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Polycyclic aromatic hydrocarbon emissions from joss paper furnaces
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Atmospheric Environment 39 (2005) 3305–3312 www.elsevier.com/locate/atmosenv
Polycyclic aromatic hydrocarbon emissions from joss paper furnaces Hsi-Hsien Yanga,, Ray-Chen Junga, Ya-Fen Wangb, Lien-Te Hsiehc a
Department of Environmental Engineering and Management, Chaoyang University of Technology, Wufong, Taichung 41349, Taiwan b Bioenvironmental Engineering of Chung Yuan Christian University, 22, Pu-Jen, Pu-Chung Li, Chung-Li, 320, Taiwan c Department of Environmental Engineering and Science, National Ping Tung University of Science and Technology, Nei Pu 91207, Ping Tung, Taiwan Received 27 October 2004; received in revised form 17 January 2005; accepted 26 January 2005
Abstract The emissions of polycyclic aromatic hydrocarbons (PAHs) were quantified for two joss paper furnaces burning two kinds of joss papers (recycled paper made and virgin bamboo made). A cyclone and a wet scrubber were installed in series on one of the two furnaces. Particulate and gaseous PAHs were collected with a sampling system meeting the criteria of U.S. EPA Modified Method 5. Twenty-one species of PAH were analyzed by GC/MS. Individual PAH emission factors vary from less than 1 mg kg1 fuel to several tens of mg kg1 fuel. The total (sum of 21 compounds) and the carcinogenic PAH (benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indeno[1,2,3,-cd]pyrene, dibenz[a,h]anthracene) emission factors were not statistically different for the two furnaces and averaged 71.0 and 3.2 mg kg1, respectively. The PAH profiles showed a predominance of naphthalene (58.1%), phenanthrene (11.7%) and fluorene (7.5%). Of the two joss papers examined, bamboo-made joss paper showed less emission in both particulate and gaseous PAHs. For particulate and gaseous PAHs, the removal efficiencies of total PAHs by the air pollution control devices were 42.5% and 11.7%, respectively. PAH emission factors in high airflow conditions were generally lower than those in low airflow condition. r 2005 Elsevier Ltd. All rights reserved. Keywords: Joss paper; Emission profile; Characteristic ratio; Emission factor; Carcinogen
1. Introduction Buddhism and Taoism are the two most popular religions for Chinese and some countries in Asia. Joss paper and incense burning is an important ceremonial practice for deity worshipping in these religions. The devotees observe this ritual on the first and the fifteenth day of a Chinese lunar month (The new moon and full Corresponding author. Tel.: +886 4 2332 3000x4451; fax: +886 4 2374 2365. E-mail address: [email protected] (H.-H. Yang).
moon are set as the first day and the fifteenth day of each month, which lasts as long as the time required for the moon to complete a revolution around the earth). The other important festival days are Zhong Yuan Jie—A festival on the seventh full moon in a lunar year, known as the commemoration of the dead. The pilgrims go to the temples for the commemoration of the dead on this day and Qing Ming Jie—The Chinese grave sweeping day. People sweep their ancestor’s graves at this day, and the birthdays of the deities. Chinese immigrants and oriental religious believers are also performing this ritual in western countries. It has been shown that incense
1352-2310/$ - see front matter r 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2005.01.052
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burning is a significant source of particulate matters, metal elements (Lau and Luk, 2001; Fang et al., 2003) and polycyclic aromatic hydrocarbons (PAHs) (Lin et al., 2002; Lung and Hu, 2003) in ambient air. In temples, joss papers are burned in furnaces. Modern combustors have tall stacks, scientificallydesigned combustion chambers and high-efficiency flue gas cleaning systems that minimize the impact of emissions. In contract, emissions from joss paper furnaces are released at low elevation, without the benefit of atmospheric dispersion to dilute pollutants. In addition, the low combustion temperature and locally oxygen-starved conditions associated with joss paper burning almost always result in incomplete combustion and increase pollutant emissions. Among the formed air pollutants are polycyclic aromatic compounds, including, as a subgroup, PAHs which have only carbon and hydrogen in their molecular structure. Some PAHs are potential mutagenic and carcinogenic to man (International Agency for Research on Cancer (IARC), 1987). Many human activities, e.g., vehicles driving, residential heating, industrial processes and waste incineration, result in the formation of PAHs. Most temples are located in urban areas with high population density. It is not only an academic curiosity but also a practical importance to estimate PAH exposure levels from joss paper burning for management consideration. PAH profiles have been used to identify vehicular emissions following the use of unleaded gasoline in many countries that deprives lead as a vehicular source marker (Li and Kamens, 1993; Khalili et al., 1995). PAH profiles were also performed as reliably as inorganic compound profiles in PAH source apportionment studies (Harrison et al., 1996). Air pollutant emission from joss paper burning has never been investigated. Many studies have characterized PAH emission from different biomass burning in particulate and gaseous
phases (Oanh et al., 1999; Korenaga et al., 2001; Gullett et al., 2003; Zou et al., 2003). The studies have shown that PAH emissions are closely related to fuel types, burning conditions and the type of appliance. The main purposes of this study were to determine the emissions from two kinds of commonly-used joss papers and to investigate the profiles of the PAHs. The study provides useful information for public awareness concerning PAH emission from joss paper burning.
2. Experimental section 2.1. Preparation of joss papers There are over 10 kinds of joss papers in Taiwan, each with a name and denomination of value. They are different in shape and size, and are used for different worshipping purposes. Generally, three to four kinds of joss papers were combined for a particular worshipping. Tian Gong Jin, Si Fang Jin, Da Fu Jin and Shou Jin, the most commonly used joss papers for worshipping, were selected for testing in this study. Recycled paper and bamboo are the major building materials for joss papers. The compositions of the joss papers were listed in Table 1. It is observed that the carbon and the heating value were higher for the bamboo-made joss paper. 2.2. Description of the furnaces and operating conditions Two joss paper furnaces (denoted as Furnaces 1 and 2), located beside two temples, were selected in this study. The furnaces were both octagonal with height 6.0 and 5.0 m, and the areas of the joss paper feeding aperture were 0.40 and 0.35 m2 for Furnaces 1 and 2. Furnace 1 was equipped with air pollution control devices including a cyclone and a wet scrubber (Fig. 1),
Table 1 Composition of joss paper ðn ¼ 3Þ Analytical method Proximate analysis (%) Moisture Ash Combustible content Ultimate analysis (%) Carbon Hydrocarbon Oxygen Nitrogen Sulfur Chlorine Higher heating value (Dry basis, kcal kg1) N.D.: Not detectable.
