025) 0.8 (0.4) 0.9 (0.09) 0.7 (0.07) 0.9 (0.09) 0.4 (0.04) 4.0 (0.04)
2007
2008
0.2 (0.2) 0.3 (0.15) 0.4 (0.04) 0.8 (0.08) 0.7 (0.07) 14 (0.14)
0.2 (0.2) 0.3 (0.15) 0.5 (0.05) 0.8 (0.08) 0.8 (0.08) 14 (0.14)
2006
2007
2008
2009
2006
2007
2008
2009
0.2 (0.2) 0.2 (0.1) 0.4 (0.04) 0.4 (0.04) 0.4 (0.04) 5.2 (0.052)
0.2 (0.2) 0.2 (0.1) 0.10 (0.01) 0.4 (0.04) 0.4 (0.04) 5.2 (0.052)
0.2 (0.2)) 0.2 (0.1) 0.4 (0.04) 0.4 (0.04) 0.4 (0.04) 4.8 (0.048)
0.2 (0.2) 0.2 (0.1) 0.4 (0.04) 0.4 (0.04) 0.5 (0.05) 5.7 (0.057)
0.2 (0.2) 0.2 (0.1) 0.4 (0.04) 0.4 (0.04) 0.4 (0.04) 3.6 (0.036)
38 (0.038)
43 (0.043)
59 (0.059)
0.2 (0.2) 0.2 (0.1) 0.4 (0.04) 0.4 (0.04) 0.4 (0.04) 4.5 (0.045) 53 (0.053) 0.3 (0.03) 0.2 (0.01)
0.7 (0.35) 1 (0.1) 0.7 (0.07) 0.9 (0.09) 0.4 (0.04) 4.2 (0.042)
1 (0.5) 1.3 (0.13) 0.8 (0.08) 1.1 (0.11) 0.4 (0.04) 5.5 (0.055) 0.7 (0.007) 18 (0.018)
0.3 (0.15) 0.5 (0.05) 0.4 (0.04) 0.6 (0.06) 0.4 (0.04) 3.0 (0.03)
0.3 (0.15) 0.5 (0.05) 0.4 (0.04) 0.5 (0.05) 0.4 (0.04) 3.2 (0.032)
0.2 (0.1) 0.6 (0.06) 0.4 (0.04) 0.6 (0.06) 0.4 (0.04) 3.3 (0.033)
0.4 (0.2) 0.5 (0.05) 0.5 (0.05) 0.5 (0.05) 0.4 (0.04) 3.0 (0.030)
0.3 (0.15) 0.4 (0.04) 0.5 (0.05) 0.5 (0.05) 0.4 (0.04) 2.5 (0.025)
0.2 (0.2) 0.2 (0.1) 0.4 (0.04) 0.4 (0.04) 0.5 (0.05) 4.4 (0.044) 42 (0.042) 0.7 (0.07) 0.5 (0.025) 0.8 (0.4) 1.7 (0.17) 1 (0.1) 1.2 (0.12) 0.6 (0.06) 9 (0.009)
0.6 (0.006)
1.2 (0.012)
0.6 (0.006)
0.6 (0.006)
7.4 (0.0074)
0.2 (0.2) 0.2 (0.1) 0.4 (0.04) 0.4 (0.04) 0.4 (0.04) 5.1 (0.051) 58 (0.058) 0.3 (0.03) 0.3 (0.015) 0.3 (0.15) 0.5 (0.05) 0.4 (0.04) 0.5 (0.05) 0.4 (0.04) 2.8 (0.028) 0.6 (0.006) 10 (0.010)
8.8 (0.0088)
8.8 (0.0088)
9.2 (0.0092)
11 (0.011)
100 (0.69) 30 (1.1) 130 (1.8)
45 (0.32)
64 (0.34)
44 (0.29)
48 (0.32)
66 (0.36)
43 (0.28)
58 (0.31)
48 (0.33)
13 (0.40) 58 (0.72)
16 (0.40) 80 (0.74)
15 (0.38) 59 (0.67)
15 (0.37) 64 (0.69)
16 (0.51) 82 (0.86)
16 (0.39) 59 (0.67)
16 (0.26) 74 (0.57)
55 (1.1) 103 (1.4)
1 (0.5) 2.5 (0.25) 1.5 (0.15) 1.7 (0.17) 0.4 (0.04) 10 (0.10)
0.6 (0.006) 0.6 (0.006) 1.5 (0.015) 1,2,3,4,6,7,8,9-OCDF 10 (0.01) 15 (0.015) 17 (0.017)
a b
92 (0.59)
PCDF sumb Total sumb
19(0.81) 111 (1.4)
140 (0.71) 108 (0.69) 24 (0.78) 37 (1.3) 164 (1.5) 145 (2.0)
2009
Soil concentration site 3a ng kg 1 dw (ng-TEQ kg 1 d.w.)
0.2 (0.2) 0.4 (0.2) 0.4 (0.04) 0.9 (0.09) 1 (0.1) 9.7 (0.097) 92 87 123 (0.123) (0.092) (0.087) 0.6 (0.06) 0.7 (0.07) 1 (0.01) 0.5 (0.025) 0.8 (0.04) 0.8 (0.04)
1,2,3,4,7,8,9-HpCDF
PCDD sumb
Soil concentration site 2a ng kg 1 dw (ng-TEQ kg 1 d.w.)
38 (0.038) 0.3 (0.03) 0.2 (0.01)
0.6 (0.006)
38.1 (0.0381) 0.3 (0.03) 0.3 (0.03) 0.8 (0.08) 0.3 (0.03) 0.4 (0.020) 0.3 (0.015) 0.3 (0.015) 0.2 (0.01)
0.2 (0.1) 0.4 (0.04) 0.4 (0.04) 0.4 (0.04) 0.4 (0.04) 2.7 (0.027) 0.6 (0.006) 11 (0.011)
2 (0.002) 38 (0.038)
Numbers in italics correspond to sample below the limit of quantification (LOQ). The flux has been calculated using the LOQ. For the calculation of PCDDs flux, PCDFs flux and total flux, the congener flux below LOQ was included using half of the LOQ.
cooperation for Accreditation) and ILAC (International Laboratory Accreditation Cooperation) international arrangement.
3. Results and discussion 3.1. Deposition fluxes of PCDD/Fs PCDD/Fs atmospheric deposition fluxes are shown in Table 2. Data, expressed as pg m 2 d 1 or in terms of equivalent toxicity (TEQ) as pg-TEQ m 2 d 1, have been calculated as an average value of the sampling period, which generally varies between 30 d and 40 d. Total flow has been obtained by summing the fluxes of single congeners; the species whose concentration has been below the limit of quantification (LOQ) have been summed as LOQ/2, as suggested by the Italian Institute of Health (ISS) (Clarke, 1998; Finkelstein and Verma, 2002; Menichini and Viviano, 2004). Total deposition fluxes vary between 14.3 pg m 2 d 1 and 89.9 pg m 2 d 1 (0.65–3.73 pg-TEQ m 2 d 1). The same magnitude of deposition fluxes has been reported by other authors: Guerzoni et al. (2004), Moon et al. (2005), and Vandecasteele et al. (2007). These fluxes are relatively low. Indeed, it has been estimated, according to a chain model, that the lower tolerable daily intake suggested by WHO (1998), corresponding to 1 pg-TEQ kg 1 d 1, is reached if PCDD/Fs air concentrations are such that the transfer flux from atmosphere to soil and/or vegetation is 6.8 pgTEQ m 2 d 1 (as the average deposition value) (Van Lieshout et al., 2001). Consequently, it is likely that much lower depositions may result in air contaminations having less impact on the population. The fluxes registered in the last years are significantly lower than those observed in 2001 campaigns. However, total deposition fluxes of PCDDs and PCDFs at the different sites, monitored during the same period (Table 2), are quite similar. No considerable
differences can be seen among the values found in the most affected sites (according to the dispersion model, i.e. sites 1 and 2), and the reference one (site 3). In all cases, PCDD flow is greater than that of PCDFs, while in terms of toxicity equivalent factors, the opposite occurs. This is due to the fact that PCDDs are mainly present as congeners 1,2,3,4,6,7,8-HpCDD e 1,2,3,4,6,7,8,9-OCDD, as discussed below. It is also interesting to observe that during the last two sampling campaigns, at site 1, there is no significant decrease, and instead an increase in PCDF deposition occurs, even though the plant was shut down for 6 months from February 2008, and then operated at reduced capacity for the following period. At site 3, the other for which a comparison with the years 2006 and 2007 is possible, similar considerations can be made, even if, in this case, there seems to be no direct influence of the plant.
