Human dietary exposure to polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in Taiwan

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) levels in a total of 25 food items in Taiwan were surveyed. It was observed that shellfish and saltwater fish possessed the highest PCDD/Fs levels, 9.82 and 3.60 pg WHO-TEQ/g, respectively, on the lipid basis. The dietary intakes of humans at the ages of 12-18, 19-64, and over 65 were determined. The estimated intake were between 21.8 pg (female teenagers) and 37.6 pg (male seniors) WHO-TEQ/day; the levels varied with the dietary habits. The PCDD/F intakes for all human groups are far below the tolerable limit of 70 pg WHO-TEQ/kg b.w./month. In addition, the daily PCDD/F intake levels for duck-farmers consuming average and large amounts of PCDD/F contaminated duck eggs were examined. The result shows that consuming more than one duck egg with level higher than 10 pg WHO-TEQ/g lipid of PCDD/Fs per day could lead to a PCDD/F intake level higher than the tolerable limit. However, for normal population, there is a little risk to ingest intolerable amount of PCDD/Fs because of consuming contaminated duck eggs.     

Comparative analysis of PCDD/Fs in soil around waste incineration plants in China using CALUX bioassay and HRGC/HRMS

In this study, the contamination of soil by PCDD/Fs and other dioxin-like chemicals in the vicinity of Municipal Solid Waste Incinerators (MSWIs) and Hazardous Waste Incinerators (HWIs) is estimated by the XDS-CALUX bioassay. The resulting CALUX-TEQ value is compared with the WHO-TEQ value obtained from HRGC/HRMS analysis, in order to validate the CALUX bioassay as suitable screening method for PCDD/Fs determination of soil samples. The results show that the CALUX-TEQ and the WHO-TEQ values are significantly correlated (R = 0.87). The WHO-TEQ and CALUX-TEQ of soil samples collected from four waste incineration plants in China were in the range from 1.72 to 31.4 pg-TEQ/g and 1.71 to 44.2 pg-TEQ/g respectively, with a mean value of 6.09 pg-TEQ/g and 11.0 pg-TEQ/g. Considering the homologue patterns, a principal component analysis (PCA) and a hierarchical cluster analysis (HCA) of the PCDD/Fs in the soil samples, the emissions of MSWIs and HWIs were probably not the only source of PCDD/Fs.     

Comparisons of levels of polychlorinated dibenzo-p-dioxins/dibenzofurans in the surrounding environment and workplace of two municipal solid waste incinerators

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the surrounding environment (outdoor) and workplace air of two municipal solid waste incinerators (MSWIs, T and M) were characterized and compared. T and M represented two typical municipal solid waste incinerators in the north of Taiwan, which have different processes for controlling the PCDD/F emissions. The results of this study are summarized as follows. (1) The total PCDD/F and the total PCDD/F WHO-TEQ concentrations in the workplace air were 5-13 and 5-15 times higher than those in the outdoor air, respectively. Obviously, it is worthwhile to explore more on health risk assessment for exposure of PCDD/Fs emitted from MSWIs, particularly in the workplace air. (2) Mean total PCDD/F I-TEQ concentrations in the outdoor air ranged between 0.0216 and 0.155 pg I-TEQ/Nm(3) and averaged 0.0783 pg I-TEQ/Nm(3) (0.0828 pg WHO-TEQ/Nm(3)) during two seasons for two MSWIs, which were 6.5-fold higher than that of a remote site (0.0119 pg I-TEQ/Nm(3) or 0.0132 pg WHO-TEQ/Nm(3)) in Taiwan. However, the above outdoor air concentration levels in the MSWIs were still much lower than the air quality limitation of PCDD/Fs (0.6 pg I-TEQ/Nm(3)) in Japan []. (3) PCDFs were the primary toxicity distributors for PCDD/Fs in the outdoor air, since the ratios of PCDDs/PCDFs (I-TEQ) at all sampling sites ranged from 0.180 to 0.492 and were less than unity. (4) The OCDD, OCDF, 1,2,3,4,6,7,8-HpCDD and 1,2,3,4,6,7,8-HpCDF were the four dominant species in both workplace and outdoor air near MSWIs. (5) By spraying water on and wetting both the fly and bottom ashes, the mean total PCDD/F I-TEQ concentration in the workplace air was reduced 86.9% in the T MSWI. The above results indicate an appropriate improving action did inhibit the fugitive emission of PCDD/Fs and reduce the health risk of workers during work handling ashes in MSWIs.     

