PCDDs/PCDFs in ambient air (<1 fg m−3) – The CTDEP long term sampling (30 d) method

The Connecticut Department of Environmental Protection (CTDEP) commenced monitoring for PCDDs/PCDFs (polychlorinated dibenzodioxins and polychlorinated dibenzofurans) in ambient air in 1987 and adopted the long term (30 d) sampling approach in 1993. The CTDEP method represents the first use of isotopically labeled PCDDs/PCDFs as field surrogates to monitor the behavior of native PCDDs/PCDFs present in actual ambient air samples. This feature first introduced in 1987 was later adopted by US EPA in revisions to sampling methods for PCDDs/PCDFs in ambient air (EPA Method TO9A) as well as development of EPA Reference Method 23 for measurement of PCDDs/PCFDs in stationary source emissions. Results are provided here for a total of twenty-three (23) samples (reported as pairs) representing twelve (12) 30 d sampling events conducted at a site located in metropolitan Hartford CT. Samples were collected in winter months during calendar years 2002–2008. PCDDs/PCDFs concentration data (pg m⁻³) are reported as both congener sums (Cl₄–Cl₈) and 2378-substitued congeners. Total PCDDs/PCDFs concentrations for these twelve (12) sampling events ranged from 0.68 pg m⁻³ (2003) to 4.18 pg m⁻³ (2004) with a mean concentration of 2.04 pg m⁻³.Method performance was monitored through use of collocated samples, in field isotopically labeled compounds, isotopically labeled laboratory applied internal standards and field blank samples. Method performance consistently exceeded goals established in USEPA Method TO9A for these same parameters. Average recoveries of in field labeled PCDDs/PCDFs ranged from 97.5% to 104.2%. Average (mean) recoveries for each of the ten (10) isotopically labeled internal standards ranged from 77.0% (¹³C-OCDF) to 95.5% (¹³C-2,3,7,8-TCDF). Method precision defined as % RPD data for collocated sampler pairs ranged from 8% to 14% for PCDDs and from 5% to 12% for PCDFs. The mean RPD for all PCDDs/PCDFs combined is 9.6%. Field monitoring results demonstrate method sensitivity for all PCDDs/PCDFs congeners and 2378-substituted congeners to be well below concentrations typically found for these compounds in ambient air (all reported data represent measured concentrations). Quantities (pg) found in field blanks represent the major determinant to achieving further enhancements in method sensitivity for selected congeners (OCDD < 42 fg m⁻³; 1,2,3,4,6,7,8-HpCDD < 5.7 fg m⁻³; and 1,2,3,4,6,7,8-HpCDF < 2.1 fg m⁻³). The CTDEP method represents a highly sensitive and reliable technique for monitoring of PCDDs/PCDFs congeners and other persistent organic pollutants (POPs) at ultra trace levels in ambient air (fg m⁻³).     

Atmospheric concentrations, occurrence and deposition of persistent organic pollutants (POPs) in a Mediterranean coastal site (Etang de Thau, France)

Atmospheric concentrations and deposition fluxes of PCDD/F and PCB have been evaluated over a 1-year period in a Mediterranean coastal lagoon (Etang de Thau, France). Indicative PBDE air concentrations in the hot season are also reported in this work. ∑2,3,7,8-PCDD/Fs and ∑18PCBs (gas + particulate) air concentrations ranged from 67 to 1700 fg m⁻³ and from 13 to 95 pg m⁻³, respectively whereas ∑8PBDEs (gas + particulate) summer time levels varied from 158 to 230 pg m⁻³. The PCDD/F and PCB atmospheric occurrence over Thau lagoon and subsequent inputs to the surface waters are determined by an assemble of factors, being the seasonality of atmospheric concentration, the air mass origin and meteorological conditions important drivers. Total (wet + dry) ∑2,3,7,8-PCDD/Fs and ∑18PCBs deposition fluxes to Thau Lagoon waters are 117 and 715 pg m⁻² d⁻¹, respectively.     

