Aquatic Reclamation in the Athabasca, Canada, Oil Sands: Naphthenate and Salt Effects on Phytoplankton Communities

Abstract

Microcosm experiments with natural indigenous phytoplankton communities were conducted to assess the effects of waters from oil sands extraction processes, emphasizing the naphthenate and salt constituents. Process waters of varying ages (zero to eight years) remediation histories, and chemical composition were obtained from outdoor mesocosms and inoculated with phytoplankton assemblages from a reference lake in the study area. Community composition measures, including percentage model affinity (PMA) and canonical correspondence analysis (CCA), revealed significant community effects of water from systems less than five years old, with naphthenate concentrations greater than 20 mg/L, compared to water from the reference lake. Canonical correspondence analysis, PMA, and regression analyses further showed that naphthenate concentration was significantly correlated with community structure. Using CCA, groups of taxa characteristic of waters with > 20 mg/L naphthenates (including Botryococcus braunii, Gloeococcus schroeteri, Cosmarium depressum, Chrysococcus rufescens, Chromulina spp., Ochromonas spp., and Keratococcus spp.) were identified. Salinity, as reflected in conductivity, was positively correlated with naphthenate concentration and itself appeared to influence the community structure. The results confirmed an important role for naphthenates in ecological effects of process waters from oil sands mining, but the influence of covarying factors such as salinity requires further investigation.

Examining the Microbial Degradation of Naphthenic Acids Using Stable Isotope Analysis of Carbon and Nitrogen

“…Using the GC-MS technique to characterize the NAs, Scott et al (2005) showed that commercial NAs, with a greater proportion of lower molecular weight NAs with shorter carbon chains and fewer rings, were more easily degraded than the oil sands derived NAs. Other studies have also documented differences in the makeup of NA (Herman et al 1993;Herman et al 1994;Lai et al 1996;Clemente et al 2004;Del Rio et al 2006). It is possible that only a limited fraction of the NAs within the oil sands derived mixture is readily degraded, whereas the commercial mix may be more broadly metabolized.…”

“…In any case, previous studies have shown no degradation of oil sands derived NAs under anaerobic conditions over 180 days (Gervais 2004). Factors affecting degradation, particularly concentrations of dissolved oxygen (Gervais 2004) and inorganic nutrients (Lai et al 1996) are important variables in oil sands aquatic reclamation and as such further study on the impact of these factors on isotope signatures of both biomass and DIC is required.…”

“…Their prevalence, and findings of acute toxicity in oil sands tailings (MacKinnon and Boerger 1986) has led to investigations of the toxicity of oil sands process-derived NAs to fish (Nero et al 2006) and phytoplankton (Leung et al 2001;Hayes 2005). Although reviews by Headley and McMartin (2004), Quagraine et al (2005) and Clemente and Fedorak (2005) have highlighted the recent advances in the qualitative and quantitative analyses of NAs, such analyses continue to be a real challenge in studies initiated to assess the environmental risk and/or the biodegradation of NAs.…”

“…Hall et al (1999) found differences in the δ 13 C values of CO 2 depending on the chemical degraded (phenol vs. benzoate) and the species of microorganism used, but found no change in the δ 13 C values of microbial biomass. While there is information on the rate of biodegradation of various surrogate NAs (Herman et al 1993;Lai et al 1996;Del Rio et al 2006) as well as commercial and oil sands processderived NA mixtures (Herman et al 1994;Clemente et al 2004;Scott et al 2005;Del Rio et al 2006), there has been no tracking of stable isotopes during microbial degradation of NAs.…”

Process water treatment in Canada’s oil sands industry: I. Target pollutants and treatment objectives

“…While earlier studies focused mainly on the acute toxicity of TPW, more recent studies have addressed the chronic effects of process waters on aquatic and terrestrial biota in constructed wetlands and ponds (e.g., van den Heuvel et al 1999bHeuvel et al , 2000Siwik et al 2000;Bendell-Young et al 2000;Pollet and Bendell-Young 2000;Leung et al 2001;Colavecchia et al 2004) (for a summary see Table 3). This research will be discussed in greater detail after a brief review of the land reclamation options currently under consideration.…”