Identification of dioxin and dioxin-like polychlorbiphenyls in plant tissues and contaminated soils

The environmental analysis laboratory (EAL) of the Taiwan environmental protection administration (TEPA) has been monitoring certain sites polluted in southern Taiwan by pentachlorophenol manufacture. The analytical results revealed peculiarities in the concentration distributions in plant tissues. There are no available data on dioxin and dioxin-like polychlorbiphenyls (DL-PCBs), which can be taken up from contaminated soils by plant tissues. Thus, the aims of this study were to identify, understand, and to validate these dioxin and DL-PCBs concentrations in plant tissues of the contaminated soils. This research analyzed ten species of plant tissues, including tappa (Boussonetia papyrifera) and common jasmin orange (Murraya paniculata) from sites in southern Taiwan, with different levels of contamination. Dioxin concentrations in these plant tissues ranged from 12.7 to 2919 ng WHO-TEQ(DF)/kg dry weight (d.w.), with average of 463 ng WHO-TEQ(DF)/kg d.w. (n=16). The DL-PCBs concentrations ranged from 0.236 to 1.75 ng WHO-TEQp/kg d.w., with an average of 0.605 ng WHO-TEQp/kg d.w. (n=8). Tappa is one of the most common and fastest growing plants in Taiwan. It also shows the highest tolerance to environmental contaminants and accumulates dioxin and DL-PCBs. This is one of the best species to take up dioxins and DL-PCBs effectively. It can be recommended as a candidate for dioxin and DL-PCB phyto-remediation. These data are useful to evaluate bioaccumulation of dioxin and DL-PCBs, and to study the capability of phyto-remediation in contaminated soils.     

Distribution of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/Fs) and dioxin-like polychlorinated biphenyls (dioxin-like PCBs) in the soil in a typical area of eastern China

The distribution and concentrations of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (dioxin-like PCBs, also called co-PCBs) in a typical area of eastern China were evaluated by analysis of 21 soil and 6 sediment samples. The range of WHO-TEQ values for the PCDD/Fs and dioxin-like PCBs in 17 soil samples representing the background investigation in the study area was 0.017-5.04 pg g(-1) (dry weight, dw), with a mean value 0.967(+/-1.361)pg g(-1) and medium value 0.348 pg g(-1), which indicates that the levels of PCDD/Fs and dioxin-like PCBs over the major part of this district were low. However, the WHO-TEQ values (6.52-16.7 pg g(-1) dw) for PCDD/Fs and dioxin-like PCBs in soil samples to the leeward of a known contaminated disassembly industrial park were much higher than that of the background investigation, and the levels of sediment samples downstream of this area were in the range 2.25-34.6 pg g(-1) (dw). The levels of WHO-TEQ in soil and sediment samples decreased with an increase in distance from the researched pollution source. The principal component analysis demonstrated that the PCDD/Fs and dioxin-like PCBs in major part of contaminated sediment and soil samples derived from the correlative matrix. Yet the different distribution patterns of them in part of sediment samples strongly indicate that other potential sources may be exist, further researches should be done to get more information about the sources and the distributions of the PCDD/Fs and PCBs.     

Evaluating the environmental impact of an old municipal waste incinerator: PCDD/F levels in soil and vegetation samples

In order to determine the temporal variation in the levels of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in the vicinity of an old municipal solid waste incinerator (MSWI) (S. Adrià del Besòs, Barcelona, Spain), 24 soil and vegetation samples were collected at the same sampling points in which samples had been taken 1 year before. Each sample was analyzed for PCDDs and PCDFs by high-resolution gas chromatography/high-resolution mass spectrometry. While in the previous study PCDD/F concentrations in soil ranged from 1.22 to 34. 28 ng I-TEQ/kg (median and mean values: 9.06 and 12.24 ng I-TEQ/kg), in the present study, PCDD/F levels ranged from 1.33 to 54.23 ng I-TEQ/kg (median and mean values: 11.85 and 14.41 ng I-TEQ/kg). On the other hand, in the previous study, PCDD/F levels in vegetation ranged from 0.33 to 1.98 ng I-TEQ/kg (median and mean values: 0.58 and 0.70 ng I-TEQ/kg), whereas in the present study, PCDD/F levels ranged from 0.32 to 2.52 ng I-TEQ/kg (median and mean values: 0.82 and 0.97 ng I-TEQ/kg). During the last 12 months, PCDD/F levels increased in 16 of the 24 soil samples and in 17 of the 24 vegetation samples analyzed. However, no significant differences in the median I-TEQ concentrations of both studies were found either in soil or vegetation samples.     