Levels and congener profiles of PCBs and PCDD/Fs in blue shark (Prionace glauca) liver from the South-Eastern Mediterranean Sea (Italy)

Liver of blue shark (Prionace glauca) specimens from the South-Eastern Mediterranean Sea were analyzed for the presence of polychlorinated biphenyls (PCBs), including coplanar congeners, polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). PCBs were the dominant chemicals, followed by PCDFs and PCDDs. The pattern of PCB congener concentrations in the hepatic tissue was dominated by higher chlorinated compounds. The specific profile of toxic PCDD/F congeners was characterized mainly by 2,3,7,8-TCDF and 2,3,7,8-TCDD, followed by 1,2,3,6,7,8-HxCDD and 2,3,4,6,7,8-HxCDF. The total 2,3,7,8-TCDD toxic equivalent (TEQs) was 149 pg g⁻¹ lipid wt. The profile of TEQ shows that PCDDs present the greatest risk to this species contributing to total toxicity with a percentage approximately of 60%, while the contribution of PCDFs and DL-PCBs is almost the same being 22.4% and 21.6%, respectively. Further investigations are urgently needed to characterize the PCDD/Fs contamination levels not only in elasmobranch fish but in all Mediterranean marine biota.     

Pollution characterization and diurnal variation of PBDEs in the atmosphere of an E-waste dismantling region

Diurnal air samples were collected from the E-waste dismantling region Guiyu and the underwear industry region Chendian. This was the first report to present the diurnal variation of PBDEs in the atmosphere. The average concentrations of 11 PBDE congeners were 11,742 pg m⁻³ in the daytime, and 4830 pg m⁻³ at night in Guiyu, while the concentrations were lower in Chendian with 376 pg m⁻³ in the daytime, and 237 pg m⁻³ at night. BDE-209 accounted for 22% and 31.3% of the total PBDEs in Guiyu and Chendian, respectively. The diurnal variation trends of BDE-47, -99, -153, -183, and -209 were also analyzed in detail in the two regions.     

Polychlorinated dibenzo-p-dioxin and dibenzofuran in urban air of an Andean city

Particle-bound polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in ambient air were monitored together with particulate matter less than 10 μm (PM₁₀) at three sampling sites of the Andean city of Manizales, Colombia; during September 2009 and July 2010. PCDD/Fs ambient air emissions ranged from 1 fg WHO-TEQ m⁻³ to 52 fg WHO-TEQ m⁻³ in particulate fraction. The PM₁₀ concentrations ranged from 23 μg m⁻³ to 54 μg m⁻³. Concentrations of PM₁₀ and PCDD/Fs in ambient air observed for Manizales - a medium sized city with a population of 380 000 - were comparable to concentrations in larger cities. The highest concentrations of PCDD/Fs and PM₁₀ found in this study were determined at the central zone of the city, characterized by public transportation density, where diesel as principal fuel is used. In addition, hypothetical gas fractions of PCDD/Fs were calculated from theoretical K_p data. Congener profiles of PCDD/Fs exhibited ratios associated with different combustion sources at the different sampling locations, ranging from steel recycling to gasoline and diesel engines. Taking into account particle and gas hypothetical fraction of PCDD/Fs, Manizales exhibited values of PCDD/Fs equivalent to rural and urban-industrial sites in the southeast and center of the city respectively. Poor correlation of PCDDs with PM₁₀ (r = −0.55 and r = 0.52) suggests ambient air PCDDs were derived from various combustion sources. Stronger correlation was observed of PCDFs with PM₁₀. Poor correlation between precipitation and reduced PM₁₀ concentration in ambient air (r = −0.45) suggested low PM₁₀ removal by rainfall.     

Mechanochemical degradation of chlorinated contaminants in fly ash with a calcium-based degradation reagent

This report presents our results in a low-temperature mechanochemical hydrodechlorination process applied to fly ash coming from a municipal waste incinerator in order to efficiently remove all traces of PCDDs, PCDFs and PCBs. We found that the most suitable degradation agent is a mixture of metallic calcium and calcium oxide. A sample of fly ash presenting a TEQ of 5200 pg g⁻¹ was completely detoxified (no traces of PCDDs, PCDFs and PCBs detected) after ball-milling at 400 rpm over night.     

Polychlorinated biphenyls (PCBs) in the atmosphere of sub-alpine northern Italy

The main objective of this work was to assess the atmospheric concentrations and seasonal variations of selected POPs in a sub-alpine location where few data are available. A monitoring and research station was set up at the JRC Ispra EMEP site (Italy). We present and discuss a one-year data set (2005-2006) on PCB air concentrations. ∑7PCBs monthly averaged concentration varied from 31 to 76 pg m⁻³. Concentrations in the gas phase (21-72 pg m⁻³) were higher than those in the particulate phase (3-10 pg m⁻³). Advection of air masses and re-volatilization from local sources seem to play a dominant role as drivers of PCB atmospheric concentrations in the area. Indications of seasonal variation affecting PCB congener patterns and the gas/particulate partitioning were found. Modeling calculations suggest a predominant importance of the wet deposition in this region (1 μg m⁻² yr⁻¹ ∑7PCBs yearly total wet deposition flux; 650-2400 pg L⁻¹ rainwater concentrations).     

