Identification and characterization of the atmospheric emission of polychlorinated naphthalenes from electric arc furnaces

Electric arc furnaces (EAF) are well recognized as significant sources of dioxins. EAFs have also been speculated to be sources of polychlorinated naphthalenes (PCNs) due to the close correlation between dioxin and PCN formation. However, assessment on PCN emissions from EAFs has not been carried out. The primary aim of this preliminary study is to identify and characterize the atmospheric emission of PCNs from EAFs. In this preliminary study, stack gas samples from two typical EAFs with different scales (EAF-1, 160?t batch(-1); and EAF-2, 60?t batch(-1)) were collected by automatic isokinetic sampling technique, and PCN congeners in samples were analyzed by isotope dilution high-resolution gas chromatography combined with high-resolution mass spectrometry method. Emission concentrations of PCNs were 458 and 1,099?ng?m(-3) for EAF-1 and EAF-2, respectively. The emission factors of PCNs to air were 21.6 and 30.1?ng toxic equivalent t(-1) for EAF-1 and EAF-2, respectively, which suggested that EAF is an important source of PCN release. With regard to the characteristics of PCNs from EAFs, lower chlorinated homologues were dominant. The PCN congeners comprised of CN27/30, CN52/60, CN66/67, and CN73 were the most abundant congeners for tetra-, penta-, hexa-, and hepta-chlorinated homologues, respectively. EAFs were identified to be an important PCN source, and the obtained data are useful for developing a PCN inventory. The congener profiles of PCNs presented here might provide helpful information for identifying the specific sources of PCNs emitted from EAFs.     

Assessment of the temporal and spatial distribution of atmospheric PCNs and their air–soil exchange using passive air samplers in Shanghai,East China

A total of 47 passive air samples and 25 soil samples were collected to study the temporal trend, distribution, and air–soil exchange of polychlorinated naphthalenes (PCNs) in Shanghai, China. Atmospheric PCNs ranged from 3.44 to 44.1 pg/m³ (average of 21.9 pg/m³) in summer and 13.6 to 153 pg/m³ (average of 40.0 pg/m³) in winter. In the soil samples, PCN concentrations were 54.7–1382 pg/g dry weight (average of 319 pg/g). Tri-CNs and tetra-CNs were two dominant homolog groups in air samples, while di-CNs were also found at comparable proportions to tri-CNs and tetra-CNs in soil samples. Most air and soil samples from the industrial and urban areas showed higher PCN concentrations than those from suburban areas. However, some soil samples in urban centers presented higher PCN concentrations than industrial areas. Analysis of PCN sources indicated that both industrial thermal process and historical usage of commercial PCN mixtures contributed to the PCN burden in most areas. The fugacity fraction results indicated a strong tendency of volatilization for lighter PCNs (tri- to hexa-CNs) in both seasons, and air–soil deposition for octa-CNs. Moreover, air–soil exchange fluxes indicate that soil was an important source of atmospheric PCNs in some areas. The results of this study provide information for use in the evaluation of the potential impact and human health risk of PCNs around the study areas.

     

Persistent organic pollutants in Detroit River suspended sediments: polychlorinated dibenzo-p-dioxins and dibenzofurans,dioxin-like polychlorinated biphenyls and polychlorinated naphthalenes

Suspended sediments from the Detroit River were collected in 1999 and 2000 using sediment traps at sites ranging from western Lake Erie to southern Lake St. Clair and analyzed to determine the spatial distributions of contaminants including polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/PCDFs), dioxin-like PCBs (DLPCBs) and polychlorinated naphthalenes (PCNs). Concentrations of all three contaminant classes were clearly elevated at sites in the lower reaches of the river in the Trenton Channel. The potential influence of the Trenton Channel as a source of contamination to western Lake Erie was further evidenced by PCDD/PCDF homologue profiles, which indicated a contribution from chemical manufacturing in addition to the normal background combustion profile. Toxic equivalents (TEQs) for PCDDs/PCDFs generally exceeded those for DLPCBs; combined total TEQs in July 2000 for these two compound classes ranged from 2.30 pg/g in southern Lake St. Clair to 306 pg/g at a station just downstream of the outflow of Monguagon Creek in the Trenton Channel. The spatial distribution of PCN contamination was similar to that of PCDDs/PCDFs and DLPCBs, with the highest level of total PCNs (8200 ng/g) detected at a site in the Trenton Channel near Elizabeth Park; TEQs for PCNs in the Trenton Channel ranged from 73 to 3300 pg/g. The data indicate that PCNs represent a significant contribution to dioxin-like biological activity in Detroit River suspended sediments.     