The characterization of PCDDs, PCDFs and coplanar PCBs during the past 50 years in Gwangyang Bay, South Korea

The PCDD/DFs and coplanar PCBs (co-PCBs) in sediment samples from Gwangyang Bay in South Korea was investigated. The total concentration of dioxins and their toxic equivalent quantity (TEQ; calculated with the WHO 2005 Toxic Equivalency Factors) value in the surface sediment of the outer site (261 pg g(-1) TOC, 4.4 pg-TEQ g(-1)) were 3-fold higher than the inner site (90 pg g(-1) TOC, 1.1 pg-TEQ g(-1)) in the Bay. The dioxin in the sediment samples was found to come from a mixture of the impurities of pentachlorophenol (PCP), chloronitrofen (CNP) and combustion based on the result of hierarchical cluster analysis (HCA). These dioxin sources have been influenced by the characterization associated with this region which was both an agricultural-centered and industrial-centered area. According to principal component analysis (PCA) related to the Kow values for the congener-specific composition of co-PCBs in the sediment core, the Kanechlor (KC)-500 and the atmospheric deposition were identified as the possible sources. The maximum burden in the sediment core was 1.3 kg for 1967-1974 and the total burdens of PCDD/DFs and co-PCBs in the sediment core were estimated to be 6.6 kg during the past 50 years. The cumulative burdens of dioxin are still increasing in Gwangyang Bay.     

二恶英发生源的建立及其性能分析

针对如何在臭氧紫外光-滑动弧系统中建立稳定的二恶英发生源用于降解二恶英的实验系统.该发生源以医疗垃圾飞灰为对象,通过加热飞灰本身和飞灰索提液的方式使其中的二恶英在一段时间内连续挥发.结果表明,290℃时在飞灰发生源系统中,二恶英初始阶段挥发速率极快,后续的挥发速率急剧减小并趋于稳定,总挥发量仅为总量的10%,且难以再提高.相比而言索提液发生源系统挥发出的二恶英更多更稳定,但其挥发量受温度和注射速度的影响较大:当注射速度为1μL.min-1时,在300℃、400℃、500℃三个不同温度段分别为2.78%、7.88%和9.56%;当温度为500℃,注射速度为0.2 mL.min-1时,其挥发率提高到48.7%.研究还发现,注射针头与管壁的残余量是影响挥发效率的两个重要因素,当温度为500℃,载气为1000 mL.min-1,注射速度为0.2 mL.min-1时,连续进样1 h后,两者的残余量分别占注射总量的40.0%和16.7%.     

Validation of the CALUX bioassay as a screening and semi-quantitative method for PCDD/F levels in cow's milk

The objectives of this study were first to set up and validate the quality criteria of the Xenobiotic Detection Systems-chemical activated luciferase gene expression (CALUX) bioassay for the analysis of cow's milk samples spiked with polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs). The application of this bioassay was then tested by analyzing 28 commercially available pasteurized milk samples and comparing the data with the reference method for PCDD/F analysis. The CALUX criteria from the U.S. EPA and the European Union (EU) were calculated from 16 replaced spiked milk (SM) samples and 8 performance evaluation (PE) samples to validate the CALUX bioassay system. The CALUX bioassay criteria included control chart for quality control (QC) standards, recovery efficiency, and data comparability. The control chart for QC standards were both within the micro+/-2sigma range. The recovery efficiencies ranged from 60.4% to 106% with an average of 79.9% (relative standard deviation (RSD): 20.7%). The mean of data comparability (i.e., relative percent difference, RPD) between CALUX bioassay and high-resolution gas chromatography and high-resolution mass spectrometry (HRGC/HRMS) was 19.0% for SM samples. For the PE samples, Pearson's correlation coefficient between CALUX and the HRGC/HRMS method was 0.953. The high correlation shows that the CALUX system is suitable as a screening method and a semi-quantitative method to analyze the PCDD/F concentration in milk samples. Next, the validated CALUX bioassay was applied to measure 28 commercially available pasteurized milk samples. These milk samples were also analyzed with the HRGC/HRMS method to compare the analysis data from two different methods. There is no false negative sample when applying the bioassay to pasteurized milk and PE samples as a screening method and a semi-quantitative method. The present study indicates that CALUX is a powerful bioassay method for screening a large number of milk samples.     

