Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants in urban atmospheres. Several PAHs are known carcinogens or are the precursors to carcinogenic daughter compounds. Understanding the contributions of the various emission sources is critical to appropriately managing PAH levels in the environment. The sources of PAHs to ambient air in Baltimore, MD, were determined by using three source apportionment methods, principal component analysis with multiple linear regression, UNMIX, and positive matrix factorization. Determining the source apportionment through multiple techniques mitigates weaknesses in individual methods and strengthens the overlapping conclusions. Overall source contributions compare well among methods. Vehicles, both diesel and gasoline, contribute on average 16-26%, coal 28-36%, oil 15-23%, and wood/other having the greatest disparity of 23-35% of the total (gas- plus particle-phase) PAHs. Seasonal trends were found for both coal and oil. Coal was the dominate PAH source during the summer while oil dominated during the winter. Positive matrix factorization was the only method to segregate diesel from gasoline sources. These methods indicate the number and relative strength of PAH sources to the ambient urban atmosphere. As with all source apportionment techniques, these methods require the user to objectively interpret the resulting source profiles.

The congener 2,2',3,3',4,4',5,5',6,6'-decabromodiphenyl ether (BDE 209) is the primary component in a commonly used flame retardant known as decaBDE. This flame retardant constitutes approximately 80% of the world market demand for polybrominated diphenyl ethers (PBDEs). Because this compound is very hydrophobic (log K(ow) approximately 10), it has been suggested that BDE 209 has very low bioavailability, although debromination to more bioavailable metabolites has also been suggested to occur in fish tissues. In the present study, juvenile carp were exposed to BDE 209 amended food on a daily basis for 60 days, followed by a 40-day depuration period in which the fate of BDE 209 was monitored in whole fish and liver tissues separately. No net accumulation of BDE 209 was observed throughout the experiment despite an exposure concentration of 940 ng/day/fish. However, seven apparent debrominated products of BDE 209 accumulated in whole fish and liver tissues over the exposure period. These debrominated metabolites of BDE 209 were identified as penta- to octaBDEs using both GC/ECNI-MS and GC/HRMS. Using estimation methods for relative retention times of phenyl substitution patterns, we have identified possible structures for the hexa- and heptabromodiphenyl ethers identified in the carp tissues. Although exposure of carp to BDE 209 did not result in the accumulation of BDE 209 in carp tissues, our results indicate evidence of limited BDE 209 bioavailability from food in the form of lower brominated metabolites.

Concentrations of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) were measured in the atmosphere and surface waters of Lake Superior to estimate the direction and magnitude of their fluxes across the air-water interface. Atmospheric PAH concentrations ( [ ] = 3.8 ± 1.7 mg/m3, 13 PAHs) were typical of levels found in continental background air. Atmospheric PCB concentrations (x = 1.2 ng/m3) have remained relatively constant over the Great Lakes during the past 10 years despite lower PCB loadings. PCB congener fugacity gradients suggest PCB volatilization from Lake Superior's surface waters in August 1986. Mean volatilization fluxes of total PCBs (19 ng/m2-day) are similar to estimates of gross atmospheric deposition to the lake, supporting the hypothesis of nonequilibrium, steady-state PCB exchange across the air-water interface. PAH fluxes could not be calculated due to uncertainties in PAH Henry's law constants.

