Air and soil dioxin levels at three sites in Italy in proximity to MSW incineration plants

Levels of polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) in both air and soil samples were measured at three different sites in Italy, in proximity to three municipal solid waste incinerators (MSWIs) to determine baseline contamination and the contributory role of incinerator emissions. At the first site, located in an agricultural, cattle-breeding, typically flattish area of the Po Valley, the dioxin concentrations had already been measured before the start-up of the new MSWI. These dioxin concentrations were then again measured after two years of continual operation of the incinerator. Despite the presence of the plant, the PCDD/Fs concentrations appear not to have been affected and were found to be in a range of 22-125 fg I-TEQ m(-3) in the air samples and 0.7-1.5 pg I-TEQ g(-1) in the soil samples. The second site is located in an industrial district of the Veneto Region, in the surroundings of an old MSWI that is not equipped with Best Available Technology (BAT) dioxin removal system. The PCDD/Fs concentrations in the air samples were between 144 and 337 fg I-TEQ m(-3). This is a typical range of values for industrial areas, while the soil samples showed contamination levels between 1.1 and 1.4 pg I-TEQ g(-1). The third site lies in the Adige Valley, near a MSWI that has been equipped with BAT for flue gas cleaning. The observed values ranged from 10 to 67 fg I-TEQ m(-3) for the air samples and 0.08-1.2 pg I-TEQ g(-1) for the soil samples. The contributory factors of the varying characteristics of the different areas together with the types of technology adopted at each MSWI plant are discussed. The PCDD/Fs levels are subsequently compared with established values from previous studies.     

Levels of PCDD/FS in ambient air and soil in the vicinity of a municipal solid waste incinerator in Hsinchu

Levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were determined in twenty-one ambient air samples, eight soil samples and two stack gas samples, collected near or in a municipal solid waste incinerator (MSWI) in Hsinchu, Taiwan. A systematic decrease of PCDD/Fs in the ambient air from the northeastern area was observed. PCDD/Fs levels measured in the ambient air range from 0.058 to 0.127 pg-TEQ/m3. Higher PCDD/Fs levels in the ambient air were found during winter. In addition, PCDD/Fs levels measured in the soil range from 0.524 to 5.02 pg-TEQ/g d.m. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) did not provide sufficient evidence that the environmental PCDD/Fs contamination was caused by emissions from the Hsinchu MSWI. An unknown PCDD/Fs source was proposed using congener profile analysis and supported by both PCA and HCA.     

Assessment of PCDD/F risk after implementation of emission reduction at a MSWI

Municipal solid waste incinerators (MSWIs) have been shown to be important sources of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). The emission of PCDD/Fs by MSWIs is a controversial subject in human health risk assessment. In this study the effect of a MSWI on a residential area was assessed before and after the installation of an additional treatment system for flue gas. This additional treatment system resulted in a dramatic decrease in PCDD/F concentrations in stack flue gas samples by 99.98%, while the concentrations in air decreased by approximately 50% (36,500 and 0.75 pg I-TEQ m(-3) for air in 1999; 3.5 and 0.38 pg I-TEQ m(-3) in 2002; 1.6 and 0.076 pg I-TEQ m(-3) in 2005 for stack gas and air, respectively). Considering the congener distributions of PCDD/Fs between stack flue gas and air samples, the study area seemed to have been contaminated by other urban sources as well as the MSWI. ISC3 model results support the conclusion that this incinerator became only a minor contributor to the study area after installation of the supplementary systems. This resulted from both proper MSWI operation using modern technology and additional sources of contaminants in this region. Finally, PCDD/F uptake by humans through inhalation of contaminated air was estimated. Assuming that inhalation exposure contributes 10% of total exposure, total exposure was lower than WHO guidelines. These results confirm that proper operation and maintenance of the incinerator led to a reduction in emissions and potential health impacts of PCDD/Fs.     

