The Liber Team

Affiliation: University of Saskatchewan, Toxicology Centre
Principal Investigator: Dr. Karsten Liber
Research Associate: None at present
Current Graduate Students: None at present

Team Role: The Liber team is analyzing and documenting partitioning of trace metal concentrations in water and sediments, tracking and assessing toxicity of water from experimental trenches and focal wetlands using lab cultured zooplankton. They are also investigating the role of salinity in aquatic toxicity, its influences on toxicity of other chemical stressors, and how these relationships change over time and influence wetland succession (in collaboration with the University of Waterloo).





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Past Graduate Students and Postdoctoral Fellows/>

Navdeep Toor
  1. Navdeep Toor (Ph.D.)
  2. Completed: 2012
  3. Thesis Title: Degradation and Aquatic Toxicity of Oil Sands Naphthenic Acids Using Simulated Wetlands

Thesis Abstract: Oil sands process-affected waters (OSPW) from the Athabasca oil sands (AOS) located in northern Alberta, Canada, are toxic to aquatic organisms due to the presence of organic and inorganic constituents. Much of this toxicity is related to a group of dissolved organic acids known as naphthenic acids (NAs). Naphthenic acids are a natural component of bitumen and are released into process water during the caustic hot water extraction process used to separate the bitumen from the oil sand ore. This complex mixture of non-cyclic and mono- and poly-cyclic alkanes containing carboxyl groups are characterized by the general formula CnH2n+zO2, where n indicates the carbon number, and Z represents the number of fused rings in the structure. Currently, all process-affected waters are stored within large holding ponds and settling basins on the oil sands mining lease sites with the understanding that eventual reclamation of this water must be undertaken. Successful reclamation of OSPW is expected to require a reduction in total NAs concentrations in the OSPW and the removal of the toxic character of the water. Natural or enhanced bioremediation in lakes and wetlands within the lease closure landscapes will play a critical role in meeting these two requirements. This research investigated the potential for the reduction of total NAs concentrations in OSPW due to biotic (e.g., biodegradation) and abiotic (e.g., sorption) processes, and its relationship to the overall toxicity of OSPW. The specific goals of this research were to determine if natural degradation of NAs in simulated wetland environments could be enhanced by manipulating various physical and chemical factors of the environment, to describe and quantify the selective biodegradation rates of NAs congeners, and to correlate observed changes in total NAs concentration and composition with changes in the aquatic toxicity of OSPW.

The complexity of both OSPW and NAs mixtures presented an unusual set of challenges. A preliminary investigation was used to determine the contributions of salinity and NAs to the total aquatic toxicity of OSPW in order to identify a suitable test organism that would respond to NAs concentrations while tolerating the high ionic content of OSPW for the main simulated wetland microcosm study. Seven-day Ceriodaphnia dubia chronic toxicity tests, using both unmanipulated (containing NAs) and manipulated (substantially reduced NAs) samples of OSPW, identified salinity as a potential contributing factor to the overall toxicity of this complex water. Only a 5% reduction in acute toxicity and an 11% reduction in chronic toxicity was observed with a 91% reduction in total NAs concentration (from 67.2 to 5.9 mg/L; removed by solvent extraction). However, when the same samples were tested using the salt tolerant bacteria Vibrio fischeri in the Microtox® bioassay system, the 91% reduction in total NAs concentration, the toxicity was removed (EC50 changed from 57.8 to >100%). These results suggested that salts in OSPW may drive the toxicity of OSPW to some freshwater invertebrates, such as C. dubia, and that the Microtox® bioassay was better suited to track the overall toxic potential of NAs in OSPW.