Flux estimates and sedimentation of polychlorinated naphthalenes in the northern part of the Baltic Sea

The concentrations and fluxes of polychlorinated naphthalenes (PCNs) were measured in surface sediments, and settling particulate matter collected in sediment traps, at two coastal and two offshore sampling stations in the Gulf of Bothnia, northern Baltic Sea, Sweden. The PCN concentrations (of tetra- to hepta-chloro congeners) in the surface sediments ranged from 0.27 to 2.8 ng/g dry weight and were of the same order of magnitude as background concentrations reported previously in Europe. The PCN fluxes in the southern basin (0.93 and 0.86 microg/m2/year) of the Gulf of Bothnia were higher than those in the northern basin (0.58 and 0.49 microg/m2/year); they were also higher near the coast than in the open sea. These PCN fluxes are similar to the pre-industrial levels determined from lake sediments in northwest England. The PCN homologue distribution changed from a relatively even distribution in samples collected near the coast, to TeCNs dominating in the samples from the open sea. This indicates that higher chlorinated PCNs are deposited and retained in sediments to a higher degree near the coast. The total annual deposition of PCNs in sediments in the Gulf of Bothnia was estimated to be 91 kg/year.     

Thermal destruction of wastes containing polychlorinated naphthalenes in an industrial waste incinerator

A series of verification tests were carried out in order to confirm that polychlorinated naphthalenes (PCNs) contained in synthetic rubber products (Neoprene FB products) and aerosol adhesives, which were accidentally imported into Japan, could be thermally destroyed using an industrial waste incinerator. In the verification tests, Neoprene FB products containing PCNs at a concentration of 2800 mg/kg were added to industrial wastes at a ratio of 600 mg Neoprene FB product/kg-waste, and then incinerated at an average temperature of 985 °C. Total PCN concentrations were 14 ng/m³N in stack gas, 5.7 ng/g in bottom ash, 0.98 ng/g in boiler dust, and 1.2 ng/g in fly ash. Destruction efficiency (DE) and destruction removal efficiency (DRE) of congener No. 38/40, which is considered an input marker congener, were 99.9974 and 99.9995 %, respectively. The following dioxin concentrations were found: 0.11 ng-TEQ/m³N for the stack gas, 0.096 ng-TEQ/g for the bottom ash, 0.010 ng-TEQ/g for the boiler dust, and 0.072 ng-TEQ/g for the fly ash. Since the PCN levels in the PCN destruction test were even at slightly lower concentrations than in the baseline test without PCN addition, the detected PCNs are to a large degree unintentionally produced PCNs and does not mainly stem from input material. Also, the dioxin levels did not change. From these results, we confirmed that PCNs contained in Neoprene FB products and aerosol adhesives could be destroyed to a high degree by high-temperature incineration. Therefore, all recalled Neoprene FB products and aerosol adhesives containing PCNs were successfully treated under the same conditions as the verification tests.     

Polychlorinated naphthalenes in human adipose tissue from New York, USA

Polychlorinated naphthalenes (PCNs) are persistent, bioaccumulative, and toxic contaminants. Prior to this study, the occurrence of PCNs in human adipose tissues from the USA has not been analyzed. Here, we have measured concentrations of PCNs in human adipose tissue samples collected in New York City during 2003-2005. Concentrations of PCNs were in the range of 61-2500 pg/g lipid wt. in males and 21-910 pg/g lipid wt. in females. PCN congeners 52/60 (1,2,3,5,7/1,2,4,6,7) and 66/67 (1,2,3,4,6,7/1,2,3,5,6,7) were predominant, collectively accounting for 66% of the total PCN concentrations. Concentrations of PCNs in human adipose tissues were 2-3 orders of magnitude lower than the previously reported concentrations of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). Concentrations of PCNs were not correlated with PCB concentrations. The contribution of PCNs to dioxin-like toxic equivalents (TEQs) in human adipose tissues was estimated to be <1% of the polychlorinated dibenzo-p-dioxin/dibenzofuran (PCDD/F)-TEQs.     

