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