Bamboo-made
Recycled-paper-made
ASTM E 955 ASTM E 955 ASTM E 955
6.9 2.8 90.3
6.9 6.8 86.3
Elemental Elemental Elemental Elemental Elemental Elemental
43.0 4.83 46.8 0.08 0.58 0.08
40.6 5.60 46.7 0.11 N.D. 0.02
analyzer analyzer analyzer analyzer analyzer analyzer
Calorimeter
3718
2905
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Sampling position
Wet scrubber
Sampling position
Cyclone
Fig. 1. Schema of Furnace 1.
but Furnace 2 was not. Both temples are typical Buddhist–Taoist combined temples, located in central Taiwan. The sampling campaigns were conducted on the non-festival days during January 2004 and April 2004. One of the purposes of this study is to compare PAH emission of recycled-paper-made joss paper with that of bamboo-made joss paper burning. If there were many pilgrims (usually on the festival days), both recycledpaper-made joss paper and bamboo-made joss paper might be fed into the furnace. On the non-festival days, we fed in the most joss papers into the furnace. Thus, the bamboo-made and recycled-paper-made joss papers can be burned and tested separately. The burning of joss paper was conducted with natural air supply through an opening inlet of the furnace. The joss paper was fed into the furnace steadily. The feeding rate was about 1 kg min1. The weights of joss papers burned were recorded for the calculation of PAH emission factors. Recycled-paper-made joss papers were burned in both Furnaces 1 and 2. For Furnace 1, PAHs were measured before and after air pollution control devices. In order to investigate PAH emission from different joss papers, bamboo-made joss papers were also burned in Furnace 2. 2.3. PAH sampling system for flue gas The samples were taken by a PAH sampling system (Anderson-Graseby Auto5) modified by Li-Teh Co., Taiwan, in accordance with the U.S. EPA Modified Method 5 (40CFR60). This system has been adopted for PAH sampling in many studies (Oanh et al., 1999; Lee et al., 2002; Yang et al., 2002). Sampling at the same velocity as that of the gas in the stack is known as isokinetic sampling, which guarantees that the concentration of the particulate entering the sampling probe is
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the same as that in the stack. All samples were collected within the acceptable sampling range of 90–110% of isokinetically. Starting at the stack, the PAH sampling system constituted in sequence a sampling probe, a filter, a cooling device, three glass cartridges, a pump, a flow meter and a control computer. Tube-type glass fiber filter (cleaned by heating to 450 1C) was to collect particulate and particulate PAHs. The glass cartridge packed with XAD-16 resin and supported by a polyurethane foam (PUF) plug was to collect the gaseous PAHs. After each sampling cycle the sampling train was rinsed with n-hexane. Three breakthrough tests were investigated by three stages of XAD-16/PUF cartridge. Each stage of cartridge was analyzed individually and compared for the PAH mass collected. Breakthrough tests showed that there were no discernable PAH collected in the third stage cartridge. PAH sampling is described in detail elsewhere (Yang et al., 2002). 2.4. PAH analysis PAH-containing filters and cartridges were Soxhlet extracted with a mixed solvent (n-hexane and dichloromethane, v : v ¼ 1 : 1) for 24 h. The extract was then concentrated by purging with ultra-pure nitrogen to 2 ml for the cleanup procedure. The cleanup procedure removes pollutants which would coelute with PAHs from the GC column. The cleanup column contained some glass wool in the bottom (I.D. ¼ 1 cm). Seventeen grams of 6% deactivated silica gel was mixed with 60 ml n-hexane, loaded into the cleanup column, and topped with 1.5 cm of anhydrous sodium sulfate. Next, 60 ml of hexane was added to wash the sodium sulfate and the silica gel. Right before the sodium sulfate layer was exposed to the air, the elution of hexane is stopped and the eluant is discarded. The concentrated sample was then transferred onto the column, the wall of vessel had been rinsed twice with 2 ml hexane which was also added to the column. Next, 200 ml of 6% ethylether in hexane was added to the column and allowed to flow through the column at a rate of 3–5 ml min1, and the eluant was collected. The collected eluant from the cleanup procedure was reconcentrated to 0.5 ml with nitrogen. A gas chromatograph (GC), Agilent 6890, with an Agilent capillary column (Agilent Ultra 2–50 m 0.32 mm 0.17 mm), a mass selective (MS) detector (Agilent 5973) and a computer workstation were used for the PAH analysis. The masses of molecular and fragment ions of PAHs were determined by using the scan mode for pure PAH standards. Qualification of PAHs was performed by using the selected ion monitoring (SIM) mode (Yang and Chen, 2004). The concentrations of the following PAHs were determined: naphthalene (Nap), acenaphthylene (AcPy), acenaphthene (Acp), fluorene (Flu), phenanthrene (PA),
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anthracene (Ant), fluoranthene (FL), pyrene (Pyr), cyclopenta[c,d]pyrene (CYC), benz[a]anthracene (BaA), chrysene (CHR), benzo[b]fluoranthene (BbF), benzo[k]fluoranthene (BkF), benzo[e]pyrene (BeP), benzo[a]pyrene (BaP), perylene (PER), indeno[1,2,3,-cd]pyrene (IND), dibenz[a,h]anthracene (DBA), benzo[b]chrysene (BbC), benzo[ghi]perylene (BghiP), and coronene (COR). Analysis of serial dilutions of PAH standards showed the method detection limit (MDL) between 0.001 and 0.072 mg ml1. The minimum quantitative limits (MQLs) are between 0.005 and 0.024 mg ml1. All the concentrations of the PAHs analyzed were higher than MQLs. PAH recovery efficiencies were determined by processing a solution containing known PAH concentrations following the same experimental procedure used for the samples. This study showed that the recovery efficiency of PAHs varied between 72% and 113% and averaged 84%. Blank tests for PAHs were accomplished by performing the same procedure as the recovery efficiency tests without adding the standard solution before extraction. Analyses of field blanks including filters and PUF/XAD-16 cartridges found no discernable contamination (GC/MS integrated area was less than detection limit).
