Atmospheric deposition of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in Guangzhou,China

Atmospheric deposition of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) was investigated at four locations, namely at Yuancun, Wushan, Haizhu and Changban in Guangzhou City, Guangdong Province. The annual deposition fluxes of tetra- to octa-CDD/Fs (total PCDD/Fs) were found to range from 170 to 3000 (mean 1500) pg m⁻² day⁻¹, and the fluxes of total 2, 3, 7, 8-substituted PCDD/F congeners ranged from 2.1 to 41 (mean 20) pg WHO-TEQ m⁻² day⁻¹ at Wushan. The average deposition fluxes of total 2, 3, 7, 8-substituted PCDD/F congeners in rainy season were found to be 37, 27 and 28 pg WHO-TEQ m⁻² day⁻¹ at Yuancun, Haizhu and Changban, respectively, and the PCDD/F deposition fluxes behaved obviously higher in rainy season than in dry season. Results from regression analysis showed that number of rainy days, the amount of wet precipitation, PCDD/F concentrations in particles and organic carbon content played important roles in the variation of PCDD/F deposition fluxes. Monthly average temperatures change little over the year. Therefore, it only played a minor role in monthly variation of PCDD/F deposition fluxes. Particle deposition fluxes were generally not considered as the factor that could cause the differences in PCDD/F deposition fluxes between rainy and dry season, but were found to be related with PCDD/F deposition fluxes in rainy season or dry season. It was found that the profiles of PCDD/F homologs or congeners in the samples were the same either spatially or temporally, indicating that the PCDD/F emission sources were similar to one another. The similarities in PCDD/F homolog patterns and the differences in deposition fluxes between samples collected from heavy-traffic roadside and nearby residence house roof indicated that vehicle exhaust might be an important source for PCDD/F in Guangzhou. PCDD/F concentrations and profiles of PCDD/F homologs in atmospheric deposition were compared with those in both total suspended particles in air and soils, and conclusions indicated that atmospheric deposition possibly tended to remove lower-chlorinated DD/Fs from air and was one of sources for PCDD/Fs in soils.     

Precipitation scavenging of particle-bound contaminants – A case study of PCDD/Fs

Precipitation scavenging of particles is a major mechanism for atmospheric deposition of organic contaminants, but there have been few field studies. We studied precipitation scavenging of PCDD/Fs with the aim of deepening understanding of environmental variables influencing this process. Bulk deposition of PCDD/Fs and their concentrations in ambient air measured at a background site in Sweden were used to calculate precipitation scavenging ratios. Contrary to expectations, increasing scavenging ratios with decreasing degree of chlorination of the PCDD/F congeners were observed when the particle-associated PCDD/F concentrations in air were used for the calculation. This was attributed to differences in temperature and thereby in the gas – particle partitioning of the PCDD/Fs between ground level and clouds where much of the particle scavenging occurs. When the particle-associated PCDD/F concentrations were recalculated for a 10–20 °C lower temperature, the scavenging ratios of the different PCDD/F congeners were similar. Hence differences between ground level and in-cloud temperature should be considered when calculating scavenging ratios from field observations and when modeling this process. The scavenging ratios averaged ～200 000, with lower values when the particle-associated PCDD/F concentration in air was lower. The soot concentration in air was a good predictor of bulk deposition of PCDD/Fs.     

Assessment of variations in atmospheric PCDD/Fs by Asian dust in Southeastern Korea

Atmospheric concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were measured in southeastern Korea during the spring of 2002. During this period, severe Asian dust events (ADs) occurred throughout Korea. Total suspended particulates (TSP) of ADs (456.8 μg m⁻³) increased approximately 3.6-fold compared with non-Asian dust events (NADs; 128.5 μg m⁻³). However, the concentrations of PCDD/Fs (average concentration, 3.34 pg m⁻³) did not increase as much as TSP; there was not a significant difference in the concentrations of particle-bound PCDD/Fs collected between ADs (2.45 pg m⁻³) and NADs (2.05 pg m⁻³). Meanwhile, according to TSP levels, the concentrations during NADs were 2.8-fold higher than ADs (16.73 and 5.98 ng g⁻¹-TSP, respectively). High TSP levels during sand storms without an increase in PCDD/Fs reflected an increase in coarse and accumulation mode particles. Gas/particle partitioning studies revealed the additional inputs of particulate matters to the air during ADs which did not relate with the increase of PCDD/Fs. Furthermore, emissions from ADs may consist of relatively complex atmospheric particles; back trajectories showed air masses moving at low altitudes over Korea, but there were no differences in PCDD/Fs or atmospheric pollutants regardless of air movements. The study area, which is located in southeastern Korea, might be affected by both marine and regional anthropogenic sources, which do not appear to cause clear differences in PCDD/F concentrations or congener profiles between different air trajectories.     

