Environ. Sci. Technol. 2009, 43, 5205–5211
Electric Arc Furnaces for Steel-Making: Hot Spots for Persistent Organic Pollutants M U S T A F A O D A B A S I , * ,† ABDURRAHMAN BAYRAM,† TOLGA ELBIR,† REMZI SEYFIOGLU,† YETKIN DUMANOGLU,† AYSE BOZLAKER,† HULUSI DEMIRCIOGLU,† HASAN ALTIOK,† SINAN YATKIN,‡ AND BANU CETIN§ Department of Environmental Engineering, Faculty of Engineering, Dokuz Eylul University, Kaynaklar Campus, 35160 Buca, Izmir, Turkey, Department of Environmental Engineering, Faculty of Engineering, Namı´k Kemal University, Corlu, Tekirdag, Turkey, and Department of Environmental Engineering, Faculty of Engineering, Pamukkale University, Denizli, Turkey
Received March 23, 2009. Revised manuscript received June 1, 2009. Accepted June 1, 2009.
Persistent organic pollutant (POP) concentrations were measured in stack-gases of ferrous scrap processing steel plants with electric arc furnaces (EAFs) (n ) 5) in Aliaga, Izmir, Turkey and in air (n ) 11) at a site near those plants. Measured stack-gas concentrations for the four plants without scrap preheating (611 ( 311, 165 000 ( 285 000, and 33 ( 3 ng m-3, average ( SD for Σ41PCBs, Σ16PAHs, and Σ7PBDEs, respectively) indicated that they are significant sources for polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs). POP emissions from the plant with scrap preheating were significantly higher (13 500, 445 000, and 91 ng m-3 for Σ41PCBs, Σ16PAHs, and Σ7PBDEs, respectively). It was also shown that the steel plants emit considerable amounts of fugitive POPs in particle-phase. Estimated emissions using the emission factors generated in this study and the production amounts suggested that the steel plants with EAFs may significantly contribute to local and global PAH, PCB, and PBDE emissions. Several other compounds (aromatic and aliphatic hydrocarbons, oxygen, sulfur, nitrogen, and chlorine-containing organic compounds, n ) 49) were identified and determined semiquantitatively in the stack-gas and ambient air samples. Ambient air concentrations (62 ( 35, 320 ( 134 ng m-3, 1451 ( 954 pg m-3, for Σ41PCBs, Σ16PAHs, and Σ7PBDEs, respectively) were significantly higher than those measured previously around the world and in the region, further confirming that the steel plants with EAFs are “hot spots” for POPs.
Introduction A significant portion (32%) of the world’s steel requirement (1244 million tons year-1) is produced from ferrous scrap * Corresponding author phone: 90-232-4127122; fax: 90-2324127080; e-mail:
[email protected]. † Dokuz Eylul University. ‡ Namı´k Kemal University. § Pamukkale University. 10.1021/es900863s CCC: $40.75
Published on Web 06/12/2009
2009 American Chemical Society
metals by iron-steel plants with electric arc furnaces (EAFs) (1). The U.S. steel industry produced about 106 million tons of raw steel in 2006, and approximately 93 steel plants with EAFs accounted for 57% of the total U.S. steel production. The contribution of EAFs in steel production has increased dramatically over the past 30 years (from 10% in 1970 to 57% in 2006) (2). Iron-steel production is also an important industrial process in Turkey, where the present study was conducted. In Turkey, ∼23.3 million tons of steel was produced in 2006. Plants with EAFs accounted for 71% of this production (17.6 million tons year-1). Most of the ferrous scrap (75%) used in EAFs was imported (1). Emission generating operations during the EAF steelmaking are charging the scrap, melting and refining, removing slag, tapping steel, continuous casting, and ladle metallurgy processes. Emissions from EAFs are generally collected using direct shell evacuation supplemented with a canopy hood located above the EAF. In general, the captured emissions are routed to bag filters for particulate matter (PM) control (2, 3). The EAF processes produce particle and gas-phase pollutants. The amount and composition of the PM emitted can vary depending on the scrap composition and types and amounts of furnace additives. Iron and its oxides are the primary PM components. In addition, zinc, chromium, nickel, lead, cadmium, and other metals (and metal oxides) are also present in the PM. Gaseous pollutants, such as NOx, SO2, CO, HF, and HCl may also be emitted depending on the equipment, operating practices and the additional fuels used. Several organics like volatile organic compounds (VOCs), chlorobenzenes, and polychlorinated dibenzo-p-dioxins/ furans (PCDD/Fs) are also emitted. Other than these mostly regulated pollutants, EAFs emit persistent organic pollutants (POPs) like polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) (2-4). POPs covered in this study are emitted by different mechanisms. PAHs may be present in the scrap and are evaporated during production processes or they may form as a result of incomplete combustion of scrap organic matter, fuels, and additives like coal (3). PCBs are also present in the scrap (3). They may also form by de novo synthesis in thermal processes, similar to PCDD/Fs (3). Ferrous scrap contains impurities like plastic and foam that could