3. Results and discussions 3.1. PAH emission levels Median values and standard deviations of particulate+gaseous PAH emission factors on a fuel-weight basis (dry basis, mg kg1) from Furnace 1 before air pollution control devices (not in effect) and Furnace 2 using recycled-paper-made joss paper were listed in Table 2. Individual PAH emission factors vary from lower than 1 mg kg1 fuel to several tens of mg kg1 fuel levels, with Nap predominating. Total PAH (sum of 21 PAHs) emission factor of Furnace 2 (74.6 mg kg1) is slightly higher than that of Furnace 1 (67.3 mg kg1). But the differences are not statistically significant (t-test, po0:05). If considering only the carcinogenic PAHs (BaA, CHR, BbF, BkF, BaP, IND, DBA), the emission factors are 3.0 and 3.4 mg kg1 for Furnaces 1 and 2, respectively. The differences are also not statistically significant (t-test, po0:05). Incense burning is also an important ceremonial practice for deity worshipping. Lung and Hu (2003) found that the emission factors of 13 particulate PAHs (Acp, PA, Ant, FL, Pyr, CYC, BaA, CHR, BbF, BkF, BeP, BaP, PER, IND, DBA, BbC, BghiP, and COR) were 17.1 and 28.3 mg kg1 for two kinds of incense sticks. Some PAH emission factors for other similar biofuel (or bio-mass) burning in recent years were listed in Table 3. For most PAHs, the emission factors of joss paper burning were slightly lower than that of wood
Table 2 Emission factors of total (gaseous+particulate phase) PAHs for recycled-paper-made joss paper from Furnaces 1 before air pollution control devices and Furnace 2 (mg kg1) Furnace
Furnace 1
PAHs
Median
Nap AcPy Acp Flu PA Ant FL Pyr CYC BaA CHR BbF BkF BeP BaP PER IND DBA BbC BghiP COR
37.3 4.00 1.75 4.33 7.67 0.25 1.06 0.40 0.83 0.01 0.34 1.48 0.25 1.26 0.23 0.80 0.46 0.25 0.70 0.21 2.25
Total
67.3
Furnace 2 Standard deviation 7.66 1.39 0.39 1.14 1.46 0.16 0.39 0.21 0.24 0.01 0.27 1.07 0.37 1.03 0.23 0.61 0.30 0.30 0.56 0.13 0.56 17.6
Median
Standard deviation
45.1 2.43 1.80 6.11 8.51 0.31 0.54 0.29 0.25 0.07 0.59 1.36 0.35 1.05 0.34 0.69 0.36 0.31 1.22 0.28 1.51
19.0 0.39 0.18 1.70 2.91 0.15 0.32 0.10 0.16 0.01 0.21 0.39 0.11 0.19 0.11 0.35 0.24 0.15 0.41 0.10 1.09
74.6
19.4
combustion and much lower than that of open burning of agricultural debris (Oanh et al., 1999; Mcdonald et al., 2000; Kakareka and Kukharchyk, 2003). Considering the carcinogenic PAHs, the emission factor of wood combustion reported by Oanh et al. (1999) was 5.11 mg kg1, which was 1.5 times higher than that of joss paper burning. For the emission of PAHs is a function of fuel, stove and burning parameters, which are different in different studies, thus the comparison of the emission factors with literature values listed in Table 3 is ordinal at best. 3.2. Profiles and characteristic ratios of PAH emissions Since joss paper burning is potentially an important emission source of PAHs, it is useful to build up PAH emission profile and characteristic ratios for source apportion analysis. Individual PAH emission factors (particulate+gaseous) were normalized by the sum of the 21 PAHs to obtain PAH emission profiles for the two furnaces. To test the independence of the two profiles, w2 test was performed. It results no significant differences for these two furnaces ðpo0:05Þ: Thus, these profiles were averaged to obtain a representative PAH profiles shown in Fig. 2, which can be a useful source
ARTICLE IN PRESS H.-H. Yang et al. / Atmospheric Environment 39 (2005) 3305–3312 Table 3 Literature value of emission factors of total (gaseous+particulate phase) PAHs for bio-fuel burning (mg kg1) Fuel (combustor)
Wooda (domestic combustion)
Hardwoodb (fireplace)
Agricultural debrisc (open burning)
Nap AcPy Acp Flu PA Ant FL Pyr CYC BaA CHR BbF BkF BeP BaP PER IND DBA BbC BghiP COR
39.1 11.0 35.5 4.83 4.46 1.83 4.94 2.44
60.86 8.18 0.77 3.09 17.62 3.46 4.47
0.82 0.88 0.54 0.45 0.41 0.69
0.48 0.59
25.2 33.8 9 43 145 61.2 40.1 16.6 — 15.3 6.8 4.2 1.1 — 5.7 — 0.6 ND — 1.7 —
0.25 0.3
1.13 0.60 0.50 0.05
0.21 0.08
a
Oanh et al. (1999). Mcdonald et al. (2000). c Kakareka and Kukharchyk (2003). b
PAH profile (%)
100 10 1 0.1
Nap AcPy Acp Flu PA Ant FL Pyr CYC BaA CHR BbF BkF BeP BaP PER IND DBA BbC BghiP COR
0.01
PAHs
3309
principal components are extracted, the retained principal components are labeled. The meaning of the principal components can be given by considering the influential loadings and the names assigned to them should be referred to the source markers in the literature. The source markers for joss paper combustion identified in this study offer basic information for the recognition of emission sources in PCA analysis. Many studies have suggested that ratios between PAH compounds may be used for source identification (Li and Kamens, 1993; Guo et al., 2003). The estimated values for the most common ratios of PAHs are presented along with some literature values in Table 4. The PAH ratios vary significantly across emission sources. Furthermore, there exists wide variability for some PAH ratios for the same emission sources obtained by different studies. Nonetheless, it is informative that most PAH ratios of joss paper burning were close to those of wood combustion in values (Table 4). For the problem of high variation in the ratios, it is suggested more studies with proper design be conducted to confirm the PAH ratios for the burning of similar fuels. 3.3. PAH emissions for different joss papers The two kinds of joss papers, i.e., bamboo-made and recycled-paper-made, were burned in Furnace 2. Of the two different joss papers examined, bamboo-made joss paper has smaller emission factors for both gaseous and particulate PAHs (Fig. 3). The bamboo-made joss paper has higher combustible content (90.3%) and heating value (Table 1). These characteristics render a shorter smoldering stage in burning. The exhaust gas temperature was obtained by the sampling system. The result showed that the average temperature was higher for bamboo-made joss paper (417 1C) than that of the recycled-paper-made joss paper (296 1C). These better burning conditions might be the reason for less PAH emission in bamboo-made joss paper burning (Zou et al., 2003). The results indicate that bamboo-made joss paper is a ‘‘cleaner’’ joss paper and must be the choice for the control of PAH emission.
Fig. 2. PAH source profiles normalized by the sum of 20 PAHs.
