Patterns and sources of PCDD/Fs and dioxin-like PCBs in surface sediments from the East River, China

The contamination status of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs) was preliminarily investigated in surface sediments collected from the East River during April 2007. The contamination levels of PCDD/Fs and DL-PCBs ranged from 2.1 to 9.8 with mean concentration of 4.5 pg WHO₉₈-TEQ g⁻¹ and ranged from 0.042 to 0.45 with mean concentration of 0.19 pg WHO₉₈-TEQ g⁻¹, respectively. All sediments were characterized by the elevated levels of PCDDs, especially OCDD. Higher concentrations of PCDD/Fs were found in the sediments from Guangzhou and Dongguan. Source analysis revealed that PCDD/Fs in the sediments from Guangzhou were mainly from the secondary copper smelters and steel-making plants, and PCDD/Fs in the sediment from Dongguan were mainly from MSWIs. PCP and paper mills were unlikely to be the main sources.     

Polychlorinated dibenzo-p-dioxins/dibenzofurans distributions in ash from different units in a municipal solid waste incinerator

This study determined the polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) contents in ash in the super heater (SH), economizer (EC), semi-dryer absorber (SDA), fabric filter (FF), fly ash pit (FAP) and bottom residue (BR) in a municipal solid waste incinerator (MSWI). A high-resolution gas chromatograph/high-resolution mass spectrometer (HRGC/HRMS) was utilized for analyzing 17 PCDD/F species. Experimental results showed that average PCDD/F contents in ash samples from the SH, EC, SDA, FF, FAP and BR were 0.102, 0.788, 0.210, 1.95, 2.04 and 0.0218 ng I-TEQ g(-1), respectively. PCDD/F content was very low in the SH and BR due to high temperatures (around 461 degrees C in the SH and 914 degrees C in combustion chamber). Conversely, total PCDD/F content was significantly high in ash samples from the EC (around 340 degrees C), mainly because the temperature is within the favorable range of 250-400 degrees C for PCDD/F formation due to de nova reformation mechanisms. Although the SDA operated at 245 degrees C, the PCDD/F content decreased very significantly, mainly because the temperature was relatively low and because calcium carbonate was introduced into flue gases to dechlorinate and dilute chlorine-containing species. PCDD/Fs were captured by the active carbon in the FF. Furthermore, the duration that fly ash remained in the FF was longer than that for other incinerator units, and thus causing an increasing trend of PCDD/Fs level downstream (except the SDA). Total PCDD/Fs emission factors (microg tonnes-waste(-1); microg I-TEQ tonnes-waste(-1)) in ash samples from different units were: SH (42.3; 0.846), EC (326; 6.12), SDA (58.1; 1.10), FF (1540; 61.3), FAP (2950; 107) and BR (537; 4.31). Most PCDD/Fs in ash were contributed by the FF (about 56%), and the generation of PCDD/Fs in ash was significant (about 35%) during the transfer process from different units to the FAP. A strong and positive correlation in a logarithmic form existed between PCDD/Fs and chlorine (Cl(-1)) contents in ash. In Taiwan, the government policy for incineration residues advocates their reuse as road sub-bases or secondary building materials provided that total PCDD/Fs content is below the legal limit (1 ng I-TEQ g(-1)). Thus, ash with total PCDD/Fs content below the legal limit, such as that from the SH, EC, SDA and BR, can be collected and transferred to the FAP and reused. Ash with total PCDD/Fs content exceeding the legal limit, such as that from the FF, should be collected separately and be treated properly before being disposal in a landfill.     

Evaluation of PCDD/F partitioning between vapor and solid phases in MWI flue gases with temperature variation

Partitioning of PCDD/Fs (polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofuran) between vapor and solid phases in flue gas is affected by several factors including temperature variation. In this study, PCDD/F removal efficiencies achieved with activated carbon injection (ACI) and partitioning of vapor/solid phase PCDD/Fs in flue gases with temperature variation in a municipal waste incinerator (MWI) are evaluated via intensive flue gas sampling. Results indicate that most PCDD/Fs in flue gas downstream of the ACI+bag filter (BF) exist in vapor phase (over 90%) while the removal efficiencies of vapor and solid phase PCDD/Fs are 98.5-99.6% and 99.8-99.9%, respectively. The results of flue gas samplings also indicate that there is optimal operating temperature for PCDD/F removal achieved with ACI. Additionally, a pilot-scale adsorption system (PAS) is constructed in this study to evaluate the PCDD/F partitioning affected by temperature. The results of the PAS experimentation indicate that about 55% and 25% vapor phase PCDD/Fs passing through the filter cake (adsorbent) are transferred to solid phase at 150 and 200 degrees C, respectively. As the temperature is increased to 250 degrees C, filter cake (adsorbent) cannot effectively adsorb vapor phase PCDD/Fs and significant PCDD/Fs are formed via de novo synthesis.     

Emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans from a heavy oil-fueled power plant in northern Taiwan

We measured the concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from the flue gas and the ambient atmosphere of a power plant fueled by heavy oil in northern Taiwan. The mean emission concentration and I-TEQ concentration of total PCDD/Fs were 0.292 ng/Nm(3) and 0.016 ng I-TEQ/Nm(3), respectively. All PCDD/F emission concentrations in the flue gas were supposed to meet the Environmental Protection Administration Executive Yuan, R.O.C. standard (1.0 ng I-TEQ/Nm(3) from 2008). Furthermore, the mean I-TEQ concentration in the ambient atmosphere was 0.011 pg I-TEQ/Nm(3), which was much lower than the environmental quality standards for dioxins in Japan (0.6 pg TEQ/Nm(3)). Also, the PCDD/F emission factor was 0.188 ng I-TEQ/L fuel, which was comparable to the data issued in US EPA [EPA, Locating and estimating air emissions from sources of dioxins and furans, Office of Air Quality Planning and Standards, Research Triangle Park, NC, DCN No. 95-298130-54-01, 1997] (0.2 ng I-TEQ/L of fuel). Also, the result of the correlations of PCDD/Fs and operational parameters illustrated that the positively significant correlation (r=0.502, p=0.048) was found only between PCDD/Fs (I-TEQ) and the flue gas emission temperature (125-157 degrees C). However, PCDD-TEQ/PCDF-TEQ ratios were statistically significantly associated with the decreased flue gas flow (r=-0.659, p=0.006), moisture (r=-0.612, p=0.012) and flue gas temperature (r=-0.503, p=0.047). For proper environmental management of dioxins, it is necessary to establish a complete emission inventory of PCDD/Fs, and, in particular, the government should pay more attention to power plants to address the information shortage.     

Removal characteristics of PCDD/Fs by the dual bag filter system of a fly ash treatment plant

In this study, a dual bag filter system was established to decrease the concentration of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in the stack flue gases of a fly ash treatment plant, which retained zinc from the fly ash of electric arc furnaces. Compared to the original single bag filter system with activated carbon injection (ACI) of 40 kg h(-1), the PCDD/F concentrations in the stack flue gas after the plant was equipped with the dual bag filter system dropped enormously from 3.38-7.73 ng I-TEQNm(-3) to 0.03 ng I-TEQNm(-3), and the total PCDD/F I-TEQ removal efficiency increased from 97.6% to 99.3% with ACI of 16 kg h(-1), that is, about 40% of the original AC usage. The AC utilization efficiency (0.560 mg I-TEQ absorbed kg ACI(-1)) of the dual bag filter system (AC: 16 kg h(-1)) was estimated about three times higher than that (0.192 mg I-TEQ absorbed kg ACI(-1)) of single bag filter system with ACI (40 kg h(-1)). The reason is that the particulate phase PCDD/Fs and some gas phase PCDD/Fs (captured by the recycled AC/ash mixture) were removed first by the first bag filter, and the rest of the gas phase PCDD/Fs were able to be adsorbed more completely by the AC/ash mixture due to a lower fly ash load, and then were removed by the second bag filter.     

Evaluation of gas-particle partition of dioxins in flue gas I: evaluation of gasification behavior of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in fly ash by thermal treatment

The gasification behavior of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in fly ash by thermal treatment has been investigated to estimate gas-particle partition in flue gas. The results obtained in thermal experiments under various conditions showed that gasification of PCDD/Fs depends on air flow rate and treatment weight of fly ash as well as treatment temperature. On the other hand, the results obtained in the thermal experiments using dioxin-free fly ash revealed that during thermal treatment, the de novo synthesis, gasification, and decomposition of PCDFs proceeded at different rates. This difference in the reaction rates indicates that thermal treatment time is also a factor in determining the gas-particle partition of PCDD/Fs in fly ash. Therefore, reasonable thermal treatment conditions were established and applied to three ash samples. For all samples, PCDD/Fs started to gasify at 350 degrees C treatment, whereas 53-98% of PCDD/F homologs gasified at 400 degrees C treatment, implying that gaseous PCDD/Fs are dominant in flue gas at temperatures in the range 350-400 degrees C regardless of particle concentration.     

