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.     

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).     

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.     

Influence of a municipal solid waste incinerator on ambient air and soil PCDD/Fs levels

To examine the influence of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) emissions from a municipal solid waste incinerator (MSWI) on the environment, we measured the levels of PCDD/Fs in ambient air and soil samples collected near a MSWI in Bucheon, Korea. The PCDD/Fs concentrations in the ambient air samples ranged from 0.22 to 1.16 pg I-TEQm(-3) (13.39-75.16 pg m(-3)), with an average of 0.66 pg I-TEQ m(-3) (35.62 pg m(-3)). The soil samples contained between 1.25 and 74.98 pg I-TEQ g(-1) (38.15-3,303.33 pg g(-1)), with an average of 19.06 pg I-TEQ g(-1) (1,077.11 pg g(-1)). These levels were higher than those previously reported by other investigators in a number of surveys. The furan homologues predominated in the air samples and some soil samples, and the soil PCDD/Fs levels decreased with increasing distance from the MSWI. Comparison of the homologue patterns and a multivariate statistical analysis showed that PCDD/Fs emission from the MSWI directly affected the pattern of PCDD/Fs in air, while the PCDD/Fs patterns in soil differed according to the location relative to the MSWI, roads, and construction sites. These results collectively indicate that the MSWI was the major PCDD/Fs emission source in this area, but that unidentified combustion sources and vehicles might influence the environment to some extent.     

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.     

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.     

Environmental impact of a new hazardous waste incinerator in Catalonia,Spain: PCDD/PCDF levels in herbage samples

In April 1996 and 1998, the concentrations of polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) were determined in 40 herbage samples collected in the neighborhood of a hazardous waste incinerator (HWI) under construction in Constanti (Catalonia, Spain). In April 2000, 20 months after the HWI began operating, herbage samples were again collected at the same sampling points in which samples had been taken in the previous surveys. PCDD/F concentrations ranged between 0.13 and 0.65 ng I-TEQ/kg (dry matter), with a median and mean values of 0.29 and 0.32 ng I-TEQ/kg (dry matter), respectively. The results were compared with those obtained in the 1996 (median, 0.53 ng I-TEQ/kg; mean, 0.61 ng I-TEQ/kg) and the 1998 (median, 0.23 ng I-TEQ/kg; mean, 0.31 ng I-TEQ/kg) surveys. While in the period 1996-1998 a significant decrease (49%, P < 0.001) in the mean PCDD/F levels was noted, in the period 1998-2000 an increase of 3% (P > 0.05) was found in the concentrations of PCDD/Fs. The analysis of the results suggests two potential hypotheses: either the emissions of PCDD/Fs from the HWI are not negligible, or the current PCDD/F emissions from other sources near the HWI remained at similar levels to those reached in 1998. Anyhow, an exhaustive evaluation of the present data shows an absence of notable PCDD/F contamination by the HWI in the area under its direct influence. It seems also probable that the decline in the atmospheric levels of PCDD/Fs due other emission sources of PCDD/Fs in this area is currently stopped.     

Sampling and analysis of ambient dioxins in northern Taiwan

In this study, ambient air samples were taken concurrently in the vicinity area of a large-scale municipal waste incinerator (MWI) and the background area for measuring polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) concentrations from November 1999 through July 2000 in northern Taiwan. The results obtained from eighteen ambient air samples indicate that the mean PCDD/F concentration of seventeen 2,3,7,8-substituted congeners in wintertime (188–348 fg-I-TEQ/m³) is significantly higher than that measured in summertime (56–166 fg-I-TEQ/m³). In addition, the seasonal PCDD/F concentrations are compared with the ambient air quality data including CO, NO₂, PM₁₀ and TSP sampled from Taipei area to gain better insights. It indicates that the variation of ambient air PCDD/F concentrations is closely correlated with that of PM₁₀ concentrations. Besides, the results indicate that the I-TEQ concentration of ambient air in sampling site B (directly downwind of the MWI) is of the highest while the sampling site A (upwind of MWI) is of the lowest among all sampling sites. This implies that existing MWI can be a significant emitter of PCDD/Fs in this area. Furthermore, the patterns of the PCDD/F congener distribution at all sampling sites (including the background site in Taoyuan) are quite similar. OCDD concentration is of the highest among seventeen PCDD/F congeners investigated and accounts for about 35% of the total concentration. As for the I-TEQ concentrations, 2,3,4,7,8-PeCDF is the most significant contributor, generally being responsible for 30–45% of the total I-TEQ values depending on the sampling sites and seasons.     