3.1.1. Profile of PCDD/Fs congeners in atmospheric deposition The study of the congener profile in environmental samples, deriving from the typical emission compositions from different processes, can provide information about the contribution of a specific source in the vicinity (Sandalls et al., 1998; Alcock and Jones, 1996; Everaert and Baeyens, 2002). The average relative distributions of congeners in the three sampling sites are quite constant, both in time and in space (see Fig. 2). Pearson correlation coefficients are always greater than 0.9 when the comparison is made between congeners sampled during the same period. The most abundant congeners are the higher chlorinated ones. On average, at the three sites, 40.6–52.6% of OCDD, 11.4–15.2% of HpCDD, 8.0–10.0% of 1,2,3,4,6,7,8-HpCDF, and 6.8–9.2% of OCDF are found, while all the other congeners contribute for less than 5%. The abundance of OCDD can be explained by the fact that, on the one hand, it is one of the most stable congeners in the
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70 Site 1
Relative Distribution (%)
60
Site 2 Site 3
50 40 30 20
1,2,3,4,6,7,8,9-OCDF
1,2,3,4,7,8,9-HpCDF
1,2,3,4,6,7,8-HpCDF
1,2,3,7,8,9-HxCDF
2,3,4,6,7,8-HxCDF
1,2,3,6,7,8-HxCDF
1,2,3,4,7,8-HxCDF
2,3,4,7,8-PeCDF
1,2,3,7,8-PeCDF
2,3,7,8-TCDF
1,2,3,4,6,7,8,9-OCDD
1,2,3,4,6,7,8-HpCDD
1,2,3,7,8,9-HxCDD
1,2,3,4,7,8-HxCDD
1,2,3,6,7,8-HxCDD
1,2,3,7,8-PeCDD
0
2,3,7,8-TCDD
10
Fig. 2. Average PCDD/F (%) congeners profile in atmospheric depositions collected at the three sampling sites (bars indicate data standard deviation).
atmosphere (Mackay et al., 2006) and, on the other, it is emitted in great amounts by multiple sources, such as industrial boilers, solid waste incinerators and vehicular traffic (Cleverly et al., 1997; Domingo et al., 2001; Stanmore, 2004; Floret et al., 2007; Zhu et al., 2008). Thus, OCDD distribution cannot be considered a characterizing factor of a specific emission source. However, considering both HpCDD/OCDD ratio and low/high chlorinated PCDF congeners ratio, the deposition profile seems to reflect what is generally found in other studies focusing on urban or suburban areas, mainly characterized by traffic, house heating and domestic emissions. The PCDD/Fs congeners distributions reported in these papers are characterized by a HpCDD/OCDD ratio ranging between 0.1 and 0.3; whereas low/high chlorinated PCDF ratio is quite variable (Chang et al., 2004; Correa et al., 2006; Ren et al., 2007; Castro-Jimenez et al., 2008; Mari et al., 2008; Vives et al., 2008; Zhu et al., 2008). As for the toxicological aspect, the most significant amount comes from 2,3,4,7,8-PeCDD, which contributes an average of 32.9–43.1% of the total toxicity. TCDD, despite is highest absolute toxicity, makes a low contribution, since it amounts to less than 1% in weight.
In comparison with atmospheric depositions, the abundance of PCDDs is greater, compared to PCDFs, but in this case, also, this is almost exclusively due to the high concentration of congeners with seven or eight chlorine atoms, as discussed below. PCDD/PCDF vary from 2.6 to 5.8 (the only exception is the last datum, measured in 2009, at site 3).
3.2. PCDD/Fs concentration in soil
3.3. Incinerator fingerprinting
Soil represents the final fate of PCDD/Fs, since they are strongly bound and poorly degraded in it. The study of PCDD/Fs accumulation in soil can thus give information about the degree of long-term PCDD/F contamination (Andersson and Ottesen, 2008). At the three sampling sites, over four monitoring years, PCDD/Fs, content (Table 3) varies from 57.7 ng kg 1 d.w to 164 ng kg 1 d.w. (average value 93.8 ng kg 1 d.w.). These concentrations are five or ten times lower than the limits set by Italian law for residential or private soils (D.Lgs. 152/06). The amount of PCDD/Fs in surface soil does not exhibit a growing trend in the 4 years of monitoring (Table 3). Unlike what has been observed for atmospheric depositions, there are considerable variations among the three sites. In particular, at site 1, the closest to the urban area and highway, PCDD/Fs concentration is on average about twice that measured at reference site (site 3) and site 2, that is located in the area which is expected to be the most affected by incinerator emissions.
PCDD/Fs emission from a municipal solid waste Incinerator is greatly affected by the composition of input waste, the type of furnace, and the flue gas treatment systems (Cleverly et al., 1997). For this reason, the emissions of each plant are characterized by different congener profiles, and can exhibit a high variability. For the studied plant, PCDD/Fs stack emissions have been calculated on the average value obtained from 16 direct measurements, performed approximately every 20 d, in 2009 (Fig. 4). Different authors report emission profiles which are similar to those found in the present study (Domingo et al., 2001; Abad et al., 2006; Wang et al., 2009; Wu et al., 2009), while others, apart from congener profiles, attest a PCDD/PCDF ratio <1 (Everaert and Baeyens, 2002; Stanmore, 2004; Littarru, 2006). Highly chlorinated congeners are in general the most abundant; among them, OCDD covers a half of the total weight, on average. As for PCDFs, low-chlorinated PCDDs also make an important contribution to the overall load. The PCDD/PCDF ratio equals 0.8,
3.2.1. Profile of congeners of PCDD/Fs in soil Congener distribution patterns are quite similar, both in space and in time, a sign of a clear homogeneity of the PCDD/Fs profiles determined in soils (Fig. 3). This suggests that contamination is due to similar sources, or that the emission of the territorial source is widespread and efficiently transported over the entire studied area. In line with what has been observed for atmospheric depositions, the congener profile is dominated by the most chlorinated ones: OCDD constitutes about 70% in weight, followed by HpCDD (10%), OCDF (15%), and 1,2,3,4,6,7,8-HpCDF (5%). The remaining congeners contribute for a total of less than 2%. However, in terms of the toxicity equivalent factor, 2,3,4,7,8-PeCDD prevails, on average, corresponding to approximately 20%.
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90 80
Site 1
Relative Distribution (%)
Site 2
70
Site 3
60 50 40 30 20 10 1,2,3,4,6,7,8,9-OCDF
1,2,3,4,7,8,9-HpCDF
1,2,3,4,6,7,8-HpCDF
1,2,3,7,8,9-HxCDF
2,3,4,6,7,8-HxCDF
1,2,3,6,7,8-HxCDF
1,2,3,4,7,8-HxCDF
2,3,4,7,8-PeCDF
1,2,3,7,8-PeCDF
2,3,7,8-TCDF
1,2,3,4,6,7,8,9-OCDD
1,2,3,4,6,7,8-HpCDD
1,2,3,7,8,9- HxCDD
1,2,3,6,7,8- HxCDD
1,2,3,4,7,8- HxCDD
1,2,3,7,8-PeCDD
2,3,7,8- TCDD
0
Fig. 3. Average PCDD/F (%) congeners profile in soil samples collected in the three sampling sites (bars indicate data standard deviation).
