Long-term automated sampling of PCDD/PCDF flue gas: current status and critical issues

After entry into force of the Stockholm Convention and Aarhus Protocol and in order to implement the upcoming European legal background, the European countries are asked to apply control measures to reduce the release of persistent organic pollutants (POPs) such as dioxins and furans (PCDD/PCDF) and polychlorinated biphenyls as well as to establish POPs release inventories. In this perspective, development of measuring techniques of emissions is a focal issue in acquiring useful information. In this paper, results of various measurement campaigns at different municipal waste incineration (MWI) plants using long-term automated sampling of PCDD/PCDF are presented. The samples collected from both manual and automated campaigns were analyzed following the European Standard EN-1948:2006 by high-resolution gas chromatograph/high-resolution mass spectrometer. Performances of two different commercial systems have been investigated. Anomalous values occurred during one long-term campaign (22.16 pg I-toxic equivalent (TEQ)/Nm(3)), compared to average values (4-5 pg I-TEQ/Nm(3)) of the MWI. At this maximum value, a main occurrence of abnormal and instable operating conditions has been found. Sampling based on long-term basis was found to be more reliable to monitor PCDD/PCDF emissions than occasional short-term sampling. Nevertheless, the results of long-term campaigns demonstrate that emission levels detected in 15-30 days campaigns, when unsteady operating conditions can occur, as start-up and shut down, are not immediately comparable to the typical levels in a 6-8 h, when operating conditions are generally stable. Moreover, there are often differences observed in the congener profiles between short- and long-term campaigns.     

Emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans from various industrial sources

This study characterized the emissions of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) from the stack flue gases of 17 industrial sources, which were classified into 10 categories. The results show that the mean PCDD/PCDF concentration of secondary zinc smelter (Zn-S) and secondary copper smelter (Cu-S) is 2.44 ng international toxic equivalent (I-TEQ)/Nm3 (N represents normal conditions at 0 degrees C, 760 mmHg), which was found to be significantly greater than that of industrial waste incinerators (mean concentration = 0.15 ng I-TEQ/Nm3). These results imply that the controlling of secondary metallurgical melting processes is more important than industrial waste incineration for the reduction of PCDD/PCDF emissions. The mean emission factors of cement production, Zn-S and Cu-S, are 0.052, 1.99, and 1.73 microg I-TEQ/t product, respectively. For industrial waste incineration, the mean emission factors of waste rubber, waste liquor, waste sludge, industrial waste solid (IWI)-1, IWI-2, IWI-3, and IWI-4 are 0.752, 0.435, 0.760, 6.64, 1.67, 2.38, and 0.094 microg I-TEQ/t feed, respectively. Most of the PCDD/PCDF emission factors established in this study are less than those reported in previous studies, which could be because of the more stringent regulations for PCDD/PCDF emissions in recent years.     

Destruction of PCDD/Fs by SCR from flue gases of municipal waste incinerator and metal smelting plant

Partitioning of PCDD/F congeners between vapor/solid phases and removal and destruction efficiencies achieved with selective catalytic reduction (SCR) system for PCDD/Fs at an existing municipal waste incinerator (MWI) and metal smelting plant (MSP) in Taiwan are evaluated via stack sampling and analysis. The MWI investigated is equipped with electrostatic precipitators (EP, operating temperature: 230 degrees C), wet scrubbers (WS, operating temperature: 70 degrees C) and SCR (operating temperature: 220 degrees C) as major air pollution control devices (APCDs). PCDD/F concentration measured at stack gas of the MWI investigated is 0.728 ng-TEQ/Nm(3). The removal efficiency of WS+SCR system for PCDD/Fs reaches 93% in the MWI investigated. The MSP investigated is equipped with EP (operating temperature: 240 degrees C) and SCR (operating temperature: 290 degrees C) as APCDs. The flue gas sampling results also indicate that PCDD/F concentration treated with SCR is 1.35 ng-TEQ/Nm(3). The SCR system adopted in MSP can remove 52.3% PCDD/Fs from flue gases (SCR operating temperature: 290 degrees C, Gas flow rate: 660 kN m(3)/h). In addition, the distributions of PCDD/F congeners observed in the flue gases of the MWI and MSP investigated are significantly different. This study also indicates that the PCDD/F congeners measured in the flue gases of those two facilities are mostly distributed in vapor phase prior to the SCR system and shift to solid phase (vapor-phase PCDD/Fs are effectively decomposed) after being treated with catalyst. Besides, the results also indicate that with SCR highly chlorinated PCDD/F congeners can be transformed to lowly chlorinated PCDD/F congeners probably by dechlorination, while the removal efficiencies of vapor-phase PCDD/Fs increase with increasing chlorination.     

