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Identifying contemporary and historic sources of soil polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in an industrial urban setting
Science of the Total Environment 370 (2006) 61 – 69 www.elsevier.com/locate/scitotenv
Identifying contemporary and historic sources of soil polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in an industrial urban setting Catherine G. Vizard a,1 , David L. Rimmer b,⁎, Tanja Pless-Mulloli a , Ian Singleton c , Vivienne S. Air d a
School of Population and Health Sciences, William Leech Building, University of Newcastle, Newcastle upon Tyne NE2 4HH, UK School of Civil Engineering and Geosciences, Drummond Building, University of Newcastle, Newcastle upon Tyne NE1 7RU, UK School of Biology, Institute for Research on the Environment and Sustainability, University of Newcastle, Newcastle upon Tyne NE1 7RU, UK d Public Health and Environmental Protection, Newcastle City Council, Civic Centre, Newcastle upon Tyne NE1 8PR, UK b
c
Received 10 February 2006; received in revised form 1 June 2006; accepted 8 June 2006 Available online 17 July 2006
Abstract A study of soil polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F) concentrations was undertaken in the vicinity of a municipal solid waste incinerator (MSWI) in Newcastle upon Tyne as a result of concerns raised by local residents about potential contamination from fugitive and stack emissions. The study area was divided into four sectors (north-east (NE), south-east (SE), north-west (NW) and south-west (SW)) around the MSWI, and sampling sites were located up to a distance of 2.25 km. Based on air dispersion modelling, the sampling density was four times greater in the NE (downwind) sector compared to the SW (upwind) direction, and twice as great in the NW and SE sectors. PCDD/F concentrations found in soil samples ranged from 6 to 1911 ng I-TEQ/kg DW with a median of 32 ng I-TEQ/kg DW. There was no evidence of elevated concentrations downwind of the MSWI compared to other directions, nor of any trend in concentration at increasing distance from the MSWI. We concluded, therefore, that the MSWI fugitive and stack emissions were not a major source of PCDD/F contamination. Analysis of PCDD/F homologue profiles showed that samples exhibiting furan-dominated and OCDD-dominated profiles and a profile characteristic of the MSWI ash occurred in distinct clusters. Those samples showing the furan-dominated profile had the largest PCDD/F concentrations measured as I-TEQ, followed by samples with the incinerator profile, the deposition profile, and the OCDD-dominated profile. We identified some contamination hotspots located in the SW and SE sampling sectors (upwind of the MSWI), and potential sources for these hotspots were sought by using historic land use data from maps of the locality dating back to 1856. We concluded that the cluster of very high concentrations of PCDD/F in soils showing the furan homologue profile were most likely to have resulted from the disposal of graphite electrode sludges from brine electrolysis carried out at a chemical works between the 1890s and the 1930s. © 2006 Elsevier B.V. All rights reserved. Keywords: Urban environment; MSWI emissions; PCDD/F; Soils
⁎ Corresponding author. Tel.: +44 191 222 6916; fax: +44 191 222 5322. E-mail address: [email protected] (D.L. Rimmer). 1 Current address: Environment Agency West Area Office, Red Kite House, Howbery Park, Crowmarsh Gifford, Wallingford, Oxfordshire, OX10 8BD, UK. 0048-9697/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.scitotenv.2006.06.006
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1. Introduction Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F) are contaminants that are widespread in today's environment (Zook and Rappe, 1994). These compounds can be formed from any combustion process involving organic matter and chlorine compounds. PCDD/F contamination is particularly linked to atmospheric emissions from industrial processes. Evidence from sediment cores and archived samples suggests that inputs of PCDD/F to the environment probably peaked in the late 1960s/early 1970s (Duarte-Davidson et al., 1997). The subsequent reduction in emissions was due in part to the regulation of industrial processes and the introduction of abatement technology (Alcock and Jones, 1996). However, PCDD/F tend to persist and bioaccumulate in environmental compartments and their stable nature means that PCDD/F can remain in the soil for many decades (Duarte-Davidson et al., 1997). This means that in industrialized urban areas there can often be a cumulative build-up from historic and contemporary sources, resulting in concern for human health. Exposure to PCDD/F can lead to cancer and reproductive/developmental effects (Birnbaum and Farland, 2003). Alcock et al. (2001) undertook a congener-specific atmospheric emission inventory and found that primary regulated industrial sources could potentially account for between 30% and 86% of the total PCDD/F emitted into the atmosphere, and that unregulated non-industrial sources, such as road traffic, could