Polychlorinated dibenzo-p-dioxins, dibenzofurans, biphenyls, naphthalenes and polybrominated diphenyl ethers in the edible fish caught from the Baltic Sea and lakes in Finland

A total of 156 fish composite samples were collected from five areas of the Baltic Sea and from three lakes and analysed for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs) and polybrominated diphenyl ethers (PBDEs). The European Union's maximum permissible level for PCDD/Fs, 4 pg WHO-TEQ/g fresh weight (fw), was exceeded in salmon, river lamprey and Baltic herring. In other species from the Baltic Sea, the 90th percentile was 3.42 pg WHO(PCDD/F)-TEQ/g fw. In the lake fish, the concentrations of PCDD/Fs, PCBs and PCNs were only 29-46% of those in the same species caught from the Baltic Sea, whereas the concentrations of PBDEs in the lake fish were as high as in the Baltic Sea fish. Dioxin-like PCBs contributed to the total dioxin-like toxicity of PCBs and PCDD/Fs by 49+/-12% in all the analysed samples.     

Dioxins,furans and polycyclic aromatic hydrocarbons emissions from a hospital and cemetery waste incinerator

An experimental campaign was carried out on a hospital and cemetery waste incineration plant in order to assess the emissions of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polycyclic aromatic hydrocarbons (PAHs). Raw gases were sampled in the afterburning chamber, using a specifically designed device, after the heat recovery section and at the stack. Samples of slags from the combustion chamber and fly ashes from the bag filter were also collected and analyzed. PCDD/Fs and PAHs concentrations in exhaust gas after the heat exchanger (200–350 °C) decreased in comparison with the values detected in the afterburning chamber. Pollutant mass balance regarding the heat exchanger did not confirm literature findings about the de novo synthesis of PCDD/Fs in the heat exchange process. In spite of a consistent reduction of PCDD/Fs in the flue gas treatment system (from 77% up to 98%), the limit of 0.1 ng ITEQ Nm⁻³ at the stack was not accomplished. PCDD/Fs emission factors for air spanned from 2.3 up to 44 μg ITEQ t⁻¹ of burned waste, whereas those through solid residues (mainly fly ashes) were in the range 41–3700 μg ITEQ t⁻¹. Tests run with cemetery wastes generally showed lower PCDD/F emission factors than those with hospital wastes. PAH total emission factors (91–414 μg kg⁻¹ of burned waste) were in the range of values reported for incineration of municipal and industrial wastes. In spite of the observed release from the scrubber, carcinogenic PAHs concentrations at the stack (0.018–0.5 μg Nm⁻³) were below the Italian limit of 10 μg Nm⁻³.     

PCDD/F formation from oxy-PAH precursors in waste incinerator flyash

The yield of PCDD/F in relation to the presence of oxygenated PAH in model waste incinerator flyash has been investigated in a fixed bed laboratory scale reactor. Experiments were undertaken by thermal treatment of the model flyash at 250 and 350 °C under a simulated flue gas stream for 2 h. After reaction, the PCDD/F content of the reacted flyash and the PCDD/F released into the exhaust gas, and subsequently trapped by XAD-II resin in a down-stream condensation system were analyzed. The PAHs investigated were, dibenzofuran and benzo[b]naphtho[2,3-d]furan and were spiked onto the model flyash as reactant precursors for PCDD/F formation. The results showed significant formation of furans from both of the PAH investigated, however except from some highly chlorinated dioxin congeners, the formation of dioxins was not so common. Benzonaphthofuran was significantly more reactive than dibenzofuran in PCDD/F formation, in spite of the fact that dibenzofuran is structurally more similar to that of PCDD/F. Thus, there was no clear attribution between the chemical structure of PAH used and the formation of PCDD/F. There were considerable differences between the yields of PCDD/F congeners in the gaseous species and those in the reacted flyash under the same operational conditions. The concentration of PCDD/Fs was reduced at the higher reaction temperature of 350 °C; however, the higher temperature resulted in the majority of the PCDD/F formed on the flyash being released into the gas phase.     