45
Relative Distribution (%)
40 35 30 25 20 15 10 5 1,2,3,4,6,7,8,9-OCDF
1,2,3,4,7,8,9-HpCDF
1,2,3,4,6,7,8-HpCDF
1,2,3,7,8,9-HxCDF
2,3,4,6,7,8-HxCDF
1,2,3,6,7,8-HxCDF
1,2,3,4,7,8-HxCDF
2,3,4,7,8-PeCDF
1,2,3,7,8-PeCDF
2,3,4,8-TCDF
1,2,3,4,6,7,8,9-OCDD
1,2,3,4,6,7,8,9-HpCDD
1,2,3,7,8,9-HxCDD
1,2,3,6,7,8-HxCDD
1,2,3,4,7,8-HxCDD
1,2,3,7,8-PeCDD
2,3,7,8-TCDD
0
Fig. 4. Average PCDD/F (%) congeners profile in 17 stack emission samples collected from the MSWI plant in 2009 (bars indicate data standard deviation).
on average; however, a strong variability of this result can be observed. 3.4. Comparison of profiles The resulting congener profile emitted by the incinerator (Fig. 4) shows considerable differences compared to that observed for atmospheric deposition (Fig. 2) and soil (Fig. 3). In general the relative concentration of low-chlorinated PCDD/F in incinerator emissions are less than in deposition and soil. Usually, the lower environmental concentration of all the lightest congeners may be due to selective degradation processes. The estimated degradation time in atmosphere of low-chlorinated PCDD/Fs is about a day instead of the weeks required for high-chlorinated PCDD/Fs with a consequent relative enrichment of the most chlorinated congeners as the distance from the source increases (Atkinson, 1991; Kwok et al., 1995). The congeners with seven or eight chlorine atoms, besides being more stable, are less
volatile and are mainly associated to particulate, resulting in a greater atmospheric removal (Oh et al., 2001; Lohmann and Jones, 1998). These degradation and selective removal mechanisms, may explain the characteristic background pattern of PCDD/Fs distribution in areas far from local contamination sources. In our case the monitoring sites are at most 2.5 km far from the incinerator and the typical wind speed in the considered area is about 1 m/s. In these conditions, pollutants emitted by the plant can reach the samplers in a short time (few hours), which is not sufficient to allow the degradation of over two thirds of the low-chlorinated compounds and, even less, the variation of HpCDD/OCDD ratio. From the official environmental statement of incinerator, PCDD/ Fs stack concentrations were, on average, 0.007 ng-TEQ Nm 3 in 2006, 0.008 ng-TEQ Nm 3 in 2007, 0.015 ng-TEQ Nm 3 in 2008 and 0.019 ng-TEQ Nm 3 in 2009, being always about one or two orders of magnitude lower than the actual legal limits (0.1 ng-TEQ Nm 3) (Directive 76/2000/EC). The yearly mass fluxes was respectively 1.5 mg-TEQ y 1 in 2006, 7 mg-TEQ y 1 in 2007,
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0.004 mg-TEQ y 1 in 2008 (during most of this year the plant was stopped for modernization works) and 4.7 mg-TEQ y 1 in 2009. The resulting annual PCDD/F emission flow amounts, although not negligible, do not comport an appreciable differences in deposition fluxes among sites 1 and 2 and site 3. In conclusion, the differences found between congener profiles of environmental samples and stack emissions, the apparent homogeneity of concentration and deposition fluxes at all three monitoring sites, even during the inactivity of the plant, can be explained only hypothesizing that the incinerator is not the only source affecting the area. Therefore, atmospheric background contamination and contribution of local diffuse emission sources seem to affect deposition fluxes in a greater extent than the incinerator. 4. Conclusion The deposition fluxes recorded in the studied area, compared to other studies, show a low concentration of PCDD/F in atmospheric depositions. A low contamination burden has been also determined in the soil samples. The similar relative composition of the congener mix in all the samples of the same environmental matrices and the absence of significant differences between the sites more heavily subject to the incinerator emissions and the reference site indicate that the whole territory is affected by a homogeneous contamination. This is hardly explainable considering only the air dispersion of plant emissions and suggests that more sources are present in the whole area. PCDD/F mixtures show the same relative composition of congeners at the three different sites, with a noticeably different pattern compared to that typical of plant emissions, in particular in relation to the PCDD/Fs ratio. The incinerator’s relative contribution to the total pollutant load seems to be negligible compared to a higher background concentration, which could be ascribed to the nearby urban area. This is confirmed by the observation that deposition fluxes during the 40 d sampled in 2008 are not significantly lower than the other years, even though the plant was shut down for 6 months. Acknowledgments The Authors wish to acknowledge Hera s.p.a. for having funded this study and Interuniversity National Consortium ‘‘Chemistry for the Environment’’ (INCA) for analysis support. References Abad, E., Martinez, K., Caixach, J., Rivera, J., 2006. Polychlorinated dibenzo-p-dioxins, dibenzofurans and ‘‘dioxin-like’’ PCBs in flue gas emissions from municipal solid waste management plants. Chemosphere 63, 570–580. Alcock, R.E., Jones, K.C., 1996. Dioxins in the environment: a review of trend data. Environ. Sci. Technol. 30, 3133–3143. Alcock, R.E., Sweetman, A.J., Jones, K.C., 2001. A congener-specific PCDD/F emission inventory for the UK: do current stimates account for the measured atmospheric burden? Chemosphere 43, 183–194. Altarawneh, M., Dlugogorski, B.Z., Kennedy, E.M., Mackie, J.C., 2009. Mechanisms for formation, chlorination, dechlorination and destruction of polychlorinated dibenzo-p-dioxins and dibenzofurani (PCDD/Fs). Prog. Energy Combust. Sci. 35, 245–274. Andersson, M., Ottesen, R.T., 2008. Levels of dioxins and furans in urban surface soil in Trondheim, Norway. Environ. Pollut. 152, 553–558. Atkinson, R., 1991. Atmospheric lifetimes of dibenzo-p-dioxins and dibenzofurans. Sci. Total Environ. 104, 17–33. Brzuzy, L.P., Hites, R.A., 1996. Global mass balance for polychlorinated dibenzo-pdioxins and dibenzofurans. Environ. Sci. Technol. 30, 1797–1804. Castro-Jimenez, J., Mariani, G., Eisenreich, S.J., Christoph, E.H., Hanke, G., Canuti, E., Skejo, H., Umlauf, G., 2008. Atmospheric input of POPs into Lake Maggiore (Northern Italy): PCDD/F and dioxin-like PCB profiles and fluxes in the atmosphere and aquatic system. Chemosphere 73, S122–S130. Chang, M.B., Chang, S.H., Chen, W.C., Hsu, H.C., 2004. Dioxin emission factors for automobiles from tunnel air sampling in Northern Taiwan. Sci. Total Environ. 325, 129–138.