Effects of burnings of wax apple stubble and rice straw on polychlorinated dibenzo-p-dioxin and dibenzofuran concentrations in air and soil

Measurements of the concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were made in ambient air, ash, and soil impacted by the open burning of wax apple and rice straw residues. Measurements showed that the mean PCDD/F concentration (0.458 pg I-TEQ/Nm3; international toxicity equivalence) in air at two wax apple orchards during open burning increased markedly, -8.1 times higher than that (0.057 pg I-TEQ/Nm3); before open burning. In addition, the mean PCDD/F concentration (0.409 pg I-TEQ/Nm3) in ambient air at a rice straw field was 4.6 times higher than that (0.089 pg I-TEQ/Nm3) before open burning. After burning the residues of wax apple stubble and rice straw, the contents of PCDD/F in ashes were 1.393 and 1.568 ng I-TEQ/kg-ash, respectively, and the contents of PCDD/F in soil were 2.258 and 2.890 ng I-TEQ/kg-soil, respectively. Therefore, the turnover of soil with the ash after open burning over years will result in the accumulation of PCDD/Fs in farm soils.     

Long-term monitoring and modeling of polychlorinated dibenzo-p-dioxins and dibenzofurans from municipal solid waste incinerators and surrounding area in northern Taiwan

Municipal solid waste incinerators (MSWIs) have long been the major contributors of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) to ambient air in Taiwan. After stringent MSWI emission standards were introduced in 2001, the long-term continuous monitoring of flue gas and ambient air quality became necessary to ensure the effectiveness of the related control strategies. Three MSWIs and the surrounding ambient air were investigated in the current study for PCDD/F characteristics during 2006 to 2011. The average concentrations in the flue gas ranged from 0.008?~?0.0488 ng I-TEQ/Nm³, which is much less than the emission standard in Taiwan (0.1 ng I-TEQ/Nm³) (I-TEQ is the abbreviation of International Toxic Equivalent). This led to extremely low levels in the ambient air, 0.0255 pg I-TEQ/Nm³, much less than the levels seen in most urban areas around the world. Additionally, the results obtained using the Industrial Source Complex Short-Term Dispersion Model (ISCST3) indicate that the PCDD/F contributions from the three MSWIs to the ambient air were only in the range from 0.164?~?0.723 %. Principal component analysis (PCA) showed that the PCDD/Fs in the air samples had very similar characteristics to those from mobile sources. The results thus show that stringent regulations have been an effective control strategy, especially for urban areas, such as Taipei City.     

Evaluation of PCDD/F levels in ambient air and soils and estimation of deposition rates in Kocaeli, Turkey

PCDD/F analyses were made in soil and ambient air samples taken from Kocaeli, an industrialized area of Turkey. Results showed that the levels of PCDD/F pollution are comparable to the levels observed in the various urban areas in the world. PCDD/F concentrations in surface soils ranged between 0.4 and 4.27 pg I-TEQ kg(-1) with a geometric mean of 0.76 pg I-TEQ kg(-1), while those in ambient air were between 23 and 563 f gm(-3), with geometric mean of 82.0 f gm(-3). Ambient air PCDD/F concentration in the city center was about 10 times higher than those in the rural area. Combustion activities present in the area were assessed to be the most significant source of the PCDD/F pollution based on the congener and homologue profiles and statistical analysis of the data. The deposition rate modeling of USEPA was applied and the deposition rates were determined in the range between 7.6 and 66.3 ng I-TEQ m(-2)year(-1) with a geometric mean of 15.9 ng I-TEQ m(-2)year(-1). The rates were higher than the recommended deposition rates in relation to the tolerable daily intake (TDI) range of PCDD/Fs for humans. The deposition velocities computed were also found to be high in both low and highly chlorinated PCDD/Fs, and this was attributed to the vapor phase deposition of volatile PCDD/Fs, and the scavenging effect of the precipitation on the particle-bound PCDD/Fs.     

PCDD/Fs levels in indoor environments and blood of workers of three municipal waste incinerators in Taiwan

This study monitored ambient air concentrations of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in three municipal waste incineration plants. Blood PCDD/Fs levels of 133 workers randomly selected from these plants were also measured. The associations between workers' blood PCDD/Fs concentrations and occupational exposures to PCDD/Fs were assessed. Means of air PCDD/Fs levels ranged from 0.08 to 3.01 pg/m3 in international toxic equivalents (I-TEQ). The geometric means of blood PCDD/Fs concentrations were 14.6, 15.8, 19.1 pg/g lipid in World Health Organization (WHO) TEQ, respectively, for workers from three plants. Air levels of total I-TEQ and all congeners, except 2,3,7,8-tetrachlorinated dibenzo-p-dioxin (TeCDD) and 1,2,3,4,7,8,9-heptachlorinated dibenzofuran (HpCDF), were significantly higher in plant B. However, blood concentrations of 2,3,7,8-TeCDD, 1,2,3,7,8-PeCDD, 2,3,7,8-TeCDF, 1,2,3,7,8-PeCDF and 1,2,3,4,7,8,9-HpCDF were significantly elevated in plant C workers. Although job contents, duration of employment and time spent in certain location were significantly different among incineration plants, they were not significantly associated with blood concentrations of any congener. Furthermore, results of the multiple regression analysis that assessed important occupational factors simultaneously and adjusted for potential confounders, showed significant associations between four congeners and incineration plant or job contents. However, the results were limited by small R-squares of the regression models. In conclusion, blood concentrations of several PCDD/Fs congeners were significantly different among three incineration plants. The differences were not explained by the discrepancy in job contents, duration of employment, and time activity in these plants.     

