Abstract
Abstract. The rapidly expanding and energy-intensive production from the Canadian oil sands, one of the largest oil reserves globally, accounts for almost 12 % of Canada's greenhouse gas emissions according to inventories. Developing approaches for evaluating reported methane (CH4) emission is crucial for developing effective mitigation policies, but only one study has characterized CH4 sources in the Athabasca oil sands region (AOSR). We tested the use of 14C and 13C carbon isotope measurements in ambient CH4 from the AOSR to estimate source contributions from key regional CH4 sources: (1) tailings ponds, (2) surface mines and processing facilities, and (3) wetlands. The isotopic signatures of ambient CH4 indicate that the CH4 enrichments measured at the site were mainly influenced by fossil CH4 emissions from surface mining and processing facilities (56 ± 18 %), followed by fossil CH4 emissions from tailings ponds (34 ± 18 %) and to a lesser extent modern CH4 emissions from wetlands (10 ± <1 %). Our results confirm the importance of tailings ponds in regional CH4 emissions and show that this method can successfully distinguish wetland CH4 emissions. In the future, the isotopic characterization of CH4 sources and measurements from different seasons and wind directions are needed to provide a better source attribution in the AOSR.
Highlights
Methane (CH4) is an important greenhouse gas that has 32 times the global warming potential of carbon dioxide (CO2) on a 100-year timescale and which contributes to the production of ozone, water vapour, and CO2 in the atmosphere (Myhre et al, 2013; Etminan et al, 2016)
Based on the previous aircraft source attribution study (Baray et al, 2018), we identified two main CH4 source categories: CH4 emissions related to the mining and processing of bitumen and tailings pond CH4 emissions
We added wetlands as a third source of regional CH4 emissions as they are estimated to cover approximately 60 % of the Athabasca oil sands region (Rooney et al, 2012), and the wetland CH4 emissions in the province of Alberta have been estimated to be roughly half of the total anthropogenic emissions (Baray et al, 2021)
Summary
Methane (CH4) is an important greenhouse gas that has 32 times the global warming potential (mass basis) of carbon dioxide (CO2) on a 100-year timescale and which contributes to the production of ozone, water vapour (in the stratosphere), and CO2 in the atmosphere (Myhre et al, 2013; Etminan et al, 2016). Global CH4 concentration in the atmosphere has almost tripled compared to pre-industrial values (Rubino et al, 2019), largely due to increased anthropogenic activities that include fossil fuel production and use and agriculture (Jackson et al, 2020; Turner et al, 2019). Since most fossil fuel emissions originate from coal, oil, and natural gas exploitation, transportation, and use (Jackson et al, 2020; Saunois et al, 2020), mitigating CH4 emissions from these activities is necessary to fulfil governmental CH4 emissions reduction goals. Canada contains approximately 10 % of the world’s proven crude oil reserves, with 82 % of these reserves located in the Athabasca oil sands region (AOSR) in Alberta (Alberta Energy Regulator, 2015).
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