No abstract

Polybrominated diphenyl ether (PBDE) congener patterns in biota are often enriched in tetra-, penta-, and hexabrominated diphenyl ethers, which is believed to result from the use of the commercial “pentaBDE” formulation. However, our evidence suggests that debromination of PBDEs occurs within fish tissues leading to appreciable ac cumulation of less brominated congeners. This suggests that PBDE body burdens can reflect both direct uptake from exposure and debromination of more highly brominated congeners. We conducted two independent dietary exposure studies using the common carp (Cyprinus carpio) to trace the fate of 2,2‘,4,4‘,5-pentabromodiphenyl ether (BDE 99) and 2,2‘,3,4,4‘,5‘,6-heptabromodiphenyl ether (BDE 183) in fish tissues. Carp were fed food spiked with individual BDE congeners for 62 d, and depuration was monitored during the following 37 d. Significant debromination was observed, converting BDE 99 to 2,2‘,4,4‘-tetrabromodiphenyl ether (BDE 47) and BDE 183 to 2,2‘,4,4‘,5,6-hexabromodiphenyl ether (BDE 154) and another as yet unidentified hexa-BDE congener. The BDE 99 concentration rapidly declined from 400 ± 40 ng/g ww in the food to 53 ± 12 ng/g ww in the gut content material sampled 2.5 ± 1 h following feeding. At least 9.5 ± 0.8% of the BDE 99 mass in the gut was debrominated to BDE 47 and assimilated in carp tissues. In the BDE 183 exposure, approximately 17% of the BDE 183 mass was debrominated and accumulated in carp tissues in the form of two hexa-BDE congeners. In both exposure studies, the concentration of the exposure compound decreased significantly in the gut within 2.5 ± 1 h following ingestion. This rapid decrease in the concentration of the BDE congeners could not be explained entirely by debromination to quantified products or fecal egestion. Reactions occurring within the gut transform BDE congeners to other products that may accumulate or be excreted. Further studies are needed to identify and determine the effects of these BDE metabolites.

The Henry's law constants for 26 polychlorinated biphenyl (PCB) congeners were measured using a gas-stripping apparatus at five environmentally relevant temperatures between (4 and 31) °C. The Henry's law constants ranged between (0.079 ± 0.003) Pa·m3·mol-1 for 2,2‘,3,3‘,4,4‘,5,6-octachlorobiphenyl (IUPAC congener #195) at 4 °C and (308 ± 29) Pa·m3·mol-1 for 2,2‘,3,3‘,4,5‘,6,6‘-octachlorobiphenyl (IUPAC congener #201) at 31 °C. The temperature dependence of each PCB congener's Henry's law constant was modeled to calculate the enthalpy and entropy of the phase change between the gaseous and dissolved phases. For many PCB congeners, this study reports the first experimentally measured temperature variations of their Henry's law constants. The enthalpies of phase change (ΔH H) ranged between (14.5 ± 3.4) kJ·mol-1 for 2,2‘,4,6,6‘-pentachlorobiphenyl (IUPAC congener #104) and (167 ± 13) kJ·mol-1 for 2,2‘,3,3‘,4,4‘,5,6-octachlorobiphenyl (IUPAC congener #195). These data can be used to predict PCB congener Henry's law values within the experimental temperature range within a relative standard error of less than 10%.

No abstract

Dissolved and gas-phase concentrations of nine polycyclic aromatic hydrocarbons and 46 polychlorinated biphenyl congeners were measured at eight sites on the Chesapeake Bay at four different times of the year to estimate net diffusive air−water gas exchange rates. Gaseous PAHs are absorbed into the bay's surface waters during the spring, and lighter compounds revolatilize in the late summer and early fall due to seasonal changes in surface water temperature and atmospheric PAH levels. On an annual basis, the atmosphere is a net source of volatile PAHs to the Chesapeake Bay, and gas absorption may be the largest external source of fluorene and phenanthrene, providing up to three times the combined loadings from wet and dry aerosol deposition and from tributaries. Largest PAH absorptive fluxes occurred in the northern Chesapeake when prevailing winds carried PAH-enriched air from the Baltimore-Washington urban area over the bay. In contrast to PAHs, PCBs volatilize from the Chesapeake Bay throughout the year, with the largest fluxes occurring in September and the smallest fluxes in June. However, higher chlorinated ( − ) homologues are absorbed by bay waters during most of the year. Highest PCB volatilization rates were observed in the northern Chesapeake Bay and near the James River in the southern bay, indicating volatilization offsets PCB loading from the bay's tributaries. Volatilization is the dominant removal process for PCBs from the Chesapeake Bay, removing an estimated 400 kg/year. This value is larger than current external PCB loadings, suggesting that release of PCBs from historically contaminated sediments supports volatilization from the bay.