Human exposure to polychlorinated naphthalenes through the consumption of edible marine species

The concentrations of polychlorinated naphthalenes (PCNs) were determined in samples of 14 edible marine species (sardine, tuna, anchovy, mackerel, swordfish, salmon, hake, red mullet, sole, cuttlefish, squid, clam, mussel and shrimp), which are widely consumed by the population of Catalonia, Spain. The daily intake of PCNs associated with this consumption was also determined. A total of 42 composite samples were analyzed by HRGC/HRMS. The highest PCN levels (ng/kg of fresh weight) were found in salmon (227) followed by mackerel (95) and red mullet (68), while the lowest levels of total PCNs corresponded to shrimp (4.9) and cuttlefish (2.7). With the exception of cephalopods and shellfish species, in which tetra-CN was the predominant homologue, penta-CN (60%) was the predominant contributor to total PCNs. For a standard male adult, PCN intake through the consumption of edible marine species was 1.53 ng/day. The highest contributions to this intake (ng/day) corresponded to salmon (0.41), sole (0.28) and tuna (0.24). Concerning health risks, species-specific TEFs such as those reported by WHO and NATO for PCDD/Fs and dioxin-like PCBs are not currently available for PCN congeners. Although in general terms the results of the present study do not seem to suggest specific risks derived from exposure to PCNs through fish and seafood consumption, to establish the contribution of individual PCN congeners to total TEQ is clearly necessary for the assessment of human health risks.     

Spatial and temporal trends of metals and arsenic in German freshwater compartments

Cadmium, lead, mercury, copper, nickel, zinc, and arsenic were analyzed in suspended particulate matter (SPM), zebra mussels, and bream sampled yearly under the program of the German Environmental Specimen Bank (ESB) in the rivers Rhine, Elbe, Danube, Saar, Mulde, and Saale and in Lake Belau. Temporal and spatial trends were analyzed, correlations between metal levels in different specimen types assessed, and sampling sites ranked according to their metal levels by calculating a Multi-Metal Index (MMI) for every specimen type and site. SPM: Highest metal loads were detected in Mulde, Saale, and Elbe right downstream of the Saale confluence. In the Elbe, metal loads in SPM were mostly highest in the upper and middle section of the river while in Rhine and Saar concentrations increased downstream. Temporal trends since 2005 were detected only at three sites. Zebra mussel: MMIs were highest in the tidal section of the Elbe and the lower Rhine and lowest in Lake Belau and the upper Danube. Different temporal trends were detected since the early 1990s depending on site and metal. Bream: As, Pb, Cu, and Hg were analyzed in muscle tissue and Pb, Cd, Cu, and Zn in liver. For both tissues, MMIs were highest in Mulde and Saale and the lower and middle Elbe. Since the early 1990s, Hg, Pb, and Cu decreased in bream muscle at many sites while As increased at 6 of the 17 sites. The findings indicate that Hg, Pb, and Cu have obviously decreased in many freshwater ecosystems in recent years, whereas As and Ni levels have increased at several sites. Metal levels and temporal trends mostly differed between the specimen types under investigation and only few correlations between specimen types were detected. This underlines the importance of including different components of an ecosystem when assessing its environmental quality.     

Correlation of polychlorinated naphthalenes with polychlorinated dibenzofurans formed from waste incineration

Isomer composition of polychlorinated naphthalenes (PCNs) was measured for municipal waste incinerator fly ash samples and for emission samples produced from soot and copper-deposit experiments conducted at the United States Environmental Protection Agency (US-EPA). Two types of PCN isomer patterns were identified. One pattern contained specific PCN isomers in which chlorine atoms are substituted as if the peri(alpha-) position were dechlorinated from the higher chlorinated PCNs one by one. In another pattern, the isomers had a tendency for the chlorine atoms to assume successive positions on the naphthalene ring, which may be caused by specifically oriented chlorination. Some of these isomers increased, together with several polychlorinated dibenzofuran (PCDF) and a few polychlorinated dibenzo-p-dioxin (PCDD) isomers. The ratios between some specific PCN, PCDF, and PCDD isomers measured for the fly ash samples agree with those obtained from the soot and copper-deposit experiments. The observations suggest that these isomers were formed possibly from de novo synthesis utilizing the carbon structure contained in soot under the catalytic effect of a copper compound. Typical isomers for PCNs and PCDFs produced from incineration emissions were identified.     