Polychlorinated dibenzo-p-dioxins/dibenzofuran mass distribution in both start-up and normal condition in the whole municipal solid waste incinerator

Although many researches focused on the polychlorinated dibenzo-p-dioxins/dibenzofuran (PCDD/F) emissions from stack, in the bottom ash and in the surrounding environment, researches focused on PCDD/F mass distributions in the whole incineration plant have seldom been addressed. This study determined PCDD/F emissions in the whole plant. A high-resolution gas chromatograph/high-resolution mass spectrometer was utilized for analyzing 17 PCDD/F species. Experimental results displayed that PCDD/Fs were formed during fly ash from super heater (SH), economizer (EC), semi-dryer absorber (SDA) and fabric filter (FF) was transferred to fly ash pit. Mass distribution ratios of PCDD/Fs in g I-TEQ (Toxicity Equivalency Quantity) per week from stack, SH, EC, SDA, FF, generation and bottom residue (BR) in start-up operations were 14.6%, 0.1%, 8.3%, 1.0%, 41.7%, 33.4% and 0.9%, respectively. Above results indicated that main PCDD/F source in the MSWI was from fly ash. However, the fly ash is easily controlled and PCDD/F emitted from stack flue gases will be difficult to be handled. Therefore, we should pay more attention on PCDD/F emission from flue gases especially from start-up procedure. Besides, fly ash should be controlled by sodium hypophosphite before being landfilled. MSWI did require further detoxification treatments for the solid residues and flue gases.     

A novel method to enhance polychlorinated dibenzo-p-dioxins and dibenzofurans removal by adding bio-solution in EAF dust treatment plant

In order to understand the effect of different amounts of powder-activated carbon (PAC) injection and bio-solution (NOE-7F) addition on the removal efficiencies of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in a fly ash treatment plant with Waelz rotary kiln process, the PCDD/F concentrations in the stack flue gasses were measured and discussed. In the amount of 20, 40 and 50 kg/h PAC injection, the removal efficiencies of PCDD/Fs in the stack flue gas were 86, 96 and 97%, respectively. While adding more amounts of PAC did enhance the removal efficiencies, the reduction fractions of low chlorinated PCDD/F congeners were much higher than those of highly chlorinated PCDD/F congeners. Particularly, a lower amount of PAC injection (20 kg/h), not only cannot remove highly chlorinated PCDD/Fs, but also the carbon surface of the PAC can act as a precursor for the formation promotion of highly chlorinated PCDD/F congeners. The addition of NOE-7F in the raw materials had the dechlorination effect on the PCDD/F removal and mainly inhibited highly chlorinated PCDD/F formation. The combination of both PAC injection and NOE-7F addition has a high potential for practical application.     

Characteristic of polychlorinated dibenzo-p-dioxins and dibenzofurans in fly ash from incinerators in china

Fly ash from municipal solid waste (MSW), medical waste (MW) and electrical power plant (EPP) incinerators were analyzed for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). The study showed that the PCDD/F levels in fly ash were EPP < MSW < MW. The homologue profiles of PCDD/Fs in fly ash produced from waste incinerators were similar. However, the homologue profiles of PCDD/Fs in fly ash from electrostatic precipitator (ESP) of electrical power plant were different from that from waste incinerator. The strong correlation was found between the concentration of 2,3,4,7,8-PeCDF and the I-TEQ value of fly ash regardless of the different fly ashes sources.     