Levels of dioxins and furans in urban surface soil in Trondheim, Norway

A study was conducted on polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in surface soil in order to determine the concentration levels and possibly distinguishing between known and potential sources. The concentration levels are low (0.16-14 ng I-TEQ kg(-1)). The results show a clear pattern where the highest concentration levels were found in the oldest parts of the city. A number of sources were recognised in the soil samples through congener profiles, not all of them active, although similar congener profiles make it extremely difficult to distinguish between different sources. Estimations show that the municipal solid waste incinerator (MSWI) and domestic wood burning are the largest PCDD/F pollution sources within the area.     

Exposure of arc-furnace-plant workers to polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs)

This study aimed to evaluate serum polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) levels in electric-arc-furnace workers according to their corresponding occupational exposure. In addition, the ambient PCDD/Fs of the work environment were measured to provide additional support for the exposure and accumulation inside the electric arc furnace. The ambient PCDD/F concentrations inside the electric arc furnace were 1.557-1.917 pg-TEQ/Nm(3), 5-24 folds higher than those outside (0.080-0.385 pg-TEQ/N m(3)). In addition, higher average serum levels were measured in the workers with high occupational dioxin exposure (24.0 pg WHO-TEQ/g lipid) than in those with lower occupational dioxin exposure (13.8 pg WHO-TEQ/g lipid). Higher PCDFs/PCDDs ratios were found in serum samples from high-exposure groups than in low-exposure groups. The higher ratio of PCDFs/PCDDs was also found in ambient samples consistent with other metallurgical processes reported previously. Our results suggest that PCDD/Fs exposure exits in the smelting process of electric arc furnace, and the occupational hygiene should be taken more seriously concern in that workplace.     

A study of polychlorinated dibenzo-p-dioxins and dibenzofurans in the atmosphere of Hong Kong

A total of 27 ambient air samples of were collected from six locations in Hong kong during the period of January-August, 2000 and analysed for polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). In all sampling locations, higher concentrations of PCDDs/PCDFs, ranging from 0.03 to 0.43 pg I-TEQ/m3 were measured in winter months (January and March) than in the summer months (July and August) of concentrations at 0.018-0.025 pg I-TEQ/m3. These concentrations are similar to annual ranges reported earlier for two Hong Kong urban sites and other urban cities in Asia. Europe, and the United States. Despite significant seasonal variations in ambient air concentrations of PCDD/Fs (expressed in I-TEQ) were observed, the congener profiles of all the samples in this study period were similar, with OCDD, 1,2,3,4,6,7,8-HpCDD, OCDF and 1,2,3,4,6,7,8-HpCDF being the predominant species. However, the homologue profiles for the samples collected at the six locations of this study were found to display significantly different spatial and seasonal trends.     

Atmospheric deposition of PCDD/Fs near an old municipal solid waste incinerator: levels in soil and vegetation

The levels of polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) were determined in soil and vegetation samples taken from 24 sites in the vicinity of an old municipal solid waste incinerator (San Adrià del Besòs, Barcelona, Spain). Duplicate samples were collected within a radius of 3 km from the stack. PCDD/F concentrations in soils ranged from 1.22 to 34.28 ng I-TEQ/kg (d.m.) with median and mean values of 9.06 and 12.24 ng I-TEQ/kg, respectively. In turn, the levels of PCDD/Fs in vegetation samples ranged from 0.33 to 1.98 ng I-TEQ/kg (d.m.), with median and mean values of 0.58 and 0.70 ng I-TEQ/kg, respectively. Although the present PCDD/F concentrations in soil samples were higher than those recently found in soils taken near other incinerators from Catalonia, they are of the same order of magnitude than the levels of these pollutants found in incinerators from other countries. By contrast, the concentrations of PCDD/Fs in herbage samples were comparable to those found in recent surveys carried out in Catalonia.     