PCDDs and PCDFs in sewage sludges from two wastewater treatment plants in Beijing, China

The levels of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) were analyzed by an isotope-dilution high-resolution mass spectrometric in 16 sewage sludges, sampled from 2004 to 2009, from two municipal wastewater treatment plants (WWTPs) in Beijing. Total toxicity equivalent (TEQ) values were evaluated using the toxicity equivalent factors proposed by International for PCDD/Fs. The I-TEQs for these sewage sludges were from 0.97 to 15.0 pg g⁻¹ dry weight (dw) with a mean value 4.43 pg g⁻¹ dw, indicating that all I-TEQs were below Chinese legislation limit value regulated for agricultural use in soils.The results from limited samples (16 samples) showed that the levels of PCDD/Fs might be correlated with the sludge age. Meanwhile, the temporal trends of PCD/Fs suggested that the I-TEQs may correlate with rainfall in the present study.     

Atmospheric organochlorine pesticide (OCP) levels in a metropolitan city in Turkey

Air concentrations of organochlorine pesticides (OCPs) were measured at four different sites in Bursa, Turkey to determine current levels. For this purpose, about 35 samples were collected from June 2008 to June 2009 using a high volume air sampler (HVAS) equipped with particle and gas-phase units. Ten OCP compounds (alpha-, beta-, gamma-, delta-hexachlorocyclohexane, Heptachlor epoxide, Endrin, Endosulfan beta, Endrin aldehyde, p,p′-DDT and Methoxychlor) were reported within the scope of this study. The average concentrations of total (particle + gas) ∑OCPs were 550.9 ± 277.6 pg m⁻³ (coastal), 1030.7 ± 453.5 pg m⁻³ (urban/traffic), 519.7 ± 277.5 pg m⁻³ (semi-rural) and 722.8 ± 351.8 pg m⁻³ (urban/residential). The individual OCP concentrations were in line with reported concentrations. The maximum particle and gas-phase concentrations were determined for Endosulfan beta and beta-HCH for all sites, respectively. Available gas/particle partitioning models were applied in order to investigate the compatibility of the experimental data and the significant relationships were observed.     

Suppressive effect of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and dioxin-like polychlorinated biphenyls transfer from feed to eggs of laying hens by activated carbon as feed additive

In this study, we investigated the suppressive effect of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (DL-PCBs) transfer from the feed to the eggs of laying hens by using activated carbon as a feed additive. Four groups of six hens (White Leghorn egg-layers; age, 11 weeks) were housed as two control groups and two exposure groups for a period of 20 weeks. Two control groups were fed with either the basal feed “Control” or basal feed additing activated carbon “Control + C”. Another two exposure groups were fed with feed contaminated (about 6 ng TEQ kg⁻¹ feed) by standard solutions of PCDDs/PCDFs and DL-PCBs “Exposure” alone and contaminated feed adding activated carbon “Exposure + C”. There was no significant effect on each groups for the growth rate, biochemical blood components, and egg production: these were around the standard levels for poultry in general. Moreover the results in this study showed the availability of activated carbon as a feed additive owing to the reduction in the risk of food pollution by PCDDs/PCDFs and DL-PCBs. The concentration in the eggs of the Exposure group gradually increased following the start of egg-laying but reached a steady state after about 1 month. In contrast, the concentration for the Exposure + C group was stationary and below the maximum EU level (6 pg TEQ g⁻¹ fat). In comparison to the Exposure group, the Exposure + C group showed a significant decline in the percentage of bioaccumulation into the egg. This reduction due to activated carbon was also observed in the muscle and abdominal fat. The reductions were compound- and congener-dependent for DL-PCBs as follows: PCDDs/PCDFs, non-ortho-PCBs, and mono-ortho-PCBs were more than 90%, 80%, and 50%, respectively, irrespective of the type of tissues. Fat soluble vitamin concentrations in the eggs of the Exposure + C group showed lower trends than the Exposure group. The γ-tocopherol and α-tocopherol concentrations in eggs of Exposure + C group showed a significant reduction of about 40%. However, the addition of activated carbon into animal feed could obviate the remote potential for accidents causing unintentional food pollution with PCDDs/PCDFs and DL-PCBs.     