Polychlorinated dibenzo-p-dioxin and dibenzofuran emissions from an industrial park clustered with metallurgical industries

Emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from an industrial park operated as Taiwan's center of metallurgical industries were investigated. The characteristics of mean PCDD/F I-TEQ concentrations, congener profiles and emission factors of each source were studied over samples of stack flue gases of individual sources. Different characteristics of congener profiles and large variations of emission factors of secondary aluminum smelters (ALSs) were observed. The mean emission factors of electric arc furnaces were comparable to those for ALSs and much greater than those of municipal solid waste incinerators and sinter plants, but still less than that of clinical waste incinerators. Annual PCDD/F emission contribution of each source was estimated, raising critical concerns over the overall PCDD/F emissions from metallurgical processes. The metallurgical industries altogether contributed approximately 98.1% of the total annual emissions, while waste incinerators only 1.9%. The contributions by sinter plants and metallurgical industries to the total annual emissions of the Park were much higher than the corresponding national averages of Taiwan. The combined dioxin emissions from the entire metallurgical processes and their controls should be seriously envisaged by industrial parks devoted to metal productions.     

Dioxins and dioxin-like PCBs in different fish from the river Elbe and its tributaries, Germany

In a long-term program polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) as well as dioxin-like polychlorinated biphenyls (DL-PCBs) were analyzed in the muscle tissue of eels (Anguilla anguilla), bream (Abramis brama), European chub (Leuciscus cephalus) and ide (Leuciscus idus) from the river Elbe and its tributaries Mulde and Saale. The variation of the PCDD/F and DL-PCB concentrations in all fish samples is very large, whereby the DL-PCBs predominate in comparison to the PCDD/Fs. In the eels, the concentrations (pg WHO-TEQ/g ww) for the PCDD/Fs lie in the range of 0.48-22 and for the DL-PCBs between 8.5 and 59. In the whitefish, the concentration range is 0.48-12 for the PCDD/Fs and 1.2-14 for the DL-PCBs. Statistical analysis using relative congener patterns for PCDD/Fs allow spatial correlations to be examined for sub-populations of eels and whitefish. The results are compared to the maximum levels laid down in the European Commission Regulation (EC) No. 466/2001 and the action levels of the European Commission Recommendation 2006/88/EC. Eels caught directly after the major flood in August 2002 as well as eels near Hamburg (years 1996 and 1998) show high concentration peaks. Compared to the eels whitefish is less contaminated with PCDD/Fs and DL-PCBs.     

Enzyme-linked immunosorbent assay for monitoring toxic dioxin congeners in milk based on a newly generated monoclonal anti-dioxin antibody

To develop an enzyme-linked immunosorbent assay (ELISA) for monitoring the toxicity due to polychlorinated dibenzo-p-dioxins and dibenzofurans contaminated in human breast milk, we have generated novel monoclonal antibodies using some haptenic derivatives linked to bovine serum albumin via the C-1 or C-2 position on the dioxin skeleton. BALB/c or A/J mice were repeatedly immunized with the immunogen, and spleen cells were fused with P3/NS1/1-Ag4-1 myeloma cells. After five fusion experiments, a hybridoma clone was established that secretes an antibody D9-36 group specifically recognizing the major toxic congeners, 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD), 1,2,3,7,8-pentachlorodibenzo-p-dioxin, and 2,3,4,7,8-pentachlorodibenzofran. An ELISA is developed on the basis of the competitive and labeled-antigen format. The toxic congeners extracted from butter or milk specimens by a novel extraction cartridge and a peroxidase-labeled dioxin analogue were sequentially reacted with a fixed amount of D9-36 in the presence of Triton X-100. The bound fraction was captured on a microtiter plate, immobilizing a second antibody, and the enzyme activity was colorimetrically determined. This ELISA afforded a practical sensitivity (measurable range, 1-100 pg/assay; detection limit, 1.0 pg/assay as 2,3,7,8-TCDD equivalent). The assay values for milk and butter samples were in reasonable accordance with the sum of the toxicity-equivalent quantity of each congener, which had been determined by a high-resolution gas chromatography/high-resolution mass spectrometry method.     