3.4. Influence of airflow and air pollution control devices on PAH reduction efficiency
signature in PAH emission source apportion analysis. The PAH profile shows large shares in Nap (58.1%), PA (11.7%) and Flu (7.5%). The predominance of the lower molecular weight PAH compounds is similar to that of wood combustion (Oanh et al., 1999; Venkataraman et al., 2002). Principal component analysis is widely used as an exploratory tool to identify the major PAH emission sources (Guo et al., 2003; Fang et al., 2004; Kalaitzoglou et al., 2004). For principal component analysis, after the
To study the efficiency of air pollution control devices, a cyclone and a wet scrubber were installed in Furnace 1. When the air pollution control devices (APCD) were operating, the airflow would increase. The average flow velocities at the sampling port were 12.9 and 15.8 m s1 with and without the operation of APCD, separately. The exhaust gas before APCD was sampled and analyzed with and without the operation of APCD. The ratios and standard deviations of the emission factors under the two burning conditions were
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Table 4 Comparison of PAH characteristic ratios PAH ratios BghiP/IND CHR/BeP BaA/BaP BaP/BghiP Pyr/BaP BaA/CHR
Joss paper burning 0.6070.32 0.4070.14 0.1470.7 1.270.25 1.270.35 0.0970.04
Wood combustion
Gasoline exhaust
a
a
3.5 2.5a 0.5a 1.25d 1.5d
0.8 2.4a, 0.25b 1.0a, 0.1b 0.71b 0.93c
Diesel exhaust
Coal
a
1.1 1.6a 1.0a, 12.9e 0.88e 11d, 34.7e
0.9–6.6f
1.0–1.2c
Total PAH. a
Li and Kamens (1993), particulate PAH only. Khalili et al. (1995), total PAHs. c Gschwend and Hites (1981), particulate PAH only. d Masclet et al. (1987), particulate PAH only. e Abrantes et al. (2004), total PAHs. f Daisey et al. (1979), particulate PAH only.
1
0.5 High/low airflow
Bamboo/Recycle paper
b
0.0 Gas PAH Particulate PAH PAHs
Fig. 3. Comparison of PAH emission factors for recycledpaper-made and bamboo-made joss papers.
0 Nap Acpy Acp Flu PA Ant FL Pyr CYC BaA CHR BbF BkF BeP BaP PER IND DBA BbC BghiP COR
Total PAH
PAHs Fig. 4. Total PAH emission factor ratios (high/low airflow).
shown in Fig. 4. Except for AcPy and PA, all PAHs have lower emission factors under the high airflow condition. For total (particulate+gaseous) PAHs, the ratio was 0.82, indicating high airflow result in 18% PAH emission reduction. PAH formation process is complex and sensitive to combustion conditions (Masclet et al., 1987; Zou et al., 2003). For instance, PAH emission can be reduced by increasing oxygen supply to enhance burning efficiency. Some newly constructed furnaces have been equipped with APCD. Cyclone and wet scrubber were the common devices used, and designed primarily to reduce the emission of criteria air pollutants (especially PM), but not PAHs. The PAH emission was measured before and after APCD in this study. The removal efficiencies of low molecular weight (LMW, molecular weight p178), middle molecular weight (MMW, 178o molecular weight p228), high molecular weight (HMW,
molecular weight 4228) and total PAHs were shown in Fig. 5. For particulate phase PAHs, the removal efficiencies of LMW, MMW, HMW and total PAHs were 27.8%, 46.7%, 53.1% and 42.5%, respectively. For gaseous PAHs, the removal efficiencies of LMW, MMW, HMW and total PAHs were 9.1%, 16.8%, 26.5% and 11.7%, respectively. For both particulate and gaseous phase PAHs, the removal efficiencies were in the order of LMW PAHsoMMW PAHsoHMW PAHs. This ranking may be explicable by the fact that higher molecular weight PAHs are primary in the form of particulate state (Naumova et al., 2003), which can be more effectively collected by cyclone and wet scrubber. For the same reason, the removal efficiencies was higher for particulate phase PAHs than that of gaseous phase PAHs.
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The reduction of PAH emission can be expected when this strategy is commonly accepted and practiced.
60
Removal efficiency (%)
50
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Particulate PAHs Gaseous PAHs
40
References 30 20 10 0 LMW
MMW HMW PAHs
Total
Fig. 5. PAH removal efficiencies of a cyclone/wet scrubber control device installed on a joss paper furnace.
4. Conclusions PAH emissions for joss paper burning from two joss paper furnaces were investigated. Individual PAH emission factors vary from less than 1 mg kg1 fuel to several tens of mg kg1 fuel. The total and the carcinogenic PAH emission factors for these furnaces were 71.0 mg kg1 and 3.2 mg kg1, respectively. Nap dominates in the PAH emission. The PAH profiles show a predominance of Nap (58.1%), PA (11.7%) and Flu (7.5%). Two kinds of joss papers were burned in Furnace 2. Of the two joss papers examined, bamboomade joss papers generate less PAH emission than recycled-paper-made joss papers in both gaseous and particulate PAHs. By using the same joss paper in the same furnace, PAH emission under low airflow condition was higher than that under high airflow condition, for high airflow brought in more O2 available for the higher temperature burning which enhance combustion efficiency. The removal efficiencies of LMW, MMW, HMW and total PAHs by cyclone and wet scrubber were 27.8%, 46.7%, 53.1%, 42.5% for particulate PAHs and 9.1%, 16.8%, 26.5%, 11.7% for gaseous PAHs, respectively. The removal efficiencies were in the order of LMW PAHsoMMW PAHsoHMW PAHs. This ranking is in line with the fact that higher molecular weight PAHs are primary in the form of particulate state, which can be more effectively collected by cyclone and wet scrubber. In recent period, APCD is increasingly being installed on the joss paper furnaces in Taiwan. Besides, Taiwan EPA has encouraged people burn the joss paper in the municipal solid waste incinerator and collected the joss paper from the worshipers on the festival days. The combustion in municipal solid waste incinerator is better controlled, more complete and results in lower formation of PAHs.