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.     

Dioxin concentrations in sediments of the Baltic Sea--a survey of existing data

Recent survey results for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs, dioxins) in Baltic Sea sediments from Finland, Sweden and Denmark were merged with previously published Baltic Sea data. Regional distribution of concentration levels, differences in congener patterns, and temporal changes in sediment profiles were examined. One of the main objectives was to study if any major point sources for different PCDD/F congeners could be identified on a regional scale, based on sediment records. The survey confirmed the impact of chlorophenol production derived highly chlorinated PCDF-congeners on the total toxicity in sediments in the Gulf of Finland near the Kymijoki river estuary. Signatures of other point sources or combined point sources pertinent to specific industry branches or particular production processes (such as pulp bleaching, vinyl chloride production, thermal processes) may be discerned. However, the findings did not support any of the known point sources significantly influencing those congeners that are most abundant in Baltic herring and salmon. Instead, regional distributions in the Baltic Sea indicate that atmospheric deposition may act as a major source for those congeners and especially for 2,3,4,7,8-PeCDF. There were clear indications of declines in levels in sediment in some areas, but generally the levels of highly chlorinated PCDD/Fs on the northern coast of the Gulf of Finland were still high when compared with other areas of the Baltic Sea. Major areas with data gaps cover the south-eastern and eastern coastal regions of the Baltic Proper and the southern Gulf of Finland.     

PCDD/Fs and PCBs in Baltic herring during the 1990s

Baltic herring samples caught from the Baltic Sea during the spring periods of 1993-1994 and 1999 were analysed for polychlorinated dibenzo-p-dioxins (PCDD), polychlorinated dibenzofurans (PCDF), and polychlorinated biphenyls (PCB). For analyses, 1570 individual herring were combined to 120 pools. Correlations between concentrations of congeners 1,2,3,7,8-PeCDD, 1,2,3,7,8-PeCDF, 2,3,4,7,8-PeCDF, and 2,3,4,6,7,8-HxCDF, and age of herring were the strongest (r>0.8) followed by correlations between PCB congeners PCB 105, 118, 126, 156, 169 and 180 (r>0.7), and age of herring. Due to higher fat percentage in herring in the Gulf of Bothnia the concentrations of PCDD/Fs and PCBs on fresh weight (fw) basis were higher than in herring in the Gulf of Finland. The concentrations of WHO(PCDD/F)-TEQs ranged from 1 to 27 pg/g fw, depending on the age and catchment area of herring, and concentrations of WHO(PCB)-TEQs reached 32 pg/g fw. Between the two studied time points no clear downward trend in concentrations was observed.     

Gas/particle partitioning of polychlorinated dibenzo-p-dioxins and dibenzofurans in atmosphere; evaluation of predicting models

The gas/particle partitioning of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) was measured at three sites for a year in order to monitor the variation of PCDD/Fs levels and describe their partitioning. The air concentrations of PCDD/Fs ranged from 71 to 1161 fg I-TEQ/m³ and large changes in these levels did not correlate with seasonal changes during this study. Different homolog patterns were observed in the gas/particle phase. High chlorinated dioxin/furans dominated the particle phase while low chlorinated dioxin/furans dominated the gas phase. The high correlation coefficient between log [(PCDD/Fs_vap)(TSP)/(PCDD/Fs_pat)] and 1/T was observed in lower chlorinated dioxin/furans unlike in OCDD/F. The slope of homolog ranged from −0.410 to −1.025 and that of 2,3,7,8-substituted isomers ranged from −0.379 to −0.772 in plots of the log partition coefficient (K_p) versus the log subcooled vapor pressure (P_L°).The octanol/air partition coefficient (K_oa)-based model of PCDD/Fs is more compatible with experimental data than those of the Junge–Pankow model that tends to overestimate results, even though both models include some level of uncertainty. However, both models can underestimate the particle phase of PCDD/Fs, especially when the ambient air temperature is extremely low in winter.     