Improvements in dioxin abatement strategies at a municipal waste management plant in Barcelona

This study presents the results of a dioxin abatement programme undertaken in the municipal waste incineration plant of Montcada i Reixac (Barcelona, Spain) after the replacement of an obsolete air cleaning device by a new flue gas treatment system. A number of sampling campaigns were conducted with the aim of characterising stack gas emission levels of polychlorinated dibenzo-p-dioxins (PCDDs)/polychlorinated dibenzofurans (PCDFs) and to evaluate initial specifications of dioxin stack gas emission values below 0.1 ng I-TEQ/Nm(3). Preliminary results revealed levels between 44 and 111 ng I-TEQ/Nm(3) when the gas-cleaning system consisted only of an old electrostatic precipitator (ESP). Decreased levels around 15 ng I-TEQ/Nm(3) were observed when the semi-dry scrubber began to operate and the ESP was switched off. Again, remarkable dioxin removal was observed after the installation of the fabric filter and levels around 0.3-0.4 ng I-TEQ/Nm(3) were soon achieved. Nevertheless, the limit of 0.1 ng I-TEQ/Nm(3) was reached by additional injection of activated carbon which helped to lower PCDD/PCDF levels to around 0.036 ng I-TEQ/Nm(3). The results also demonstrated a significant change in the dioxin distribution present in combustion-derived materials (stack gas emission, bottom ash and solid waste from gas treatment). The major dioxin fraction was found in gaseous matrices before the flue gas control system was upgraded. After this step, the major dioxin fraction content was observed in solid waste from gas treatment.     

Evaluation of PCDD/F congener distributions in MWI flue gas treated with SCR catalysts

Partitioning of PCDD/F congeners between gaseous and particulate phases and removal efficiencies of the air pollution control devices (APCDs) for PCDD/Fs at an existing municipal waste incinerator (MWI) in Taiwan are evaluated via stack sampling and analysis. The MWI investigated is equipped with electrostatic precipitators (EP), wet scrubbers (WS) and selective catalytic reduction system (SCR) as APCDs. The average PCDD/F concentration of stack gas is 1.49 ng/N m³, and the International Toxic Equivalent Quantity (I-TEQ) is 0.043 ng-I-TEQ/N m³. The EP increases PCDD/F concentration by 174.0% while the average removal efficiency of WS + SCR system for PCDD/Fs reaches 99.1%. In addition, the PCDF removal efficiency achieved with WS + SCR system (97.1–99.8%) is higher than that for PCDDs (96.5–99.3%). The results obtained on gas/particulate partitioning in flue gas indicate that the particulate-phase PCDD/Fs accounted for 65% at the inlet of EP, 20% at the outlet of EP and 50% at the stack, respectively, of the total PCDD/F concentrations. This study also indicates that as the chlorination level of PCDD/F congeners increases, the percentage of PCDD/Fs existing in gas phase decreases in all flue gas samples.     

PCDD/PCDF emissions from small firing systems in households

This report presents results of emission measurements of polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) in the flue gas of seven oil, nine gas, and two wood firing systems under laboratory conditions. The burn rate of the combustion was in the range of the rated useful heat output. Two additional test series varied the amount of combustion air and thus the heat output. The PCDD/PCDF emissions for oil- and gas-fired boilers are in the range of 0.0020-0.0142 ng I-TEQ/m3 (referring to 3% O2 in the dry flue gas). No correlation between the combustion technique and the PCDD/PCDF emissions could be established. In the tests with the wood-fired furnaces PCDD/PCDF concentrations in the flue gas ranging from 0.014 to 0.076 ng I-TEQ/m3 (referring to 13% O2 in the dry flue gas) were found. A significant correlation between the firing rate of the heating insert and the measured PCDD/PCDF concentrations was found. On examination of three typical 2,3,7,8-CDD/CDF congener profiles, a comparable pattern could be observed with natural gas and light fuel oil. The congener distribution for wood combustion is considerably different.     