Quality control for sampling of PCDD/PCDF emissions from open combustion sources

Both long duration (>6 h) and high temperature (up to 139 °C) sampling efforts were conducted using ambient air sampling methods to determine if either high volume throughput or higher than ambient air sampling temperatures resulted in loss of target polychlorinated dibenzodioxins/dibenzofurans (PCDDs/PCDFs) from a polyurethane foam (PUF) sorbent. Emissions from open burning of simulated military forward operating base waste were sampled using EPA Method TO-9A for 185 min duration using a filter/PUF/PUF in series combination. After a 54 m³ sample was collected, the sampler was removed from the combustion source and the second PUF was replaced with a fresh, clean PUF. An additional 6 h of ambient air sampling (171 m³) was conducted and the second PUF was analyzed to determine if the PCDD/PCDF transferred from the filter and the first PUF. Less than 4.4% of the initial PCDD/PCDF was lost to the second PUF. To assess the potential for blow off of PCDD/PCDF analytes during open air sampling, the mobility of spiked mono- to hepta-PCDD/PCDF standards across a PUF sorbent was evaluated from ambient air temperatures to 145 °C with total volumes between 600 L and 2400 L. Lower molecular weight compounds and higher flow amounts increased release of the spiked standards consistent with vapor pressure values. At 600 L total sampled volume, the release temperature for 1% of the tetra-CDD (the lowest chlorinated homologue with a toxic compound) was 87 °C; increasing the volume fourfold reduced this temperature to 73 °C.     

Atmospheric bulk deposition of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the vicinity of an iron and steel making plant

An IRA-743 resin bulk sampler was validated to monitor long-term bulk deposition of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Six consecutive sampling campaigns (2008-2009) were conducted at four sites around steel complexes in Pohang, South Korea to investigate spatial and seasonal variations of PCDD/F bulk deposition. The bulk deposition within the steel complex showed the highest ∑_4-8PCDD/F (Tetra-Octa) fluxes, ranging from 204 to 608 (mean: 352) pg m⁻² d⁻¹, indicating steel complexes were major sources of PCDD/Fs. The homologue profiles were dominated with lower chlorinated PCDFs. Furthermore, the prevailing winds were confirmed to influence the spatial distribution of PCDD/F deposition. There were apparent seasonal variations of the bulk deposition at each site, and seasonal homologue patterns of PCDD/Fs were clearly observed. According to the passive air sampling, however, no significant seasonal change of ambient air concentrations of PCDD/Fs was observed. Therefore, it was concluded that the seasonal variations of deposition fluxes of PCDD/Fs probably resulted from temperature-dependent gas/particle partitioning.     

Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) in breast milk of first-time Irish mothers: impact of the 2008 dioxin incident in Ireland

The 2008 dioxin incident in Ireland resulted in elevated concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) in Irish pork and pork products, due to the consumption of contaminated animal feed by pigs. In order to investigate any resulting impact on the Irish population, these contaminants were measured in pooled breast milk samples from 109 first-time mothers, collected in 2010. A comparison of the results with similar data from 2002 revealed generally lower concentrations of PCDD/Fs and dioxin-like PCBs in the 2010 samples, confirming the declining trend reported by many authors. Contaminant concentration levels for both 2002 and 2010 were generally slightly lower than those reported internationally, with a mean combined PCDD/F and PCB WHO-TEQ of 9.66 pg g⁻¹ fat, for an overall pooled sample of milk from 2010. An apparent slight increase in PCDFs was observed between 2002 and 2010 (from 2.73 pg WHO-TEQ g⁻¹ fat to 3.21 pg WHO-TEQ g⁻¹ fat), with the main contributory congener being 2,3,4,7,8-PentaCDF. While it cannot be totally discounted that the slight increase in 2,3,4,7,8-PentaCDF and in the overall PCDF WHO-TEQ in breast milk could be attributable to consumption of Irish pork during the 2008 incident, we consider that it is more likely that this was due to other factors, including the predominantly urban/industrial sampling locations for the 2010 samples, compared to 2002.     