Site-specific health risk assessment of dioxins and furans in an industrial region with numerous emission sources

While the sources of releasing dioxins have received much attention, the health risks of incinerators are studied considerably more than those of other sources, such as metallurgical industry. Furthermore, risk assessments focus primarily on the effects of single sources; few have addressed the aggregate risks from multiple sources in a region. When many sources of dioxins exist in an area, such as the Industrial Park located in the densely populated district—Siaogang District in southern Taiwan where 17 primary known PCDD/F stationary emission sources are clustered, is the aggregate exposure to these sources imposing high risks even though individual sources comply with emission standards? The study combined the multimedia and multiple pathway exposure modeling and site-specific exposure scenario to assess dioxin risks contributed by the 17 emission sources in the District, including municipal waste incinerators, medical waste incinerators, sinter plants, electric arc furnace, secondary aluminum smelters, cement kilns, etc. The average cancer risk of a resident living in the District was found to be 3.43E−04 under the site-specific exposure scenario. The top emission source is the sinter plant, followed by the electric arc furnace. The information has driven the local government to conduct more complete assessment and at the same time to consider enforcing a stricter local standard of dioxin emissions in the Siaogang District.     

A seasonality study of polychlorinated dibenzo-p-dioxins and dibenzofurans in ambient air in Kaohsiung (Taiwan) clustered with metallurgical industries

As a comprehensive monitoring survey on polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in Kaohsiung, 40 ambient air samples taken from 10 locations in four seasons were studied. PCDD/F concentrations at 0.312-4.58pgNm(-3) and I-TEQ values, ranging from 0.0319 to 0.256pgNm(-3) were determined for these samples, which were comparable to those of other urban cities. However, unlike studies on some other urban cities, the ambient air in Kaohsiung did not exhibit regular seasonality in PCDD/F concentrations. All samples were predominated, in common, by congeners OCDD, 1,2,3,4,6,7,8-HpCDF, 1,2,3,4,6,7,8-HpCDD, OCDF and 2,3,4,7,8-PeCDF. The congener profiles of the samples generally did not display any seasonal trend, either. The insignificant seasonality and constancy of congener profiles with time were attributed to the constant influence by emission sources in a metal-producing center, thereby resulting in high atmospheric dioxin levels in the nearby district. Principal component analyses identified that dioxin emissions in ambient air of the city originated from electric arc furnaces (EAFs) and sinter plants in the center. Concentration isopleth analyses assessing pollution sources and ambient air of the district also confirmed that its atmosphere was affected largely by the EAFs and sinter plants.     

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in water and suspended particulate matter from the Xijiang River, China

Concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in water and suspended particulate matter (SPM) collected from the Xijiang River, China, were measured by the quarter from September 2005 to June 2006. Total PCDD/F concentration ranged from 2.659 to 4.596pg/L for water and from 562.4 to 3259.5pg/g for SPM. Concentrations were high in summer and low in winter. I-TEQ values in water and SPM were low, ranging from 0.012 to 0.075pg/L, with a mean value of 0.039pg/L. Calculated annual loadings of total PCDD/Fs and I-TEQ were 8.55kg and 0.026kg, respectively. Composition and homologue distribution of PCDD/Fs were varied because of large seasonal differences in discharge from the Xijiang River into the South China Sea. Comparison of the PCDD/Fs homologue and congener profiles of atmospheric deposition, soil, and water revealed that soil was the dominant source of PCDD/Fs in the Xijiang River. Industrial effluents were also possible sources of PCDD/Fs. A good correlation between logK(oc) and logK(ow) was observed for 2,3,7,8-substituted PCDDs and PCDFs and correlation coefficients were 0.71 and 0.84, indicating organic matter in SPM played a dominant role in PCDD/Fs partition between SPM and water.     

Dioxin levels in fly ash coming from the combustion of bagasse

Levels of dioxins (PCDD/Fs) were determined in fly ash samples collected from a power plant burning bagasse for production of electricity. The concentrations ranged from 2.2 pgWHO-TEQ/g to 190 pg WHO-TEQ/g with samples collected after ESP containing significantly much higher (more than 12 times on average) levels than samples collected before ESP. Our results seem to indicate that both the de novo and the precursor mechanisms are significantly involved in the formation of dioxins the fly ash during combustion of bagasse.     

Relation of chlorine, copper and sulphur to dioxin emission factors

Dioxin emission factors for different combustion categories range over five orders of magnitude. Both chlorine (Cl(2)) and transition metals, including copper (Cu) have been suggested to promote the formation of dioxin in incinerators, and sulphur (S) has been suggested to inhibit dioxin formation. We show that dioxin (PCDD and PCDF) emission factors from 17 different combustion categories are approximately linearly correlated with the average copper or chlorine content of the combusted material, and inverse linearly correlated with the average sulphur content of the material. Copper and chlorine are correlated and, thus cannot be distinguished. The analysis suggests that the wide range of dioxin emission factors could be explained by the content of sulphur and transition metals or chlorine in combusted materials.     