Concentrations of polychlorinated dibenzo-p-dioxins, dibenzofurans and non-ortho substituted biphenyls in polar bear milk from Svalbard (Norway)

Polychlorinated dibenzo-p-dioxins (PCDD), dibenzofurans (PCDF) and non-ortho substituted biphenyls (PCB, CB) were determined in 6 polar bear milk samples from Svalbard (Norway). For these compounds, no data for polar bears have been reported before from this region. Most of the PCDD/PCDF congeners were found at detectable levels. Concentrations expressed as 2,3,7,8-TCDD equivalents (Nordic model) were in the order of 1–3 pg/g⁻¹ fat (0.2–1.6 pg ml⁻¹ milk) which is comparable with ringed and harp seal blubber from the same region. On whole milk basis, concentrations were similar to those found in human milk. An estimation of the daily uptake via milk showed that the intake is lower for polar bears compared to humans. As in human milk, relatively high levels of OCDD were found in some polar bear milk samples. The PCDD/PCDF congener pattern in the milk was different to that found in polar bear fat from the Canadian Arctic. Non-ortho substituted PCB levels in polar bear milk were similar to those found in polar bear fat from the Canadian North. However, CB 77 or 169 dominated in the milk while CB 126 was the most abundant congener in fat. PCDD/PCDF levels expressed as 2,3,7,8-TE were highly correlated with the fat content of the milk. No correlation between CB and PCDD/PCDF concentrations was found. Some data indicate that PCDD/PCDF concentrations in polar bear milk decrease with increasing time after delivery.     

Partitioning and removal of dioxin-like congeners in flue gases treated with activated carbon adsorption

Activated carbon adsorption is commonly used to control dioxin-like congener (PCDD/Fs and PCBs) emissions. Partitioning of PCDD/Fs and PCBs between vapor and solid phases and their removal efficiencies achieved with existing air pollution control devices (APCDs) at a large-scale municipal waste incinerator (MWI) and an industrial waste incinerator (IWI) are evaluated via intensive stack sampling and analysis. Those two facilities investigated are equipped with activated carbon injection (ACI) with bag filter (BF) and fixed activated carbon bed (FACB) as major PCDD/F control devices, respectively. Average PCDD/F and PCB concentrations of stack gas with ACI+BF as APCDs are 0.031 and 0.006ng-TEQ/Nm(3), and that achieved with FACB are 1.74 and 0.19ng-TEQ/Nm(3) in MWI and IWI, respectively. The results show that FACB could reduce vapor-phase PCDD/Fs and PCBs concentrations in flue gas, while the ACI+BF can effectively adsorb the vapor-phase dioxin-like congener and collect the solid-phase PCDD/Fs and PCBs in the meantime. Additionally, the results of the pilot-scale adsorption system (PAS) experimentation indicate that each gram activated carbon adsorbs 105-115ng-PCDD/Fs and each surface area (m(2)) of activated carbon adsorbs 10-25ng-PCDD/Fs. Based on the results of PAS experimentation, this study confirms that the surface area of mesopore+macropore (20-200A) of the activated carbon is a critical factor affecting PCDD/F adsorption capacity.     

PCDD/PCDF,chlorinated pesticides and PAH in Chinese teas

Four samples of Chinese tea (two green teas, and two brick teas) were analyzed for their concentrations of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/PCDF), chlorinated pesticides and PAH. The infusions prepared from these teas were also analyzed for PCDD/PCDF. The levels of DDT and its metabolites in tea leaves were within the safety limit of 0.2 mg/kg. Rather high levels of total PAH were obtained in brick tea (1048–1162 mg/kg), when compared with green tea (497–517 mg/kg). In terms of PCDD/PCDF, the concentrations of green tea and brick tea differed by a factor of 16, while the concentrations of all infusions were within a factor of 2. The dioxin concentrations in green tea leaves can be explained through uptake of atmospheric PCDD/PCDF. The higher concentrations in the brick tea leaves are due the longer exposure time, and to certain extent, the use of old leaves, branches and roots when making the tea, and additional components such as soil particulates through contamination. Certain Chinese populations drinking a large amount of brick tea (>3 l per day) indicated that individuals of these populations consume more tea than Europeans or North Americans result in a comparably higher intake of PCDD/PCDF. Tea consumption can attribute to up to 10% of the TDI recommended by WHO (only PCDD/PCDF considered, no PCB analyzed).     