account for the remainder. All of the possible 75 PCDD and 135 PCDF isomers and congeners can be produced from waste incinerators, independent of type of incinerator or waste composition (DCDEP, 1989). Variation in the amounts of PCDD/F can occur over time at any one incinerator and at different types of incinerator plant due to variations in temperature, feed, and trace elements, such as copper (DCDEP, 1989). PCDD/F can be found in residue streams, grate residues, wash waters, fly ash and chimney stack emissions (DCDEP, 1989). In recent years, a number of studies concerning PCDD/ F concentrations in soil samples collected near MSWIs have been carried out (see, for example, De Jong et al., 1993; Abbott et al., 1997; Pirard et al., 2005; Oh et al., 2006). Of particular interest are a series of investigations at MSWI sites in Spain reported by Schumacher, Domingo and co-workers (Domingo et al., 2000, 2001a,b, 2002; Nadal et al., 2002; Schuhmacher et al., 1997, 1998, 1999, 2000; Schuhmacher and Domingo, 2006). Analysis of homologue and congener profiles has been widely used to aid the identification of sources of PCDD/F contamination (Cleverly et al., 1997). In parti-
cular, homologue and congener profiles have been used to determine whether soil PCDD/F in the vicinity of MSWIs were mainly due to PCDD/F emissions from those plants (Domingo et al., 2001b). The Byker plant is located in Newcastle upon Tyne, UK. Between 1979 and 1998 it produced refuse-derived fuel (RDF), which was burnt in the adjacent waste-to-energy facility. Approximately one-third of the 100,000 tonnes of waste treated per year was incinerated. The abatement equipment at the Byker plant comprised a dry lime scrubber and a bag filter. Releases to air between 1993 and 1998 had a mean value of 0.118 g of PCCD/F per annum. There have been a number of site-specific studies of environmental PCDD/F concentrations in Newcastle related to the Byker MSWI (Pless-Mulloli et al., 2000, 2001a,b, 2004). In these studies a homologue profile typical of that found in MSWI ash was identified in the soil samples. The pattern was used to identify PCDD/F contamination arising from the ash itself or from fugitive and stack emissions. However, due to the presence of other emission sources, homologue profiles, which were unrelated to the MSWI, were also identified. Unlike the previous studies, which investigated contamination at specific sites, the aim of the present work was to carry out a systematic survey of PCDD/F soil contamination over a wide area that might have been affected by stack and fugitive emissions from the MSWI. In order to identify whether any PCDD/F soil contamination was from the MSWI or from other industrial or non-industrial sources, PCDD/F homologue profiles were also assessed. Identification of both current and historic sources was carried out by using maps of the locality dating back to 1856. 2. Materials and methods 2.1. Soil sampling The study area was divided into four sectors (NE, SE, NW, and SW) around the MSWI. The area was further divided into concentric distance bands of 50 m up to a distance of 750 m, and thereafter into bands of 250 m up to a distance of 2.25 km (Fig. 1). The predicted dispersion pattern obtained from modelling undertaken by Newcastle City Council showed that the direction of the plume would be predominantly to the NE of the MSWI. The sampling frame comprised three sites within each distance band in the NE sector, two within each band in the NW and SE sectors, and one within each band in the SW sector. All 163 sampling sites were in areas with public access (Rimmer et al., 2006).
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Fig. 1. Location of the 86 sampling sites.
The sampling sites were randomly generated using geostatistical software (S-Plus 6). If generated sites were located in areas without public access, or on buildings or roads, they were moved to the nearest area of public open space and denoted ‘judgmental’ sites. When visited, some locations were found to have poor access due to overgrown shrubs and undergrowth. Unsuitable for sampling, these sites were also relocated and denoted as ‘judgmental’. PCDD/F analyses were carried out on samples from 83 of the 163 sites, approximately 40% of which were random and 60% judgmental. These samples were selected systematically by taking every second sampling site. Subsequently a further three samples taken from the SW sector were also analyzed, giving a total of 86 samples. These additional samples were used because initial analyses showed that there was a hotspot of contamination in this sector. The sampling density in the sector was very low, so more information on the extent of the contamination could be obtained by analysing more of the existing samples. Soil cores were taken (5 cm diameter and 5 cm depth) within an area of 50 m by 50 m centred on each site. To give a composite sample for each site, soil cores were collected from two to eight points, depending on the proportion of public open space at each location, and the material from them was combined. Soil samples were