Using flow-through, laboratory microcosms to mimic natural wetlands, it was demonstrated that the reduction in total NAs concentration, based on the Fourier Transform Infrared (FTIR) spectroscopy analysis, was dependent upon hydraulic retention time (HRT), but appeared to be unaffected by nutrient addition (nitrogen and phosphorus). Microcosms with a longer HRT (for two OSPW types; Syncrude and Suncor) showed higher reductions in total NAs concentrations (64 to 74% NAs reduction) after the 52-week test period, while nutrient enrichment appeared to have little effect. While the total NAs concentrations decreased in the waters from the microcosms, a 96-hr static acute rainbow trout (Oncorhynchus mykiss) bioassay showed that the initial acute toxicity of Syncrude OSPW (LC50 = 67% v/v) was reduced (LC50 >100% v/v) independent of HRT. However, EC20s from the Microtox® bioassays were relatively unchanged when comparing the input and output microcosm waters maintained at both HRTs over the 52- week study period, indicating that some sub-lethal toxicity persisted under these experimental conditions. The study demonstrated that given sufficiently long HRTs, simulated wetland microcosms containing OSPW significantly reduced total NAs concentrations and acute toxicity, but left behind a persistent component of the NAs mixture associated with residual toxicity.

Further investigations aimed to describe and quantify the selective biodegradation of NAs congeners and correlate the observed changes in total NAs concentration and composition (i.e., NAs fingerprint profile) with the aquatic toxicity of OSPW. High performance liquid chromatography/quadrupole time of flight-mass spectrometry (HPLC/QTOF-MS) analysis was used to track the changes in NAs mixture profiles or ‘fingerprints’ in each experimental treatment over time. Based on first-order degradation kinetics, rapid degradation was observed for NAs that had lower carbon numbers (11 to 16) and fewer degrees of cyclization (Z series -2 to -4; half-lives between 19 to 28 weeks). Within the NAs mixture fingerprint, the two most persistent groups of NAs homologues were identified (NAs with carbon numbers 17 to 20 and Z series -6 to -12; half-lives between 37 to 52 weeks). Their persistence may have resulted in the residual chronic toxicological response as measured by the Microtox® bioassay (EC20).

An additional study was conducted to characterize potential changes in the total concentration and composition of NAs in OSPW due to sorption to organic wetland sediments. The batchreactor investigation showed a rapid (<1 day) and significant reduction in total NAs concentrations in OSPW when mixed with the wetland sediment at a ratio of 2:1 v/v (OSPW:sediment). The mean percent reduction of NAs in OSPW was 67% during the 14-day test period, suggesting a significant influence of sorption on the removal of NAs than previously expected. However, no preferential sorption was observed based on the distribution of NAs congeners with respect to carbon number, Z series, and arbitrarily defined clusters. The potential sorption of OSPW NAs as a result of using substrates with high organic carbon content (e.g., 27.6% total organic carbon content) in designed wetlands may enhance the mitigative capabilities of these reclamation landscapes at the AOS. Further investigations into understanding NAs sorption kinetics without substrate agitation are warranted before these results can be extrapolated to the field.

Finally, to test the hypothesis that persistent components of an OSPW NAs mixture (e.g., NAs congeners with higher carbon numbers and degrees of cyclization) may be responsible for the observed residual chronic toxicity identified in the previous simulated wetland microcosm study, the fractionation of OSPW NAs was attempted using both off-line anion exchange chromatography and batch-wise co-polymer filtration and elution. Although complete separation was not achieved in this investigation, the results suggested that specific variations of the copolymer were most effective and showed the most promise for separating the NAs mixtures based on polarity and size. With further refinements to the procedure, future investigations may be able to achieve adequate separation of the NAs mixture into fractions with compositions different enough to conduct toxicity bioassays.

 


Naveen Puttaswamy
  1. Naveen Puttaswamy (Ph.D.)
  2. Completed: 2011
  3. Thesis Title: Evaluation of Metals Release from Oil Sands Coke: An Ecotoxicological Assessment of Risk and Hazard to Aquatic Invertebrates.

Thesis Abstract: The oil sands operations in northeast Alberta, Canada, employ unconventional processes to produce synthetic crude oil (SCO). Because the extracted bitumen, 'the form of oil in oil sands', is highly viscous, it requires thermal upgrading to produce SCO. Coking technology is used to convert heavy bitumen fractions to lighter volatile fractions. During this process, an enormous volume of solid coke is produced and the metal impurities (e.g. Al, Fe, Mn, Ni, Ti and V) present in bitumen fractions end-up in the coke particles. As coke demands significant space for storage, oil sands companies are exploring options for placing coke into reclamation landscapes for long term storage and recovery. However, coke holds appreciable amounts of potentially leachable metals that may impede the performance of reclamation landscapes. Although two previous coke leaching studies had showed that coke released metals into water at concentrations exceeding the Canadian guidelines for the protection of aquatic life, the ecotoxicological hazard and risk of these metals were not well characterized. Therefore, the overall goal of this research was to characterize the fate and toxicity of metals associated with coke.

