There are many challenges environmental consultants encounter during an investigation and one of them is being able to correctly identify contamination. Hydrocarbons are common contaminants on oil and gas sites, but can also be found in soil as a result of natural processes.
One such hydrocarbon is toluene, and evaluators must use a combination of scientific knowledge and professional judgement to distinguish between real impacts and natural occurrences. Toluene is a constituent of crude oil and is a product of biogenesis, or natural production, particularly in peatlands which have high organic matter contents.
On February 25, Solstice Canada Corp. presented at the 2016 Canadian Land Reclamation Association Conference on the biogenesis of toluene underneath well pads on peatlands. In a recent series of Phase II environmental site assessments, Solstice discovered isolated appearances of toluene limited to the peat layers of a soil profile at several well sites. The high levels of toluene observed were not due to contamination typically observed at wellsites, it was isolated from other site contaminants, was not located in areas of potential concern, and did not appear to be a by-product of the breakdown of other common contamination. For these reasons toluene contamination at the sites seemed unlikely.
Haleigh Mines, a University of Alberta Augustana campus Environmental Science student, helped Solstice conduct a literature review on the presence of toluene in northern Alberta peatlands. Her review revealed that microbes in soil with low oxygen concentrations are responsible for the biodegradation of organic matter which produces toluene, and that this mechanism is especially prevalent in cold weather climates like here in Alberta. Well pads are generally constructed and packed using clay backfill material and potentially creates a barrier preventing oxygen from diffusing into the peat. Solstice’s findings showed that toluene levels were considerably higher at the wellsites than in background locations and it appeared that toluene was accumulating beneath the pad in these anaerobic conditions. This is a previously undocumented effect that may have implications for remediation and reclamation planning.
The differentiation of natural toluene from contamination is an emerging issue in the oil and gas industry. This is important because toluene is toxic to fish, freshwater invertebrates, and amphibians at very low concentrations (in the parts per billion ranges) and is largely un-researched in peatlands leaving many questions to be answered. Solstice’s work was based on preliminary results mainly from data collected at bog ecositesand information for other ecosites remains unavailable. What would the implications be if the pads were in a fen? Is there any room for improvement in sampling design or analytical technique? What about the potential to develop a background-based guideline? What other apparent contaminants could arise from biogenesis in peatlands? How do contaminants specifically affect peatland receptors?
Alberta’s Tier 1 Guidelines for peat are based on coarse mineral soil and is not representative of peatlands. Solstice speculated that under certain circumstances toluene accumulation under clay pads may be appropriately addressed during reclamation and may not require remediation, but each region is unique. Solstice Canada Corp. is currently conducting a meta-analysis by pooling data from other environmental assessments in the northern Alberta peatlands that had come across similar instances with elevated toluene under a well pad. More research is required to further establish the guidelines and a better understanding of several issues would be a key addition for the development of guidelines specific to peatlands.
Jüttner, F. and J.J. Henatsch. 1986. Anoxic hypolimnion is a significant source of biogenic toluene. Nature, 323, 797-798. doi: 10.1038/323797a0
 Di Marzio W and Saenz ME. 2006. QSARS for aromatic hydrocarbons at several trophic levels. Environ Toxicol 21(2):118-24
 Canadian Council of Ministers of the Environment. 1999. Canadian water quality guidelines for the protection of aquatic life: Toluene. In: Canadian environmental quality guidelines, 1999, Canadian Council of Ministers of the Environment, Winnipeg.
 Alberta Environment and Sustainable Resource Development. (2014). Alberta Tier 1 soil and groundwater remediation guidelines. Edmonton, AB: Land and Forestry Policy Branch, Policy Division.