The oil and gas (O&G) sector represents a large source of greenhouse gas (GHG) emissions globally. However, estimates of O&G emissions rely upon bottom-up approaches, and are rarely evaluated through ...atmospheric measurements. Here, we use aircraft measurements over the Canadian oil sands (OS) to derive the first top-down, measurement-based determination of the their annual CO2 emissions and intensities. The results indicate that CO2 emission intensities for OS facilities are 13–123% larger than those estimated using publically available data. This leads to 64% higher annual GHG emissions from surface mining operations, and 30% higher overall OS GHG emissions (17 Mt) compared to that reported by industry, despite emissions reporting which uses the most up to date and recommended bottom-up approaches. Given the similarity in bottom-up reporting methods across the entire O&G sector, these results suggest that O&G CO2 emissions inventory data may be more uncertain than previously considered.Evaluating GHG emissions reported to inventories for the oil and gas (O&G) sector is important for countries with resource-based economies. Here the authors provide a top-down assessment of GHG emissions from the Canadian oil sands and find previous inventory reports underestimate emissions, by as much as 64% for surface mining facilities and 30% for the entire oil sands compared with their assessment.
Worldwide heavy oil and bitumen deposits amount to 9 trillion barrels of oil distributed in over 280 basins around the world, with Canada home to oil sands deposits of 1.7 trillion barrels. The ...global development of this resource and the increase in oil production from oil sands has caused environmental concerns over the presence of toxic compounds in nearby ecosystems and acid deposition. The contribution of oil sands exploration to secondary organic aerosol formation, an important component of atmospheric particulate matter that affects air quality and climate, remains poorly understood. Here we use data from airborne measurements over the Canadian oil sands, laboratory experiments and a box-model study to provide a quantitative assessment of the magnitude of secondary organic aerosol production from oil sands emissions. We find that the evaporation and atmospheric oxidation of low-volatility organic vapours from the mined oil sands material is directly responsible for the majority of the observed secondary organic aerosol mass. The resultant production rates of 45-84 tonnes per day make the oil sands one of the largest sources of anthropogenic secondary organic aerosols in North America. Heavy oil and bitumen account for over ten per cent of global oil production today, and this figure continues to grow. Our findings suggest that the production of the more viscous crude oils could be a large source of secondary organic aerosols in many production and refining regions worldwide, and that such production should be considered when assessing the environmental impacts of current and planned bitumen and heavy oil extraction projects globally.
TROPOspheric Monitoring Instrument (TROPOMI), on‐board the Sentinel‐5 Precurser satellite, is a nadir‐viewing spectrometer measuring reflected sunlight in the ultraviolet, visible, near‐infrared, and ...shortwave infrared. From these spectra several important air quality and climate‐related atmospheric constituents are retrieved, including nitrogen dioxide (NO2) at unprecedented spatial resolution from a satellite platform. We present the first retrievals of TROPOMI NO2 over the Canadian Oil Sands, contrasting them with observations from the Ozone Monitoring Instrument satellite instrument, and demonstrate TROPOMI's ability to resolve individual plumes and highlight its potential for deriving emissions from individual mining facilities. Further, the first TROPOMI NO2 validation is presented, consisting of aircraft and surface in situ NO2 observations, and ground‐based remote‐sensing measurements between March and May 2018. Our comparisons show that the TROPOMI NO2 vertical column densities are highly correlated with the aircraft and surface in situ NO2 observations, and the ground‐based remote‐sensing measurements with a low bias (15–30 %); this bias can be reduced by improved air mass factors.
Plain Language Summary
Nitrogen dioxide (NO2) is a pollutant that is linked to respiratory health issues and has negative environmental impacts such as soil and water acidification. Near the surface the most significant sources of NO2 are fossil fuel combustion and biomass burning. With a recently launched satellite instrument (TROPOspheric Monitoring Instrument TROPOMI), NO2 can be measured with an unprecedented combination of accuracy, spatial coverage, and resolution. This work presents the first TROPOMI NO2 measurements near the Canadian Oil Sands and shows that these measurements have an outstanding ability to detect NO2 on a very high horizontal resolution that is unprecedented for satellite NO2 observations. Further, these satellite measurements are in excellent agreement with aircraft and ground‐based measurements.
Key Points
First evaluation of the TROPOMI NO2 retrieval product
The quality of the TROPOMI NO2 data is excellent and captures variation on a very high spatial resolution
TROPOMI tropospheric NO2 retrievals can be corrected with higher‐resolution input data
The oil and gas (O&G) sector represents a large source of greenhouse gas (GHG) emissions globally. However, estimates of O&G emissions rely upon bottom-up approaches, and are rarely evaluated through ...atmospheric measurements. Here, we use aircraft measurements over the Canadian oil sands (OS) to derive the first top-down, measurement-based determination of the their annual CO
emissions and intensities. The results indicate that CO
emission intensities for OS facilities are 13-123% larger than those estimated using publically available data. This leads to 64% higher annual GHG emissions from surface mining operations, and 30% higher overall OS GHG emissions (17 Mt) compared to that reported by industry, despite emissions reporting which uses the most up to date and recommended bottom-up approaches. Given the similarity in bottom-up reporting methods across the entire O&G sector, these results suggest that O&G CO
emissions inventory data may be more uncertain than previously considered.