PCDD/Fs and PCBs in airborne particulate matter of the greater Thessaloniki area, N. Greece

Particle-bound polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) were monitored at two sites in northern Greece for an eight-month period in 1999. PCDD/F concentrations were close to the lower end of reported values worldwide. Excepting a few cases, the PCDD/Fs homologue profile was stable. The gaseous PCDD/F fractions calculated were found to account for a small percentage of the total concentrations (<2% for OCDD/Fs and HpCDD/Fs, while 30-35% for TCDFs). Particle-bound PCBs were also found at low concentrations which, however, were higher at the urban site. Calculations of the dry deposition of particulate PCDD/ Fs and PCBs gave mean values of 0.52 and 0.59 pg I-TEQ/m2/day of PCDD/Fs, while 242 and 74 pg/m2/day of sigmaPCBs for the urban and the semirural areas respectively. An anticorrelation of PCDD/F concentrations with ambient temperature was derived particularly for the lower chlorinated congeners. A weak association with winds of western and southern origin was also observed. Factor analysis and literature source profiles were employed to identify possible emission sources. It was appeared that the PCDD/F compositional pattern of TSP is influenced by mixed sources the most prominent being uncontrolled fires and car exhausts.     

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.     

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.     

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.     

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.     

Cluster Analysis for Polychlorinated Dibenzo-p-Dioxins and Dibenzofurans Concentrations in Southern Taiwan

Abstract

This study investigates the characteristics of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the ambient air of two municipal solid waste incinerators (MSWIs: GS and RW) and a coal-fired power plant (PW) in the Kaohsiung County (KC) area in Taiwan. The results show that the toxic equivalency (TEQ) concentration in the flue gas of GS and RW averaged 0.090 and 0.044 ng international toxic equivalents (I-TEQ)/N·m³, respectively. The TEQ concentration in the flue gas of PW averaged 0.050 ng I-TEQ/N·m³. All PCDD/Fs concentrations from the stack flue gas are lower than the Taiwan Environmental Protection Administration emission standard. Furthermore, the mean I-TEQ concentration in the ambient atmosphere ranged from approximately 0.019 to 0.165 pg I-TEQ/N·m³, much lower than the environmental quality standards for dioxins in Japan (0.6 pg TEQ/N·m³). This work classified all sampling sites into three clusters according to k-means cluster analysis. The result shows a probable direct correlation between the GS incinerator and site C. Although the concentration from the PW plant did not exceed the emission standard, it was much higher than that in Fernández-Martínez’s study. For proper environmental management of dioxins, establishing a complete emission inventory of PCDD/Fs is necessary. The government of Taiwan should particularly pay more attention to power plants to address the information shortage.     

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.     

Fate of Polychlorinated Dibenzo-p-Dioxins and Dibenzofurans in a Fly Ash Treatment Plant

Abstract

To understand the fate of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in a fly ash treatment plant that used the Waelz rotary kiln process (hereafter the Waelz process), the samples of input and output media were collected and analyzed. The most important PCDD/F source in input mass was electric arc furnace (EAF) fly ash, which had a mean PCDD/F content of 18.51 ng/g and contributed more than 99% of PCDD/F input mass, whereas the PCDD/F input mass fractions contributed by the coke, sand, and ambient air were only 0.04%, 0.02%, and 0.000002%, respectively. For the PCDD/F output mass in the Waelz process, the major total PCDD/F contents of 43.73 and 10.78 ng/g were in bag-filter and cyclone ashes, which accounted for approximately 69% and 17%, respectively, whereas those of stack flue gas and slag were 14% and 0.423%, respectively. The Waelz process has a dechlorination mechanism for higher chlorinated congeners, but it is difficult to decompose the aromatic rings of PCDD/Fs. Therefore, this resulted in the accumulation of lower chlorinated congeners. The output/input ratio of total PCDD/F mass and total PCDD/F international toxicity equivalence (I-TEQ) was 0.62 and 1.19, respectively. Thus, the Waelz process for the depletion effect of total PCDD/F mass was positive but minor, whereas the effect for total PCDD/F I-TEQ was adverse overall.     