air-dried. Any plant material (roots, leaves) was removed manually and the soil sieved to < 2 mm. 2.2. PCDD/F analyses Analyses were undertaken by Ergo Laboratories, Hamburg, Germany. Quantitative determinations of PCDD/F according to the isotope dilution method were carried out by means of 2,3,7,8-PCDD/F substituted with 13C-ULlabelled internal standards. After spiking, samples were extracted with toluene. The clean-up was carried out on multicolumn systems involving a combination of neutral, acidic and basic silica, florisil, as well as carbon on celite. Determination was carried out using a combination of high resolution gas chromatography and high resolution mass spectrometry (HR-GC/MS: VG-AutoSpec/Finnigan MAT 95 XL) and DB5 and SP2331 capillary columns. For each substance, two isotope masses were recorded. The concentrations of the PCDD/F were reported in units of ng I-TEQ per kg of dry soil for the 17 toxic congeners and the 10 homologue groups. Furthermore the pattern of total homologues, as well as the pattern of toxic congeners, was taken into account. Numerous procedures can be used to derive a homologue or congener profile and there is no agreed convention (Cleverly et al., 1997). As a result we
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Table 1 PCDD/F concentrations (ng I-TEQ/kg DW) in soil samples for each sector Sector
n
Mean
Median
Min
Max
NE NW SE SW Overall
31 21 21 13 86
48 54 65 487 120
26 16 38 169 32
6 7 7 14 6
554 494 481 1911 1911
Environment Agency pollution inventory database was conducted to identify industries with a significant potential to pollute (‘Part A’ industries) within a 5mile radius of the MSWI. Information about industrial plants that pollute to a lesser extent (‘Part B’ industries) in the vicinity of the MSWI was obtained from the local authorities in Newcastle and Gateshead. 3. Results and discussion
have presented homologue profiles derived from the sum of all isomers within a group e.g. all tetra-CDD compared with all penta-, hexa-, hepta-, and octa-CDDs and CDFs. 2.3. Historic and current land use The GIS package Arcview 3.1 was used to view and reproduce ‘Landmark’ historic maps held by the local authorities in Newcastle and Gateshead. Maps were reproduced from Ordnance Survey Historical Data for the periods 1856 to 1895; 1895 to 1898; 1916 to 1920; 1932 to 1942; 1952 to 1963; and 1955 to 1984. Information about the history of specific industries or areas was obtained from the Central Library in Newcastle. Current land use was assessed by viewing and reproducing Ordnance Survey Landline Data and CRWorld Aerial Images. In addition, a search of the
3.1. Concentrations of PCDD/F and homologue profiles Over the whole study area the concentration of soil PCDD/F ranged between 6 and 1911 ng I-TEQ/kg DW with a mean of 120 ng I-TEQ/kg DW and a median of 32 ng I-TEQ/kg DW. Fifteen samples exceeded the normal range of PCDD/F concentrations in UK urban soils (i.e. were greater than 87 ng I-TEQ/kg DW (HMIP, 1995); more recent data on the concentrations in UK soils and herbage will be available soon from the UK Environment Agency). The mean, median and range of concentrations of PCDD/F in the NE, NW, SE and SW sectors are shown in Table 1. Elevated soil PCDD/F concentrations were expected in the north-east sampling sector as a result of deposition from fugitive and stack emissions from the MSWI. However, the north-east sector had the lowest mean concentration
Fig. 2. Soil PCDD/F concentrations (ng I-TEQ/kg DW) by distance band and sector.
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among the four sectors (Table 1). The distributions were skewed in all sectors by a small number of large values. PCDD/F concentrations in the majority of
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samples in the sectors NE, NW, and SE were of the same order of magnitude and showed similar levels of variation. However, in the SW sector, PCDD/F
Fig. 3. Typical homologue profiles: a) incinerator homologue profile; b) deposition homologue profile; c) furan-dominated homologue profile; and d) the OCDD homologue profile.
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concentrations greater than 1000 ng I-TEQ/kg DW were found in some hotspot locations. In order to assess the distribution within each sector, we plotted the concentrations as a function of distance (Fig. 2). This showed localised elevation of concentrations (>87 ng I-TEQ/kg DW) in four samples within 100 m of the MSWI stack in the NW and NE sectors. This was most likely to be the result of material blown from fly ash piles and skips
used on site. The concentrations greater than 1000 ng ITEQ/kg DW in the SW sector were located in the 500, 600, 700 and 1000 m distance bands. These occurred in a cluster along the banks of the River Tyne. In the SE sector elevated soil concentrations were found in the 500 m band. It had been anticipated that with increasing distance from the MSWI, there would be a decrease in soil PCDD/F concentrations. However, no such gradient was observed
Fig. 4. The distribution of homologue profiles: a) across the whole survey area, and b) within 250 m of the MSWI.