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PCDD/Fs atmospheric deposition fluxes and soil contamination close to a municipal solid waste incinerator Ivano Vassura a, Fabrizio Passarini a, Laura Ferroni b, Elena Bernardi a, Luciano Morselli a,⇑ a b
University of Bologna, Department of Industrial Chemistry and Materials, Viale Risorgimento 4, I-40146 Bologna, Italy University of Bologna, Rimini Branch, Via Angherà 22, I-47900 Rimini, Italy
a r t i c l e
i n f o
Article history: Received 23 August 2010 Received in revised form 25 January 2011 Accepted 27 February 2011 Available online 2 April 2011 Keywords: PCDD/Fs Monitoring Bulk deposition Atmospheric fallout Stack emissions Air pollution
a b s t r a c t Bulk depositions and surface soil were collected in a suburban area, near the Adriatic Sea, in order to assess the contribution of a municipal solid waste incinerator to the area’s total contamination with polychlorinated dibenzodioxins and polychlorinated dibenzofurans (PCDDs and PCDFs). Samples were collected at two sites, situated in the area most affected by plant emissions (according to the results of the Calpuff air dispersion model), and at an external site, considered as a reference. Results show that the studied area is subject to low contamination, as far as these compounds are concerned. Deposition fluxes range from 14.3 pg m 2 d 1 to 89.9 pg m 2 d 1 (0.75 pg-TEQ m 2 d 1 to 3.73 pg-TEQ m 2 d 1) and no significant flow differences are observed among the three monitored sites. Total soil concentration amounts to 93.8 ng kg 1 d.w. and 1.35 ng-TEQ kg 1 d.w, on average, and confirms a strong homogeneity in the studied area. Furthermore, from 2006 to 2009, no PCDD/Fs enrichment in the soil was noticed. Comparing the relative congener distributions in environmental samples with those found in stack emissions from the incineration plant, significant differences are observed in the PCDD:PCDF ratio and in the contribution of the most chlorinated congeners. From this study we can conclude that the incineration plant is not the main source of PCDD/Fs in the studied area, which is apparently characterized by a homogeneous and widespread contamination situation, typical of an urban area. Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction Incineration is an important process of municipal solid waste (MSW) treatment. In Europe-27, about 20% in weight of this kind of waste is incinerated (Eurostat, 2010). Up until the 1990s, many incinerators had considerable impact on the environment and health, because of their inefficient flue gas treatment, which entailed a high exposure of people to pollution agents (Italian Association of Epidemiology, 2008). Among these, there are major concerns over persistent organic pollutants (POPs), such as polychlorodibenzo-p-dioxins (PCDDs) and polychlorodibenzo furans (PDCFs). New generation plants, built after European Directive 2000/76/EC and the implementation of Best Available Techniques (according to IPPC Directive 96/61/EC), reduced the PCDD/Fs emissions by two or more orders of magnitude (Quaß et al., 2004). From a global perspective, the environmental release of these compounds showed a peak in the 1960s–1970s, then decreased continually (Hays and Aylward, 2003); in Europe today, stack emission fluxes are comparable to or lower than those of
⇑ Corresponding author. Tel./fax: +39 051 2093863. E-mail address: [email protected] (L. Morselli). 0045-6535/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2011.02.072
other sources, such as industries and vehicular traffic, as shown by various environmental studies (UNEP, 2001). PCDD/Fs are almost always formed as undesired by-products from all thermal processes when chlorine, oxygen, hydrogen and carbon are present (McKay, 2002; Stanmore, 2004; Altarawneh et al., 2009; Zhu et al., 2009). The main sources are combustion processes, taking place in incinerators, metallurgical industries and automobiles, but also other industrial activities (Brzuzy and Hites, 1996; Alcock et al., 2001; Ren et al., 2007). Even though PCDD/Fs undergo photolysis processes in the atmosphere, the main removal pathway is by wet and dry deposition (Horstmann and McLachlan, 1997; Schroder et al., 1997), resulting in a transportation of these compounds to soil and vegetation. In the soil, PCDD/Fs are strongly adsorbed on organic carbon and, due to the difficult degradation processes, their low mobility, and the high-persistency half-life of decades, they tend to accumulate (Sinkkonen and Paasivirta, 2000; Kapp, 2005). The main goal of this study is to assess the temporal trend of atmospheric depositions of PCDD/Fs in different environmental media, in the vicinity of a medium-sized incineration plant (according to Italian standards) located near Rimini, in the Emilia-Romagna Region (Northern Italy). In order to estimate the contribution of the incinerator with respect to other potential
I. Vassura et al. / Chemosphere 83 (2011) 1366–1373
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Fig. 1. Map of mean deposition fluxes of particulate from the incineration stack. The extent of deposition in the different areas is scaled according to a relative range (depending on the concentration of the studied pollutant in the emission). The three sampling sites are evidenced.
sources, a comparison was performed with the concentration of the same compounds monitored in a control site.
2. Materials and methods 2.1. Sampling The incineration plant studied in this research has been in operation since 1976, and is situated in a suburban area, not far from a tourist town (Riccione), an important Italian highway (A14), and the Adriatic coast. This plant is authorized to burn 127 600 t per year of urban, hospital, and cemetery solid waste. Initially equipped with two separate incineration lines able to treat 120 t of municipal solid waste (MSW) per day each, plant capacity was increased of 200 t per day with a third line in 1992. From February 2008, the plant was revamped, with the construction of a new incineration line and the dismantling of the oldest ones; for this reason, the incinerator shut down its activity for about 6 months and while for another 6 months it operated at reduced capacity. Sampling net was drawn on the basis of the dispersion map calculated by the atmospheric dispersion model Calpuff, applied to incinerator emissions. This model has been officially suggested by US-EPA as a recommended model for long-range transportation in non-steady-state conditions. Calpuff simulates the effects of temporal and spatial variations in meteoclimatic conditions on pollutant transportation, transformation, and removal. Meteoclimatic conditions over a 3year period were provided by Regional Environmental Protection Agency, based on Calmet meteorological model (ARPA database, www.arpa.emr.it/sim/?osservazioni_e_dati/datiqaria). The three stacks of the considered incineration plant (point source) are 40 m high, have an inner diameter respectively of 1.1 m for the first two lines and 1.5 m for the third one. In each line the average linear emission velocity is of 15 m s 1 and the emission exit temperature of 433 K. The studied area, the dispersion model results and the monitoring sites are reported in Fig. 1.
The three sampling sites were located in zones affected by various deposition amounts, due to their different positions with respect to the incineration plant and main roads. In the area mostly influenced by the incineration plant (green1 area in Fig. 1), two sites were selected. The first site (site 1) was located on a 60 m asl hill ridge following the main wind axis between the incineration plant and the site itself. Moreover, it is placed in a suburban area approximately 2.5 km far from the plant and at about 600 m far from the A14 motorway, which runs roughly 30 m below; it receives pollutants coming from coastal urban area, incinerator and road traffic. The second site (site 2) was located about 7 km far from the shoreline, in a rural area 1.5 km far from the plant, pointed out by the dispersion model as the main incineration stack emission fallout zone. The third site (site 3) was located in an area of minimum plant emission deposition. This rural site is affected mainly by pollution from costal urban area. From 2006 to 2009, four surface soil samples from each monitoring site were collected yearly. Over the same period, a total of five campaigns for the collection of bulk atmospheric deposition samples, representative of summer and winter periods, were performed two by two (according to the scheme shown in Table 1). Results were compared with those sampled in a previous campaign (2001–2002).
2.1.1. Bulk deposition sampling Atmospheric depositions were collected by means of a bulk sampler consisting of a funnel directly connected to a collection bottle (10 L). The device is made of Pyrex glass and is placed in a polymer structure support hung from a pole 2 m from the ground. Before each sampling, the funnel and bottle are treated according to the following procedure: washing with HNO3 10% solution, then with bidistilled H2O, and lastly with acetone; this is followed by a silanization of the glass with dimethyldichlorosilane (5% in toluene) and subsequent rinse with toluene and then with methanol.
1 For interpretation of color in Fig. 1, the reader is referred to the web version of this article.
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I. Vassura et al. / Chemosphere 83 (2011) 1366–1373
Table 1 Periods and sites of atmospheric deposition sampling during the different campaigns. Sampling period
Sample Id.
Exposure time (d)
26/10/2001–7/12/2001 11/12/2001–16/1/2002 02/08/2006–21/09/2006 2/01/2007–01/03/2007 10/08/2007–10/09/2007 25/03/2008–04/05/2008 24/01/2009–12/03/2009
2001-I 2001-II 2006-I 2007-I 2007-II 2008-I 2009-I
43 47 50 37 31 41 48
Site 1
X X X X X
Site 2
Site 3
X X
X X X X X X
X
2.1.2. Soil sampling Soil sampling is carried out for each site, using a statistical approach: the selected area is approximately delimited by a circumference with a radius of 30 m, centered on the point in which the sampler is placed. At least nine samples of surface soil (0–15 cm), about 250 g each, are collected within this area using a stainless steel manual auger. Afterwards, samples are manually cleared of vegetation and combined in a single sample of about 2–2.5 kg. In the laboratory,
Table 2 PCDD/Fs deposition flows (pg m Average temperature (°C)
2,3,7,8-TCDD 1,2,3,7,8-PeCDD 1,2,3,6,7,8-HxCDD 1,2,3,4,7,8-HxCDD 1,2,3,7,8,9-HxCDD 1,2,3,4,6,7,8-HpCDD 1,2,3,4,6,7,8,9-OCDD 2,3,7,8-TCDF 1,2,3,7,8-PeCDF 2,3,4,7,8-PeCDF 1,2,3,4,7,8-HxCDF 1,2,3,6,7,8-HxCDF 2,3,4,6,7,8-HxCDF 1,2,3,7,8,9-HxCDF 1,2,3,4,6,7,8-HpCDF 1,2,3,4,7,8,9-HpCDF 1,2,3,4,6,7,8,9-OCDF Total EPCDDb Total EPCDFb Tot PCDD-PCDFb PCDD/PCDF ratio a b
2
d
1
and pg m
2
d
samples are dried at room temperature in a laminar flow hood. Then they are manually ground, sieved through a 2 mm square mesh screen and, lastly, homogenized. The resulting sample is kept in a glass container at 4 °C until the analytical stage.