Evaluation of PCDD/Fs emission from fluidized bed incinerators co-firing MSW with coal in China

The levels and homologue profile of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from stack gas of three typical fluidized bed incinerators co-firing municipal solid waste (MSW) with Chinese coal were measured. The PCDD/Fs emission was in the range of 0.0054-0.1961 ng I-TEQ/N m(3). Comparison of PCDD/Fs detection results by HRGC/HRMS and HRGC/LRMS suggested that it was feasible to detect fly ash with high PCDD/Fs concentration by HRGC/LRMS. Several factors on PCDD/Fs emission were discussed. The primary reason for the lower PCDD/Fs emission was the inhibition mechanism of relatively high sulfur in feeding coal on PCDD/Fs formation. The emission results also showed that there was no directly correlation between PCDD/Fs levels and CO, O(2) and HCl concentration in flue gas. It was estimated that about 0.1034 g I-TEQ was annually emitted to atmosphere from the tested three MSW incinerators (total daily treatment capacity is 800 tonnes MSW).     

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

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

Removal of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans by three coagulants in simulated coagulation processes for drinking water treatment

Surface water from Guangzhou to which standard polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were added was treated by coagulation with ferric chloride (FC), polyaluminium chloride (PAC), and aluminium sulfate (AS) at optimum removal dosages for nature organic matter (NOM) to assess the polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) removal efficiencies. PCDD/Fs in suspended particulate matter (SPM) and treated water (TW) after coagulation were analysed. Low residual levels of PCDD/Fs were found in treated water after coagulation: 0.8% for FC, 0.9% for PAC, and 3.1% for AS. The removal efficiency calculated using these results was >99% for FC and PAC and 97-98% for AS. Most PCDD/Fs congeners could be removed by the three coagulation processes; the removal efficiency of FC and PAC was similar, and slightly higher than that of AS. The results also demonstrate that coagulation with FC preferentially removed tetra- and penta-substituted PCDD/Fs from raw water.     

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

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

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

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

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

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

Elevated concentrations of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans and polybrominated diphenyl ethers in hair from workers at an electronic waste recycling facility in eastern China

Hair samples collected from e-waste recycling workers (n=23 males, n=4 females) were analyzed to assess occupational exposures to polybrominated diphenyl ethers (PBDEs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) at a large e-waste recycling facility in Taizhou, eastern China. Hair samples from a reference population composed of residents of Shanghai (n=11) were analyzed for comparison. The mean concentration of ∑PBDEs (range, 22.8-1020 ng/g dw; mean, 157 ng/g dw) found in hair samples from e-waste recycling workers was approximately 3 times higher than the mean determined for the reference samples. The congener profiles of PBDEs in hair from e-waste recycling workers were dominated by BDE 209, whereas the profiles in the reference-population samples showed comparable levels of BDE 47 and BDE 209. Total PCDD/F concentrations in hair from e-waste workers (range, 126-5820 pg/g dw; mean, 1670 pg/g dw) were approximately 18-fold greater than the concentrations measured in hair from the reference population. Concentrations of PCDFs were greater than concentrations of PCDDs, in all of the hair samples analyzed (samples from e-waste and non-e-waste sites). Tetrachlorodibenzofurans (TCDFs) were the major homologues in hair samples. Overall, e-waste recycling workers had elevated concentrations of both PBDEs and PCDD/Fs, indicating that they are exposed to high levels of multiple persistent organic pollutants.     

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

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

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

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

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

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

Shape-selective extraction of PCBs and dioxins from fish and fish oil using in-cell carbon fractionation pressurized liquid extraction

This paper describes a new shape-selective, pressurized liquid extraction (PLE) procedure for extracting polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and PCBs from food and feed samples with an integrated carbon fractionation step. Initially this was done using specially designed inserts for 34-mL cells, but subsequently, large solid cells (66 mL) were machined to increase the capacity and robustness of the system. Depending on the carbon load and extraction solvent strength, the non-ortho PCBs were recovered either with the bulk of the PCBs or with the PCDD/Fs. The former is preferable if PCDD/Fs are the targets. In most cases, however, data are required for all indicator PCBs, WHO-PCBs, and PCDD/Fs. Therefore, further efforts focused on developing, optimizing, and validating a cost- and time-efficient PLE procedure that can extract these targets, separate non-ortho PCBs and PCDD/Fs from the bulk of the PCBs, allow gravimetric fat determinations, and requires a minimum of postextraction cleanup. The performance of the resulting procedure was assessed in experiments with a fish tissue reference material. The trueness of the WHO-PCB-TEQ, PCDD/F-TEQ, and total-TEQ data were -8, -5, and -7%, respectively, and the corresponding CVs were 1.5, 0.5, and 1.3%; within the limits set by the European community for gas chromatography-high-resolution mass spectrometry methods for food and feed control.