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outside the boundary of the plant (Fig. 2). Therefore there was little evidence to suggest that stack and fugitive emissions from the MSWI have had a measurable effect on the average soil contamination within its vicinity. This finding was reinforced by the homologue profiles, which were examined with the aim of identifying the sources of elevated PCDD/F concentrations detected in this study (Fig. 3). There was a profile typical of the waste combustion process at Byker plant, which had been identified in earlier studies (Pless-Mulloli et al., 2000, 2001a,b). It was similar to the incinerator profiles of Zook and Rappe (1994) and Brzuzy and Hites (1996). Sixteen (18%) of the 86 samples analysed were identified as having this ‘incinerator’ homologue profile. A second homologue profile was similar to the ‘deposition’ profile of Creaser et al. (1990) and represents a profile often found in environmental samples from urban environments. 43 samples (50%) were identified as exhibiting the deposition homologue profile. An OCDD-dominated profile is characteristic of profiles found in compost, sewage sludge or pentachlorophenol samples (Zook and Rappe, 1994). 10% of the 86 samples exhibited an OCDD-dominated pattern. A fourth homologue profile identified was dominated by PCDF homologues with low concentrations of PCDDs. An example of a similar homologue profile has been reported by Zook and Rappe (1994) who named it the ‘chlorine pattern’ attributable to electrode sludge waste. Ten samples (12%) exhibited this furandominated profile. Eight samples (10%) showed profiles which could not be attributed to one of the specific groups. These were most likely the result of a mixture of profiles. Sampling locations exhibiting the furan-dominated, OCDD and incinerator homologue profiles occurred in distinct clusters (Fig. 4). Samples with a deposition homologue profile occurred across the whole study area. Table 2 shows the extent of PCDD/F contamination for each homologue profile group. Samples showing the furan-dominated profile had the greatest PCDD/F concentrations (mean: 671 ng I-TEQ/kg DW), followed by samples with the incinerator profile (mean: 108 ng ITEQ/kg DW), and the deposition and OCDD profiles (means: 31 and 30 ng I-TEQ/kg DW). Three of the samTable 2 PCDD/F concentrations (ng I-TEQ/kg DW) in soil samples classified by homologue profile Profile
n
Mean
Median
Min
Max
OCDD Incinerator Deposition Furan-dominated Other
9 16 43 10 8
30 108 31 671 30
21 38 25 372 27
7 12 6 69 15
95 554 102 1911 49
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ples exhibiting the incineration pattern had elevated PCDD/F concentrations, and these were located within the boundaries of the MSWI. Fly-ash was once stored in heaps on the site and this could have been the source of some fugitive emissions. However, a further six samples inside the plant boundaries and seven samples further away from the plant exhibiting this pattern did not show elevated concentrations of PCDD/F. Ten samples exhibited the furan-dominated pattern, all of which occurred in the southern sectors. These were located in a cluster along the southern bank of the River Tyne. The historic land-use survey indicated that the very high concentrations of PCDD/F in soils to the SW and SE of the plant were most likely to be the result of graphite electrode sludges used in brine electrolysis at chemical works between the early 1890s and 1930s. Earth movement and relocation during landscaping in the early 1970s is likely to have contributed to re-distribution of contaminated soils. Nine samples exhibited the OCDD-dominated pattern. Eight of these came from the NW sector and they were located in a distinct cluster, which could be identified as the location of a culverted stream. 3.2. Comparison with other studies in the Newcastle area We compared the results of this study with two earlier studies in the Newcastle area (Pless-Mulloli et al., 2001b, 2002). Concentrations of soil PCDD/F in the previous investigations ranged between 5.5 and 1310 ng I-TEQ/ kg DW with a mean of 120 ng I-TEQ/kg DW and a median of 32 ng I-TEQ/kg DW. The second study included an investigation of soils from an allotment site adjacent to the Byker plant. The PCDD/F concentrations ranged between 18 and 1310 ng I-TEQ/kg DW, with a mean and median of 188 and 49 ng I-TEQ/kg DW, respectively (Pless-Mulloli et al., 2002). Concentrations reported in that investigation were generally greater than those in the current study. The sources of the contamination were similar to those in the current study: 11 out of 22 samples (50%) showed the deposition profile, 5 (23%) showed the incineration profile, 5 (23%) showed an OCDD profile and there was 1 unidentifiable profile (Pless-Mulloli et al., 2002). In the current study the proportions were deposition, 50%; incineration, 18%; OCDD, 10%. 3.3. Comparison with other studies in the vicinity of MSWIs The only other UK study of soil PCDD/F from MSWIs (Abbott et al., 1997) showed that the
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concentrations of PCDD/F were generally smaller than in those found in the present study with a range from 2 to 160 ng I-TEQ/kg DW. These smaller values probably reflect the fact that the MSWIs were located in a rural, rather than urban, environment. The conclusion from the large number of Spanish studies on the effects of MSWIs in urban environments (see for example, Schuhmacher and Domingo, 2006) was that they were not solely responsible for local soil PCDD/F contents. Oh et al. (2006) found that the soil PCDD/F concentrations decreased with distance from the MSWI. But they also reported that the homologue profiles in soil differed with location depending on the proximity of road traffic and construction sites. In other studies in which homologue profiles have been reported (for example, Domingo et al., 2002) attribution of the source has been more difficult. This reinforces the conclusion that in most cases, and particularly in urban areas, it is unlikely that the MSWI was the only source of PCDD/ F contamination. 4. Conclusions Because of the previous pollution of these soils, any effect of the MSWI has been largely masked. This study has therefore produced no evidence to suggest that fugitive and stack emissions made a significant contribution to soil contamination with PCDD/F outside the boundaries of the MSWI. However, there was evidence of elevated concentrations within the plant boundaries. Samples with elevated PCDD/F concentrations and/or distinctive homologue profiles located in clusters were linked to historic industrial land use dating back to approximately 1890s. While homologue profiles have been used by others previously, they have not been used to identify both contemporary and historic sources of contamination, as in this investigation. The identification of historic sources was aided by the use of historic land use information from maps of the locality. Acknowledgments We thank Terry Lisle of the University of Newcastle for her efficient organisation of the sampling campaign and for collating the sampling data, Michael Elund of Newcastle City Council for his contribution to selection of sites and the mapping of the results, and the Ergo Laboratory and Zoe Keatinge for the chemical analyses.
