1. Oil Sands: integrate natural processes in hazard assessment
Diogo N. Cardosoa,
João L. T. Pestanaa, Ana Rita R. Silvaa, Amadeu M.V.M. Soaresa, Frederick J. Wronab,c, Susana Loureiroa
a Department of Biology, CESAM, University of Aveiro
b Alberta Environment and Parks, Environmental Monitoring and Science Division, Edmonton, Canada
c Department of Biological Sciences, University of Calgary, Canada
Abstract
One of the largest petroleum reserves in the world is located in the Cretaceous oil-sands in the Athabasca Basin in North-eastern Alberta, Canada. Contamination of the aquatic environment occurs naturally and/or as the results of anthropogenic factors. In that specific area, the Athabasca river and its tributaries flows through bitumen deposits (McMurray formation) and consequently receive bitumen and bitumen-associated contaminants inputs mainly from erosion processes (slumping material falling into the streams). Therefore it is crucial to discriminate between effects caused by oil sands mining activities and those occurring from natural conditions. Ecotoxicological tests were conducted using parental natural geological material collected from river banks near the oil exploitation area (Alberta, Canada), at four different locations/rivers. These geological samples were used to assess effects in the midge Chironomus riparius and the luminescent bacteria Vibrio fischeri.
Oil sands deposits have several specific and unique characteristics that make them a special case study, having both a high potential for expanding hydrocarbon extraction and a region to assess associated cumulative environmental impacts.
Key issue: discrimination between natural and anthropogenic sources of contamination and the effects of oil sands geological samples in aquatic ecosystems’ structure and function.
An ecologically approach was chosen to assess how organisms respond to hydrocarbon-associated contaminants arising from hydrologic natural processes (e.g., input of bitumen sands through river bank erosion) to establish reference conditions in aquatic ecosystems within oil sands regions. This will contribute to a better Environmental Risk Assessment (ERA) of anthropogenic activities such as oil sands mining and upgrading of oil.
Objectives
Explore the toxicity of solid samples from the field when entering into aquatic systems;
Use of different approaches with aquatic organisms to assess the toxicity of bitumen;
Stablish a comparison between the patterns of toxicity of samples from different spots of the studied area – heterogeneity of the samples/areas.
Results
STB SP
ELLs
ATB
Source: Conly et al (after Green 1972) *
Fig 2 / Slumping area being eroded with natural formations of bitumen exposed to the air.
Fig 3 / Eroded slumping natural material entering into the rivers in oil sands region.
Fig 1 / Samples used in both bioassays were denominated: SP – Steepbank River slump (site 1); ATB – Athabasca River; STB – Steepbank River (site 2); ELLs- Ells River and were collected in the oil sands region, Alberta, Canada.
Fig 4 / Scheme of the experimental design: 1) slumping material being eroded into and by the river, 2) material sampling, 3) collected samples, 4) solid material in a MICRTOX® solid phase test and 5) Chironomus riparius 28-days partial life cycle test.
Chironomus riparius sediment test
MICROTOX® solid phase test
SP sample
ATB sample
ELLs sample
Graph 1 / Growth of Chironomus riparius larvae exposed over 10 days to different % of Oil Sands solid samples mixed in sediment. Data are expressed as average+SE; *significant differences compared to the control (0) treatment (p<0.05).
STB sample
ELLs sample
STB sample
Graph 3 / Cumulative emergence of Chironomus riparius larvae exposed to different % of Oil Sands solid samples mixed in sediment. * denotes a significant difference compared to the control (p<0.05).
Graph 2 / Adults’ body weight of Chironomus riparius exposed over 28 days to different % of Oil Sands solid samples mixed in sediment. Data are expressed as average+SE; *significant differences compared to the control (0) treatment (p<0.05).
Graph 4 / Luminescence inhibition of the marine bacteria Vibrio fischeri exposed to a series of dilutions of elutriates extracted from Oil Sands SP, ATB, STB and and ELLs solid samples, on a MICROTOX® solid phase test.
Discussion/conclusions
Geological materials from the lower Ells (ELLs) and Steepbank (STB) Rivers had the highest toxicity, compared to samples from the Athabasca mainstream (ATB) and from Steepbank River (SP1).
Different site-specific patterns were observed when analyzing the toxicity that could be related to the grade (quantity and quality) of bitumen content.
Geological context of the area must be taken into consideration when assessing the ecological effects of the natural material – definition of background reference conditions.
This study highlights the need for a better discrimination of the ecotoxicological effects of natural processes vs. anthropogenic sources (e.g. mining-related activities) in oil sands region.
This study received financial support from CESAM (UID/AMB/ POCI FEDER ), through FCT/MEC national funds, and the co-funding by the FEDER, within the PT2020 Partnership Agreement and Compete 2020.