2.2. PCDD/Fs determination The PCDDs and PCDFs studied are the ‘‘dirty 17’’ with the highest toxicity equivalent factors. The specific congeners are listed in Table 2 and in Table 3. The sample extraction, purification, and analysis of PCDD/Fs were performed following the EPA 1613B method, developed for isomerspecific determination of the 2,3,7,8-substituted, dibenzo-p-dioxins and dibenzofurans in aqueous, solid, and tissue matrices by isotope dilution, high resolution capillary column gas chromatography (HRGC)/high resolution mass spectrometry (HRMS). The analyses were performed at the Interuniversity Consortium ‘‘Chemistry for the Environment’’ (INCA). QC/QA of the analysis was guarantee by the SINAL (now ACCREDIA) laboratory accreditation procedures for the PCDD/F analysis, in conformity to the UNI CEI EN ISO/IEC 17025:2005. This National System operates within the EA (European
1
TEQ) during all sampling campaigns.
a
Bulk deposition flux site 1 pg m 2 d 1 (pg-TEQ m 2 d 1)
Bulk deposition flux site 2a pg m 2 d 1(pg-TEQ m 2 d 1)
Bulk deposition flux site 3a pg m 2 d 1(pg-TEQ m 2 d 1) 2001-I 12
2001-II 2
2006-I 22
2007-I 9
2007-II 22
2008-I 13
0.32 (0.32) 0.32 (0.16) 0.64 (0.064) 0.77 (0.077) 0.64 (0.064) 9.0 (0.090) 48 (0.048) 0.83 (0.083) 0.77 (0.039) 1.5 (0.77)
0.37 (0.37) 0.74 (0.37) 0.74 (0.074) 1.3 (0.13)
0.28 (0.28) 0.28 (0.14) 0.55 (0.055) 0.55 (0.055) 0.55 (0.055) 1.5 (0.015) 6.7 (0.0067) 0.33 (0.033) 0.28 (0.014) 0.33 (0.17) 0.55 (0.055) 0.55 (0.055) 0.55 (0.055) 0.55 (0.055) 1.3 (0.013) 0.83 (0.0083) 1.4 (0.0014)
0.37 (0.37) 0.37 (0.19) 0.74 (0.074) 0.74 (0.074) 0.74 (0.074) 4.6 (0.046) 15 (0.015) 0.60 (0.060) 0.60 (0.030) 0.86 (0.43) 0.77 (0.077) 0.74 (0.074) 0.78 (0.078) 0.74 (0.074) 2.7 (0.027) 1.1 (0.011) 2.2 (0.0022)
0.44 (0.44) 0.44 (0.22) 0.89 (0.089) 0.89 (0.089) 0.89 (0.089) 3.9 (0.039) 17 (0.017) 0.53 (0.053) 0.44 (0.022) 0.80 (0.40) 0.89 (0.089) 0.89 (0.089) 0.89 (0.089) 0.89 (0.089) 3.5 (0.035) 1.3 (0.013) 3.0 (0.0030)
0.34 (0.34) 0.34 (0.17) 0.67 (0.067) 0.67 (0.067) 0.67 (0.067) 3.1 (0.031) 15 (0.015) 0.54 (0.054) 0.67 (0.034) 0.81 (0.40) 0.74 (0.074) 0.74 (0.074) 0.74 (0.074) 0.67 (0.067) 2.1 (0.021) 1.0 (0.010) 1.8 (0.0018)
2006-I 22
2007-I 9
2007-II 22
2008-I 13
2009-I 7
2001-I 12
2001-II 2
0.28 (0.28) 0.28 (0.14) 0.55 (0.055) 0.55 (0.055) 0.55 (0.055) 2.0 (0.020) 14 (0.014) 0.33 (0.033) 0.28 (0.14) 0.39 (0.19) 0.55 (0.055) 0.55 (0.055) 0.55 (0.055) 0.55 (0.055) 1.3 (0.013) 0.83 (0.008) 1.7 (0.0017)
0.37 (0.37) 0.37 (0.19) 0.74 (0.074) 0.74 (0.074) 0.74 (0.074) 4.7 (0.047) 30 (0.030) 0.57 (0.057) 0.63 (0.031) 0.80 (0.40) 0.77 (0.077) 0.74 (0.074) 0.80 (0.080) 0.74 (0.074) 2.7 (0.027) 1.1 (0.011) 1.9 (0.0019)
0.44 (0.44) 0.44 (0.22) 0.89 (0.089) 0.89 (0.089) 0.89 (0.089) 4.3 (0.043) 12 (0.012) 0.53 (0.053) 0.53 (0.027) 0.80 (0.40) 0.98 (0.098) 0.89 (0.089) 1.2 (0.12) 0.89 (0.089) 6.1 (0.061) 1.3 (0.013) 3.0 (0.0030)
0.34 (0.34) 0.34 (0.17) 0.67 (0.067) 0.67 (0.067) 0.67 (0.067) 2.6 (0.026) 13 (0.013) 0.47 (0.047) 0.47 (0.024) 0.60 (0.30) 0.67 (0.067) 0.67 (0.067) 0.74 (0.074) 0.67 (0.067) 2.2 (0.022) 1.0 (0.010) 1.7 (0.0017)
0.14 (0.14) 0.36 (0.18) 0.67 (0.067) 0.69 (0.069) 0.57 (0.057) 6.0 (0.060) 17 (0.017) 1.2 (0.12)
0.32 (0.32) 0.51 (0.26) 0.67 (0.067) 1.2 (0.12) 0.96 (0.096) 13 (0.13)
0.37 (0.37) 0.60 (0.30) 0.67 (0.067) 1.1 (0.11)
17 (0.32) 5.4 (0.37) 22 (0.69) 3.1
36 (0.47) 8.5 (0.75) 45 (1.2) 4.2
18 (0.52) 17 (0.39) 15 (0.86) 7.2 (0.61) 33 (1.4) 24 (1.0) 1.2 2.4
2009-I 7
0.14 (0.14) 0.42 (0.21) 0.32 (0.032) 0.90 (0.090) 1.0 (0.10) 0.61 (0.061) 11 (0.11) 7.3 (0.073) 25 21 (0.025) (0.021) 2.3 (0.23) 1.4 (0.14)
37 (0.037) 1.7 (0.17) 1.0 1.4 1.8 (0.052) (0.071) (0.090) 1.8 (0.92) 2.6 (1.3) 3.4 (1.7)
1.3 (0.065) 2.2 (1.1)
1.4 (0.14) 2.2 (0.22) 1.3 (0.13) 2.1 (0.21) 1.6 (0.16) 2.8 (0.28) 0.67 0.67 (0.067) (0.067) 4.5 7.3 (0.045) (0.073) 0.63 1.0 (0.0063) (0.010) 5.1 5.7 (0.0051) (0.0057)
0.29 (0.029) 5.53 (0.053) 0.82 (0.0082) 6.6 (0.0066)
0.74 (0.074) 13 (0.13) 46 (0.046) 1.9 (0.19) 1.8 (0.089) 3.0 (1.5)
2.5 (0.25) 1.9 (0.19) 1.1 (0.11) 2.3 (0.23) 2.2 (0.22) 1.6 (0.16) 0.96 2.0 (0.20) (0.096) 2.8 (0.28) 2.0 (0.20) 1.3 (0.13) 2.8 (0.28) 0.67 (0.067) 6.9 (0.069) 0.89 (0.0089) 5.6 (0.0056)
0.64 (0.064) 3.6 (0.036) 0.64 (0.0064) 3.6 (0.0036)
0.74 (0.074) 7.0 (0.070) 0.97 (0.0097) 6.0 (0.0060)
25 (0.47) 52 (0.82) 39 (0.87) 30 (0.56) 58 (0.44) 62 (0.95) 9.4 (0.31) 21 (0.45) 19 (1.6) 27 (2.4) 29 (2.9) 23 (1.9) 14 (1.3) 28 (2.6) 5.0 (0.33) 9.8 (0.78) 44 (2.1) 79 (3.2) 68 (3.7) 54 (2.5) 73 (1.7) 90 (3.5) 14 (0.65) 31 (1.2) 1.4 1.9 1.4 1.3 4.1 2.2 1.9 2.2
Numbers in italics correspond to sample below the limit of quantification (LOQ). The flux has been calculated using the LOQ. For the calculation of PCDDs flux, PCDFs flux and total flux, the congener flux below LOQ was included using half of the LOQ.