Synergistic effect of transition metal oxides and ozone on PCDD/F destruction

Catalytic oxidations of PCDD/Fs (polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans) with ozone on the transition metal oxides (iron oxide or manganese oxide) at the temperature range of 120-180 degrees C were investigated. These two catalysts were prepared by precipitation methods. Iron oxide has a higher surface area (330 m(2)/g) than manganese oxide (53 m(2)/g). In the absence of ozone, the removal efficiencies of PCDD/Fs achieved with iron oxide or manganese oxide were between 83% and 85%, while the destruction efficiencies were only between 20% and 25% at 180 degrees C. It indicates that adsorption was the main removal mechanism of PCDD/Fs over these two catalysts. On the other hand, ozone addition greatly enhanced the catalytic activity of iron oxide or manganese oxide catalysts on the oxidation of gaseous PCDD/Fs. At 180 degrees C, the destruction efficiencies of gaseous PCDD/Fs achieved with iron oxide or manganese oxide with 100 ppm O(3) exceeded 90%. It indicates that catalytic ozonation achieved with iron oxide or manganese oxide is effective in decomposing PCDD/Fs and the application of ozone lowers the reaction temperature of PCDD/F oxidation below 200 degrees C. Furthermore, the synergistic effect of iron oxide and ozone is superior to that of manganese oxide due to the fact that the surface of iron oxide has more hydroxyl groups, which easily form hydrogen bonds with ozone and decompose to form atomic oxygen for the further reaction with dioxin molecules.     

Thermal treatment of polychlorinated dibenzo-p-dioxins and dibenzofurans from contaminated soils

Thermal treatment technology was used to remove polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from heavily contaminated soil. For a soil with an original PCDD/F content of 35,970ng International Toxic Equivalents (I-TEQ)/kg, >99.99% PCDD/F removal efficiency was obtained with a primary furnace at two different treatment temperatures (750 degrees C and 850 degrees C), while a secondary furnace at 1200 degrees C gave >98% decomposition efficiency. The total PCDD/F I-TEQ contents in treated soils at 750 degrees C and 850 degrees C were 1.56ngI-TEQ/kg and 2.15ngI-TEQ/kg, respectively, which were far below the soil pollution standard of Taiwan (1000ngI-TEQ/kg soil). Although air pollution control devices had significant effects on the removal of PCDD/Fs, the total I-TEQ concentrations in the upstream flue gas of PUF cartridge at 750 degrees C and 850 degrees C (2.61ngI-TEQ/Nm(3) and 2.38ngI-TEQ/Nm(3), respectively) were still higher than the stationary emission limit of the Taiwan EPA (0.5ngI-TEQ/Nm(3)). The above results also suggested that additional APCDs, such as activated carbon injection in front of the filter are needed to enhance PCDD/F removal efficiency.     

Atmospheric dry deposition of polychlorinated dibenzo-p-dioxins and dibenzofurans in the vicinity of municipal solid waste incinerators

This study focuses on the atmospheric dry deposition flux of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the vicinity of the two municipal solid waste incinerators (MSWIs) located in southern Taiwan. PCDD/Fs in ambient air were taken and analyzed for seventeen 2,3,7,8-substituted PCDD/Fs during November 2004 and July 2005. Results show that the mean concentrations of PCDD/Fs in the ambient air near MSWI-GS and MSWI-RW were 0.090 and 0.097pg I-TEQ/Nm(3), respectively. Dry deposition fluxes of total PCDD/Fs were 18.0 and 23.5pg I-TEQ/(m(2)d) in the ambient air near MSWI-GS and MSWI-RW, respectively, which were considerably higher than that measured in Guangzhou, China. Annual dry deposition fluxes of total PCDD/Fs in the ambient air near MSWI-GS and MSWI-RW were 189 and 217ng/(m(2)year), respectively, which were also much higher than dry deposition of total PCDD/Fs to the Atlantic Ocean. The results of the present study strongly suggest that exposure to PCDD/Fs in this area should be reduced. In addition, parametric sensitivity shows that dry deposition flux of PCDD/Fs is most sensitive to dry deposition velocity of the particle-phase, followed by air temperature and concentration of total suspended particulate but least sensitive to dry deposition velocity of the gas-phase.