Seasonal and annual air-water exchange of polychlorinated biphenyls across Baltimore Harbor and the northern Chesapeake Bay

As part of the Atmospheric Exchange Over Lakes and Oceans Study (AEOLOS), air-water exchange fluxes of polychlorinated biphenyls (PCBs) were determined along a transect in the Baltimore Harbor from the Inner Harbor of Baltimore, MD, to the mainstem of the northern Chesapeake Bay to assess the overall contributions of urban source PCBs through air-water exchange and their impacts on coastal waters. Six sites were sampled during three intensive sampling periods in June 1996, February 1997, and July 1997 and at two sites (urban and rural) every ninth day between March 1997 and March 1998 to measure spatial and temporal variability in the PCB air-water exchange fluxes. During the intensive sampling campaigns, net total PCB (t-PCBs) volatilization fluxes ranged between 5 and 2120 ng m(-2) day(-1), varying on both temporal and spatial scales. Volatilization fluxes were highest in February, driven by high winds and elevated dissolved PCB concentrations. Throughout the annual sampling period, t-PCB volatilization fluxes were similar between urban (130 microg m(-2) yr(-1)) and rural (120 microg m(-2) yr(-1)) sites. Approximately 10% of the dissolved t-PCB inventory in the water column in Baltimore Harbor exchanges with the atmosphere each day. From air-water exchange alone, the estimated residence time of dissolved t-PCBs in the harbor is approximately 10 days (estimated hydraulic residence time of water in the harbor is between 7 and 14 days), indicating that air-water exchange is an efficient removal mechanism of t-PCBs from urban coastal waters. Furthermore, the annual flux of t-PCBs volatilizing from Baltimore Harbor is approximately 12% of the gas-phase t-PCB inventory over the water, and at the northern Chesapeake Bay site, the t-PCB flux is approximately 40% of the gas-phase t-PCB inventory. This suggests that air-water exchange of t-PCBs has the potential to be a significant source of PCBs to the rural atmosphere.     

Dynamic air-water exchange of polychlorinated biphenyls in the New York-New Jersey Harbor Estuary

Simultaneous measurements of polychlorinated biphenyls (PCBs) in the air and water over Raritan Bay and New York Harbor were taken in July 1998, allowing the first determinations of air-water exchange fluxes for this heavily impacted system. Average gas-phase concentrations of sigmaPCBs were 1.0 ng m(-3) above Raritan Bay and 3.1 ng m(-3) above New York Harbor. A similar gradient was observed for dissolved water concentrations (1.6 and 3.8 ng L(-1), respectively). Shallow slopes of log K(oc) vs log K(ow) plots indicated a colloidal contribution to the dissolved concentrations, and a three-phase partitioning model was therefore applied. PCBs associated with colloids ranged from 6% to 93% for trichloro- to nonachlorobiphenyls, respectively. Air-water gas exchange fluxes of sigmaPCBs exhibited net volatilization for both Raritan Bay at +400 ng m(-2) day(-1) and New York Harbor at +2100 ng m(-2) day(-1). The correction for the colloidal interactions decreased the volatilization flux of sigmaPCBs by about 15%. Net air-water exchange fluxes of PCBs are expected to remain positive throughout the year due to the large water-air fugacity gradient and relatively constant seasonal water concentrations. The volatilization fluxes are approximately 40 times greater than atmospheric deposition of PCBs via both wet and dry particle deposition, suggesting that the estuary acts as a net source of PCBs to the atmosphere year-round.     

Air-water exchange of polychlorinated biphenyls in the Delaware River

The air-water exchange of polychlorinated biphenyls (PCBs) often results in net volatilization, which is thought to be the most important loss process for PCBs in many systems. Previous investigations of the air-water exchange of PCBs have been hampered by difficulties in treatment of the uncertainty in the calculation of air/water fugacity ratios. This work presents a new framework for the treatment of uncertainty, where uncertainty in physical constants is handled differently from random measurement uncertainty associated with random samples, and it further investigates the sorption of PCBs to colloids (dissolved organic carbon). Simultaneous measurements of PCBs in the air and water of five water quality management zones of the Delaware River were taken in 2002 in support of the total maximum daily load (TMDL) process. Gas-phase concentrations of IPCBs ranged from 110 to 1350 pg m(-3), while dissolved water concentrations were between 420 and 1650 pg L(-1). Shallow slopes of log Koc vs. log Kow plots indicated a colloidal contribution to the apparent dissolved-phase concentrations, such that a three-phase partitioning model was applied. Fugacity ratios for individual congeners were calculated under the most conservative assumptions, and their values (log-transformed) were examined via a single-sample T-test to determine whether they were significantly less than 1 at the 95% confidence level. This method demonstrated that air-water exchange resulted in net volatilization in all zones over all cruises for all but seven high molecular weight congeners. Calculated net fluxes ranged from +360 to +3000 ng m(-2) d(-1) for sigma PCBs. The colloidal correction decreased the volatilization flux of sigma PCBs by approximately 30%. The decachlorinated congener (PCB 209), exhibited unusually high concentrations in the suspended solids, especially in the southern portions of the river, indicating that there is a distinct source of PCB 209 in the Delaware River.     

