19 environmental tox of oil sands Flashcards
what is the outline of this lecture?
-what is oil sand? how is it processed to extract petroleum?
-why and how does alberta oil sands (AOS) operation impact the environment?
-what are the short and long term toxic implication of AOS to the environment?
-current remediation strategies and their pitfalls
what is crude oil?
-animal and plant remains from millions of years ago sand to the bottom of the ocean, and were covered by layers of sand and sediment over time
-as the layers increased, the resultant pressure and hear resulted in the formation of petroleum
what is conventional oil?
conventional oil: can be recovered as a liquid at atmospheric pressure
-due to its buoyancy and ability to flow upwards without stimulation or processing, it can be extracted via simple vertical drilling to conventional oil traps
what is the process of oil sands formation?
-algae and other marine life decomposed into light oil
-microbes in trapped oxygenated water fed off the lighter hydrocarbon molecules (biodegradation), leaving behind a heavier complex hydrocarbon with sulphur and trace metals (oil sands)
what is the composition of oil sands?
oil sands (tar sands): mixture of sand, clay, water and bitumen (a thick, viscous form of petroleum)
-deposits average 10% bitumen, 5% water and 85% solids (silica sand and fine clays)
what is unconventional oil?
unconventional oil: can’t be extracted by conventional drilling and requires some form of processing
-bitumen is highly viscous form of unconventional oil; it does not normally flow. Therefore it must be either diluted or heated prior to extraction
-bitumen reserves have been increasingly used since 2000s-> largest bitumen reserve in the world are the alberta oil sands
how large are the alberta oil sands?
-140,200 square kilometers of land in the Athabasca, Cold Lake and Peace river areas in northern alberta
-contain 1.7-2.5 trillion barrels of crude bitumen
-10% of this volume (170 billion barrels) is recoverable using current technology
-97% of canadian oil reserves and 75% of total north american petroleum reserves
what are the economic benefits of AOS?
-alberta’s oil sands has the fourth-largest oil reserves in the world, after venezuela, saudi arabia and iran
-over the next 25 years is expected to create $444 billion in tax revenue
-approx. 70% of the annual non-renewable resource revenue
what are oil sands structure?
-oil sands are made up of sand particles covered in a thin water envelope, mixed inside a bitumen film
-millions of years ago bacteria likely broke down the lighter petroleum chemicals in the oil, leaving behind the heavier hydrocarbons-> bitumen has a “cold molasses” consistency
how are oil sands extracted?
surface mining (for oil sands up to 75m below surface)
in-situ mining (up to 80% of oil sands below 75m)
-use steam to liquify and decrease bitumen viscosity
-solvent based approach
what is steam assisted gravity drainage?
most common in situ method, invented in 1978
-2 vertical wells:
-top well injected with steam
-bottom well collects softened bitumen
-less land disturbance
-no tailings ponds
-high water and energy use
what are the steps in open-pit/surface mining?
- large pits dug expose sand reserves, loaded onto trucks
- oil sands are transported to crushers
- oil sands are then mixed with hot water, allowing for the bitumen to separate from the sand and water (clark hot water processing)
- bitumen can then be used to create synthetic crude oil
2 tonnes of oil sand to produce 1 barrel (159L) of synthetic crude oil
what are the environmental issues of emissions?
oil sand refineries release a variety of pollutants, including:
-CO2, SO2, NOx
-metals (e.g. Hg)
-PAHs
what is the impact of athabasca oil sands operation on mercury levels in air and deposition?
-average air concentrations of total oxidized Hg in the AOSR were elevated up to 60% within 50km of the oil sands Hg emission sources
-AOS Hg emissions were responsible for significant enhancements in Hg deposition in the immediate vicinity of oil sands operation areas
what is a warning that threatens ecosystems?
-acid precipitations are going up each year around oil reserve
-our ponds/waters are more alkaline (more buffering capacity)
what is the environmental issue of water use?
-freshwater is required for in situ and surface mining
-current limit on lower athabasca river usage: all oil sands projects can’t withdraw above 3% of average yearly flow, or 1.3% during low river flow
surface mining: 8-10 barrels of water per barrel of oil produced; 40-70% of the water used is recycled
in-situ: about 2.5-4 barrels of water per barrel of oil produced; 70-90% of the water used in recycled
what are tailings ponds?
large pools of water mixed with sand, slit, clay, metals and PAHs
-high concentrations of HCO3-
-inorganics: vanadium, mercury, arsenic
-organics: naphthenic acids, PAHs
what are oil sands PAHs?
-occur naturally in bituminous fossil fuels, such as coal and crude oil
-diagenesis: the low temperature (100-150 celcius) combustion of organic material over an extended period of time
-the process favors the formation of alkylated PAHs (addition of one or more CH3 groups)
-unsubstituted PAHs are relatively low in abundance in crude oil
-alkyl-substituted PAHs are generally more toxic, more persistent and less water-soluble (can bioaccumulate more)
what are the major mechanisms of toxicity of PAHs?
- nonpolar necrosis-> altered membrane fluidity
- activation of aryl hydrocarbon receptor (AhR)
- bioactivation of ultimate carcinogens
- bioactivation of quinones (redox activated compounds so can create ROS)-> production of quinones-> oxidative stress
what was the case of snowpack study?
regional aquatic monitoring program (RAMP): no elevated PAH levels
-criticized due to inadequate sampling
independent monitoring looked at samples along athabasca river
-found high PAH deposition in snowbank up to 50km away from oil sand processing plant
-would result in pulses of PAH into water in spring
why is this especially problematic? (snowpack study)
-fish reproduce at the same time as the PAH pulses
-PAHs are very toxic to early fish life stages via AhR activation: CYP1A1 induction, spinal deformities, hemorrhaging, pericardial edema
what were the highlights of distributions versus consumption?
what are the environmental issues of OSPW exposure?
fresh OSPW (oil sand process affected water) exhibits both acute and chronic toxicity
-chronic includes: developmental, reproductive, and immunotoxic effects
-toxic potency reduces over time as bacteria break down compounds
what does estrogen do?
estrogen disrupting effects of OSPW
-affects gene expression in the hypothalamus, pituitary gland, and gonads
-feminization of males-> vitellogenin genes induced
-decreased estradiol concentration in females, lower fecundity
-decreased secondary sex characteristics in both male and female fish
what is the immunotoxic effects of OSPW?
rainbow trout exposure to OSPW reduces B- and T- cells count in spleen
what component of OSPW drives toxicity?
what are NAs?
-organic acids naturally found in crude oil and bitumen
-have a polar and non-polar section
-vary in size and concentration: generally in the 20-120mg/L range
what are the cellular mechanisms of NAs toxicity?
what happens with OSPW?
which fraction affects aquatic life?
what is the water quality and metal levels in aged OPSW?
what else happens with OSPW?
what is the conclusion?