contain significant amounts of PBDEs (4). PBDEs are emitted during the steel production process, during scrap charging (mostly in the particle-phase), scrap preheating, and at the beginning of the melting cycle (mostly in the gas-phase) (3, 4). All these POPs are semivolatile. They may be predominantly in the gas/particle-phases or distributed between two phases, depending on temperature and their physicochemical properties. Fugitive emissions of PM (and POPs contained in particles) may also be significant (5-8). The fraction of the EAF gases that could not be collected is emitted from the openings in the roof (2). Also scrap, slag, filter dust storage, transfer, and dumping operations may emit significant amounts of particle-phase POPs (3). Recent studies based on soil and ambient air sampling have shown that the ferrous scrap processing steel plants with EAFs in Aliaga industrial region in Turkey are important local sources for PAHs, PCBs, and PBDEs (5-8). However, there have been a limited number of studies in the literature on EAF source characterization and emission factor generation for PAHs and PCBs (3, 9, 10) while no studies exist for PBDEs. The objectives of this study were (1) the measurement of emissions and generating emission factors for PAHs, PCBs, VOL. 43, NO. 14, 2009 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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FIGURE 1. Map of the study area. Wind roses show the frequency (%) of prevailing wind directions. and PBDEs from ferrous scrap processing steel plants with EAFs and (2) measurement of ambient air levels of POPs near these industries in Aliaga industrial region in Turkey.
Materials and Methods Ambient Air and Stack-Gas Sampling. The study area is located at the Aliaga industrial region, ∼5 km south of the Aliaga city center and ∼45 km north of the metropolitan city of Izmir, Turkey. The area contains several pollutant sources including a large petroleum refinery and a petrochemical complex, scrap processing iron-steel plants with EAFs, scrap storage and classification sites, steel rolling mills, a natural gas-fired power plant, a very dense transportation activity of ferrous scrap trucks, heavy road and rail traffic, a ship dismantling area, and busy ports with scrap iron dockyards (Figure 1). Daily ambient air samples (n ) 11) were collected at a site near the iron-steel plants between April 26 and May 7, 2007. Meteorological data were obtained from a meteorological station located near the Horozgedigi village (Figure 1). Wind speed ranged between 1.4-4.8 m s-1 during the sampling program. The prevailing wind directions in the area are WNW and NW. There were both northerly and southerly winds during the sampling program. The location of the sampling site relative to the steel plants and these wind directions indicate that the sampling site is affected from the steel plant emissions. A sampling site located at SE of the present site would be preferable to better capture the emissions of all five steel-plants. However, an alternative secure sampling site with power supply was not available. As a result, the measured air concentrations may have been mainly affected from the three plants located at NW, WNW, and SW of the sampling site. The wind direction having the least possible influence is SE that was encountered only on one sampling day (Figure 1). Stack-gas samples were collected from the five scrap processing iron-steel plants with EAFs located near the air sampling site. Four of the stacks were sampled once whereas one stack was sampled twice (n ) 6). The production 5206
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capacities, stack-gas flow rates, and number of the electric arc furnaces of the plants range between 94 and 163 ton h-1, 640 000 and 1 227 000 Nm3 h-1 (at 1 atm and 273 K), and 1 and 2, respectively. Air samples were collected using a modified high-volume sampler model GPS-11 (Thermo-Andersen Inc.). Particlephase POPs were collected on 10.5 cm diameter quartz filters and the gas-phase compounds were collected in a modified cartridge containing XAD-2 resin placed between layers of polyurethane foam (PUF). Stack-gas samples were collected isokinetically using a sampling train consisting of a heated sampling probe, a filter cartridge, a condenser, a water-cooled resin (XAD-2) cartridge, a vacuum pump with flow controller, and a gas-meter (see Supporting Information (SI) Figure S1). Stack-gas particle-phase POPs were collected on glass-fiber thimble filters and the gas-phase compounds were collected in the XAD-2 resin cartridge. Average sampling duration was ∼24 h for ambient air while it was 2.5 h for stack-gases (covering at least three production cycles). The average sampling volumes (measured with an uncertainty < 3%) were 300 ( 40 m3 and 3.1 ( 0.8 m3 for ambient air and stack-gas samples, respectively. The average temperatures were 17 ( 3 °C (n ) 11) and 91 ( 7 °C (n ) 5) at ambient air and stack-gas samples, respectively. Sample Preparation and Analysis. Prior to extraction, all samples