Formation of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) from a refinery process for zinc oxide used in feed additives: a source of dioxin contamination in Chilean pork

The Republic of Korea found dioxin at concentrations exceeding the Korean maximum residue limit (MRL) in pork (2 pg TEQ g⁻¹ fat) imported from Chile in June 2008. Korea and Chile collaborated and investigated to find out the sources of contamination. An isotope dilution method and high resolution gas chromatography/mass spectrometry (HR-GC/MS) were used for the analysis of PCDD/Fs. PCDD/Fs were found from 2.17 to 36.7 pg TEQ g⁻¹ fat from Chilean pork. 2,3,4,7,8-PeCDF, 1,2,3,4,7,8-HxCDF, 1,2,3,6,7,8-HxCDF, and 2,3,4,6,7,8-HxCDF were found as the major congeners in pork samples. 2,3,4,7,8-PeCDF showed the highest concentration and contributed about 30% among the congeners in most of the samples. 2,3,7,8-TCDD, 1,2,3,7,8,9-HxCDD, OCDD, 2,3,7,8-TCDF, 1,2,3,7,8-PeCDF, 1,2,3,7,8,9-HxCDF, and OCDF were not detected or exist at background levels in the less contaminated samples. Remarkably high concentrations of PCDD/Fs were found in samples of zinc oxide (17 147 pg TEQ g⁻¹), zinc oxide based premix (6673 pg TEQ g⁻¹), and the residue crust (800 pg TEQ g⁻¹) in a mixing chamber in the feed mill. From the results of various investigations, this case concluded that zinc oxide in the feed was the major source of the dioxin contamination in pork. The dioxins were formed from a metal refinery process to collect zinc oxide.     

Evaluation of atmospheric sources of PCDD/Fs, PCBs and PBDEs around a steel industrial complex in northeast China using passive air samplers

The concern about emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) from steel industrial parks has increased in the past decades. In this study, polyurethane foam (PUF)-disk based passive air samples were collected in and around a big steel industrial park of Anshan, Northeast China from June 2008 to March 2009. The levels, seasonal variations and potential sources of PCDD/Fs, PCBs and PBDEs in the atmosphere around the steel industrial complex were investigated, and potential contribution of these three groups of persistent organic pollutants (POPs) from iron and steel production was also assessed. The air concentrations of ∑₁₇PCDD/Fs (summer: 0.02-2.77 pg m⁻³; winter: 0.20-9.79 pg m⁻³), ∑₁₉PCBs (summer: 23.5-155.8 pg m⁻³; winter: 14.6-81.3 pg m⁻³) and ∑₁₃PBDEs (summer: 2.91-10.7 pg m⁻³; winter: 1.10-3.89 pg m⁻³) in this targeted industrial park were relatively low in comparison to other studies, which implied that the industrial activities of iron and steel had not resulted in serious contamination to the ambient air in this area. On the whole, the air concentrations of PCDD/Fs in winter were higher than those of summer, whereas the concentrations of PCBs and PBDEs showed opposite trends. The result from principal component analysis indicated that coal combustion might be the main contributor of PCDD/F sources in this area.     

Polychlorinated dibenzo-p-dioxins,dibenzofurans, biphenyls,paraffins and polybrominated diphenyl ethers in marine fish species from Ebro River Delta (Spain)

The results of a surveillance programme on the determination of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and short chain chlorinated paraffins (SCCPs) in marine fish and shellfish species which are fished, commercialised and consumed in the Ebro River Delta area (NE, Spain) are presented. The study included the analysis of five marine fish species (sardine, gilthead sea bream, conger, eel and flounder) and three shellfish species (murex, carpet shell and mussel) collected in 2012 in five fishing harbours near to this area. WHO-TEQ concentrations for PCDD/Fs and dioxin like PCBs (dl-PCBs) ranged from 0.03 to 0.31 pg WHO-TEQ_2005PCDD/F g⁻¹ wet weight (ww) and from 0.02 to 3.15 pg WHO-TEQ_2005PCB g⁻¹ ww, respectively. All levels were below the maximum concentrations established by the EU Regulation. The PCBs and PCDD/Fs accumulation pattern found in the samples analysed showed a distribution typically reported for marine samples. For marker PCBs and PBDEs, concentration levels ranging from 929 to 57 494 pg g⁻¹ ww and from 36.2 to 827 pg g⁻¹ ww were obtained, respectively, meanwhile for SCCPs levels were between 3.1 and 141 ng g⁻¹ ww. Finally, the trends in the levels of PCDD/F and dl-PCBs found from 2006 to 2012 in fish and shellfish species were studied. A slight decrease of PCDD/F and dl-PCB concentrations was found since 2006.     