Fate of polychlorinated dibenzo-p-dioxins and dibenzofurans in a fly ash treatment plant

To understand the fate of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in a fly ash treatment plant that used the Waelz rotary kiln process (hereafter the Waelz process), the samples of input and output media were collected and analyzed. The most important PCDD/F source in input mass was electric arc furnace (EAF) fly ash, which had a mean PCDD/F content of 18.51 ng/g and contributed more than 99% of PCDD/F input mass, whereas the PCDD/F input mass fractions contributed by the coke, sand, and ambient air were only 0.04%, 0.02%, and 0.000002%, respectively. For the PCDD/F output mass in the Waelz process, the major total PCDD/F contents of 43.73 and 10.78 ng/g were in bag-filter and cyclone ashes, which accounted for approximately 69% and 17%, respectively, whereas those of stack flue gas and slag were 14% and 0.423%, respectively. The Waelz process has a dechlorination mechanism for higher chlorinated congeners, but it is difficult to decompose the aromatic rings of PCDD/Fs. Therefore, this resulted in the accumulation of lower chlorinated congeners. The output/input ratio of total PCDD/F mass and total PCDD/F international toxicity equivalence (I-TEQ) was 0.62 and 1.19, respectively. Thus, the Waelz process for the depletion effect of total PCDD/F mass was positive but minor, whereas the effect for total PCDD/F I-TEQ was adverse overall.     

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.     

Human exposure to dioxins and furans: application of the substance flow analysis to health risk assessment

Substance Flow Analysis (SFA) is an important instrument that allows for the undertaking of environmental management for a specific contaminant. 'Control Analysis' is a tool that assesses the effect on a target flow of changes in flows forming part of a control basis set. The purpose of the present study was to perform a modeling of the annual PCDD/F flows in Tarragona Province and to apply the model for human health risk assessment. The validation of the model has been evaluated by comparing estimated fluxes with experimental values. Eleven subsystems, as well as a set of 88 flows of the system in Tarragona Province were considered. The total PCDD/F accumulation in Tarragona Province was between 62.6 and 159.5 g I-TEQ/y. Accumulation in sediments (27.9-74.6 g I-TEQ/y) and soils (35.0-80.8 g I-TEQ/y) are the two principal modes of deposition. Estimated flow in human adipose tissue means a mean intake of PCDD/F (via ingestion and inhalation) of 243 pg I-TEQ/person/day. The food chain pathway accounts for 99% of the total daily intake. As a result of the simulation, a 100% decrease in industrial emissions would cause a 1.7% reduction in the PCDD/F accumulation in humans. In turn, a 100% reduction of PCDD/Fs in the industrial waste waters would cause only an insignificant 0.1% decrease in the accumulation of PCDD/Fs in humans.     

PCDD/F and PCB multi-media ambient concentrations, congener patterns and occurrence in a Mediterranean coastal lagoon (Etang de Thau, France)

Ambient concentrations, congener patterns and multi-media distribution of PCDD/Fs and PCBs were determined in air, water, sediment and mussels in a semi-enclosed marine ecosystem (Thau lagoon, France). summation operator2,3,7,8-PCDD/F and summation operator7ICES PCB air concentrations (0.2-1.4 and 31-57pg m(-3), respectively) were typical of rural areas. Concentrations in the water column were very low for PCDD/Fs (163-476fg L(-1)) and low for PCBs (138-708pg L(-1)). PCDD/F and PCB concentrations found in surface sediment (0.15-1.6 and 2.5-33ng g(-1) d.w., respectively) and mussel (13-21pg g(-1) d.w. and 10-39ng g(-1) d.w., respectively) were medium levels. PCDD/F congener patterns observed in air, water particulate phase and sediments were similar suggesting direct coupling among these compartments and atmospheric inputs of PCDD/Fs into the lagoon. Conversely, for the same set of samples, similar patterns were not observed for PCBs in the mentioned compartments.