were spiked with PCB, PAH, and PBDE surrogate standards. Ambient air PUFs were Soxhlet extracted for 24 h with a mixture of 1:1 acetone:hexane. The remaining samples (ambient air filters, stack-gas thimble filters, and XAD-2 resin cartridges) were ultrasonically extracted for 60 min with acetone:hexane (1:1). For the stack samples, the sampling probe was rinsed with acetone:hexane (1:1) and the solution was combined with stack-filter extract (particle-phase). The sampling line between the filter and resin cartridge was also rinsed with acetone:hexane. The condensate from the condenser before the resin cartridge was liquid-liquid extracted with dichloromethane and hexane. The extracts from the sampling line and condensate were combined with the extract from the resin cartridge (gas-phase). The extract
volumes were reduced and were transferred into hexane using a rotary evaporator and a high purity N2 stream. After concentrating to 2 mL, samples were cleaned up and fractionated on an alumina-silicic acid column containing 3 g silicic acid (deactivated with 4.5% DI water) and 2 g alumina (deactivated with 6% DI water). The column was prewashed with 20 mL dichloromethane (DCM) followed by 20 mL petroleum ether (PE). Then, the sample in 2 mL hexane was added to the column and PCBs, PBDEs, and PCNs were eluted with 35 mL PE (Fraction 1) while PAHs and organochlorine pesticides (OCPs) were eluted with 20 mL DCM (Fraction 2). The final extracts were solvent exchanged into hexane and were concentrated to 1 mL under a stream of N2. All samples were analyzed with an Agilent 6890N gas chromatograph (GC) equipped with a mass selective detector (Agilent 5973 inert MSD). PAHs and PCBs were analyzed using electron impact ionization while negative chemical ionization (NCI) mode was used for PBDEs, PCNs, and OCPs. The capillary column used for PAHs and PCBs was HP5-ms (30 m, 0.25 mm, 0.25 µm) while a DB5-ms column (15 m, 0.25 mm, 0.1 µm) was used for PBDEs. Helium was the carrier gas and high purity methane was the reagent gas for NCI. Fraction 1 was analyzed for PCBs, PBDEs, and PCNs, Fraction 2 was analyzed for OCPs in selected ion monitoring mode (SIM). Then, equal volumes of Fraction 1 and 2 were combined and analyzed for PAHs since lighter PAHs are eluted partly with Fraction 1. In this case, the MSD was run in simultaneous scan and SIM modes. Compounds were identified based on their retention times, target and qualifier ions, and were quantified using the internal standard calibration procedure. Further details for sample preparation and instrumental analysis could be found elsewhere (5-8). Other than the compounds quantified using calibration standards, several organics were tentatively identified in the stack-gas and ambient air samples using mass spectral library searches. Concentrations of compounds having a match quality >90% were determined semiquantitatively using the average response factors calculated from the responses of the calibrated compounds (PAHs). The behavior of the tentatively identified compounds in the analytical system (GC-MS) and as a result their actual response factors may deviate from those of the calibrated compounds. Therefore, the concentrations determined by this approach are only semiquantitative (11). Average recoveries for the surrogate standards were 85 ( 14% (acenaphthene-d10), 100 ( 17% (phenanthrene-d10), 94 ( 16% (chrysene-d12), 95 ( 15% (perylene-d12), 93 ( 8% (PCB14), 95 ( 8% (PCB-65), 92 ( 11% (PCB-166), and 87 ( 23% (PBDE-77). Instrumental detection limits (IDL) were determined from linear extrapolation, based on the lowest standard in calibration curve and using the area of a peak having a signal/noise ratio of 3. For 1 µL injection, the quantifiable amounts were 0.15, 0.10, and 0.05-0.35 pg for PAHs, PCBs, and PBDEs, respectively. Blank PUF cartridges, air filters, thimble filters, and resin columns were also analyzed. The limit of detection of the method (LOD, ng) was defined as the mean blank mass plus three standard deviations (LOD ) mean blank value + 3SD). Instrumental detection limit was used for the compounds that were not detected in blanks. Average analyte amounts in blanks were generally 10 (PCB-128-PCB-209, benz[a]anthracene-benzo[g,h,i]perylene, PBDE-47-PBDE-209) to reach equilibrium between the air and atmospheric particles. Therefore, several POPs are not likely to reach equilibrium between the gas and particle-phases since there are relatively short distances between the sources and the VOL. 43, NO. 14, 2009 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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sampling site (Figure 1). Gas-phase fractions of several compounds were generally decreased significantly in ambient air relative to stack-gas with average (stack gas/ambient air) ratios of 1.4 ( 0.6 (average ( SD), 6.6 ( 7.9, and 12.3 ( 12.5 for PCBs, PAHs, and PBDEs, respectively (Figures 3A-C). One of the extreme examples for this observation is PBDE209 with a log KOA value of 15.3 calculated from its dimensionless Henry’s law constant (30) and octanol-water partition coefficient (31). Gas-phase percentages of PBDE209 ranged between 19-45 and 0.3-10% in stack-gases and in air, respectively. However, dynamic uptake model estimates that several months are required for this much of a decrease in gas-phase fraction of PBDE-209 to take place (21). This suggested that there may be a significant contribution to ambient particle-phase POPs by another mechanism other than gas-particle partitioning. Therefore, variations of average stack-gas/ambient air gas and particle-phase concentration ratios with KOA were investigated (see the SI Figure S2). Particle-phase stack-gas/ambient air concentration ratios decreased significantly with KOA (from 1407 to 40, 4090 to 13, and 747 to 8 for PCBs, PAHs, and PBDEs, respectively) indicating that ambient concentrations of compounds having high KOA values were enriched by sources other than stack-gases, while gas-phase concentration ratios did not show significant and systematic variations (see the SI Figure S2). During the sampling programs it was observed that scrap iron, slag, filter dust storage, transfer and dumping processes, and vehicular traffic (especially trucks) on paved and unpaved roads around the steel plants emit significant amounts of PM. Fugitive PM10 emissions from these sources were recently estimated by a detailed emission inventory (32). It was shown that the contributions of paved roads, unpaved roads, transfer/dumping operations, wind erosion from storage piles (slag, filter dust, and scrap), and EAFs to the total PM10 emissions were 77.3, 16.1, 0.7, 0.2, and 5.7%, respectively (32). Also there have been intermittent EAF emissions during fan or bag-filter malfunctioning. These results further suggest that there is a relationship between the fugitive particle-phase emissions and sudden decrease in gas-phase fractions of the compounds with log KOA > 10 from source to receptor. The presence of the fugitive emissions also suggests that the emission factors generated and the POP emissions calculated in the present study may be underestimated, especially for compounds with high KOA values. Recently, it was suggested that BDE-209 is transported in the environment primarily in particle-phase (33, 34). Also, in recent modeling efforts on the environmental fate of PBDEs (i.e., photochemical removal/conversion), atmospheric BDE209 was assumed to be particle bound 99.1-99.98 (35) and 99.999% (36). Gas-phase fraction of BDE-209 has a crucial importance since the photolysis rate is significantly (120 times) higher in this phase according to Schenker et al. (35), whereas no photolysis takes place on particles according to Raff and Hites (36). Although there have been several studies reporting atmospheric PBDE concentrations, the number of studies that included BDE-209 is relatively small. There are an increasing number of studies reporting appreciable gasphase BDE-209 fractions. Agrell et al. (37) have measured the BDE-209 mainly in gas-phase (>90%) at an urban site, whereas it was 100% in gas-phase at a rural site. The average proportion of BDE-209 in gas-phase was 30 ( 11% at four sites in Izmir, Turkey (21). Li et al. (23) have reported that on the average, 5% of BDE-209 was associated with gasphase at three sites in southeast China. The results of the present study are very important since it was shown for the first time that significant amounts of heavy congeners like BDE-209 could be emitted in the gas-phase, contrary to common assumption. However, it is not possible to determine the net influence of being emitted in the gas-phase for 5210
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the environmental fate of BDE-209. Modeling efforts taking into account the presence of emissions in the gas-phase, higher photolysis rates in this phase relative to particle-phase, and relatively slow gas-particle partitioning are required to better assess the environmental fate of PBDEs.
Acknowledgments We thank the steel plants (HABAS, CEBITAS, EGE CELIK, IZMIR DEMIR-CELIK, and SIDER) for their support during field sampling.
Supporting Information Available Steel production by electric arc furnaces, stack-gas concentrations (gas + particle) of PAHs, PCBs, and PBDEs (Table S1), PCB emission factors for steel plants (Table S2), PAH emission factors for steel plants (Table S3), PBDE emission factors for steel plants (Table S4), tentatively identified compounds in stack gases of steel plants and in ambient air (Table S5), semiquantitative stack-gas concentrations of various compounds measured in steel plants (Table S6), ambient air concentrations (gas + particle) of PAHs, PCBs, and PBDEs (Table S7), semi-quantitative ambient air concentrations (gas + particle) of various compounds (Table S8), stack-gas sampling train (Figure S1), variation of stackgas/ambient air gas and particle-phase concentration ratios with octanol-air partition coefficient (Figure S2). This material is available free of charge via the Internet at http:// pubs.acs.org.
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