Air-surface exchange of polybrominated diphenyl ethers and polychlorinated biphenyls

Air and leaf-litter samples were collected from a rural site in southern Ontario under meteorologically stable conditions in the early spring, prior to bud burst, over a three-day period to measure the simultaneous diurnal variations in polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs). PBDEs are used in a wide range of commercial products as flame retardants and are being assessed internationally as potential persistent organic pollutants. Total PBDE concentrations in the air ranged between 88 and 1250 pg m(-3), and were dominated primarily by the lighter congeners PBDEs 17, 28, and 47, and concentrations of total PCBs ranged between 96 and 950 pg m(-3), and were dominated by the lower chlorinated (tri- to tetra-) congeners. Slopes of Clausius-Clapeyron plots indicate that both PCBs and PBDEs are experiencing active air-surface exchange. Fugacities were estimated from concentrations in the air and leaf-litter and suggest near equilibrium conditions. Following the three-day intensive sampling period, 40 air samples were collected at 24-hour intervals in an attempt to evaluate the effect of bud burst on atmospheric concentrations. Total PBDE concentrations in the daily air samples ranged between 10 and 230 pg m(-3), and were dominated by the lighter congeners PBDE 17, 28, and 47, whereas concentrations of total PCBs ranged between 30 and 450 pg m(-3) during this period. It is hypothesized thatthe high PBDE concentrations observed at the beginning of the sampling period are the result of an "early spring pulse" in which PBDEs deposited in the snowpack over the winter are released with snowmelt, resulting in elevated concentrations in the surface and air. Later in the sampling period, following bud burst, PBDE concentrations in air fell to 10 to 20 pg m(-3), possibly due to the high sorption capacity of this freshly emerging foliage compartment.     

Seasonal and spatial variation of polychlorinated naphthalenes and non-/mono-ortho-substituted polychlorinated biphenyls in arctic air

Archived extracts of weekly air samples collected at remote arctic monitoring stations at Alert and Tagish, Canada, and Dunai Island, Russia, in 1994-1995 were combined into 4-week composites and analyzed for levels and seasonal trends of polychlorinated naphthalenes (PCNs) and non- and mono-ortho-substituted polychlorinated biphenyls (PCBs). Mean annual sigmaPCN concentrations were 0.69, 0.82, and 0.38 pg/m3 at Alert, Dunai, and Tagish, respectively. PCNs exhibited a seasonal trend at Alert and Dunai, with higher levels occurring during winter when air masses originating over Eurasia influence the high arctic and coincide with the haze period. Episodic, trans-Pacific transport impacted PCN concentrations at Tagish. A seasonal trend was not evident for the non-/mono-o-PCBs. The contrary PCN and non-/mono-o-PCB trends indicate that the sources of these two compound classes to arctic air differ, and that atmospheric transport from source regions has a greater influence on PCN levels than for non-/ mono-o-PCBs. PCNs apparently originating from combustion sources contribute to levels in winter, as indicated by the presence of combustion marker congeners, but evaporative emissions from source regions are likely the dominant source. PCNs contributed 71 and 75% of dioxin toxic equivalents (TEQ) relative to the non-/mono-o-PCBs at Alert and Dunai and 30% at Tagish during the winter months, demonstrating the toxicological importance of PCNs as a compound class relative to PCBs.     

Concentrations and fluxes of salmon-derived polychlorinated biphenyls (PCBs) in lake sediments

Fourteen sediment cores were collected from 10 lakes spanning a large gradient of sockeye salmon returns (0-40 000 spawners km(-2)) in Alaska and British Columbia in 1995-98 and 2002/03. The cores were analyzed for 210Pb to determine sedimentation rates and focusing factors. Polychlorinated biphenyl (PCBs) concentrations in the surface sediments (0-2 cm) were highly correlated with the number of sockeye salmon returns to each nursery lake. For 2002/03, the correlation between PCB concentration and number of salmon spawners was best with no correction factors applied, but decreased considerably when corrected for sedimentation rates, and was improved again by correcting for sediment focusing. Although sigmaPCB concentrations were similar in 1995-98 and 2002/03, the congener patterns varied. Because salmon are the dominant source of PCBs for most of these lakes, variation in sediment congener pattern likely derives from variation in congener patterns carried by the salmon. Overall, total PCB input by salmon has remained relatively constant since 1995. Unlike temperate Great Lakes contaminant studies, the North American west-coast lakes dominated by salmon bio-transport showed no sign of recent decrease in PCBs.     