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Identifying contemporary and historic sources of soil polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in an industrial urban setting Catherine G. Vizard a,1 , David L. Rimmer b,⁎, Tanja Pless-Mulloli a , Ian Singleton c , Vivienne S. Air d a
School of Population and Health Sciences, William Leech Building, University of Newcastle, Newcastle upon Tyne NE2 4HH, UK School of Civil Engineering and Geosciences, Drummond Building, University of Newcastle, Newcastle upon Tyne NE1 7RU, UK School of Biology, Institute for Research on the Environment and Sustainability, University of Newcastle, Newcastle upon Tyne NE1 7RU, UK d Public Health and Environmental Protection, Newcastle City Council, Civic Centre, Newcastle upon Tyne NE1 8PR, UK b
c
Received 10 February 2006; received in revised form 1 June 2006; accepted 8 June 2006 Available online 17 July 2006
Abstract A study of soil polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F) concentrations was undertaken in the vicinity of a municipal solid waste incinerator (MSWI) in Newcastle upon Tyne as a result of concerns raised by local residents about potential contamination from fugitive and stack emissions. The study area was divided into four sectors (north-east (NE), south-east (SE), north-west (NW) and south-west (SW)) around the MSWI, and sampling sites were located up to a distance of 2.25 km. Based on air dispersion modelling, the sampling density was four times greater in the NE (downwind) sector compared to the SW (upwind) direction, and twice as great in the NW and SE sectors. PCDD/F concentrations found in soil samples ranged from 6 to 1911 ng I-TEQ/kg DW with a median of 32 ng I-TEQ/kg DW. There was no evidence of elevated concentrations downwind of the MSWI compared to other directions, nor of any trend in concentration at increasing distance from the MSWI. We concluded, therefore, that the MSWI fugitive and stack emissions were not a major source of PCDD/F contamination. Analysis of PCDD/F homologue profiles showed that samples exhibiting furan-dominated and OCDD-dominated profiles and a profile characteristic of the MSWI ash occurred in distinct clusters. Those samples showing the furan-dominated profile had the largest PCDD/F concentrations measured as I-TEQ, followed by samples with the incinerator profile, the deposition profile, and the OCDD-dominated profile. We identified some contamination hotspots located in the SW and SE sampling sectors (upwind of the MSWI), and potential sources for these hotspots were sought by using historic land use data from maps of the locality dating back to 1856. We concluded that the cluster of very high concentrations of PCDD/F in soils showing the furan homologue profile were most likely to have resulted from the disposal of graphite electrode sludges from brine electrolysis carried out at a chemical works between the 1890s and the 1930s. © 2006 Elsevier B.V. All rights reserved. Keywords: Urban environment; MSWI emissions; PCDD/F; Soils
⁎ Corresponding author. Tel.: +44 191 222 6916; fax: +44 191 222 5322. E-mail address: [email protected] (D.L. Rimmer). 1 Current address: Environment Agency West Area Office, Red Kite House, Howbery Park, Crowmarsh Gifford, Wallingford, Oxfordshire, OX10 8BD, UK. 0048-9697/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.scitotenv.2006.06.006
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1. Introduction Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F) are contaminants that are widespread in today's environment (Zook and Rappe, 1994). These compounds can be formed from any combustion process involving organic matter and chlorine compounds. PCDD/F contamination is particularly linked to atmospheric emissions from industrial processes. Evidence from sediment cores and archived samples suggests that inputs of PCDD/F to the environment probably peaked in the late 1960s/early 1970s (Duarte-Davidson et al., 1997). The subsequent reduction in emissions was due in part to the regulation of industrial processes and the introduction of abatement technology (Alcock and Jones, 1996). However, PCDD/F tend to persist and bioaccumulate in environmental compartments and their stable nature means that PCDD/F can remain in the soil for many decades (Duarte-Davidson et al., 1997). This means that in industrialized urban areas there can often be a cumulative build-up from historic and contemporary sources, resulting in concern for human health. Exposure to PCDD/F can lead to cancer and reproductive/developmental effects (Birnbaum and Farland, 2003). Alcock et al. (2001) undertook a congener-specific atmospheric emission inventory and found that primary regulated industrial sources could potentially account for between 30% and 86% of the total PCDD/F emitted into the atmosphere, and that unregulated non-industrial sources, such as road traffic, could account for the remainder. All of the possible 75 PCDD and 135 PCDF isomers and congeners can be produced from waste incinerators, independent of