Formation characteristics of PCDD and PCDF during pyrolysis processes

In recent years, pyrolysis processes have become technologies developed to industrial scale and discussed as alternatives to the existing waste combustion technology. However, little information is published regarding PCDD/F formation characteristics during pyrolysis processes. Two common shredder fractions – industrial light shredder (ILS) and refrigerators (REF) – both with high chlorine and copper content were pyrolysed for this pyrolysis study using a pilot plant with a capacity of 100 kg/h. At oxygen concentrations below 2% and temperatures between 430°C and 470°C, considerable amounts of PCDD/F were formed during the pyrolysis. More than 90% of total TEQ was found in the oil fraction (gas phase). The PCDD/PCDF ratio and the homologue pattern differed significantly from those formed during waste incineration. Considering mono- to octachlorinated congeners, up to 400 times more PCDF were formed compared to PCDD. For the investigated pyrolysis conditions, the formation of low chlorinated congeners was highly favoured. The distribution of TEQ within the individual congeners were very similar in all investigated runs. More than 80% of total TEQ stem from 2,3,7,8-substituted T₄CDF and P₅CDF. The isomer pattern, however, did not show significant differences compared to the common waste incineration pattern suggesting that the basic formation routes are similar.     

Correlation of PCDD/PCDF and CO values in a MSW incinerator--indication of memory effects in the high temperature/cooling section

The correlation of PCDD/PCDF levels with the CO emissions in a full-scale municipal waste incinerator was assessed during a four-week measurement effort. PCDD/PCDF concentrations in fly ashes-containing more than 99% of the total PCDD/PCDF burden of the fluidized bed incinerator (FBI)-were measured and compared with the emitted CO concentrations. The CO concentration during the sampling time showed no significant correlation to the PCDD/ PCDF amount in fly ash (R2 = 0.078). However, a comparison of the time integrated CO concentration several hours before sampling lead to a correlation with the PCDD/PCDF burden. Maximum correlation was found for the time integrated CO values of 3 and 4 h before sampling (R2 = 0.467 and R2 = 0.457 respectively). This indicates a memory effect in the high temperature cooling section of several hours. Possible mechanisms leading to the memory effect are discussed. The correlation of PCDD/PCDF with CO concentration demonstrate that the combustion conditions play an important role for PCDD/PCDF formation in FBIs. However the variability in the correlation of CO to PCDD/PCDF levels show that other factors have a significant influence on PCDD/PCDF formation.     

Characterization of polychlorinated naphthalenes in stack gas emissions from waste incinerators

Nine typical waste incinerating plants were investigated for polychlorinated naphthalene (PCN) contents in their stack gas. The incinerators investigated include those used to incinerate municipal solid, aviation, medical, and hazardous wastes including those encountered in cement kilns. PCNs were qualified and quantified by isotope dilution high resolution gas chromatography–high resolution mass spectrometry techniques. An unexpectedly high concentration of PCNs (13,000 ng?Nm^?3) was found in the stack gas emitted from one waste incinerator. The PCN concentrations ranged from 97.6 to 874 ng?Nm^?3 in the other waste incinerators. The PCN profiles were dominated by lower chlorinated homologues, with mono- to tetra-CNs being the main homologues present. Furthermore, the relationships between PCNs and other unintentional persistent organic pollutants involving polychlorinated dibenzo-p-dioxins and dibenzofurans, polychlorinated biphenyls, hexachlorobenzene, and pentachlorobenzene were examined to ascertain the closeness or otherwise of their formation mechanisms. A good correlation was observed between ΣPCN (tetra- to octa-CN) and ΣPCDF (tetra- to octa-CDF) concentrations suggesting that a close relationship may exist between their formation mechanisms. The results would provide an improved understanding of PCN emissions from waste incinerators.     

Correlation of polychlorinated naphthalenes with polychlorinated dibenzofurans formed from waste incineration

Isomer composition of polychlorinated naphthalenes (PCNs) was measured for municipal waste incinerator fly ash samples and for emission samples produced from soot and copper-deposit experiments conducted at the United States Environmental Protection Agency (US-EPA). Two types of PCN isomer patterns were identified. One pattern contained specific PCN isomers in which chlorine atoms are substituted as if the peri(alpha-) position were dechlorinated from the higher chlorinated PCNs one by one. In another pattern, the isomers had a tendency for the chlorine atoms to assume successive positions on the naphthalene ring, which may be caused by specifically oriented chlorination. Some of these isomers increased, together with several polychlorinated dibenzofuran (PCDF) and a few polychlorinated dibenzo-p-dioxin (PCDD) isomers. The ratios between some specific PCN, PCDF, and PCDD isomers measured for the fly ash samples agree with those obtained from the soot and copper-deposit experiments. The observations suggest that these isomers were formed possibly from de novo synthesis utilizing the carbon structure contained in soot under the catalytic effect of a copper compound. Typical isomers for PCNs and PCDFs produced from incineration emissions were identified.     