22 (0.52) 20 (0.40) 11 (0.70) 9.0 (0.78) 33 (1.2) 29 (1.2) 2.1 2.2
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I. Vassura et al. / Chemosphere 83 (2011) 1366–1373 Table 3 Concentration (ng kg
1
d.w.) of PCDD/Fs in the different soil samples. Soil concentration site 1a ng kg 1 d.w. (ng-TEQ kg 1 d.w.) 2006
2,3,7,8-TCDD 1,2,3,7,8-PeCDD 1,2,3,4,7,8-HxCDD 1,2,3,6,7,8-HxCDD 1,2,3,7,8,9-HxCDD 1,2,3,4,6,7,8-HpCDD
0.2 (0.2) 0.3 (0.15) 0.4 (0.04) 0.6 (0.06) 0.8 (0.08) 9.5 (0.095) 1,2,3,4,6,7,8,9-OCDD 81 (0.081) 2,3,7,8-TCDF 1,2,3,7,8-PeCDF 2,3,4,7,8-PeCDF 1,2,3,4,7,8-HxCDF 1,2,3,6,7,8-HxCDF 2,3,4,6,7,8-HxCDF 1,2,3,7,8,9-HxCDF 1,2,3,4,6,7,8-HpCDF
0.6 (0.06) 0.5 (0.025) 0.8 (0.4) 0.9 (0.09) 0.7 (0.07) 0.9 (0.09) 0.4 (0.04) 4.0 (0.04)
2007
2008
0.2 (0.2) 0.3 (0.15) 0.4 (0.04) 0.8 (0.08) 0.7 (0.07) 14 (0.14)
0.2 (0.2) 0.3 (0.15) 0.5 (0.05) 0.8 (0.08) 0.8 (0.08) 14 (0.14)
2006
2007
2008
2009
2006
2007
2008
2009
0.2 (0.2) 0.2 (0.1) 0.4 (0.04) 0.4 (0.04) 0.4 (0.04) 5.2 (0.052)
0.2 (0.2) 0.2 (0.1) 0.10 (0.01) 0.4 (0.04) 0.4 (0.04) 5.2 (0.052)
0.2 (0.2)) 0.2 (0.1) 0.4 (0.04) 0.4 (0.04) 0.4 (0.04) 4.8 (0.048)
0.2 (0.2) 0.2 (0.1) 0.4 (0.04) 0.4 (0.04) 0.5 (0.05) 5.7 (0.057)
0.2 (0.2) 0.2 (0.1) 0.4 (0.04) 0.4 (0.04) 0.4 (0.04) 3.6 (0.036)
38 (0.038)
43 (0.043)
59 (0.059)
0.2 (0.2) 0.2 (0.1) 0.4 (0.04) 0.4 (0.04) 0.4 (0.04) 4.5 (0.045) 53 (0.053) 0.3 (0.03) 0.2 (0.01)
0.7 (0.35) 1 (0.1) 0.7 (0.07) 0.9 (0.09) 0.4 (0.04) 4.2 (0.042)
1 (0.5) 1.3 (0.13) 0.8 (0.08) 1.1 (0.11) 0.4 (0.04) 5.5 (0.055) 0.7 (0.007) 18 (0.018)
0.3 (0.15) 0.5 (0.05) 0.4 (0.04) 0.6 (0.06) 0.4 (0.04) 3.0 (0.03)
0.3 (0.15) 0.5 (0.05) 0.4 (0.04) 0.5 (0.05) 0.4 (0.04) 3.2 (0.032)
0.2 (0.1) 0.6 (0.06) 0.4 (0.04) 0.6 (0.06) 0.4 (0.04) 3.3 (0.033)
0.4 (0.2) 0.5 (0.05) 0.5 (0.05) 0.5 (0.05) 0.4 (0.04) 3.0 (0.030)
0.3 (0.15) 0.4 (0.04) 0.5 (0.05) 0.5 (0.05) 0.4 (0.04) 2.5 (0.025)
0.2 (0.2) 0.2 (0.1) 0.4 (0.04) 0.4 (0.04) 0.5 (0.05) 4.4 (0.044) 42 (0.042) 0.7 (0.07) 0.5 (0.025) 0.8 (0.4) 1.7 (0.17) 1 (0.1) 1.2 (0.12) 0.6 (0.06) 9 (0.009)
0.6 (0.006)
1.2 (0.012)
0.6 (0.006)
0.6 (0.006)
7.4 (0.0074)
0.2 (0.2) 0.2 (0.1) 0.4 (0.04) 0.4 (0.04) 0.4 (0.04) 5.1 (0.051) 58 (0.058) 0.3 (0.03) 0.3 (0.015) 0.3 (0.15) 0.5 (0.05) 0.4 (0.04) 0.5 (0.05) 0.4 (0.04) 2.8 (0.028) 0.6 (0.006) 10 (0.010)
8.8 (0.0088)
8.8 (0.0088)
9.2 (0.0092)
11 (0.011)
100 (0.69) 30 (1.1) 130 (1.8)
45 (0.32)
64 (0.34)
44 (0.29)
48 (0.32)
66 (0.36)
43 (0.28)
58 (0.31)
48 (0.33)
13 (0.40) 58 (0.72)
16 (0.40) 80 (0.74)
15 (0.38) 59 (0.67)
15 (0.37) 64 (0.69)
16 (0.51) 82 (0.86)
16 (0.39) 59 (0.67)
16 (0.26) 74 (0.57)
55 (1.1) 103 (1.4)
1 (0.5) 2.5 (0.25) 1.5 (0.15) 1.7 (0.17) 0.4 (0.04) 10 (0.10)
0.6 (0.006) 0.6 (0.006) 1.5 (0.015) 1,2,3,4,6,7,8,9-OCDF 10 (0.01) 15 (0.015) 17 (0.017)
a b
92 (0.59)
PCDF sumb Total sumb
19(0.81) 111 (1.4)
140 (0.71) 108 (0.69) 24 (0.78) 37 (1.3) 164 (1.5) 145 (2.0)
2009
Soil concentration site 3a ng kg 1 dw (ng-TEQ kg 1 d.w.)
0.2 (0.2) 0.4 (0.2) 0.4 (0.04) 0.9 (0.09) 1 (0.1) 9.7 (0.097) 92 87 123 (0.123) (0.092) (0.087) 0.6 (0.06) 0.7 (0.07) 1 (0.01) 0.5 (0.025) 0.8 (0.04) 0.8 (0.04)
1,2,3,4,7,8,9-HpCDF
PCDD sumb
Soil concentration site 2a ng kg 1 dw (ng-TEQ kg 1 d.w.)
38 (0.038) 0.3 (0.03) 0.2 (0.01)
0.6 (0.006)
38.1 (0.0381) 0.3 (0.03) 0.3 (0.03) 0.8 (0.08) 0.3 (0.03) 0.4 (0.020) 0.3 (0.015) 0.3 (0.015) 0.2 (0.01)
0.2 (0.1) 0.4 (0.04) 0.4 (0.04) 0.4 (0.04) 0.4 (0.04) 2.7 (0.027) 0.6 (0.006) 11 (0.011)
2 (0.002) 38 (0.038)
Numbers in italics correspond to sample below the limit of quantification (LOQ). The flux has been calculated using the LOQ. For the calculation of PCDDs flux, PCDFs flux and total flux, the congener flux below LOQ was included using half of the LOQ.
cooperation for Accreditation) and ILAC (International Laboratory Accreditation Cooperation) international arrangement.