Atmospheric deposition of PCDD/Fs measured via automated and traditional samplers in Northern Taiwan

Most polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the atmosphere are bound to particles which are suspended in the atmosphere, and eventually settle on soil, vegetation, water bodies or other receptors in the environment. Monitoring atmospheric deposition fluxes (dry/wet) is important in tracing the environmental fate and behavior of PCDD/Fs. PCDD/F depositions were collected via an automated PCDD/F ambient sampler and traditional cylindrical vessels, respectively, from April 2007 to February 2008. The automated PCDD/F ambient sampler used in this study can prevent both re-suspension and photo degradation of the PCDD/Fs collected and effectively separates the PCDD/F samples into dry and wet contributions. The results indicated that the ambient PCDD/F concentrations collected using the PS-1 sampler ranged from 0.02 pg I-TEQ/m³ to 0.16 pg I-TEQ/m³ in Northern Taiwan. The results also indicated that the PCDD/F deposition flux collected using the automated PCDD/F sampler (17.5 pg I-TEQ/m² d to 25.8 pg I-TEQ/m² d) was significantly higher than that sampled with the cylindrical vessels (2.0 pg I-TEQ/m² d to 9.9 pg I-TEQ/m² d). The difference was attributed to the fact that part of the PCDD/F depositions collected using the traditional cylindrical vessels had undergone photo degradation and evaporation. In addition, the wet deposition flux of PCDD/Fs (39.4 pg I-TEQ/m² rainy day to 228 pg I-TEQ/m² rainy day) observed in this study was significantly higher than the dry deposition flux (12.3 pg I-TEQ/m² sunny day to 16.7 pg I-TEQ/m² sunny day). These results demonstrated that wet deposition is the major PCDD/F removal mechanism in the atmosphere.     

PCDD/F concentrations in milk of nonoccupationally exposed women living in southern Catalonia, Spain

Concentrations of 17 toxic 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) have been determined in pooled samples of breast milk from 15 mothers living in two residential areas (Tarragona downtown and an industrial area) in the vicinity of a new hazardous waste incinerator (HWI), now under construction in Tarragona (southern Catalonia, Spain). PCDD/Fs in human milk samples ranged between 5.9 and 17.1 pg I-TEQ/g fat (162-498 pg I-TEQ/l), with a mean value of 11.8 pg I-TEQ/g fat (310.8 pg I-TEQ/l). The percentages of fat ranged between 1.53 and 3.52. Although PCDD/F levels in milk from mothers living in the industrial area were found to be slightly higher than those observed in women living Tarragona downtown, most differences did not reach the level of statistical significance. In general terms, PCDD/F concentrations in human milk (pooled) samples of mothers living in the area of Tarragona are similar or lower than those previously reported for most industrialized countries.     

Levels and characteristic homologue patterns of polychlorinated dibenzo-p-dioxins and dibenzofurans in various incinerator emissions and in air collected near an incinerator

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were monitored in stack gas and fly ash of various Korean incinerators and in air samples collected near the facilities. Concentrations of PCDD/Fs in emissions were investigated, and characteristic PCDD/F homologue patterns were classified using statistical analyses. The PCDD/F emission levels in stack gas and fly ash samples from small incinerators (SIs) were higher than those from municipal solid waste incinerators (MSWIs). The PCDD/F concentrations ranged between 0.38 and 1.16 pg I-TEQ/m3 (21.2-75.2 pg/m3) in ambient air samples. The lower-chlorinated furans were the dominant components in most of the stack gas and fly ash samples from SIs, although this was not the case for fly ash from MSWIs. This homologue pattern is consistent with other studies reporting a high fraction of lower-chlorinated furans in most environmental samples affected by incinerator emissions, and it can be used as an indicator to assess the impact of such facilities on the surrounding environment.     

