Characterization of Naphthenic Acids and Other Dissolved Organics in Natural Water from the Athabasca Oil Sands Region, Canada

Abstract

With growth of the Canadian oil sands industry, concerns have been raised about possible seepage of toxic oil sands process-affected water (OSPW) into the Athabasca River (AR). A sampling campaign in fall 2015 was undertaken to monitor for anthropogenic seepage while also considering natural sources. Naphthenic acids (NAs) and thousands of bitumen-derived organics were characterized in surface water, groundwater, and OSPW using a highly sensitive online solid phase extraction-HPLC-Orbitrap method. Elevated NA concentrations and bitumen-derived organics were detected in McLean Creek (30.1 μg/L) and Beaver Creek (190 μg/L), two tributaries that are physically impacted by tailings structures. This was suggestive of OSPW seepage, but conclusive differentiation of anthropogenic and natural sources remained difficult. High NA concentrations and bitumen-derived organics were also observed in natural water located far north of the industry, including exceedingly high concentrations in AR groundwater (A5w-GW, 2000 μg/L) and elevated concentration in a tributary river (Pierre River, 34.7 μg/L). Despite these evidence for both natural and anthropogenic seepage, no evidence of any bitumen-derived organics was detected at any location in AR mainstem surface water. The chemical significance of any bitumen-derived seepage to the AR was therefore minimal, and focused monitoring in tributaries will be valuable in the future.

Overview of Existing Science to Inform Oil Sands Process Water Release: A Technical Workshop Summary

“…Many of the activities discussed under this theme are currently being addressed under regional monitoring programs (Table ). There are extensive environmental quality and quantity monitoring programs currently in place to identify changes in surface water and sediment quality (EMSD ; Sun et al ) near oil sands development. Many of these programs cover a large geographic area but are also accompanied by additional programs examining change in organisms residing in the Athabasca River Watershed (Arens et al ).…”

Formation waters discharge to rivers near oil sands projects

“…Groundwater aquifer characterization using tracers such as sulphur, boron, lithium isotopes and organics such as naphthenic acids (Harkness et al, 2017;Headley, Barrow, Fahlman, Frank, & Bickerton, 2011;Sun et al, 2017) combined with improved hydrochemical monitoring of main stem rivers, tributaries, and groundwaters may help better assess industry impacts on groundwater discharges and better estimate time intervals formation waters take to traverse aquifers and enter rivers.…”

“…All three rivers flow past numerous nearby (<10–100 km) oil sands leases (Figures and ). The quality of water in these rivers is potentially vulnerable to pollutants derived from groundwater discharges, as some regional groundwaters have high concentrations of both natural‐ and anthropogenic‐sourced naphthenic acids (Sun et al, ). Understanding links between groundwaters and river waters, and where these links are strongest, may help assess potential hazards of development to local aquatic ecosystems and improve regional water quality monitoring programs.…”

Non‐target profiling of bitumen‐influenced waters for the identification of tracers unique to oil sands processed‐affected water (OSPW) in the Athabasca watershed of Alberta, Canada

“…Within these containments are features, including clay substrates at the base and perimeters, and perimeter interceptor ditches to return seepage from the containment walls back into the ponds. However, there are numerous studies that have documented or indicated OSPW seepage into groundwater, thus raising concerns about a vector to surface water 14–20 …”

“…The OSPW recycling process, along with the hot alkaline extraction process, results in an enrichment of natural bitumen‐derived substances in OSPW. This mixture of organics has been termed supercomplex 21 and is similar in chemical profile to natural bitumen‐affected waters, making source discrimination difficult and hampering previous attempts to detect seepage 14,17,19,21–24 . Historically, attempts to identify OSPW‐affected groundwater have considered total naphthenic acids (NAs), various geochemical indicators (major cations and anions), synchronous fluorescence spectroscopy (SFS) detection of aromatic acids, a variety of isotopic tracers, and ratios of O 2 :O 4 heteroatom ion classes and SO n ‐containing species determined by ultrahigh‐resolution mass spectrometry 15,16,18,25–37 .…”