Chlorinated naphthalene formation from the oxidation of dichlorophenols

Polychlorinated naphthalenes (PCNs) formed along with dibenzo-p-dioxin and dibenzofuran products in the slow combustion of dichlorophenols (DCPs) at 600 degrees C were identified. Each DCP reactant produced a unique set of PCN products. Major PCN congeners observed in the experiments were consistent with products predicted from a mechanism involving an intermediate formed by ortho-ortho carbon coupling of phenoxy radicals; polychlorinated dibenzofurans (PCDFs) are formed from the same intermediate. Tautomerization of the intermediate and H2O elimination produces PCDFs; alternatively, CO elimination to form dihydrofulvalene and fusion produces naphthalenes. Only trace amounts of tetrachloronaphthalene congeners were formed, suggesting that the preferred PCN formation pathways from chlorinated phenols involve loss of chlorine. 3,4-DCP produced the largest yields of PCDF and PCN products with two or more chlorine substituents. 2,6-DCP did not produce tri- or tetra-chlorinated PCDF or PCN congeners. It did produce 1,8-DCN, however, which could not be explained.     

Relative importance of polychlorinated naphthalenes compared to dioxins, and polychlorinated biphenyls in human serum from Korea: Contribution to TEQs and potential sources

Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs) in human have been studied extensively; however, polychlorinated naphthalenes (PCNs) have been studied less widely. The mean concentrations of PCNs, PCDDs, PCDFs, and PCBs in 61 healthy human volunteers were 2170 pg/g lipid, 452 pg/g lipid, 116 pg/g lipid, and 120 ng/g lipid respectively, and the mean toxic equivalents (TEQs) contributed by PCNs, PCDDs, PCDFs, and PCBs were 5.88, 5.22, 5.48, and 5.33 pg/g lipid, respectively. PCNs contributed to 26.8% of the total TEQs. 1,2,3,7,8-PeCDD, 2,3,4,7,8-PeCDF, PCB126, and hepta-CN-73 accounted for >62% of the total TEQs in the human serum samples. The overall serum PCN homologue profiles of all subjects were dominated by tetra- and penta-CN homologues, and the most predominant individual congener was hepta-CN-73, which contributed 17.5% of the total serum PCN concentration. Enrichment of hepta-CN-73 in the human serum samples might be due to contributors from combustion sources.     

Polybrominated diphenyl ethers, polychlorinated naphthalenes and polycyclic musks in human fat from Italy: Comparison to polychlorinated biphenyls and organochlorine pesticides

Prior to this study, reports of occurrence of polycyclic musks and polychlorinated naphthalenes (PCNs) in human tissues from Italy were not available. In this study, concentrations of PCNs and polycyclic musks were determined in human adipose tissue from Italy collected during 2005-2006; for comparison, legacy organohalogen pollutants such as organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) were determined. ΣPCN concentrations ranged from 0.5 to 14 ng/g lipid wt (lw). Polycyclic musks such as HHCB and AHTN were found in 92% and 83% of the human samples, respectively. Concentrations of PBDEs in Italian adipose tissue ranged between 3.2 and 35.6 ng/g lw.     

Atmospheric emission of polychlorinated naphthalenes from iron ore sintering processes

Iron ore sintering processes constitute significant sources of dioxins, and studies have confirmed a close correlation between polychlorinated naphthalenes (PCNs) and dioxin formation. Thus, iron ore sintering processes are thought to be a potential source of PCNs, although intensive investigations on PCN emissions from sintering processes have not been carried out. Therefore, the aim of the present study was to qualify and quantify PCN emissions from nine sintering plants operating on different industrial scales. PCN concentrations ranged from 3 to 983 ng m⁻³ (0.4-23.3 pg TEQ_PCN m⁻³) and emission factors ranged from 14 to 1749 μg t⁻¹ (0.5-41.5 ng TEQ_PCN t⁻¹), with a geometric mean of 84 μg t⁻¹ (2.1 ng TEQ_PCN t⁻¹). The estimated annual emission of PCNs from sintering processes in China was 1390 mg TEQ_PCN. These figures will assist in the development of a PCN emissions inventory. Regarding emission characteristics, PCNs mainly comprised low-chlorinated homologs. The ratios of several characteristic PCN congeners were also measured and compared with those from other sources. Taken together, these results may provide useful information for identifying the sources of PCNs produced by iron ore sintering processes.     