In this research, the toxicity of coke leachates collected from oil sands field sites and those artificially generated in the laboratory were evaluated using a standard three-brood Ceriodaphnia dubia tests. Coke leachates (CLs) collected over a period of 20 months from two field lysimeters were found to be acutely toxic to C. dubia. Vanadium concentrations were significantly higher (p≤0.05) than concentrations of all other metals in CLs from both lysimeters, and also in leachates from a laboratory batch renewal leaching study. Furthermore, toxic unit (TU) calculations suggested that Ni and V were likely the cause of CL toxicity, but this was not explicitly proven. Therefore, a chronic toxicity identification and evaluation (TIE) approach was adopted to identify and confirm the cause(s) of CL toxicity. Coke was subjected to a 15 day batch leaching process in the laboratory at pH 5.5 and 9.5 in order to characterize the effect of pH on metals release from coke, and to generate CLs for use in TIE tests. The 7-day LC50 estimates for C. dubia survival were 6.3% and 28.7% (v/v) for CLs generated at pH 5.5 and 9.5, respectively. The dissolved concentrations of Mn, Ni and Zn were high (p≤0.05) in pH 5.5 CL, whereas Al, Mo and V were high (p≤0.05) in pH 9.5 CL. Evidence gathered from a series of chronic TIE tests revealed that Ni and V were the cause of toxicity in pH 5.5 CL, whereas V was the primary cause of toxicity in pH 9.5 CL. Further, the influence of bicarbonate, chloride and sulfate ions on metals release, speciation and Ni and V toxicity was investigated. The type and amount of metals released from coke was significantly influenced by the ion type elevated in the leaching solution. Specifically, sulfate influenced mobilization of Ni, Fe, Mn and Zn from coke, whereas bicarbonate enhanced Al, Mo and V releases from coke. With respect to toxicity, increasing bicarbonate decreased the 7-day Ni2+ IC50 from 6.3 to 2.3 μg Ni2+/L suggesting enhanced Ni toxicity at high pH or alkalinity. Conversely, sulfate showed a protective effect against V toxicity to C. dubia.

The research presented in this thesis suggests that coke will not be inert when stored in reclamation landscapes and that metals, particularly Ni and V, could reach ecotoxicologically relevant levels in surface waters or substrate porewaters, under favourable leaching conditions. Operationally, efforts should focus on remediation and monitoring of metals released from coke, particularly Ni and V, in impacted wetlands, especially before discharging water into natural wetlands and/or local streams and rivers.



Dominique Turcotte
  1. Dominique Turcotte, Ph.D. (Post-Doctoral Fellow)
  2. Completed: 2010
  3. Project: Interactive effects of salinity and naphthenic acids on toxicity of oil sands process water to freshwater invertebrates.

Project Summary: The oil sands mining industry in the Athabasca River area, uses large quantities of water during the oil extraction process. The resulting oil sands process water (OSPW) is proposed to be part of future reclamation landscapes, so understanding its toxicity to freshwater aquatic invertebrates is important in order to develop environmentally acceptable OSPW reclamation plans. OSPW typically contains elevated concentrations of salts and naphthenic acids (NAs), but low levels of other contaminants such as PAHs and metals. Variations in ionic composition have been demonstrated to influence sub-lethal effects of salinity on some invertebrate species. Ions also have the potential to interact with and alter the toxicity of various contaminants. Therefore salinity may play an important role in the toxicity of OSPW on fresh¬water invertebrates. The nature of the toxic interaction between major ions and naphthenic acids has not yet been researched and it could be a significant factor when considering the total toxicity of the OSPW on long term reclamation.

Dominique’s work investigates the toxicity of OSPW salinity on freshwater biota. She aims to determine whether or not the combined concentrations of major ions affect the toxicity of the resulting salinity, and to determine possible interactions between naphthenic acids and salinity.