Pan-arctic river fluxes of polychlorinated biphenyls

Observations of polychlorinated biphenyls (PCB) concentrations in fluvial surface sediments near the mouths of the six Great Arctic Rivers (GARs; Ob, Yenisey, Lena, Indigirka, Kolyma, and Mackenzie) were combined with annual dissolved organic carbon (DOC) and particulate organic carbon (POC) loadings and hydraulic discharge to estimate the pan-Arctic river flux of PCBs. The highest total-phase fluxes of ∑(13)PCB were found for the Ob River, with 184 kg/yr and the smallest for the Indigirka River with 3.9 kg/yr. Consistent with a continent-scale trend among the Eurasian GARs of increasing POC concentrations eastward, which is extending to the North American Mackenzie River, a general shift in the estimated PCB partitioning from dissolved to particle-associated flux was found toward the east. Pentachlorinated and hexachlorinated PCBs constituted the majority (>70%) of the total PCB fluxes in the Eurasian Rivers. In contrast, trichlorinated and tetrachlorinated congeners were the most abundant in the Mackenzie (≈ 75%). The total ∑(13)PCB fluxes from the pan-Arctic rivers are here estimated to be ～0.4 tonne/yr. This is geochemically consistent with the inventory of total PCBs in the Polar Mixed Layer of the entire Arctic Ocean (0.39 tonne) and about a factor 2 less than two new estimates of the PCB settling export to Arctic subsurface waters. Hence, the yearly Great Arctic River PCB fluxes only represent 0.001% of the historical PCB emission into the global environment. To our knowledge, this is the first estimate of circum-Arctic river flux of any organic pollutant based on a comprehensive investigation of the pollutants in several rivers and it contributes toward a more complete understanding of large-scale contaminant cycling in the Arctic.     

An assessment of air-soil exchange of polychlorinated biphenyls and organochlorine pesticides across central and southern Europe

Estimating the net flux direction of polychlorinated biphenyls and organochlorine pesticides is importantfor understanding the role of soil as a sink or source of these chemicals to the atmosphere. In this study, the soil-air equilibrium status was investigated forvarious soil categories in Central and Southern Europe using an extensive database of coupled soil and time-integrated air samples. Samples were collected from 47 sites over a period of 5 months to assess both site-specific as well as seasonal variations in fugacity fractions, calculated as a potential measure of soil-air exchange. Sampling sites were carefully selected to represent a variety of background, rural, urban, and industrial areas. Special attention was given to sites in the former Yugoslavia, a country affected by recent conflicts, where soils were found to be highly contaminated with polychlorinated biphenyls (PCBs). Industrial soils from the Czech Republic, heavily polluted as a result of previous pesticide production, were also included in the survey. Soil was found to be a sink for highly chlorinated PCBs and for dichlorodiphenyltrichloroethane (DDT); for dichlorodiphenyldichloroethylene (DDE), the status was closer to equilibrium, with a tendency for net deposition during winter and net volatilization during summer. For lower-molecular-weight PCB congeners, as well as for alpha-HCH, soil tends to be a source of pollution to the air, especially, but not exclusively, during summer. Fugacity fractions were found to decrease during the colder seasons, especially for the more volatile compounds, although in both the war-damaged areas and the heavily contaminated industrial sites, seasonal variability was very low, with fugacity fractions close to 1, indicating strong net soil-to-air transfer for all seasons. The original assumption that residents of the Western Balkans are still exposed to higher levels of PCBs due to the recent wars was confirmed. In general, the soil-air transfer of PCBs and organochlorine pesticides was found to be site-specific and dependent on the physicochemical properties of the contaminant in question, the soil properties, the historical contamination record and a site's vicinity to sources, and the local meteorological conditions.     

