Benzo[b]fluoranthene, a potential alternative to benzo[a]pyrene as an indicator of exposure to airborne PAHs in the vicinity of Söderberg aluminum smelters

Benzo[b]fluoranthene (B[b]F) was used in relative abundance ratios (RARs), a parameter obtained by dividing the concentration of individual polycyclic aromatic hydrocarbons (PAHs) found in a given sample by the concentration of B[b]F in the same sample. The B[b]F RARs were derived for PAH concentrations measured at stacks and sampling stations in the vicinity of two S?derberg aluminum horizontal stud smelters (HSSs). The samples collected were analyzed by high-performance liquid chromatography using UV and fluorescence detection. A total of 15 PAHs were analyzed, but, due to the inefficiency of the sampling method used in collecting gaseous PAHs, only particulate PAHs were considered. Comparisons between the B[b]F RARs obtained simultaneously at the source (stack) and those obtained at sampling stations at the two smelters showed that B[b]F degrades more slowly than or at the same rate as most other particulate PAHs monitored. Twenty-three months of urban sampling in the vicinity of one of the aluminum HSSs are also presented, and the results indicate that B[b]F is more stable than all other particulate PAHs investigated. Sampling conducted during a smelter shutdown period confirmed that B[b]F was a much better marker of this source than was benzo[a]pyrene (B[a]P), the usual indicator. The remarkable stability of the benzo[k]fluoranthene (B[k]F)/B[b]F ratio is also discussed.     

Use of benzo[a]pyrene relative abundance ratios to assess exposure to polycyclic aromatic hydrocarbons in the ambient atmosphere in the vicinity of a Söderberg aluminum smelter

The purpose of this study was to investigate the use of benzo[a]pyrene (B[a]P) relative abundance ratios (RARs) to assess exposure to polycyclic aromatic hydrocarbons (PAHs) in the urban atmospheric air in the vicinity of a horizontal stud S?derberg aluminum reduction facility. The B[a]P RARs refer to the concentration of individual PAHs measured in a given sample divided by the concentration of B[a]P found in the same sample. This study compared the B[a]P RARs calculated for the facility stack and three sites near the S?derberg aluminum smelter for three different sampling periods. Interperiod differences were significant for many of the PAHs, and the differences between the stations proved insignificant at p < 0.05. The differences between each individual station and the facility stack were significant for all PAHs. B[a]P RARs increased in value at the stations compared with the stack, indicating that B[a]P may be degraded or removed from the atmosphere at a rate greater than that of the majority of the measured PAHs. It is concluded that B[a]P and B[a]P RARs may be poor markers of exposure to PAHs in the vicinity of this S?derberg aluminum refinery for the entire mixture of PAHs present in the ambient atmosphere.     

Gene expression of heat shock protein 70, interleukin-1β and tumor necrosis factor α as tools to identify immunotoxic effects on Xenopus laevis: a dose-response study with benzo[a]pyrene and its degradation products

The exposure to benzo[a]pyrene (B[a]P) results in an alteration of immune function in mammals and fish, and the analysis of cytokine mRNA levels has been suggested for predicting the immunomodulatory potential of chemicals. To obtain evidence of the innate immune responses to B[a]P in Xenopus laevis, the present study monitored the mRNA expression of interleukin 1-β (IL-1β), tumor necrosis factor α (TNF-α) and heat shock protein 70 (HSP70) in a laboratorial exposure. Tadpoles exposed to 8.36, 14.64, 89.06 and 309.47 μg/L of B[a]P,were used for detecting hsp70, IL-1β and TNF-α mRNA induction. A dose-response increase in the expression of hsp70 and IL-1β mRNA was found. The results of this study confirmed the use of hsp70 and IL-1β, but not TNF-α, as sensitive indicators of immunotoxic effect of B[a]P in X. laevis. Further research would be required for the validation of these endpoints.     

In situ tracer tests to determine retention properties of a block scale fracture network in granitic rock at the Aspö Hard Rock Laboratory, Sweden

Experiments were conducted at the Asp? Hard Rock Laboratory in order to improve the understanding of radionuclide retention properties of fractured crystalline bedrock in the 10-100 m scale (TRUE Block Scale Project, jointly funded by ANDRA, ENRESA, Nirex, JNC, Posiva and SKB). A series of tracer experiments were performed using sorbing tracers in three different flow paths. The different flow paths had Euclidian lengths of 14, 17 and 33 m, respectively, and one to three water conducting structures. Four tests were performed using different cocktails made up of radioactive sorbing tracers (22,24Na+, 42K+, 47Ca2+, 85Sr2+, 83,86Rb+, 131,133Ba2+ and 134,137Cs+). For each tracer injection, the breakthrough of sorbing tracers was compared to the breakthrough of a conservative tracer, 82Br-, 131I-, HTO and 186ReO4-, respectively. In the two longer flow paths, no breakthrough of 83Rb+ and 137Cs+ was observed after 8 months of pumping. Selected tracer tests were subject to basic modelling in which a one-dimensional (1D) advection-dispersion model, including surface sorption, and an unlimited matrix diffusion were used for the interpretation of the results. The results of the modelling indicated that there is a slightly higher mass transfer into a highly porous material in the block-scale experiment compared with in situ experiments performed over shorter distances and significantly higher than what would have been expected from laboratory data obtained from studies of the interactions in nonaltered intact rock.