Allison Squires
  1. Allison Squires (M.Sc.)
  2. Completed: 2005
  3. Thesis Title: Ecotoxicological assessment of using coke in aquatic reclamation strategies at the Alberta oil sands. [PDF]

Thesis Abstract: Oil sands, also known as tar sands or bituminous sands, are sand deposits impregnated with dense, viscous petroleum called bitumen. The two major oil sand mining companies currently producing synthetic crude oil in the province of Alberta are Syncrude Canada Ltd. and Suncor Energy Inc. Coke is a waste product formed during the heavy oil upgrading processes. The amount of coke produced currently at the Syncrude and Suncor operations is significantly more than what can be combusted and/or sold. Therefore, it must be stored on site making coke a necessary component of future reclamation landscapes. It is as yet unclear whether or not coke poses a significant toxicological risk (i.e. through leaching of constituent chemicals and elements) to the aquatic or terrestrial environments if used in a long-term reclamation capacity. The primary objective of this research was to evaluate whether stockpiled Syncrude Canada Ltd. and Suncor Energy Inc. coke can safely and effectively be used as a substrate amendment in an aquatic reclamation option.

Syncrude and Suncor coke were exposed to three different sets of water quality conditions: high and low dissolved oxygen, pH (5, 7.5 and 10) and freeze-thaw cycles. These conditions have the potential to affect the leaching of constituents from coke once placed in an aquatic environment in northern Alberta. Metals were observed to leach from both coke types under all treatments. Some of these metals (cobalt, copper, manganese, molybdenum, nickel, vanadium and zinc) reached levels of toxicological interest by exceeding published LC50 values for the aquatic macroinvertebrate Chironomus sp. and/or established Canadian Water Quality Guidelines for the protection of aquatic life.

To determine the source of metals observed to leach in the leaching experiments, an accelerated weathering experiment was conducted. Coke from both Syncrude and Suncor were pre-treated by rinsing with water to remove any natural soil or sediment particles that become associated with the coke during storage, and with peroxide to remove any metals bound to the surface of the coke. It was concluded that the metals leaching into the overlying water and pore water of the coke were from either the natural soil/sediment particles, and/or were weakly bound to the surface of the coke. Rinsing coke with water before adding it as a substrate amendment in an aquatic reclamation strategy may decrease its potential toxicity to aquatic organisms by removing the soil/sediment debris and metals loosely bound to the surface of the coke, reducing initial amounts of metals available to the organisms in the pore and overlying waters.

As part of these leaching experiments, coke from both Syncrude and Suncor were further characterized with elemental analysis and qualitative analysis with polarized light microscopy and scanning electron microscopy. These analyses showed distinct differences in the physical properties (i.e. particle size and structure) of Syncrude and Suncor coke. However there appeared to be little variation in the elemental and structural composition among the different weathering treatments within each coke type.

Following leaching, coke from Syncrude and Suncor was used as a substrate in 10-d toxicity tests with Chironomus tentans. These experiments evaluated whether the leachate generated from coke, or the coke itself, caused of an adverse effect on the survival and/or growth of this aquatic invertebrate. Decreased survival and growth of C. tentans was observed when Suncor coke was used as a substrate. However, further experimentation showed that these effects were due to the physical properties of Suncor coke, rather than any constituents that leached from the coke.

In a separate experiment, combinations of fresh oil sands waste materials were added to experimental enclosures constructed at Syncrude Canada Ltd in May 2002. Core samples of these waste materials were collected after aging in situ for periods of 2 and 14 months. The aged samples along with fresh (0 month) samples, were used as substrate material in 10-d toxicity tests with C. tentans to assess the potential toxicity of both fresh and field-aged combinations of waste materials. These experiments found that there is a potential for greater initial stress or toxicity to aquatic organisms when the substrates are freshly added to the reclaimed wetlands. However, this initial potential toxicity of oil sands waste materials can decrease with aging in an aquatic environment.

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Past Undergraduate Student Projects


  1. Pola Wojnarowicz (B.Sc. - Honours in Toxicology)
  2. Completed: 2009
  3. Thesis Title: Effects of Salt Interactions in Oil Sands Process Waters on Ceriodaphnia dubia using an Isobolographic Approach. [PDF]
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