type of incinerator or waste composition (DCDEP, 1989). Variation in the amounts of PCDD/F can occur over time at any one incinerator and at different types of incinerator plant due to variations in temperature, feed, and trace elements, such as copper (DCDEP, 1989). PCDD/F can be found in residue streams, grate residues, wash waters, fly ash and chimney stack emissions (DCDEP, 1989). In recent years, a number of studies concerning PCDD/ F concentrations in soil samples collected near MSWIs have been carried out (see, for example, De Jong et al., 1993; Abbott et al., 1997; Pirard et al., 2005; Oh et al., 2006). Of particular interest are a series of investigations at MSWI sites in Spain reported by Schumacher, Domingo and co-workers (Domingo et al., 2000, 2001a,b, 2002; Nadal et al., 2002; Schuhmacher et al., 1997, 1998, 1999, 2000; Schuhmacher and Domingo, 2006). Analysis of homologue and congener profiles has been widely used to aid the identification of sources of PCDD/F contamination (Cleverly et al., 1997). In parti-
cular, homologue and congener profiles have been used to determine whether soil PCDD/F in the vicinity of MSWIs were mainly due to PCDD/F emissions from those plants (Domingo et al., 2001b). The Byker plant is located in Newcastle upon Tyne, UK. Between 1979 and 1998 it produced refuse-derived fuel (RDF), which was burnt in the adjacent waste-to-energy facility. Approximately one-third of the 100,000 tonnes of waste treated per year was incinerated. The abatement equipment at the Byker plant comprised a dry lime scrubber and a bag filter. Releases to air between 1993 and 1998 had a mean value of 0.118 g of PCCD/F per annum. There have been a number of site-specific studies of environmental PCDD/F concentrations in Newcastle related to the Byker MSWI (Pless-Mulloli et al., 2000, 2001a,b, 2004). In these studies a homologue profile typical of that found in MSWI ash was identified in the soil samples. The pattern was used to identify PCDD/F contamination arising from the ash itself or from fugitive and stack emissions. However, due to the presence of other emission sources, homologue profiles, which were unrelated to the MSWI, were also identified. Unlike the previous studies, which investigated contamination at specific sites, the aim of the present work was to carry out a systematic survey of PCDD/F soil contamination over a wide area that might have been affected by stack and fugitive emissions from the MSWI. In order to identify whether any PCDD/F soil contamination was from the MSWI or from other industrial or non-industrial sources, PCDD/F homologue profiles were also assessed. Identification of both current and historic sources was carried out by using maps of the locality dating back to 1856. 2. Materials and methods 2.1. Soil sampling The study area was divided into four sectors (NE, SE, NW, and SW) around the MSWI. The area was further divided into concentric distance bands of 50 m up to a distance of 750 m, and thereafter into bands of 250 m up to a distance of 2.25 km (Fig. 1). The predicted dispersion pattern obtained from modelling undertaken by Newcastle City Council showed that the direction of the plume would be predominantly to the NE of the MSWI. The sampling frame comprised three sites within each distance band in the NE sector, two within each band in the NW and SE sectors, and one within each band in the SW sector. All 163 sampling sites were in areas with public access (Rimmer et al., 2006).
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Fig. 1. Location of the 86 sampling sites.
The sampling sites were randomly generated using geostatistical software (S-Plus 6). If generated sites were located in areas without public access, or on buildings or roads, they were moved to the nearest area of public open space and denoted ‘judgmental’ sites. When visited, some locations were found to have poor access due to overgrown shrubs and undergrowth. Unsuitable for sampling, these sites were also relocated and denoted as ‘judgmental’. PCDD/F analyses were carried out on samples from 83 of the 163 sites, approximately 40% of which were random and 60% judgmental. These samples were selected systematically by taking every second sampling site. Subsequently a further three samples taken from the SW sector were also analyzed, giving a total of 86 samples. These additional samples were used because initial analyses showed that there was a hotspot of contamination in this sector. The sampling density in the sector was very low, so more information on the extent of the contamination could be obtained by analysing more of the existing samples. Soil cores were taken (5 cm diameter and 5 cm depth) within an area of 50 m by 50 m centred on each site. To give a composite sample for each site, soil cores were collected from two to eight points, depending on the proportion of public open space at each location, and the material from them was combined. Soil samples were