Geochemical and isotopic constraints on groundwater-surface water interactions in a highly anthropized site. The Wolfen/Bitterfeld megasite (Mulde subcatchment, Germany)

The Bitterfeld/Wolfen region is a megasite with multiple contaminant sources from more than a century of industrial activity, which have a considerable impact on the environment. At present, the contaminated groundwater covers an area of about 25km(2) and poses a threat for the surrounding aquifers and the Mulde River. This study focuses on the Schachtgraben, a man-made channel in the Mulde Floodplain that collects the effluents of the industrial area. It aims to characterise the relationship between surface water (channels, rivers) and the groundwater in the shallow Quaternary aquifer. Waters are Ca-SO(4) type with TDS reaching 3.8gL(-1) in the industrial area. Stable isotopes (delta(18)O, delta(2)H) show that two of the rivers are recharged mainly by groundwater that can be divided into two groups. Strontium isotopes ((87)Sr/(86)Sr) designate different geochemical end-members and enable the identification of mixing between natural and anthropogenic surface and groundwater.     

Polychlorinated naphthalenes: an environmental update

Polychlorinated naphthalenes (PCNs; CNs) form a complex mixture of up to 75 congeners containing from one to eight chlorine atoms per naphthalene molecule. Chloronaphthalenes are widespread global environmental pollutants which accumulate in biota. All chloronaphthalenes are planar compounds and can contribute to the aryl hydrocarbon (Ah) receptor-mediated mechanism of toxicity with a combination of various 2,3,7,8-tetrachlorodibenzo-p-dioxin like toxic responses. There are three known main sources of environmental pollution with PCNs: technical PCN formulations, technical polychlorinated biphenyl formulations, and thermal and other processes in the presence of chlorine. The purpose of this paper is to briefly review the most recent data on environmental pollution, chemistry, analysis, sources, formation, persistence, toxicity and behavior of PCNs.     

Interlaboratory study for the polychlorinated naphthalenes (PCNs): phase 1 results

An interlaboratory study was initiated to investigate consistency in reported concentrations of polychlorinated naphthalenes (PCNs). Results are reported from the first phase of a study that examined the variability associated with different quantification methodologies, instrumentation and standards. Nine participating labs from seven countries quantified individual homolog groups, summation operator PCN (the sum of 2-8 chlorinated homologs), and selected congeners in two test solutions derived from Halowax 1014. The means of the reported summation operator PCN values were within less than 15% of the known concentrations of the two test solutions and the relative standard deviation among laboratories was 11%. However, the among laboratory variability was in the range 20-40% for individual PCN homologs and individual PCN congeners. These results suggest the need for additional interlaboratory studies and for the development of reference materials for PCN analysis. Future PCN interlaboratory comparison exercises are discussed that will utilize control materials and unknowns consisting of suitable environmental matrices.     

Polychlorinated naphthalenes and coplanar polychlorinated biphenyls in tissues of harbor seals (Phoca vitulina) from the northern Gulf of Alaska

Blubber, liver and kidney samples of harbor seals (Phoca vitulina) from the northern Gulf of Alaska were collected during 2000-2001 for the analysis of polychlorinated naphthalenes (PCNs) and coplanar polychlorinated biphenyls (CoplPCBs). On the lipid weight (lw) base, the total concentrations of PCNs (Sigma PCNs) ranged from 0.3 to 27 ng/g lw, and the total concentrations of CoplPCBs (Sigma CoplPCBs) were 3.6-546 ng/g lw in all the tissue samples. Di-ortho PCBs and mono-ortho PCBs were dominant followed by non-ortho PCBs and PCNs. Sigma Mono-ortho PCBs and Sigma di-ortho PCBs in nursing seals were apparently lower than those in male adult seals, but Sigma PCNs and Sigma non-ortho PCBs in female adults were not significantly different from those in male adults. Differences in PCNs and CoplPCBs congener profiles in female and male adult seals are apparently related to their chemical structure and properties, animal's developmental stages and physiological conditions. A large quantity of mono-ortho and di-ortho PCBs might be transferred to newborns from the nursing seals during lactation, while non-ortho PCBs and PCNs were relatively accumulative in the mother seals. Sigma PCNs and Sigma CoplPCBs in the harbor seals correlated with ages, gender, body weight and blubber thickness, but the blubber Sigma PCNs and Sigma CoplPCBs in Kodiak Island and Southern Alaska Peninsula (KIAP) did not significantly differ from those in Prince William Sound (PWS). In addition to the new PCB data, this first report on PCN contamination in Alaskan harbor seal tissues is useful for the wildlife and ecosystem management and human health protection.     