3. Results and discussion 3.1. Deposition fluxes of PCDD/Fs PCDD/Fs atmospheric deposition fluxes are shown in Table 2. Data, expressed as pg m 2 d 1 or in terms of equivalent toxicity (TEQ) as pg-TEQ m 2 d 1, have been calculated as an average value of the sampling period, which generally varies between 30 d and 40 d. Total flow has been obtained by summing the fluxes of single congeners; the species whose concentration has been below the limit of quantification (LOQ) have been summed as LOQ/2, as suggested by the Italian Institute of Health (ISS) (Clarke, 1998; Finkelstein and Verma, 2002; Menichini and Viviano, 2004). Total deposition fluxes vary between 14.3 pg m 2 d 1 and 89.9 pg m 2 d 1 (0.65–3.73 pg-TEQ m 2 d 1). The same magnitude of deposition fluxes has been reported by other authors: Guerzoni et al. (2004), Moon et al. (2005), and Vandecasteele et al. (2007). These fluxes are relatively low. Indeed, it has been estimated, according to a chain model, that the lower tolerable daily intake suggested by WHO (1998), corresponding to 1 pg-TEQ kg 1 d 1, is reached if PCDD/Fs air concentrations are such that the transfer flux from atmosphere to soil and/or vegetation is 6.8 pgTEQ m 2 d 1 (as the average deposition value) (Van Lieshout et al., 2001). Consequently, it is likely that much lower depositions may result in air contaminations having less impact on the population. The fluxes registered in the last years are significantly lower than those observed in 2001 campaigns. However, total deposition fluxes of PCDDs and PCDFs at the different sites, monitored during the same period (Table 2), are quite similar. No considerable
differences can be seen among the values found in the most affected sites (according to the dispersion model, i.e. sites 1 and 2), and the reference one (site 3). In all cases, PCDD flow is greater than that of PCDFs, while in terms of toxicity equivalent factors, the opposite occurs. This is due to the fact that PCDDs are mainly present as congeners 1,2,3,4,6,7,8-HpCDD e 1,2,3,4,6,7,8,9-OCDD, as discussed below. It is also interesting to observe that during the last two sampling campaigns, at site 1, there is no significant decrease, and instead an increase in PCDF deposition occurs, even though the plant was shut down for 6 months from February 2008, and then operated at reduced capacity for the following period. At site 3, the other for which a comparison with the years 2006 and 2007 is possible, similar considerations can be made, even if, in this case, there seems to be no direct influence of the plant.
3.1.1. Profile of PCDD/Fs congeners in atmospheric deposition The study of the congener profile in environmental samples, deriving from the typical emission compositions from different processes, can provide information about the contribution of a specific source in the vicinity (Sandalls et al., 1998; Alcock and Jones, 1996; Everaert and Baeyens, 2002). The average relative distributions of congeners in the three sampling sites are quite constant, both in time and in space (see Fig. 2). Pearson correlation coefficients are always greater than 0.9 when the comparison is made between congeners sampled during the same period. The most abundant congeners are the higher chlorinated ones. On average, at the three sites, 40.6–52.6% of OCDD, 11.4–15.2% of HpCDD, 8.0–10.0% of 1,2,3,4,6,7,8-HpCDF, and 6.8–9.2% of OCDF are found, while all the other congeners contribute for less than 5%. The abundance of OCDD can be explained by the fact that, on the one hand, it is one of the most stable congeners in the
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70 Site 1
Relative Distribution (%)
60
Site 2 Site 3
50 40 30 20
1,2,3,4,6,7,8,9-OCDF
1,2,3,4,7,8,9-HpCDF
1,2,3,4,6,7,8-HpCDF
1,2,3,7,8,9-HxCDF
2,3,4,6,7,8-HxCDF
1,2,3,6,7,8-HxCDF
1,2,3,4,7,8-HxCDF
2,3,4,7,8-PeCDF
1,2,3,7,8-PeCDF
2,3,7,8-TCDF
1,2,3,4,6,7,8,9-OCDD
1,2,3,4,6,7,8-HpCDD
1,2,3,7,8,9-HxCDD
1,2,3,4,7,8-HxCDD
1,2,3,6,7,8-HxCDD
1,2,3,7,8-PeCDD
0
2,3,7,8-TCDD
10
Fig. 2. Average PCDD/F (%) congeners profile in atmospheric depositions collected at the three sampling sites (bars indicate data standard deviation).
atmosphere (Mackay et al., 2006) and, on the other, it is emitted in great amounts by multiple sources, such as industrial boilers, solid waste incinerators and vehicular traffic (Cleverly et al., 1997; Domingo et al., 2001; Stanmore, 2004; Floret et al., 2007; Zhu et al., 2008). Thus, OCDD distribution cannot be considered a characterizing factor of a specific emission source. However, considering both HpCDD/OCDD ratio and low/high chlorinated PCDF congeners ratio, the deposition profile seems to reflect what is generally found in other studies focusing on urban or suburban areas, mainly characterized by traffic, house heating and domestic emissions. The PCDD/Fs congeners distributions reported in these papers are characterized by a HpCDD/OCDD ratio ranging between 0.1 and 0.3; whereas low/high chlorinated PCDF ratio is quite variable (Chang et al., 2004; Correa et al., 2006; Ren et al., 2007; Castro-Jimenez et al., 2008; Mari et al., 2008; Vives et al., 2008; Zhu et al., 2008). As for the toxicological aspect, the most significant amount comes from 2,3,4,7,8-PeCDD, which contributes an average of 32.9–43.1% of the total toxicity. TCDD, despite is highest absolute toxicity, makes a low contribution, since it amounts to less than 1% in weight.
In comparison with atmospheric depositions, the abundance of PCDDs is greater, compared to PCDFs, but in this case, also, this is almost exclusively due to the high concentration of congeners with seven or eight chlorine atoms, as discussed below. PCDD/PCDF vary from 2.6 to 5.8 (the only exception is the last datum, measured in 2009, at site 3).
3.2. PCDD/Fs concentration in soil
3.3. Incinerator fingerprinting
Soil represents the final fate of PCDD/Fs, since they are strongly bound and poorly degraded in it. The study of PCDD/Fs accumulation in soil can thus give information about the degree of long-term PCDD/F contamination (Andersson and Ottesen, 2008). At the three sampling sites, over four monitoring years, PCDD/Fs, content (Table 3) varies from 57.7 ng kg 1 d.w to 164 ng kg 1 d.w. (average value 93.8 ng kg 1 d.w.). These concentrations are five or ten times lower than the limits set by Italian law for residential or private soils (D.Lgs. 152/06). The amount of PCDD/Fs in surface soil does not exhibit a growing trend in the 4 years of monitoring (Table 3). Unlike what has been observed for atmospheric depositions, there are considerable variations among the three sites. In particular, at site 1, the closest to the urban area and highway, PCDD/Fs concentration is on average about twice that measured at reference site (site 3) and site 2, that is located in the area which is expected to be the most affected by incinerator emissions.
PCDD/Fs emission from a municipal solid waste Incinerator is greatly affected by the composition of input waste, the type of furnace, and the flue gas treatment systems (Cleverly et al., 1997). For this reason, the emissions of each plant are characterized by different congener profiles, and can exhibit a high variability. For the studied plant, PCDD/Fs stack emissions have been calculated on the average value obtained from 16 direct measurements, performed approximately every 20 d, in 2009 (Fig. 4). Different authors report emission profiles which are similar to those found in the present study (Domingo et al., 2001; Abad et al., 2006; Wang et al., 2009; Wu et al., 2009), while others, apart from congener profiles, attest a PCDD/PCDF ratio <1 (Everaert and Baeyens, 2002; Stanmore, 2004; Littarru, 2006). Highly chlorinated congeners are in general the most abundant; among them, OCDD covers a half of the total weight, on average. As for PCDFs, low-chlorinated PCDDs also make an important contribution to the overall load. The PCDD/PCDF ratio equals 0.8,
3.2.1. Profile of congeners of PCDD/Fs in soil Congener distribution patterns are quite similar, both in space and in time, a sign of a clear homogeneity of the PCDD/Fs profiles determined in soils (Fig. 3). This suggests that contamination is due to similar sources, or that the emission of the territorial source is widespread and efficiently transported over the entire studied area. In line with what has been observed for atmospheric depositions, the congener profile is dominated by the most chlorinated ones: OCDD constitutes about 70% in weight, followed by HpCDD (10%), OCDF (15%), and 1,2,3,4,6,7,8-HpCDF (5%). The remaining congeners contribute for a total of less than 2%. However, in terms of the toxicity equivalent factor, 2,3,4,7,8-PeCDD prevails, on average, corresponding to approximately 20%.