air-dried. Any plant material (roots, leaves) was removed manually and the soil sieved to < 2 mm. 2.2. PCDD/F analyses Analyses were undertaken by Ergo Laboratories, Hamburg, Germany. Quantitative determinations of PCDD/F according to the isotope dilution method were carried out by means of 2,3,7,8-PCDD/F substituted with 13C-ULlabelled internal standards. After spiking, samples were extracted with toluene. The clean-up was carried out on multicolumn systems involving a combination of neutral, acidic and basic silica, florisil, as well as carbon on celite. Determination was carried out using a combination of high resolution gas chromatography and high resolution mass spectrometry (HR-GC/MS: VG-AutoSpec/Finnigan MAT 95 XL) and DB5 and SP2331 capillary columns. For each substance, two isotope masses were recorded. The concentrations of the PCDD/F were reported in units of ng I-TEQ per kg of dry soil for the 17 toxic congeners and the 10 homologue groups. Furthermore the pattern of total homologues, as well as the pattern of toxic congeners, was taken into account. Numerous procedures can be used to derive a homologue or congener profile and there is no agreed convention (Cleverly et al., 1997). As a result we
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Table 1 PCDD/F concentrations (ng I-TEQ/kg DW) in soil samples for each sector Sector
n
Mean
Median
Min
Max
NE NW SE SW Overall
31 21 21 13 86
48 54 65 487 120
26 16 38 169 32
6 7 7 14 6
554 494 481 1911 1911
Environment Agency pollution inventory database was conducted to identify industries with a significant potential to pollute (‘Part A’ industries) within a 5mile radius of the MSWI. Information about industrial plants that pollute to a lesser extent (‘Part B’ industries) in the vicinity of the MSWI was obtained from the local authorities in Newcastle and Gateshead. 3. Results and discussion
have presented homologue profiles derived from the sum of all isomers within a group e.g. all tetra-CDD compared with all penta-, hexa-, hepta-, and octa-CDDs and CDFs. 2.3. Historic and current land use The GIS package Arcview 3.1 was used to view and reproduce ‘Landmark’ historic maps held by the local authorities in Newcastle and Gateshead. Maps were reproduced from Ordnance Survey Historical Data for the periods 1856 to 1895; 1895 to 1898; 1916 to 1920; 1932 to 1942; 1952 to 1963; and 1955 to 1984. Information about the history of specific industries or areas was obtained from the Central Library in Newcastle. Current land use was assessed by viewing and reproducing Ordnance Survey Landline Data and CRWorld Aerial Images. In addition, a search of the
3.1. Concentrations of PCDD/F and homologue profiles Over the whole study area the concentration of soil PCDD/F ranged between 6 and 1911 ng I-TEQ/kg DW with a mean of 120 ng I-TEQ/kg DW and a median of 32 ng I-TEQ/kg DW. Fifteen samples exceeded the normal range of PCDD/F concentrations in UK urban soils (i.e. were greater than 87 ng I-TEQ/kg DW (HMIP, 1995); more recent data on the concentrations in UK soils and herbage will be available soon from the UK Environment Agency). The mean, median and range of concentrations of PCDD/F in the NE, NW, SE and SW sectors are shown in Table 1. Elevated soil PCDD/F concentrations were expected in the north-east sampling sector as a result of deposition from fugitive and stack emissions from the MSWI. However, the north-east sector had the lowest mean concentration
Fig. 2. Soil PCDD/F concentrations (ng I-TEQ/kg DW) by distance band and sector.
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among the four sectors (Table 1). The distributions were skewed in all sectors by a small number of large values. PCDD/F concentrations in the majority of
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samples in the sectors NE, NW, and SE were of the same order of magnitude and showed similar levels of variation. However, in the SW sector, PCDD/F
Fig. 3. Typical homologue profiles: a) incinerator homologue profile; b) deposition homologue profile; c) furan-dominated homologue profile; and d) the OCDD homologue profile.
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concentrations greater than 1000 ng I-TEQ/kg DW were found in some hotspot locations. In order to assess the distribution within each sector, we plotted the concentrations as a function of distance (Fig. 2). This showed localised elevation of concentrations (>87 ng I-TEQ/kg DW) in four samples within 100 m of the MSWI stack in the NW and NE sectors. This was most likely to be the result of material blown from fly ash piles and skips
used on site. The concentrations greater than 1000 ng ITEQ/kg DW in the SW sector were located in the 500, 600, 700 and 1000 m distance bands. These occurred in a cluster along the banks of the River Tyne. In the SE sector elevated soil concentrations were found in the 500 m band. It had been anticipated that with increasing distance from the MSWI, there would be a decrease in soil PCDD/F concentrations. However, no such gradient was observed
Fig. 4. The distribution of homologue profiles: a) across the whole survey area, and b) within 250 m of the MSWI.
