Comprehensive Measurements of Emission Rates of Greenhouse Gases, Volatile Organic Compounds and Reduced Sulfur Compounds from a Tailings Pond in the Alberta Oil Sands

Abstract:

Canada’s Oil Sands Region in northern Alberta contains the world’s largest deposits of commercially exploited bitumen. Extraction of synthetic crude oil from these deposits is a water intensive process, requiring large ponds for water recycling and/or final storage of tailings, already covering a total of over 100 km² of liquid surface area. The primary extraction tailings ponds primarily contain sand, silt, clay and unrecovered bitumen, while a few secondary extraction ponds also receive solvents and inorganic and organic by-products of the extraction process. Fugitive emissions of pollutants from these ponds to the atmosphere may therefore be a concern, but until recently, data on emission rates for many pollutants, other than a few reported under regulatory compliance monitoring, were sparse. We present here the results from a comprehensive field campaign to quantify the emissions from a secondary extraction pond to the atmosphere of 68 volatile organic compounds (VOCs), 32 organic acids, 22 polycyclic aromatic compounds (PACs), 8 reduced sulfur compounds as well as methane, carbon dioxide and ammonia. Three micrometeorological flux methods (eddy covariance, vertical gradients and inverse dispersion modeling) were employed after careful cross-evaluation using methane fluxes. Emission rates for 12 PACs, alkanes and aromatic VOCs, several sulfur species, and ammonia were notable. PACs were dominated by methyl naphthalenes and phenanthrenes, while diethylsulfide and n-heptane were the dominant reduced sulfur and VOC species, respectively. The role of these previously unavailable emission rates in regional pollutant budgets will be discussed.