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90 80
Site 1
Relative Distribution (%)
Site 2
70
Site 3
60 50 40 30 20 10 1,2,3,4,6,7,8,9-OCDF
1,2,3,4,7,8,9-HpCDF
1,2,3,4,6,7,8-HpCDF
1,2,3,7,8,9-HxCDF
2,3,4,6,7,8-HxCDF
1,2,3,6,7,8-HxCDF
1,2,3,4,7,8-HxCDF
2,3,4,7,8-PeCDF
1,2,3,7,8-PeCDF
2,3,7,8-TCDF
1,2,3,4,6,7,8,9-OCDD
1,2,3,4,6,7,8-HpCDD
1,2,3,7,8,9- HxCDD
1,2,3,6,7,8- HxCDD
1,2,3,4,7,8- HxCDD
1,2,3,7,8-PeCDD
2,3,7,8- TCDD
0
Fig. 3. Average PCDD/F (%) congeners profile in soil samples collected in the three sampling sites (bars indicate data standard deviation).
45
Relative Distribution (%)
40 35 30 25 20 15 10 5 1,2,3,4,6,7,8,9-OCDF
1,2,3,4,7,8,9-HpCDF
1,2,3,4,6,7,8-HpCDF
1,2,3,7,8,9-HxCDF
2,3,4,6,7,8-HxCDF
1,2,3,6,7,8-HxCDF
1,2,3,4,7,8-HxCDF
2,3,4,7,8-PeCDF
1,2,3,7,8-PeCDF
2,3,4,8-TCDF
1,2,3,4,6,7,8,9-OCDD
1,2,3,4,6,7,8,9-HpCDD
1,2,3,7,8,9-HxCDD
1,2,3,6,7,8-HxCDD
1,2,3,4,7,8-HxCDD
1,2,3,7,8-PeCDD
2,3,7,8-TCDD
0
Fig. 4. Average PCDD/F (%) congeners profile in 17 stack emission samples collected from the MSWI plant in 2009 (bars indicate data standard deviation).
on average; however, a strong variability of this result can be observed. 3.4. Comparison of profiles The resulting congener profile emitted by the incinerator (Fig. 4) shows considerable differences compared to that observed for atmospheric deposition (Fig. 2) and soil (Fig. 3). In general the relative concentration of low-chlorinated PCDD/F in incinerator emissions are less than in deposition and soil. Usually, the lower environmental concentration of all the lightest congeners may be due to selective degradation processes. The estimated degradation time in atmosphere of low-chlorinated PCDD/Fs is about a day instead of the weeks required for high-chlorinated PCDD/Fs with a consequent relative enrichment of the most chlorinated congeners as the distance from the source increases (Atkinson, 1991; Kwok et al., 1995). The congeners with seven or eight chlorine atoms, besides being more stable, are less
volatile and are mainly associated to particulate, resulting in a greater atmospheric removal (Oh et al., 2001; Lohmann and Jones, 1998). These degradation and selective removal mechanisms, may explain the characteristic background pattern of PCDD/Fs distribution in areas far from local contamination sources. In our case the monitoring sites are at most 2.5 km far from the incinerator and the typical wind speed in the considered area is about 1 m/s. In these conditions, pollutants emitted by the plant can reach the samplers in a short time (few hours), which is not sufficient to allow the degradation of over two thirds of the low-chlorinated compounds and, even less, the variation of HpCDD/OCDD ratio. From the official environmental statement of incinerator, PCDD/ Fs stack concentrations were, on average, 0.007 ng-TEQ Nm 3 in 2006, 0.008 ng-TEQ Nm 3 in 2007, 0.015 ng-TEQ Nm 3 in 2008 and 0.019 ng-TEQ Nm 3 in 2009, being always about one or two orders of magnitude lower than the actual legal limits (0.1 ng-TEQ Nm 3) (Directive 76/2000/EC). The yearly mass fluxes was respectively 1.5 mg-TEQ y 1 in 2006, 7 mg-TEQ y 1 in 2007,
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0.004 mg-TEQ y 1 in 2008 (during most of this year the plant was stopped for modernization works) and 4.7 mg-TEQ y 1 in 2009. The resulting annual PCDD/F emission flow amounts, although not negligible, do not comport an appreciable differences in deposition fluxes among sites 1 and 2 and site 3. In conclusion, the differences found between congener profiles of environmental samples and stack emissions, the apparent homogeneity of concentration and deposition fluxes at all three monitoring sites, even during the inactivity of the plant, can be explained only hypothesizing that the incinerator is not the only source affecting the area. Therefore, atmospheric background contamination and contribution of local diffuse emission sources seem to affect deposition fluxes in a greater extent than the incinerator. 4. Conclusion The deposition fluxes recorded in the studied area, compared to other studies, show a low concentration of PCDD/F in atmospheric depositions. A low contamination burden has been also determined in the soil samples. The similar relative composition of the congener mix in all the samples of the same environmental matrices and the absence of significant differences between the sites more heavily subject to the incinerator emissions and the reference site indicate that the whole territory is affected by a homogeneous contamination. This is hardly explainable considering only the air dispersion of plant emissions and suggests that more sources are present in the whole area. PCDD/F mixtures show the same relative composition of congeners at the three different sites, with a noticeably different pattern compared to that typical of plant emissions, in particular in relation to the PCDD/Fs ratio. The incinerator’s relative contribution to the total pollutant load seems to be negligible compared to a higher background concentration, which could be ascribed to the nearby urban area. This is confirmed by the observation that deposition fluxes during the 40 d sampled in 2008 are not significantly lower than the other years, even though the plant was shut down for 6 months. Acknowledgments The Authors wish to acknowledge Hera s.p.a. for having funded this study and Interuniversity National Consortium ‘‘Chemistry for the Environment’’ (INCA) for analysis support. References Abad, E., Martinez, K., Caixach, J., Rivera, J., 2006. Polychlorinated dibenzo-p-dioxins, dibenzofurans and ‘‘dioxin-like’’ PCBs in flue gas emissions from municipal solid waste management plants. Chemosphere 63, 570–580. Alcock, R.E., Jones, K.C., 1996. Dioxins in the environment: a review of trend data. Environ. Sci. Technol. 30, 3133–3143. Alcock, R.E., Sweetman, A.J., Jones, K.C., 2001. A congener-specific PCDD/F emission inventory for the UK: do current stimates account for the measured atmospheric burden? Chemosphere 43, 183–194. Altarawneh, M., Dlugogorski, B.Z., Kennedy, E.M., Mackie, J.C., 2009. Mechanisms for formation, chlorination, dechlorination and destruction of polychlorinated dibenzo-p-dioxins and dibenzofurani (PCDD/Fs). Prog. Energy Combust. Sci. 35, 245–274. Andersson, M., Ottesen, R.T., 2008. Levels of dioxins and furans in urban surface soil in Trondheim, Norway. Environ. Pollut. 152, 553–558. Atkinson, R., 1991. Atmospheric lifetimes of dibenzo-p-dioxins and dibenzofurans. Sci. Total Environ. 104, 17–33. Brzuzy, L.P., Hites, R.A., 1996. Global mass balance for polychlorinated dibenzo-pdioxins and dibenzofurans. Environ. Sci. Technol. 30, 1797–1804. Castro-Jimenez, J., Mariani, G., Eisenreich, S.J., Christoph, E.H., Hanke, G., Canuti, E., Skejo, H., Umlauf, G., 2008. Atmospheric input of POPs into Lake Maggiore (Northern Italy): PCDD/F and dioxin-like PCB profiles and fluxes in the atmosphere and aquatic system. Chemosphere 73, S122–S130. Chang, M.B., Chang, S.H., Chen, W.C., Hsu, H.C., 2004. Dioxin emission factors for automobiles from tunnel air sampling in Northern Taiwan. Sci. Total Environ. 325, 129–138.
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