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Naumova, Y.Y., Offenberg, J.H., Eisenreich, S.J., Meng, Q., Polidori, A., Turpin, B.J., Weisel, C.P., Morandi, M.T., Colome, S.D., Stock, T.H., Winer, A.M., Alimonkhtari, S., Kwon, J., Maberti, S., Shendell, D., Jones, J., Farrar, C., 2003. Gas/particle distribution of polycyclic aromatic hydrocarbons in coupled outdoor/indoor atmospheres. Atmospheric Environment 37, 703–719. Oanh, N.T.K., Reuterga˚rdh, L.B., Dung, N.T., 1999. Emission of polycyclic aromatic hydrocarbons and particulate matter from domestic combustion of selected fuels. Environmental Science and Technology 33, 2703–2709. Venkataraman, C., Negi, G., Sardar, S.B., Rastogi, R., 2002. Size distributions of polycyclic aromatic hydrocarbons in aerosol emissions from biofuel combustion. Aerosol Science 33, 503–518. Yang, H.H., Chen, C.M., 2004. Emission inventory and sources of polycyclic aromatic hydrocarbons in the atmosphere at a suburban area in Taiwan. Chemosphere 56, 879–887. Yang, H.H., Lai, S.O., Hsieh, L.T., Hsueh, H.J., Chi, T.W., 2002. Profiles of PAH emission from steel and iron industries. Chemosphere 48, 1061–1074. Zou, L.Y., Zhang, W., Atkiston, S., 2003. The characterization of polycyclic aromatic hydrocarbons emissions from burning of different firewood species in Australia. Environmental Pollution 124, 283–289.
Atmospheric Environment 39 (2005) 3305–3312 www.elsevier.com/locate/atmosenv
Polycyclic aromatic hydrocarbon emissions from joss paper furnaces Hsi-Hsien Yanga,, Ray-Chen Junga, Ya-Fen Wangb, Lien-Te Hsiehc a
Department of Environmental Engineering and Management, Chaoyang University of Technology, Wufong, Taichung 41349, Taiwan b Bioenvironmental Engineering of Chung Yuan Christian University, 22, Pu-Jen, Pu-Chung Li, Chung-Li, 320, Taiwan c Department of Environmental Engineering and Science, National Ping Tung University of Science and Technology, Nei Pu 91207, Ping Tung, Taiwan Received 27 October 2004; received in revised form 17 January 2005; accepted 26 January 2005
Abstract The emissions of polycyclic aromatic hydrocarbons (PAHs) were quantified for two joss paper furnaces burning two kinds of joss papers (recycled paper made and virgin bamboo made). A cyclone and a wet scrubber were installed in series on one of the two furnaces. Particulate and gaseous PAHs were collected with a sampling system meeting the criteria of U.S. EPA Modified Method 5. Twenty-one species of PAH were analyzed by GC/MS. Individual PAH emission factors vary from less than 1 mg kg1 fuel to several tens of mg kg1 fuel. The total (sum of 21 compounds) and the carcinogenic PAH (benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indeno[1,2,3,-cd]pyrene, dibenz[a,h]anthracene) emission factors were not statistically different for the two furnaces and averaged 71.0 and 3.2 mg kg1, respectively. The PAH profiles showed a predominance of naphthalene (58.1%), phenanthrene (11.7%) and fluorene (7.5%). Of the two joss papers examined, bamboo-made joss paper showed less emission in both particulate and gaseous PAHs. For particulate and gaseous PAHs, the removal efficiencies of total PAHs by the air pollution control devices were 42.5% and 11.7%, respectively. PAH emission factors in high airflow conditions were generally lower than those in low airflow condition. r 2005 Elsevier Ltd. All rights reserved. Keywords: Joss paper; Emission profile; Characteristic ratio; Emission factor; Carcinogen
1. Introduction Buddhism and Taoism are the two most popular religions for Chinese and some countries in Asia. Joss paper and incense burning is an important ceremonial practice for deity worshipping in these religions. The devotees observe this ritual on the first and the fifteenth day of a Chinese lunar month (The new moon and full Corresponding author. Tel.: +886 4 2332 3000x4451; fax: +886 4 2374 2365. E-mail address: [email protected] (H.-H. Yang).
moon are set as the first day and the fifteenth day of each month, which lasts as long as the time required for the moon to complete a revolution around the earth). The other important festival days are Zhong Yuan Jie—A festival on the seventh full moon in a lunar year, known as the commemoration of the dead. The pilgrims go to the temples for the commemoration of the dead on this day and Qing Ming Jie—The Chinese grave sweeping day. People sweep their ancestor’s graves at this day, and the birthdays of the deities. Chinese immigrants and oriental religious believers are also performing this ritual in western countries. It has been shown that incense
1352-2310/$ - see front matter r 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2005.01.052
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burning is a significant source of particulate matters, metal elements (Lau and Luk, 2001; Fang et al., 2003) and polycyclic aromatic hydrocarbons (PAHs) (Lin et al., 2002; Lung and Hu, 2003) in ambient air. In temples, joss papers are burned in furnaces. Modern combustors have tall stacks, scientificallydesigned combustion chambers and high-efficiency flue gas cleaning systems that minimize the impact of emissions. In contract, emissions from joss paper furnaces are released at low elevation, without the benefit of atmospheric dispersion to dilute pollutants. In addition, the low combustion temperature and locally oxygen-starved conditions associated with joss paper burning almost always result in incomplete combustion and increase pollutant emissions. Among the formed air pollutants are polycyclic aromatic compounds, including, as a subgroup, PAHs which have only carbon and hydrogen in their molecular structure. Some PAHs are potential mutagenic and carcinogenic to man (International Agency for Research on Cancer (IARC), 1987). Many human activities, e.g., vehicles driving, residential heating, industrial processes and waste incineration, result in the formation of PAHs. Most temples are located in urban areas with high population density. It is not only an academic curiosity but also a practical importance to estimate PAH exposure levels from joss paper burning for management consideration. PAH profiles have been used to identify vehicular emissions following the use of unleaded gasoline in many countries that deprives lead as a vehicular source marker (Li and Kamens, 1993; Khalili et al., 1995). PAH profiles were also performed as reliably as inorganic compound profiles in PAH source apportionment studies (Harrison et al., 1996). Air pollutant emission from joss paper burning has never been investigated. Many studies have characterized PAH emission from different biomass burning in particulate and gaseous
phases (Oanh et al., 1999; Korenaga et al., 2001; Gullett et al., 2003; Zou et al., 2003). The studies have shown that PAH emissions are closely related to fuel types, burning conditions and the type of appliance. The main purposes of this study were to determine the emissions from two kinds of commonly-used joss papers and to investigate the profiles of the PAHs. The study provides useful information for public awareness concerning PAH emission from joss paper burning.