Risk assessments of polychlorinated dibenzo- p-dioxins, polychlorinated dibenzofurans, and dioxin-like polychlorinated biphenyls in food

The polychlorinated dibenzo-p-dioxins (PCDD), polychlorinated dibenzofurans (PCDF), and dioxin-like polychlorinated biphenyls (dioxin-like PCB) are ubiquitous in food of animal origin and accumulate in fatty tissues of animals and humans. The most toxic congener is 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The toxic responses include dermal toxicity, immunotoxicity, carcinogenicity, and reproductive and developmental toxicity. Toxic equivalency factors have been established for the other PCDD, PCDF and dioxin-like PCB relative to TCDD, and the combined toxicity of a sample can be expressed as toxic equivalent (WHO-TEQ). The EC Scientific Committee for Food evaluated these compounds in 2001. The assessment used the most sensitive adverse toxicological end-points of TCDD in experimental animals. These were developmental and reproductive effects in the male offspring of rats administered TCDD during pregnancy. Because of the large difference between rats and humans in the biological half-life of TCDD, the assessment used a body burden approach to compare across species and derived a tolerable weekly intake of 14 pg TCDD/kg of body weight (bw), which was extended to include all the 2,3,7,8-substituted PCDD and PCDF, and the dioxin-like PCB, and expressed as a group tolerable weekly intake of 14 pg WHO-TEQ/kg bw. The FAO/WHO Joint Expert Committee on Food Additives (JECFA) performed a similar assessment whereas the US Environmental Protection Agency (US EPA) has paid more attention to human data on carcinogenicity.     

Seasonal and geographical variations in levels of polychlorinated biphenyls (PCB) and polybrominated diphenyl ethers (PBDE) in Polish butter fat used as an indicator of environmental contamination

The aim of this study was to evaluate the seasonal variation/geographical distribution of environmental concentration of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) across Poland using butter fat as an indicator of the contaminants. The average concentration of six indicator PCBs determined in the studied samples was 1500?pg?g^–1 fat. The average concentration of 12 dioxin-like PCBs expressed as lower-bound dioxin-equivalent toxicity was 0.684 pg TEQ g^?1 fat. The average total concentration of 14 investigated PBDE congeners was 105?pg?g^?1 fat. Statistically significant concentration differences between summer and winter samples were found. The results of this study indicate also a significant geographical diversification of butter contamination reflecting regional differences in environmental contamination. The seasonal variation of PBDE profiles evidences transformation of PBDE within the environment.     

Wet deposition of polychlorinated biphenyls in the eastern Mediterranean

The concentrations of polychlorinated biphenyls (PCBs) were measured in rain samples collected from a semiurban and a marine background site of the eastern Mediterranean. The concentration of sigmaPCB (sum of 54 PCB congeners) in the city of Heraklion (2.9 +/- 1.9 ng L(-1)) was not significantly higher than the corresponding concentration measured at the background sampling station of Finokalia (1.9 +/- 0.9 ng L(-1)). In both sites, the sum of tri- and tetrachlorinated congeners accounted for more than 55% of sigmaPCB in rainwater. For all samples, the percentage of particle-bound PCBs ranged between 6.6% and 63.8%, providing an average value of 31 +/- 18%. The washout ratios of particulate PCBs (WP) were constant for individual congeners regardless the degree of chlorination. Average WP values ranged between 1.9 x 10(5) and 5.2 x 10(5) while a value of 2.7(+/- 1.3) x 10(5) was deduced for sigmaPCB. The corresponding washout ratios for gaseous PCBs were substantially lower and ranged between 7 x 10(3) (PCB 99) and 1.3 x 10(5) (PCB 180). Washout ratios of gaseous PCBs were also calculated based on Henry's law, and they were found to be 30-920 times lower than those obtained from field measurements. On the basis of our data, the wet deposition flux of sigmaPCB in the eastern Mediterranean should approach 820 ng m(-2) yr(-1). This flux is similar with the values recently reported for several background sites of the United States and Europe, but it is 1 order of magnitude lower than the flux of PCBs measured in the western Mediterranean 16 yr ago.     

Dietary intakes of polychlorinated dibenzo- p -dioxins, dibenzofurans and polychlorinated biphenyls in Finland

Samples of cow milk, pork, beef, eggs, rainbow trout, flours and vegetables were analysed for 17 polychlorinated dibenzo- p -dioxins and dibenzofurans (PCDD/F) and 36 polychlorinated biphenyls (PCB). Daily dietary intake of PCDD/Fs as toxic equivalent (I-TEq) and PCBs (PCB-TEq) was assessed using food consumption data from a 24-h dietary recall study for 2862 Finnish adults. The calculated intake of PCDD/F was 46pg I-TEq day -1 . The current level was about half of the earlier estimation of intake in Finland made in 1992. The assessed PCB intake was 53pg PCBTEqday -1 . Thus, the total intake of PCDD/Fs and PCBs was 100pg TEqday -1 (1.3pg TEqkg -1 b.w.day -1 ), which is within the range of tolerable daily intake (TDI) proposed by the WHO (1-4pg TEqkg -1 b.w.day -1 ).