Concentrations of PCDD/PCDF in soil close to a secondary aluminum smelter

Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/Fs) were analyzed in samples of the emissions from a secondary aluminum smelter (ALS) and soil samples around the plant. The purpose was to estimate the impact of the emissions on the surrounding environment.PCDD/F soil concentrations were higher in the proximity of the plant, exceeding the limit adopted in Italy in soils for green areas and residential uses and the upper limit of several reference concentrations. The most contaminated sites were less than 500 m from the plant and the dioxin concentration with the distance from the ALS.Principal component analysis (PCA) showed that emissions from the ALS were the source of PCDD/F contamination in the soils closest to the plant. Multivariate data analyses such as PCA are therefore useful to identify sources of emission causing contamination.     

Atmospheric bulk deposition of dioxin and furans to Danish background areas

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were measured in bulk deposition at three Danish rural forest sites with a mutual maximum distance of 450 km. At one of the forest sites concentrations in the ambient atmosphere were sampled from a 12 m high tower. Sampling was carried out within a period of 3 years with sampling intervals of 1–2 months. Mean bulk deposition fluxes were 1 ng m⁻² yr⁻¹ I-TEQ and deviated less than 30% between the sites. Yearly average PCDD/F concentrations in the atmosphere were 24 fg m⁻³ I-TEQ with maximum values in the winter period. During winter months atmospheric concentrations of PCDD/F and oxidized sulphur compounds showed a positive correlation, furthermore seasonal bulk deposition showed correlation between PCDD/F and sulphate.     

流化床垃圾焚烧炉产生的有毒二噁英同类物分布研究

测定了流化床垃圾焚烧炉焚烧产生的飞灰、烟尘和烟气中的2，3，7，8位氯取代二噁英同类物的含量及其毒性当量。结果表明，产生的二噁英主要存在于飞灰中，烟气中的含量很少。飞灰中二噁英总浓度和毒性当量分别为8.44ng／g和0．80ng／g，经过布袋除尘器后的烟尘和烟气中二噁英的浓度之和与毒性当量之和分别为0．34ng／m^3和0．02ng／m^3，而布袋除尘器前的烟尘和烟气中二噁英的浓度之和与毒性当量之和分别为40．78ng／m^3和3．0ng／m^3。飞灰和烟尘中2，3，7，8位氯取代二噁英同类物的分布相似，但是与烟气中2，3，7，8位氯取代二噁英同类物的分布差别较大。通过了解有毒二噁英同类物的分布，可以进一步优化流化床垃圾焚烧炉的焚烧条件，降低二噁英的排放量，减少垃圾焚烧对环境的污染。     

Prevalence of low chlorinated dibenzo-p-dioxin/dibenzofurans in human serum

Mono- to tri-chlorinated dibenzo-p-dioxin/dibenzofurans (DD/Fs) have not been studied as extensively as the 17 toxic 2,3,7,8-substituted congeners. In this study for the first time, mono- to octa-chlorinated DD/Fs were analyzed for seventy one human serum samples collected from incinerator workers as well as residents living near and far from the facility. The mean concentrations of ∑Cl_1–8DD/Fs and 17-toxic congeners were 1890 and 398 pg g^?1 lipid (11.9 TEQ pg g^?1 lipid), respectively. 2,3,4,7,8-PeCDF, 1,2,3,7,8-PeCDD, and 1,2,3,6,7,8-HxCDD were predominant congeners that accounted for more than 78% of the TEQ concentrations. The profile for polychlorinated dibenzo-p-dioxins (PCDDs) was dominated by the most chlorinated congener, OCDD (>58%), while decreasing concentrations with increasing degree of chlorination were seen for polychlorinated dibenzofurans (PCDFs); MoCDFs (>83%) and DiCDFs (>6%). ∑Cl_1–3DD/Fs accounted for 77% of the serum concentrations of ∑Cl_1–8DD/Fs. These findings confirm that human beings are exposed to a large amount of ∑Cl_1–3DD/Fs. Moreover, MoCDFs contributed more than 60% of the ∑Cl_1–8DD/Fs and was highly correlated with ∑Cl_1–8DD/Fs. Thus, 2-MoCDF could be a predictive indicator for ∑Cl_1–8DD/Fs (r_s = 0.96), and the combination of 2-MoCDF and OCDD could explain the 95.9% variation in the serum of ∑Cl_1–8DD/Fs. These results suggest that low chlorinated DD/Fs should be studied extensively until these low chlorinated congeners will have been elucidated for their toxicities.     