2. Experimental section 2.1. Preparation of joss papers There are over 10 kinds of joss papers in Taiwan, each with a name and denomination of value. They are different in shape and size, and are used for different worshipping purposes. Generally, three to four kinds of joss papers were combined for a particular worshipping. Tian Gong Jin, Si Fang Jin, Da Fu Jin and Shou Jin, the most commonly used joss papers for worshipping, were selected for testing in this study. Recycled paper and bamboo are the major building materials for joss papers. The compositions of the joss papers were listed in Table 1. It is observed that the carbon and the heating value were higher for the bamboo-made joss paper. 2.2. Description of the furnaces and operating conditions Two joss paper furnaces (denoted as Furnaces 1 and 2), located beside two temples, were selected in this study. The furnaces were both octagonal with height 6.0 and 5.0 m, and the areas of the joss paper feeding aperture were 0.40 and 0.35 m2 for Furnaces 1 and 2. Furnace 1 was equipped with air pollution control devices including a cyclone and a wet scrubber (Fig. 1),
Table 1 Composition of joss paper ðn ¼ 3Þ Analytical method Proximate analysis (%) Moisture Ash Combustible content Ultimate analysis (%) Carbon Hydrocarbon Oxygen Nitrogen Sulfur Chlorine Higher heating value (Dry basis, kcal kg1) N.D.: Not detectable.
Bamboo-made
Recycled-paper-made
ASTM E 955 ASTM E 955 ASTM E 955
6.9 2.8 90.3
6.9 6.8 86.3
Elemental Elemental Elemental Elemental Elemental Elemental
43.0 4.83 46.8 0.08 0.58 0.08
40.6 5.60 46.7 0.11 N.D. 0.02
analyzer analyzer analyzer analyzer analyzer analyzer
Calorimeter
3718
2905
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Sampling position
Wet scrubber
Sampling position
Cyclone
Fig. 1. Schema of Furnace 1.
but Furnace 2 was not. Both temples are typical Buddhist–Taoist combined temples, located in central Taiwan. The sampling campaigns were conducted on the non-festival days during January 2004 and April 2004. One of the purposes of this study is to compare PAH emission of recycled-paper-made joss paper with that of bamboo-made joss paper burning. If there were many pilgrims (usually on the festival days), both recycledpaper-made joss paper and bamboo-made joss paper might be fed into the furnace. On the non-festival days, we fed in the most joss papers into the furnace. Thus, the bamboo-made and recycled-paper-made joss papers can be burned and tested separately. The burning of joss paper was conducted with natural air supply through an opening inlet of the furnace. The joss paper was fed into the furnace steadily. The feeding rate was about 1 kg min1. The weights of joss papers burned were recorded for the calculation of PAH emission factors. Recycled-paper-made joss papers were burned in both Furnaces 1 and 2. For Furnace 1, PAHs were measured before and after air pollution control devices. In order to investigate PAH emission from different joss papers, bamboo-made joss papers were also burned in Furnace 2. 2.3. PAH sampling system for flue gas The samples were taken by a PAH sampling system (Anderson-Graseby Auto5) modified by Li-Teh Co., Taiwan, in accordance with the U.S. EPA Modified Method 5 (40CFR60). This system has been adopted for PAH sampling in many studies (Oanh et al., 1999; Lee et al., 2002; Yang et al., 2002). Sampling at the same velocity as that of the gas in the stack is known as isokinetic sampling, which guarantees that the concentration of the particulate entering the sampling probe is
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the same as that in the stack. All samples were collected within the acceptable sampling range of 90–110% of isokinetically. Starting at the stack, the PAH sampling system constituted in sequence a sampling probe, a filter, a cooling device, three glass cartridges, a pump, a flow meter and a control computer. Tube-type glass fiber filter (cleaned by heating to 450 1C) was to collect particulate and particulate PAHs. The glass cartridge packed with XAD-16 resin and supported by a polyurethane foam (PUF) plug was to collect the gaseous PAHs. After each sampling cycle the sampling train was rinsed with n-hexane. Three breakthrough tests were investigated by three stages of XAD-16/PUF cartridge. Each stage of cartridge was analyzed individually and compared for the PAH mass collected. Breakthrough tests showed that there were no discernable PAH collected in the third stage cartridge. PAH sampling is described in detail elsewhere (Yang et al., 2002). 2.4. PAH analysis PAH-containing filters and cartridges were Soxhlet extracted with a mixed solvent (n-hexane and dichloromethane, v : v ¼ 1 : 1) for 24 h. The extract was then concentrated by purging with ultra-pure nitrogen to 2 ml for the cleanup procedure. The cleanup procedure removes pollutants which would coelute with PAHs from the GC column. The cleanup column contained some glass wool in the bottom (I.D. ¼ 1 cm). Seventeen grams of 6% deactivated silica gel was mixed with 60 ml n-hexane, loaded into the cleanup column, and topped with 1.5 cm of anhydrous sodium sulfate. Next, 60 ml of hexane was added to wash the sodium sulfate and the silica gel. Right before the sodium sulfate layer was exposed to the air, the elution of hexane is stopped and the eluant is discarded. The concentrated sample was then transferred onto the column, the wall of vessel had been rinsed twice with 2 ml hexane which was also added to the column. Next, 200 ml of 6% ethylether in hexane was added to the column and allowed to flow through the column at a rate of 3–5 ml min1, and the eluant was collected. The collected eluant from the cleanup procedure was reconcentrated to 0.5 ml with nitrogen. A gas chromatograph (GC), Agilent 6890, with an Agilent capillary column (Agilent Ultra 2–50 m 0.32 mm 0.17 mm), a mass selective (MS) detector (Agilent 5973) and a computer workstation were used for the PAH analysis. The masses of molecular and fragment ions of PAHs were determined by using the scan mode for pure PAH standards. Qualification of PAHs was performed by using the selected ion monitoring (SIM) mode (Yang and Chen, 2004). The concentrations of the following PAHs were determined: naphthalene (Nap), acenaphthylene (AcPy), acenaphthene (Acp), fluorene (Flu), phenanthrene (PA),
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anthracene (Ant), fluoranthene (FL), pyrene (Pyr), cyclopenta[c,d]pyrene (CYC), benz[a]anthracene (BaA), chrysene (CHR), benzo[b]fluoranthene (BbF), benzo[k]fluoranthene (BkF), benzo[e]pyrene (BeP), benzo[a]pyrene (BaP), perylene (PER), indeno[1,2,3,-cd]pyrene (IND), dibenz[a,h]anthracene (DBA), benzo[b]chrysene (BbC), benzo[ghi]perylene (BghiP), and coronene (COR). Analysis of serial dilutions of PAH standards showed the method detection limit (MDL) between 0.001 and 0.072 mg ml1. The minimum quantitative limits (MQLs) are between 0.005 and 0.024 mg ml1. All the concentrations of the PAHs analyzed were higher than MQLs. PAH recovery efficiencies were determined by processing a solution containing known PAH concentrations following the same experimental procedure used for the samples. This study showed that the recovery efficiency of PAHs varied between 72% and 113% and averaged 84%. Blank tests for PAHs were accomplished by performing the same procedure as the recovery efficiency tests without adding the standard solution before extraction. Analyses of field blanks including filters and PUF/XAD-16 cartridges found no discernable contamination (GC/MS integrated area was less than detection limit).