Comparison of emission of dioxins and furans from gasohol- and ethanol-powered vehicles

The exhaust emissions of 17 polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) were investigated in two spark-ignition light-duty vehicles, one gasohol-fueled and a flexible-fuel one fueled with hydrated ethanol. Gasohol is a mixture of gasoline and 22% ethanol. The influence of fuel type and quality, lubricant oil type, and use of fuel additives on the formation of these compounds was tested using standardized U.S. Federal Test Procedure (FTP)-75 cycle tests. The sampling of the PCDD/Fs followed the recommendations of a modified U.S. Environmental Protection Agency (EPA) Method 23 (www.epa.gov/ttn/ emc/promgate/m-23.pdf) and the analysis basically followed the U.S. EPA Method 8290 (http://www.epa.gov/osw/ hazard/testmethods/sw846/pdfs/8290a.pdf). Results showed that emission factors of PCDD/Fs for the.gasohol vehicle varied from undetected to 0.068 pg international toxic equivalency (I-TEQ) km(-1) (average of 0.0294 pg I-TEQ km(-1)), whereas in the ethanol vehicle they varied from 0.004 to 0.157 pg (I-TEQ) km(-1) (average of 0.031 pg I-TEQ km(-1)). In the gasohol-powered vehicle, the use of fuel additive diminished the emission of Octachlorodibenzo-p-dioxin (OCDD) significantly, whereas in the ethanol vehicle no significant associations were observed between the investigated variables and the emissions.     

Influence of start-up on PCDD/F emission of incinerators

This study aims to evaluate the influence of start-up on polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) concentration in the stack flue gas of incinerators and its contributing PCDD/F emission. The PCDD/F emission of the first sample among three consecutive stack flue gas samples of five intermittent incinerators, which sampled at a stable combustion condition after start-up, is 2-3 times higher than the mean of the others. For verifying the PCDD/F characteristics of incinerators during start-up, one continuous MSWI was investigated for two years. The elevated PCDD/F emissions of the MSWI during start-up could reach 96.9 ng I-TEQN m(-3) and still maintained a high PCDD/F emission (40 times higher than the Taiwan emission limit) even 18 h after the injection of activated carbon, indicating the memory effect. Taking the MSWI for example, which consists of four incinerators, the estimated annual PCDD/F emission from normal operational conditions was 0.112 g I-TEQ. However, one start-up procedure can generate approximately 60% of the PCDD/F emissions for one whole year of normal operations. And the PCDD/F emission, which is the result of the start-ups of four incinerators, was at least two times larger than that of a whole year's normal operations, without consideration for the PCDD/F emission contributed by the long lasting memory effect.     

Dry deposition of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in ambient air

The PCDD/Fs in the ambient air associated with concentration and dry deposition flux of four seasons were characterized in rural area. The mean PCDD/F concentrations were 0.342, 0.221, 0.675, 0.741 pg m(-3) and the mean I-TEQ values were 0.027, 0.016, 0.024, 0.063 pg m(-3) in spring, summer, fall and winter, respectively. Ambient air in winter was higher by a factor of 3.4 and 3.9 for PCDD/F concentration and I-TEQ, respectively, than in summer. The study area is located in a Tropical region. Hence, domestic heating is not found in this area and is not responsible for the elevated winter concentration in comparison to other studies. A smooth plate with a sharp leading edge that is pointed into the wind by a wind vane was used for measuring dry deposition flux of PCDD/Fs. Atmospheric dry deposition fluxes of total PCDD/Fs were 140, 116, 137, and 207 pg m(-2)day(-1) in spring, summer, fall, and winter, respectively, and averaged approximately 150 pg m(-2)day(-1). The total dry deposition flux was found to decrease as the temperature increased. Calculated dry deposition velocities of total PCDD/Fs were 0.45, 0.52, 0.32 and 0.39 cm s(-1) in spring, summer, fall, and winter, respectively, and averaged 0.42 cm s(-1).     

The PCDD/F and PBDD/F pollution in the ambient atmosphere of Shanghai, China

Rapid economic growth in the last two decades in Shanghai has had a great adverse influence on its air quality. Therefore, the atmospheric pollutants of Shanghai have received much concern. In this study, concentrations of 2,3,7,8-substituted PCDD/Fs and PBDD/Fs congeners were measured in the ambient air of four districts in Shanghai. The mean atmospheric concentrations (TEQs) of total 2,3,7,8-PCDD/Fs and 2,3,7,8-PBDD/Fs were 8031 fg m(-3) (497.1 fg I-TEQ m(-3)) and 1358 fg m(-3) (304.1 fg I-TEQ m(-3)) for Jiading District, 5308 fg m(-3) (289.0 fg I-TEQ m(-3)) and 709 fg m(-3) (146.9 fg I-TEQ m(-3)) for Zhabei District, 4014 fg m(-3) (144.4 fg I-TEQ m(-3)) and 1239 fg m(-3) (256.9 fg I-TEQ m(-3)) for Pudong District, 3348 fg m(-3) (143.2 fg I-TEQ m(-3)) and 699 fg m(-3) (148.4 fg I-TEQ m(-3)) for Huangpu District, respectively. Our results showed that almost all the PCDD/Fs and PBDD/Fs congeners were partitioned into the particulate phase except the lower chlorinated or brominated ones. The logarithm of the gas/particle partitioning coefficient K(p) has good linear correlation with that of the sub-cooled vapor pressure p(L). Concentrations of PCDD/Fs and PBDD/Fs were both positively correlated to elemental carbon in all districts except Pudong District, suggesting elemental carbon could be a good indicator for dioxins' air pollution. It is intensively suggested that more detailed and deeper studies about PBDD/Fs should be carried out due to their relatively high atmospheric concentrations in Shanghai.     

Emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans from stack gases of electric arc furnaces and secondary aluminum smelters

This study investigates the emissions of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) from four electric arc furnaces (EAFs) and eight secondary aluminum smelters (secondary ALSs) in Taiwan. The mean PCDD/F International-Toxicity Equivalents (I-TEQ) concentrations in the stack gases of these EAFs and secondary ALSs are 0.28 ng I-TEQ/Nm3 (relative standard deviation [RSD]= 100%) and 3.3 ng I-TEQ/Nm3 (RSD = 260%), respectively. The high RSDs, especially for those obtained from secondary ALSs, could be caused by the intrinsic differences in their involved feeding materials, furnace operating conditions, and air pollution control devices. The mean I-TEQ emission factor of PCDD/Fs for EAFs (1.8 microg I-TEQ/tonne-feedstock) is lower than that for secondary ALSs (37 microg I-TEQ/tonne-feedstock). This result might be because the involved furnace temperatures for secondary ALSs (650-750 degrees C) are lower than those for EAFs (1600-1700 degrees C), resulting in the deterioration of the combustion condition, leading to the formation of PCDD/Fs during the industrial process. This study found that the total PCDD/F emissions from EAFs (20 g I-TEQ/yr) and secondary ALSs (18 g I-TEQ/yr) are approximately 27, 53, and approximately 24, 49 times higher than those from municipal solid waste incinerators (MSWIs; 0.74 g I-TEQ/yr) and medical waste incinerators (MWIs; 0.37 g I-TEQ/yr), respectively; while those are 44 and 40% of total PCDD/F emission from sinter plants (45 g I-TEQ/ yr), respectively. Considering a more stringent emission limit has been applied to waste incinerators (0.1 ng I-TEQ/Nm3) in Taiwan lately, the results suggest that the control of the emissions from metallurgical processes has become the most important issue for reducing the total PCDD/F emission from industrial sectors to the ambient environment.     

Air-vegetation transfer of PCDD/PCDFs: an assessment of field data and implications for modeling

This study was designed to evaluate soil and air (gas and particle) transfer of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) to vegetation in residential and industrial areas. In a first part, soil-vegetation transfer was assessed. The levels of PCDD/Fs in 120 soil and 120 herbage samples collected from 1996 to 2002 in an industrial area of Montcada (Barcelona, Spain), near a municipal solid waste incinerator (MSWI), were determined. Some additional individual samples were also evaluated. It was concluded that high soil concentrations, which are not at steady state with the air layer above it, show a tendency for PCDD/Fs to escape via volatilization. In a second part of the study, air-vegetation transfer was examined. PCDD/F concentrations from 24 herbage samples were used, while PCDD/F concentrations were also measured in seven high-volume air samples and seven passive air-vapor samples. Scavenging coefficients (m3 air "sampled"/g grass d.m.) ranged from 1.9 to 11.3 m3/g. A good trend with K(OA) was observed for PCDDs (R=0.82), while it was lower for PCDFs (R=0.55). The current results corroborate that PCDD/F concentrations in vegetation are associated with atmospheric deposition. For the highest substituted PCDD/F congeners, the air-particle uptake from plants is the principal pathway. In regions impacted by combustion emission sources, PCDD/F gas-particle partitioning is influenced by a higher concentration of particles in the air. Particles and associated particle-bound PCDD/Fs would sorb to leaf surfaces, and are subject to removal via wash off. However, in areas where emissions to air are not very notable, vapor absorption would be the principal source of vegetation pollution. The results of this investigation can have a potential interest in risk assessment studies and environmental fate models.