Air concentrations of PCDD/Fs, PCBs and PCNs using active and passive air samplers

The concentrations of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs), polychlorinated biphenyls (PCBs) and polychlorinated naphthalenes (PCNs) were determined in air samples collected at four sampling sites located in two zones of Barcelona (Spain): near a municipal solid waste incinerator (MSWI) and a combined cycle power plant (3 sites), and at a background/control site. Samples were collected using high-volume active samplers. Moreover, 4 PUF passive samplers were deployed at the same sampling points during three months. For PCDD/Fs, total WHO-TEQ values were 27.3 and 10.9 fg WHO-TEQm(-3) at the urban/industrial and the background sites, respectively. The sum of 7 PCB congeners and the Sigma PCN levels were also higher at the industrial site than at the background site. In order to compare active and passive sampling, the accumulated amounts of PCDD/Fs, PCBs and PCNs in the four passive air samplers, as well as the total toxic equivalents in each sampling site were also determined. To assess the use of PUF passive samplers as a complementary tool for PCDD/F, PCB and PCN monitoring, sampling rates were calculated in accordance with the theory of passive air samplers. PUF disks allowed establishing differences among zones for the POP levels, showing that they can be a suitable method to determine POP concentrations in air in areas with various potential emission sources. Although both particle and gas phase were sorbed by the PUFs, data of gas phase congeners are more reproducible.     

Occurrence of polychlorinated naphthalenes, polychlorinated biphenyls and short-chain chlorinated paraffins in marine sediments from Barcelona (Spain)

Polychlorinated naphthalenes (PCNs), short-chain chlorinated paraffins (SCCPs) and polychlorinated biphenyls (PCBs) were analysed in marine sediment samples collected from the coastal area of Barcelona (Spain) and near of a submarine emissary coming from a waste water treatment plant located at the mouth of the Besòs River (Barcelona). An integrated sample treatment based on Soxhlet extraction followed by a simple clean-up with Florisil and graphitized carbon cartridge was employed. Gas chromatography coupled to ion-trap tandem mass spectrometry (GC-MS/MS) and gas chromatography-mass spectrometry in electron capture negative ionization mode, were used for PCN and SCCP determinations, respectively, while for PCB analysis gas chromatography with electron capture detection (GC-ECD) was used. The method developed provided low limits of detection (0.001-0.003 ng g(-1) dry weight (dw) for PCNs, 1.8 ng g(-1) for SCCPs and 0.006-0.014 ng g(-1)dw for PCBs) and good run-to-run precisions (lower than RSD 8%) for the analysis of sediment samples. Concentration levels ranging from 0.17 to 3.27 ng g(-1)dw for PCNs, between 0.21 and 1.17 microg g(-1)dw for SCCPs, and from 2.33 to 44.00 ng g(-1) (dw) for PCBs, were found in the coastal sediments, while for samples collected near to the submarine emissary higher levels (from 2.02 to 6.56 ng g(-1)dw for PCNs, between 1.25 and 2.09 microg g(-1)dw for SCCPs and from 22.34 to 37.74 ng g(-1)dw for PCBs) were obtained. The results obtained provide new data about the occurrence of PCN and SCCP in the coastal area of Barcelona.     

Occurrence,profile and possible sources of PCNs in Hong Kong soils,and a comparison with PCBs,PCDDs and PCDFs

Polychlorinated naphthalenes (PCNs) have been proposed for inclusion in the annexes of the Stockholm Convention by the European Union, signifying a probable increase in monitoring PCN levels at a global level. Investigations on PCN levels in the environment of Hong Kong have not been reported. In this preliminary investigation, PCN levels in surface soils samples were determined by isotope dilution HRGC/HRMS techniques, and compared with those of polychlorinated biphenyl (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). The concentrations of PCNs in the soil samples were 35–883 pg g^?1 (average, 201; and median, 94 pg g^?1), which were lower than those of PCBs PCDDs and PCDFs. This comparison suggested that PCNs are currently not priority POPs compared with dioxins and PCBs in Hong Kong soils. PCDDs were the most important contributor to the sum of toxic equivalents of PCNs, PCBs, PCDDs and PCDFs. OCDD was the most dominant dioxin congener in Hong Kong surface soils. PCB-118 was the most abundant in 12 dl-PCB congeners. PCN congeners indicating thermal related sources (CN52/60, CN66/67 and CN73) were relatively abundant in their respective homologs, which suggested PCN contamination from thermal sources. The ratio of CN73 to CN74 in soil samples suggested the contribution of PCN contaminations in soils from both thermal-related sources and evaporative emissions of technical PCN mixtures.