3. Results and discussions 3.1. PAH emission levels Median values and standard deviations of particulate+gaseous PAH emission factors on a fuel-weight basis (dry basis, mg kg1) from Furnace 1 before air pollution control devices (not in effect) and Furnace 2 using recycled-paper-made joss paper were listed in Table 2. Individual PAH emission factors vary from lower than 1 mg kg1 fuel to several tens of mg kg1 fuel levels, with Nap predominating. Total PAH (sum of 21 PAHs) emission factor of Furnace 2 (74.6 mg kg1) is slightly higher than that of Furnace 1 (67.3 mg kg1). But the differences are not statistically significant (t-test, po0:05). If considering only the carcinogenic PAHs (BaA, CHR, BbF, BkF, BaP, IND, DBA), the emission factors are 3.0 and 3.4 mg kg1 for Furnaces 1 and 2, respectively. The differences are also not statistically significant (t-test, po0:05). Incense burning is also an important ceremonial practice for deity worshipping. Lung and Hu (2003) found that the emission factors of 13 particulate PAHs (Acp, PA, Ant, FL, Pyr, CYC, BaA, CHR, BbF, BkF, BeP, BaP, PER, IND, DBA, BbC, BghiP, and COR) were 17.1 and 28.3 mg kg1 for two kinds of incense sticks. Some PAH emission factors for other similar biofuel (or bio-mass) burning in recent years were listed in Table 3. For most PAHs, the emission factors of joss paper burning were slightly lower than that of wood
Table 2 Emission factors of total (gaseous+particulate phase) PAHs for recycled-paper-made joss paper from Furnaces 1 before air pollution control devices and Furnace 2 (mg kg1) Furnace
Furnace 1
PAHs
Median
Nap AcPy Acp Flu PA Ant FL Pyr CYC BaA CHR BbF BkF BeP BaP PER IND DBA BbC BghiP COR
37.3 4.00 1.75 4.33 7.67 0.25 1.06 0.40 0.83 0.01 0.34 1.48 0.25 1.26 0.23 0.80 0.46 0.25 0.70 0.21 2.25
Total
67.3
Furnace 2 Standard deviation 7.66 1.39 0.39 1.14 1.46 0.16 0.39 0.21 0.24 0.01 0.27 1.07 0.37 1.03 0.23 0.61 0.30 0.30 0.56 0.13 0.56 17.6
Median
Standard deviation
45.1 2.43 1.80 6.11 8.51 0.31 0.54 0.29 0.25 0.07 0.59 1.36 0.35 1.05 0.34 0.69 0.36 0.31 1.22 0.28 1.51
19.0 0.39 0.18 1.70 2.91 0.15 0.32 0.10 0.16 0.01 0.21 0.39 0.11 0.19 0.11 0.35 0.24 0.15 0.41 0.10 1.09
74.6
19.4
combustion and much lower than that of open burning of agricultural debris (Oanh et al., 1999; Mcdonald et al., 2000; Kakareka and Kukharchyk, 2003). Considering the carcinogenic PAHs, the emission factor of wood combustion reported by Oanh et al. (1999) was 5.11 mg kg1, which was 1.5 times higher than that of joss paper burning. For the emission of PAHs is a function of fuel, stove and burning parameters, which are different in different studies, thus the comparison of the emission factors with literature values listed in Table 3 is ordinal at best. 3.2. Profiles and characteristic ratios of PAH emissions Since joss paper burning is potentially an important emission source of PAHs, it is useful to build up PAH emission profile and characteristic ratios for source apportion analysis. Individual PAH emission factors (particulate+gaseous) were normalized by the sum of the 21 PAHs to obtain PAH emission profiles for the two furnaces. To test the independence of the two profiles, w2 test was performed. It results no significant differences for these two furnaces ðpo0:05Þ: Thus, these profiles were averaged to obtain a representative PAH profiles shown in Fig. 2, which can be a useful source
ARTICLE IN PRESS H.-H. Yang et al. / Atmospheric Environment 39 (2005) 3305–3312 Table 3 Literature value of emission factors of total (gaseous+particulate phase) PAHs for bio-fuel burning (mg kg1) Fuel (combustor)
Wooda (domestic combustion)
Hardwoodb (fireplace)
Agricultural debrisc (open burning)
Nap AcPy Acp Flu PA Ant FL Pyr CYC BaA CHR BbF BkF BeP BaP PER IND DBA BbC BghiP COR
39.1 11.0 35.5 4.83 4.46 1.83 4.94 2.44
60.86 8.18 0.77 3.09 17.62 3.46 4.47
0.82 0.88 0.54 0.45 0.41 0.69
0.48 0.59
25.2 33.8 9 43 145 61.2 40.1 16.6 — 15.3 6.8 4.2 1.1 — 5.7 — 0.6 ND — 1.7 —
0.25 0.3
1.13 0.60 0.50 0.05
0.21 0.08
a
Oanh et al. (1999). Mcdonald et al. (2000). c Kakareka and Kukharchyk (2003). b
PAH profile (%)
100 10 1 0.1
Nap AcPy Acp Flu PA Ant FL Pyr CYC BaA CHR BbF BkF BeP BaP PER IND DBA BbC BghiP COR
0.01
PAHs
3309
principal components are extracted, the retained principal components are labeled. The meaning of the principal components can be given by considering the influential loadings and the names assigned to them should be referred to the source markers in the literature. The source markers for joss paper combustion identified in this study offer basic information for the recognition of emission sources in PCA analysis. Many studies have suggested that ratios between PAH compounds may be used for source identification (Li and Kamens, 1993; Guo et al., 2003). The estimated values for the most common ratios of PAHs are presented along with some literature values in Table 4. The PAH ratios vary significantly across emission sources. Furthermore, there exists wide variability for some PAH ratios for the same emission sources obtained by different studies. Nonetheless, it is informative that most PAH ratios of joss paper burning were close to those of wood combustion in values (Table 4). For the problem of high variation in the ratios, it is suggested more studies with proper design be conducted to confirm the PAH ratios for the burning of similar fuels. 3.3. PAH emissions for different joss papers The two kinds of joss papers, i.e., bamboo-made and recycled-paper-made, were burned in Furnace 2. Of the two different joss papers examined, bamboo-made joss paper has smaller emission factors for both gaseous and particulate PAHs (Fig. 3). The bamboo-made joss paper has higher combustible content (90.3%) and heating value (Table 1). These characteristics render a shorter smoldering stage in burning. The exhaust gas temperature was obtained by the sampling system. The result showed that the average temperature was higher for bamboo-made joss paper (417 1C) than that of the recycled-paper-made joss paper (296 1C). These better burning conditions might be the reason for less PAH emission in bamboo-made joss paper burning (Zou et al., 2003). The results indicate that bamboo-made joss paper is a ‘‘cleaner’’ joss paper and must be the choice for the control of PAH emission.