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outside the boundary of the plant (Fig. 2). Therefore there was little evidence to suggest that stack and fugitive emissions from the MSWI have had a measurable effect on the average soil contamination within its vicinity. This finding was reinforced by the homologue profiles, which were examined with the aim of identifying the sources of elevated PCDD/F concentrations detected in this study (Fig. 3). There was a profile typical of the waste combustion process at Byker plant, which had been identified in earlier studies (Pless-Mulloli et al., 2000, 2001a,b). It was similar to the incinerator profiles of Zook and Rappe (1994) and Brzuzy and Hites (1996). Sixteen (18%) of the 86 samples analysed were identified as having this ‘incinerator’ homologue profile. A second homologue profile was similar to the ‘deposition’ profile of Creaser et al. (1990) and represents a profile often found in environmental samples from urban environments. 43 samples (50%) were identified as exhibiting the deposition homologue profile. An OCDD-dominated profile is characteristic of profiles found in compost, sewage sludge or pentachlorophenol samples (Zook and Rappe, 1994). 10% of the 86 samples exhibited an OCDD-dominated pattern. A fourth homologue profile identified was dominated by PCDF homologues with low concentrations of PCDDs. An example of a similar homologue profile has been reported by Zook and Rappe (1994) who named it the ‘chlorine pattern’ attributable to electrode sludge waste. Ten samples (12%) exhibited this furandominated profile. Eight samples (10%) showed profiles which could not be attributed to one of the specific groups. These were most likely the result of a mixture of profiles. Sampling locations exhibiting the furan-dominated, OCDD and incinerator homologue profiles occurred in distinct clusters (Fig. 4). Samples with a deposition homologue profile occurred across the whole study area. Table 2 shows the extent of PCDD/F contamination for each homologue profile group. Samples showing the furan-dominated profile had the greatest PCDD/F concentrations (mean: 671 ng I-TEQ/kg DW), followed by samples with the incinerator profile (mean: 108 ng ITEQ/kg DW), and the deposition and OCDD profiles (means: 31 and 30 ng I-TEQ/kg DW). Three of the samTable 2 PCDD/F concentrations (ng I-TEQ/kg DW) in soil samples classified by homologue profile Profile
n
Mean
Median
Min
Max
OCDD Incinerator Deposition Furan-dominated Other
9 16 43 10 8
30 108 31 671 30
21 38 25 372 27
7 12 6 69 15
95 554 102 1911 49
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ples exhibiting the incineration pattern had elevated PCDD/F concentrations, and these were located within the boundaries of the MSWI. Fly-ash was once stored in heaps on the site and this could have been the source of some fugitive emissions. However, a further six samples inside the plant boundaries and seven samples further away from the plant exhibiting this pattern did not show elevated concentrations of PCDD/F. Ten samples exhibited the furan-dominated pattern, all of which occurred in the southern sectors. These were located in a cluster along the southern bank of the River Tyne. The historic land-use survey indicated that the very high concentrations of PCDD/F in soils to the SW and SE of the plant were most likely to be the result of graphite electrode sludges used in brine electrolysis at chemical works between the early 1890s and 1930s. Earth movement and relocation during landscaping in the early 1970s is likely to have contributed to re-distribution of contaminated soils. Nine samples exhibited the OCDD-dominated pattern. Eight of these came from the NW sector and they were located in a distinct cluster, which could be identified as the location of a culverted stream. 3.2. Comparison with other studies in the Newcastle area We compared the results of this study with two earlier studies in the Newcastle area (Pless-Mulloli et al., 2001b, 2002). Concentrations of soil PCDD/F in the previous investigations ranged between 5.5 and 1310 ng I-TEQ/ kg DW with a mean of 120 ng I-TEQ/kg DW and a median of 32 ng I-TEQ/kg DW. The second study included an investigation of soils from an allotment site adjacent to the Byker plant. The PCDD/F concentrations ranged between 18 and 1310 ng I-TEQ/kg DW, with a mean and median of 188 and 49 ng I-TEQ/kg DW, respectively (Pless-Mulloli et al., 2002). Concentrations reported in that investigation were generally greater than those in the current study. The sources of the contamination were similar to those in the current study: 11 out of 22 samples (50%) showed the deposition profile, 5 (23%) showed the incineration profile, 5 (23%) showed an OCDD profile and there was 1 unidentifiable profile (Pless-Mulloli et al., 2002). In the current study the proportions were deposition, 50%; incineration, 18%; OCDD, 10%. 3.3. Comparison with other studies in the vicinity of MSWIs The only other UK study of soil PCDD/F from MSWIs (Abbott et al., 1997) showed that the
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concentrations of PCDD/F were generally smaller than in those found in the present study with a range from 2 to 160 ng I-TEQ/kg DW. These smaller values probably reflect the fact that the MSWIs were located in a rural, rather than urban, environment. The conclusion from the large number of Spanish studies on the effects of MSWIs in urban environments (see for example, Schuhmacher and Domingo, 2006) was that they were not solely responsible for local soil PCDD/F contents. Oh et al. (2006) found that the soil PCDD/F concentrations decreased with distance from the MSWI. But they also reported that the homologue profiles in soil differed with location depending on the proximity of road traffic and construction sites. In other studies in which homologue profiles have been reported (for example, Domingo et al., 2002) attribution of the source has been more difficult. This reinforces the conclusion that in most cases, and particularly in urban areas, it is unlikely that the MSWI was the only source of PCDD/ F contamination. 4. Conclusions Because of the previous pollution of these soils, any effect of the MSWI has been largely masked. This study has therefore produced no evidence to suggest that fugitive and stack emissions made a significant contribution to soil contamination with PCDD/F outside the boundaries of the MSWI. However, there was evidence of elevated concentrations within the plant boundaries. Samples with elevated PCDD/F concentrations and/or distinctive homologue profiles located in clusters were linked to historic industrial land use dating back to approximately 1890s. While homologue profiles have been used by others previously, they have not been used to identify both contemporary and historic sources of contamination, as in this investigation. The identification of historic sources was aided by the use of historic land use information from maps of the locality. Acknowledgments We thank Terry Lisle of the University of Newcastle for her efficient organisation of the sampling campaign and for collating the sampling data, Michael Elund of Newcastle City Council for his contribution to selection of sites and the mapping of the results, and the Ergo Laboratory and Zoe Keatinge for the chemical analyses.
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