Polyfluorinated compounds in the atmosphere along a cruise pathway from the Japan Sea to the Arctic Ocean

Neutral polyfluorinated alkyl substances (PFASs) were measured in high-volume air samples collected on board the research vessel Snow Dragon during the 4th Chinese National Arctic Expedition from the Japan Sea to the Arctic Ocean in 2010. Four volatile and semi-volatile PFASs (fluorotelomer alcohols (FTOHs), fluorotelomer acids (FTAs), perfluoroalkyl sulfonamides (FASAs), and sulfonamidoethanols (FASEs)) were analyzed respectively in the gas and particle phases. FTOHs were the dominant PFASs in the gas phase (61-358 pg m⁻³), followed by FTAs (5.2-47.9 pg m⁻³), FASEs (1.9-15.0 pg m⁻³), and FASAs (0.5-2.1 pg m⁻³). In the particle phase, the dominant PFAS class was FTOHs (1.0-9.9 pg m⁻³). The particle-associated fraction followed the general trend of FASEs > FASAs > FTOHs. Compared with other atmospheric PFAS measurements, the ranges of concentrations of ∑FTOH in this study were similar to those reported from Toronto, north America (urban), the northeast Atlantic Ocean, and northern Germany. Significant correlations between FASEs in the gas phase and ambient air temperature indicate that cold surfaces such as sea-ice, snowpack, and surface seawater influence atmospheric FASEs.     

Deposition fluxes of PCDD/Fs in a reservoir system in northern Taiwan

In this study, polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) concentrations and depositions in ambient air, water column and sediment were measured at a coupled reservoir-watershed system in northern Taiwan. The atmospheric PCDD/F concentration measured in the vicinity of the reservoir ranged from 4.9 to 39 fg I-TEQ m⁻³ and the Asian dust storm in February accounted for the peak value, which corresponded to a total suspended particle concentration of 128 μg m⁻³. The atmospheric PCDD/F deposition ranged from 1.4 to 19 pg I-TEQ m⁻² d⁻¹, with higher deposition occurring during winter and spring (long-range transport events). During summer, when atmospheric deposition is lower, consecutive tropical cyclones (typhoons) bring heavy rainfall that enhances soil erosion and creates turbidity-driven intermediate flow. This results in significantly higher PCDD/F deposition in water column of the reservoir at 70 m water depth (179 pg I-TEQ m⁻² d⁻¹) than at 20 m (21 pg I-TEQ m⁻² d⁻¹) during typhoon event. The accumulation rate of PCDD/Fs (9.1 ng I-TEQ m⁻² y⁻¹) in the reservoir sediments (depth: 0-2 cm) was consistent with PCDD/F deposition obtained from water column (6.1 and 8.3 ng I-TEQ m⁻² y⁻¹); however, it is significantly higher when compared to the atmospheric deposition (2.0 ng I-TEQ m⁻² y⁻¹). Based on the mass balance between the measurements of atmospheric deposition and sinking particles in water column, around 54-74% of PCDD/F inputs into the reservoir were contributed by the catchment erosion during normal period. However, the PCDD/F input contributed by the enhanced catchment erosion significantly increased to 90% during intensive typhoon events.     

Dry deposition and soil-air gas exchange of polychlorinated biphenyls (PCBs) in an industrial area

Ambient air and dry deposition, and soil samples were collected at the Aliaga industrial site in Izmir, Turkey. Atmospheric total (particle + gas) ∑₄₁-PCB concentrations were higher in summer (3370 ± 1617 pg m⁻³, average + SD) than in winter (1164 ± 618 pg m⁻³), probably due to increased volatilization with temperature. Average particulate ∑₄₁-PCBs dry deposition fluxes were 349 ± 183 and 469 ± 328 ng m⁻² day⁻¹ in summer and winter, respectively. Overall average particulate deposition velocity was 5.5 ± 3.5 cm s⁻¹. The spatial distribution of ∑₄₁-PCB soil concentrations (n = 48) showed that the iron-steel plants, ship dismantling facilities, refinery and petrochemicals complex are the major sources in the area. Calculated air-soil exchange fluxes indicated that the contaminated soil is a secondary source to the atmosphere for lighter PCBs and as a sink for heavier ones. Comparable magnitude of gas exchange and dry particle deposition fluxes indicated that both mechanisms are equally important for PCB movement between air and soil in Aliaga.