Fig. 2. PAH source profiles normalized by the sum of 20 PAHs.
3.4. Influence of airflow and air pollution control devices on PAH reduction efficiency
signature in PAH emission source apportion analysis. The PAH profile shows large shares in Nap (58.1%), PA (11.7%) and Flu (7.5%). The predominance of the lower molecular weight PAH compounds is similar to that of wood combustion (Oanh et al., 1999; Venkataraman et al., 2002). Principal component analysis is widely used as an exploratory tool to identify the major PAH emission sources (Guo et al., 2003; Fang et al., 2004; Kalaitzoglou et al., 2004). For principal component analysis, after the
To study the efficiency of air pollution control devices, a cyclone and a wet scrubber were installed in Furnace 1. When the air pollution control devices (APCD) were operating, the airflow would increase. The average flow velocities at the sampling port were 12.9 and 15.8 m s1 with and without the operation of APCD, separately. The exhaust gas before APCD was sampled and analyzed with and without the operation of APCD. The ratios and standard deviations of the emission factors under the two burning conditions were
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Table 4 Comparison of PAH characteristic ratios PAH ratios BghiP/IND CHR/BeP BaA/BaP BaP/BghiP Pyr/BaP BaA/CHR
Joss paper burning 0.6070.32 0.4070.14 0.1470.7 1.270.25 1.270.35 0.0970.04
Wood combustion
Gasoline exhaust
a
a
3.5 2.5a 0.5a 1.25d 1.5d
0.8 2.4a, 0.25b 1.0a, 0.1b 0.71b 0.93c
Diesel exhaust
Coal
a
1.1 1.6a 1.0a, 12.9e 0.88e 11d, 34.7e
0.9–6.6f
1.0–1.2c
Total PAH. a
Li and Kamens (1993), particulate PAH only. Khalili et al. (1995), total PAHs. c Gschwend and Hites (1981), particulate PAH only. d Masclet et al. (1987), particulate PAH only. e Abrantes et al. (2004), total PAHs. f Daisey et al. (1979), particulate PAH only.
1
0.5 High/low airflow
Bamboo/Recycle paper
b
0.0 Gas PAH Particulate PAH PAHs
Fig. 3. Comparison of PAH emission factors for recycledpaper-made and bamboo-made joss papers.
0 Nap Acpy Acp Flu PA Ant FL Pyr CYC BaA CHR BbF BkF BeP BaP PER IND DBA BbC BghiP COR
Total PAH
PAHs Fig. 4. Total PAH emission factor ratios (high/low airflow).
shown in Fig. 4. Except for AcPy and PA, all PAHs have lower emission factors under the high airflow condition. For total (particulate+gaseous) PAHs, the ratio was 0.82, indicating high airflow result in 18% PAH emission reduction. PAH formation process is complex and sensitive to combustion conditions (Masclet et al., 1987; Zou et al., 2003). For instance, PAH emission can be reduced by increasing oxygen supply to enhance burning efficiency. Some newly constructed furnaces have been equipped with APCD. Cyclone and wet scrubber were the common devices used, and designed primarily to reduce the emission of criteria air pollutants (especially PM), but not PAHs. The PAH emission was measured before and after APCD in this study. The removal efficiencies of low molecular weight (LMW, molecular weight p178), middle molecular weight (MMW, 178o molecular weight p228), high molecular weight (HMW,
molecular weight 4228) and total PAHs were shown in Fig. 5. For particulate phase PAHs, the removal efficiencies of LMW, MMW, HMW and total PAHs were 27.8%, 46.7%, 53.1% and 42.5%, respectively. For gaseous PAHs, the removal efficiencies of LMW, MMW, HMW and total PAHs were 9.1%, 16.8%, 26.5% and 11.7%, respectively. For both particulate and gaseous phase PAHs, the removal efficiencies were in the order of LMW PAHsoMMW PAHsoHMW PAHs. This ranking may be explicable by the fact that higher molecular weight PAHs are primary in the form of particulate state (Naumova et al., 2003), which can be more effectively collected by cyclone and wet scrubber. For the same reason, the removal efficiencies was higher for particulate phase PAHs than that of gaseous phase PAHs.
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The reduction of PAH emission can be expected when this strategy is commonly accepted and practiced.
60
Removal efficiency (%)
50
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Particulate PAHs Gaseous PAHs
40
References 30 20 10 0 LMW
MMW HMW PAHs
Total
Fig. 5. PAH removal efficiencies of a cyclone/wet scrubber control device installed on a joss paper furnace.
4. Conclusions PAH emissions for joss paper burning from two joss paper furnaces were investigated. Individual PAH emission factors vary from less than 1 mg kg1 fuel to several tens of mg kg1 fuel. The total and the carcinogenic PAH emission factors for these furnaces were 71.0 mg kg1 and 3.2 mg kg1, respectively. Nap dominates in the PAH emission. The PAH profiles show a predominance of Nap (58.1%), PA (11.7%) and Flu (7.5%). Two kinds of joss papers were burned in Furnace 2. Of the two joss papers examined, bamboomade joss papers generate less PAH emission than recycled-paper-made joss papers in both gaseous and particulate PAHs. By using the same joss paper in the same furnace, PAH emission under low airflow condition was higher than that under high airflow condition, for high airflow brought in more O2 available for the higher temperature burning which enhance combustion efficiency. The removal efficiencies of LMW, MMW, HMW and total PAHs by cyclone and wet scrubber were 27.8%, 46.7%, 53.1%, 42.5% for particulate PAHs and 9.1%, 16.8%, 26.5%, 11.7% for gaseous PAHs, respectively. The removal efficiencies were in the order of LMW PAHsoMMW PAHsoHMW PAHs. This ranking is in line with the fact that higher molecular weight PAHs are primary in the form of particulate state, which can be more effectively collected by cyclone and wet scrubber. In recent period, APCD is increasingly being installed on the joss paper furnaces in Taiwan. Besides, Taiwan EPA has encouraged people burn the joss paper in the municipal solid waste incinerator and collected the joss paper from the worshipers on the festival days. The combustion in municipal solid waste incinerator is better controlled, more complete and results in lower formation of PAHs.
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