CuCl2-catalyzed PCDD/F formation and congener patterns from phenols

Homologue and isomer patterns of polychlorinated dibenzo-p-dioxin (PCDD) and polychlorinated dibenzofuran (PCDF) in CuCl2-catalyzed formation were studied in an isothermal flow reactor using a distribution of 20 phenols as measured in municipal waste incinerator (MWI) exhaust gases. A mixture of 20 phenols was synthesized and used as reactants for this study because phenols are known to be key precursors in the formation of PCDD/F. Experiments were conducted at 400 degrees C. The 92% of nitrogen (N2) and 8% of oxygen (O2) were used as a carrier gas. PCDD/F homologue and isomer patterns with dibenzo-p-dioxin (DD) and dibenzofuran (DF) were obtained from a mixture of 20 phenols. DF+PCDF formation was favored over DD+PCDD formation. The major homologue groups formed were non-chlorinated DD and DF, and PCDD/F homologue fraction decreased with the degree of chlorination. PCDD/F homologue and isomer distributions were almost constant. Phenol and lower chlorinated phenols present in high amount played an important role in PCDD/F congener distributions. The results presented here can be used as characteristics or fingerprints for homologue and isomer patterns of PCDD/F formation attribution in CuCl2-catalyzed reaction from phenols.     

Sources of dioxins in the United Kingdom: the steel industry and other sources

Several countries have compiled national inventories of dioxin (polychlorinated dibenzo-p-dioxin [PCDD] and polychlorinated dibenzofuran [PCDF]) releases that detail annual mass emission estimates for regulated sources. High temperature processes, such as commercial waste incineration and iron ore sintering used in the production of iron and steel, have been identified as point sources of dioxins. Other important releases of dioxins are from various diffuse sources such as bonfire burning and domestic heating. The PCDD/F inventory for emissions to air in the UK has decreased significantly from 1995 to 1998 because of reduced emissions from waste incinerators which now generally operate at waste gas stack emissions of 1 ng I-TEQ/Nm3 or below. The iron ore sintering process is the only noteworthy source of PCDD/Fs at integrated iron and steelworks operated by Corus (formerly British Steel plc) in the UK. The mean waste gas stack PCDD/F concentration for this process is 1,2 ng I-TEQ/Nm3 based on 94 measurements and it has been estimated that this results in an annual mass release of approximately 38 g I-TEQ per annum. Diffuse sources now form a major contribution to the UK inventory as PCDD/Fs from regulated sources have decreased, for example, the annual celebration of Bonfire Night on 5th November in the UK causes an estimated release of 30 g I-TEQ, similar to that emitted by five sinter plants in the UK.     

Occurrence, possible sources, and temporal trends of polychlorinated dibenzo-p-dioxins and dibenzofurans in water and sediment from the lower Yangtze River basin, Jiangsu and Shanghai areas of Eastern China

The concentrations, compositional profiles, and possible sources of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/PCDF) in water column and surface sediment samples from the lower reaches of the Yangtze River were investigated, and the potential risks posed by these chemicals were evaluated. Concentrations of the 17 2,3,7,8-substituted PCDD/PCDF in the water and sediment samples ranged from 0.45 to 10.0 pg TEQ/L (mean 2.34 pg TEQ/L) and from 0.31 to 51 pg TEQ/g dw (mean 5.25 pg TEQ/g dw), respectively. Water and sediments from the Nanjing–Nantong sections of the Yangtze River were found to have elevated PCDD/PCDF levels, and the PCDD/PCDF TEQ concentrations in 13 sediment samples exceeded the probable effect levels (PEL), above which adverse biological effects are likely. Multivariate statistical analysis indicated that the principal PCDD/PCDF contamination source for the water and sediment was the production and use of pentachlorophenol (PCP) or sodium pentachlorophenate (PCP-Na). PCDD/PCDF concentrations were stable over time near the Yangtze River Estuary but had increased sharply in recent decades in the Nanjing–Nantong section, which will have been related to the growth in industrial activities and other anthropogenic PCDD/PCDF sources. Total organic carbon (TOC) and PCDD/PCDF concentrations correlated significantly (R?=?0.474, P?<?0.01), suggesting that TOC plays an important role in the transport and re-distribution of PCDD/PCDF in the Yangtze River basin.     