Emissions of PCDD/Fs,PCBs, and PAHs from legacy on-road heavy-duty diesel engines

Exhaust emissions of seventeen 2,3,7,8-substituted polychlorinated dibenzo-p-dioxin/furan (PCDD/F) congeners, tetra–octa PCDD/F homologues, 12 WHO 2005 polychlorinated biphenyl (PCB) congeners, mono–nona chlorinated biphenyl homologues, and 19 polycyclic aromatic hydrocarbons (PAHs) from three legacy diesel engines were investigated. The three engines tested were a 1985 model year GM 6.2 J-series engine, a 1987 model year Detroit Diesel Corporation 6V92 engine, and a 1993 model year Cummins L10 engine. Results were compared to United States’ mobile source inventory for on-road diesel engines, as well as historic and modern diesel engine emission values. The test fuel contained chlorine at 9.8 ppm which is 1.5 orders of magnitude above what is found in current diesel fuel and 3900 ppm sulfur to simulate fuels that would have been available when these engines were produced. Results indicate PCDD/F emissions of 13.1, 7.1, and 13.6 pg International Toxic Equivalency (I-TEQ) L⁻¹ fuel consumed for the three engines respectively, where non-detects are equal to zero. This compares with a United States’ mobile source on-road diesel engine inventory value of 946 pg I-TEQ L⁻¹ fuel consumed and 1.28 pg I-TEQ L⁻¹ fuel consumed for modern engines equipped with a catalyzed diesel particle filter and urea selective catalytic reduction. PCB emissions are 2 orders of magnitude greater than modern diesel engines. PAH results are representative of engines from this era based on historical values and are 3–4 orders of magnitude greater than modern diesel engines.     

Modeling the atmospheric transport and deposition of polychlorinated dibenzo-p-dioxins and dibenzofurans in North America

The atmospheric fate of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) was simulated for the year 2000 in North America using a SMOKE/CMAQ-based chemical transport model that was modified for this purpose. The 1999 USEPA emission inventories of PCDD/Fs and criteria pollutants were used. The 1995 Canadian emission inventory of criteria pollutants and the 1995 Canadian area source emissions for PCDD/Fs were used with the 2000 Canadian point source emissions. Modifications to CMAQ involved coupling it with dual organic matter (OM) absorption and black carbon (BC) adsorption models to calculate PCDD/F gas–particle partitioning. The model satisfactorily reproduced the particle bound fractions at all rural sites for which there were measured data and across the whole domain, the modeled vs. measured differences in particle bound fractions were less than 20% for nearly all congeners. The model predicted ambient air PCDD/F concentrations were also consistent with measurements. Simulated deposition fluxes were within 58% of direct measurements. PCDD/F atmospheric depositions to each of the Great Lakes were estimated for the year 2000. The results indicate that approximately 76% of the total deposition of PCDD/Fs to the Great Lakes (in W-TEQ, or toxic equivalent units as defined by the World Health Organization) is attributed to PCDD/Fs absorbed into OM in aerosol. For all of the lakes, more than 92% of all deposition is particle phase wet deposition and only 5–8% is particle phase dry deposition. Wet deposition from the gas phase is negligible. Of the 17 toxic PCDD/F congeners, the Cl_4–5DD/F compounds contribute approximately 70% to the total atmospheric deposition to the Great Lakes. The seasonal changes in the PCDD/F deposition flux track variations in ambient temperature.     

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.     

