Levels of polycyclic aromatic hydrocarbons and dibenzothiophenes in wetland sediments and aquatic insects in the oil sands area of Northeastern Alberta, Canada

Abstract

An immense volume of tailings and tailings water is accumulating in tailings ponds located on mine leases in the oil sands area of Alberta, Canada. Oil sands mining companies have proposed to use tailings- and tailings water-amended lakes and wetlands as part of their mine remediation plans. Polycyclic aromatic hydrocarbons (PAHs) are substances of concern in oil sands tailings and tailings water. In this study, we determined concentrations of PAHs in sediments, insect larvae and adult insects collected in or adjacent to three groups of wetlands: experimental wetlands to which tailings or tailings water had been purposely added, oil sands wetlands that were located on the mine leases but which had not been experimentally manipulated and reference wetlands located near the mine leases. Alkylated PAHs dominated the PAH profile in all types of samples in the three categories of wetlands. Median and maximum PAH concentrations, especially alkylated PAH concentrations, tended to be higher in sediments and insect larvae in experimental wetlands than in the other types of wetlands. Such was not the case for adult insects, which contained higher than expected levels of PAHs in the three types of ponds. Overlap in PAH concentrations in larvae among pond types suggests that any increase in PAH levels resulting from the addition of tailings and tailings water to wetlands would be modest. Biota-sediment accumulation factors were higher for alkylated PAHs than for their parent counterparts and were lower in experimental wetlands than in oil sands and reference wetlands. Research is needed to examine factors that affect the bioavailability of PAHs in oil sands tailings- or tailings water-amended wetlands.

Reproductive development of yellow perch (Perca flavescens) exposed to oil sands–affected waters

“…The pH of the tailings interstitial water underlying the Demonstration Pond ranged from 7.5 to 8.4. Alkalinity was not consistently measured at all sites; however, data estimated for the Demonstration Pond showed a corresponding increase in mean (standard error of the mean, n) alkalinity from 305 (6.0, 8) to 527 (1.5, 3) mg/L as CaCO 3 .…”

“…Thomas et al [28] also raised the possibility that PAHs can bind to androgen receptors. It is known that tailings porewater contained PAHs [2], and they were present in sediment and insects from the Demonstration and Bison Pond [3]. Furthermore, elevated levels of bile fluorescence, particularly at phenanthrene wavelength, and induced CYP1A enzyme activity in yellow perch in the Demonstration and Bison Ponds suggested that perch were being exposed to planar aromatic structures [7].…”

“…Hoop nets were deployed in overnight sets and were 1.22 m wide  0.91 m high at the opening with a 7.6-m leader and 8-mm mesh size and no diagonal wings at the opening. Yellow perch were transported to the experimental ponds in two aerated circular polyethylene tanks with a capacity of 0.75 m 3 . Transportation time to the experimental ponds was less than 30 min (50-75 fish per tank).…”

“…Polycyclic aromatic hydrocarbons, unlike naphthenic acids, are likely to be depleted by the extraction process, because they are neutral compounds and will partition into the bitumen phase during extraction. Polycyclic aromatic hydrocarbon mixtures associated with oil sands have been observed to contain mostly alkylated PAHs and dibenzothiophenes with low representation from the parent compounds [2,3]. Recent evidence of metals introduced to the Athabasca watershed through atmospheric deposition further complicates the complex chemical puzzle of oil sands-related contamination [4].…”

Evaluating officially reported polycyclic aromatic hydrocarbon emissions in the Athabasca oil sands region with a multimedia fate model

“…However, a recent assessment of PAHs in lakesediment cores provides compelling evidence that oil sands development has led to a significant increase in PAH levels in the AOSR environment (17). Although there have been studies providing insight into concentrations of PAHs in air (18), water (13), snow (13), sediments (10,17,(19)(20)(21), tailings pond pore water (22), and tailings pond sediments (10,21) in the AOSR, thorough characterization of PAH sources, pathways, and sinks within the AOSR is still lacking.…”