PCDD/F and PCB history in dated sediments of a rural lake

Concentrations of polychlorinated dibenzo-p-dioxins (PCDD), dibenzofurans (PCDF) and biphenyls (PCB) were analysed from a sediment core, which had been sampled from a remote lake in Finland. The deepest subsamples were analysed from a depth of 4.0 m, and were more than 8000 years old. At the surface of the sediment core, low levels of industrial background contamination were detected. The sum of 2,3,7,8-substituted PCDD/Fs was 35 ng/kg d.w. (dry weight), or 1.2 ng/kg d.w. in WHO's toxicity equivalent, WHO-TEQ. The annual accumulation rate of 2,3,7,8-substituted PCDD/Fs was 1.26 ng m(-2) a(-1). Deeper in the core, PCDD/F concentrations ranged between 2.11 and 11.1 ng/kg d.w. (0.24 and 1.70 ng/kg d.w. WHO-TEQ) and the accumulation rate was 0.11 ng m(-2) a(-1). A characteristic PCDD/F congener profile was found in all pre-industrial sediment layers. The order of concentrations was OCDD > 1,2,3,4,6,7,8-HpCDD > 1,2,3,7,8,9-HxCDD > 1,2,3,4,7,8-HxCDD > 2,3,7,8-TCDD, and concentrations of 2,3,7,8-chlorinated dibenzofurans were below the detection limit. Similar congener profiles have previously been described in samples for which natural PCDD/F formation has been proposed. PCBs were present at low levels in all of the sediment samples. The sum of the PCB concentrations of the sediment subsamples ranged between 50 and 2540 ng/kg d.w., and the three predominant congeners in the core were PCBs 18, 52, and 110.     

Dioxin contents in fly ash from large-scale MSW incinerators in Taiwan

In this study, fly ash samples were collected from three municipal waste incinerators (MWI) in Taiwan. These MWIs investigated are equipped with different air pollution control devices (APCDs). Preliminary results indicated that 2,3,7,8-PCDD/Fs homologue patterns of various types of fly ash were quite similar for all three MWIs. Concentrations of higher-chlorinated congeners of PCDDs and PCDFs were remarkably higher than those of lower-chlorinated congeners. In the case of MSW-A, the PCDD/PCDF ratios of ashes were found in the decreasing order for cyclone, boiler and baghouse. The PCDD/PCDF ratios in various types of fly ash of MWI-B was boiler-A < boiler-B < ESP < boiler-C. As for MSW-C, no obvious trend has been observed for PCDD/PCDF ratio. However, the ratio in boiler ash was higher than that in baghouse ash of MWI-A. The dioxin contents in fly ash would increase as the fly ash passed through APCD zones. In other words, the environmental conditions of APCD may actually cause the increase of the dioxin contents in fly ash. The trend for dioxin contents in fly ash collected from three MSW incinerators investigated was MSW-C < MSW-A < MSW-B.     

Dechlorination of polychlorinated biphenyls, dibenzo-p-dioxins and dibenzofurans on fly ash

Dechlorination of commercial mixtures of polychlorinated biphenyls (PCB) as well as polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) on extracted and non-extracted fly ash obtained from municipal waste incinerator (MWI) was studied in closed systems under nitrogen atmosphere at temperatures of 260°C and 340°C. Decomposition results (given as the difference between PCB or PCDD/F molar amounts before and after the experiment (in %) due predominantly to dechlorination reactions) and detoxification data (expressed similarly but related to toxic PCB and PCDD/F congeners only and given in I-TEQ units) are reported. Detoxification of Delor 105/80T at 260°C and 340°C at a loading of 0.65 wt% was 99.48% and 100%, respectively. The decomposition of Delor 103 at 340°C and for the loading of 0.75 wt% corresponded to 99.99%. The detoxification capability of PCDD/Fs on extracted and non-extracted fly ash for loading of 130 and 264 ng/0.4 g of fly ash at 340°C made 96 and 98%, respectively.     

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.