Levels and homologue profiles of PCDD/Fs in sediments along the Swedish coast of the Baltic Sea

Background, aim, and scope  The primary aim of this study was to explore the variations in PCDD/F levels and homologue profiles of Baltic surface sediments by comprehensively analyzing polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in samples from a large number of sites, encompassing not only previously known hotspot areas, but also sites near other potential PCDD/F sources, in pristine reference areas (in which there was no industrial activity) and offshore sites. Materials and methods  Surface sediment samples (146 in total) were collected at various points along the Swedish coast and offshore areas. In addition, bulk deposition was sampled, monthly, at a single site in northern Sweden during 1 year. The concentrations of tetra- through octa-substituted CDD/Fs were determined in both matrices. Results  Highly elevated concentrations of PCDD/Fs were found at many sites in coastal areas and concentrations were also slightly elevated in some offshore areas. Homologue profiles varied substantially amongst samples from coastal sites, while those from offshore and other pristine sediments were relatively similar. The offshore sediments showed different profiles from those observed in the deposition samples. Sediment levels of PCDD/Fs were not generally significantly correlated to organic carbon levels, except in some pristine areas. Comparison of data obtained in this and previous studies suggest that both their levels and profiles are similar today to those observed 20 years ago in coastal and offshore areas. The only detected trend is that their levels appear to have decreased slightly in the offshore area of the Bothnian Sea. Discussion  The localization of hotspot areas along the coast, the lack of consensus between PCDD/F profiles of sediments and general background, and their weak correlations with organic carbon suggest that PCDD/Fs in the study area largely originate from local/regional emissions. However, due to complicating factors such as sediment dynamics and land upheaval, it is not possible to conclude whether these pollutants derive from recent emissions or from a combination of recent emissions and re-distribution of previous inputs. Conclusions  The results show that: elevated levels of PCDD/Fs are present in both coastal and offshore areas of the Baltic Sea, the major hotspots are close to the shore, and there are large variations in profiles, indicating that local emissions are (or have been) the major causes of pollution. Recommendations and perspectives  In order to identify other hotspot areas and trace sources, comprehensive analysis of PCDD/Fs in surface sediments is needed in all areas of the Baltic Sea that have not been previously investigated. The high levels of PCDD/Fs observed in surface sediments also indicate a need to elucidate whether they are due mainly to current emissions or a combination of recent pollution and re-distribution of historically deposited pollutants. To do so, better understanding of sediment dynamics and present-day inputs, such as riverine inputs, industrial effluents, and leakage from contaminated soil is required. There are indications that contaminated sediments have a regional impact on fish contamination levels. However, as yet there is no statistically robust evidence linking contaminated sediments with elevated levels in Baltic biota. It should also be noted that the Baltic Sea is being massively invaded by the deep-burrowing polychaete Marenzielleria ssp., whose presence in sediments has been shown to increase water concentrations of hydrophobic pollutants. In awareness of this, it is clear that high levels in sediments cannot be ignored in risk assessments. In order to investigate the emission trends more thoroughly, analysis of PCDD/Fs in offshore sediment cores throughout the Baltic Sea is also recommended. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

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.     

Polychlorinated biphenyl, polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran residues in sediments and fish of the River Nile in the Cairo region

The levels of organohalogenated contaminants, i.e. PCBs, PCDDs and PCDFs were determined in sediment and fish samples collected from different locations in the River Nile, Egypt. Thirty-six sediment and eighteen fish samples were carried out during a period of 12 months from February 2003 to February 2004. Determination of PCBs and dioxins was carried out using a high resolution GC mass spectrometer. The results indicated that the PCB and PCDD/F mean concentrations in sediment samples ranged from 1461 to 2244 and from 240 to 775pgg(-1) dry wt basis, respectively. The mean concentration of PCBs and PCDD/Fs in fish samples were found to be in the range from 695 to 853pgg(-1) fresh wt for PCB congeners and from 27.7 to 121pgg(-1) lipid for total PCDD/Fs. Moreover, the concentrations of both PCBs and PCDD/Fs were found to be different at different locations along the River Nile. It could be concluded that the contamination of the River Nile is within the permissible limits set by the FDA and the Egyptian Standards for fish and shellfish.