Aircraft-based measurements of methane (CH4) and other air pollutants in
the Athabasca Oil Sands Region (AOSR) were made during a summer intensive
field campaign between 13 August and ...7 September 2013 in support of the
Joint Canada–Alberta Implementation Plan for Oil Sands Monitoring. Chemical
signatures were used to identify CH4 sources from tailings ponds (BTEX
VOCs), open pit surface mines (NOy and rBC) and elevated plumes from
bitumen upgrading facilities (SO2 and NOy). Emission rates of
CH4 were determined for the five primary surface mining facilities in
the region using two mass-balance methods. Emission rates from source
categories within each facility were estimated when plumes from the sources
were spatially separable. Tailings ponds accounted for 45 % of total
CH4 emissions measured from the major surface mining facilities in the
region, while emissions from operations in the open pit mines accounted for
∼ 50 %. The average open pit surface mining emission rates
ranged from 1.2 to 2.8 t of CH4 h−1 for different facilities
in the AOSR. Amongst the 19 tailings ponds, Mildred Lake Settling Basin, the
oldest pond in the region, was found to be responsible for the majority of
tailings ponds emissions of CH4 (> 70 %). The sum of
measured emission rates of CH4 from the five major facilities,
19.2 ± 1.1 t CH4 h−1, was similar to a single mass-balance
determination of CH4 from all major sources in the AOSR determined from
a single flight downwind of the facilities, 23.7 ± 3.7 t CH4 h−1.
The measured hourly CH4 emission rate from all facilities in
the AOSR is 48 ± 8 % higher than that extracted for 2013 from the
Canadian Greenhouse Gas Reporting Program, a legislated facility-reported
emissions inventory, converted to hourly units. The measured emissions
correspond to an emissions rate of 0.17 ± 0.01 Tg CH4 yr−1 if
the emissions are assumed as temporally constant, which is an uncertain assumption. The
emission rates reported here are relevant for the summer season. In the future,
effort should be devoted to measurements in different seasons to further our
understanding of the seasonal parameters impacting fugitive emissions of CH4
and to allow for better estimates of annual emissions and year-to-year
variability.
Tailings ponds in the Alberta oil sands region are significant sources of fugitive emissions of methane to the atmosphere, but detailed knowledge on spatial and temporal variabilities is lacking due ...to limitations of the methods deployed under current regulatory compliance monitoring programs. To develop more robust and representative methods for quantifying fugitive emissions, three micrometeorological flux methods (eddy covariance, gradient, and inverse dispersion) were applied along with traditional flux chambers to determine fluxes over a 5-week period. Eddy covariance flux measurements provided the benchmark. A method is presented to directly calculate stability-corrected eddy diffusivities that can be applied to vertical gas profiles for gradient flux estimation. Gradient fluxes were shown to agree with eddy covariance within 18 %, while inverse dispersion model flux estimates were 30 % lower. Fluxes were shown to have only a minor diurnal cycle (15 % variability) and were weakly dependent on wind speed, air, and water surface temperatures. Flux chambers underestimated the fluxes by 64 % in this particular campaign. The results show that the larger footprint together with high temporal resolution of micrometeorological flux measurement methods may result in more robust estimates of the pond greenhouse gas emissions.
Wildfire impacts on air quality and climate are expected to be exacerbated
by climate change with the most pronounced impacts in the boreal biome.
Despite the large geographic coverage, there is ...limited information on
boreal forest wildfire emissions, particularly for organic compounds, which
are critical inputs for air quality model predictions of downwind impacts.
In this study, airborne measurements of 193 compounds from 15 instruments,
including 173 non-methane organics compounds (NMOG), were used to provide
the most detailed characterization, to date, of boreal forest wildfire
emissions. Highly speciated measurements showed a large diversity of
chemical classes highlighting the complexity of emissions. Using
measurements of the total NMOG carbon (NMOGT), the ΣNMOG was
found to be 50 % ± 3 % to 53 % ± 3 % of NMOGT, of which, the
intermediate- and semi-volatile organic compounds (I/SVOCs) were estimated
to account for 7 % to 10 %. These estimates of I/SVOC emission factors
expand the volatility range of NMOG typically reported. Despite extensive
speciation, a substantial portion of NMOGT remained unidentified
(47 % ± 15 % to 50 % ± 15 %), with expected contributions from more
highly-functionalized VOCs and I/SVOCs. The emission factors derived in this
study improve wildfire chemical speciation profiles and are especially
relevant for air quality modelling of boreal forest wildfires. These
aircraft-derived emission estimates were further linked with those derived
from satellite observations demonstrating their combined value in assessing
variability in modelled emissions. These results contribute to the
verification and improvement of models that are essential for reliable
predictions of near-source and downwind pollution resulting from boreal
forest wildfires.
A mobile laboratory equipped with state-of-the-art gaseous and particulate
instrumentation was deployed across the Greater Toronto Area (GTA) during two
seasons. A high-resolution time-of-flight ...chemical ionization mass spectrometer (HR-TOF-CIMS)
measured isocyanic acid (HNCO) and hydrogen cyanide (HCN), and a
high-sensitivity laser-induced incandescence (HS-LII) instrument measured
black carbon (BC). Results indicate that on-road vehicles are a clear source
of HNCO and HCN and that their impact is more pronounced in the winter, when
influences from biomass burning (BB) and secondary photochemistry are weakest.
Plume-based and time-based algorithms were developed to calculate
fleet-average vehicle emission factors (EFs); the algorithms were found to
yield comparable results, depending on the pollutant identity. With respect
to literature EFs for benzene, toluene, C2 benzene (sum of m-, p-, and o-xylenes and
ethylbenzene), nitrogen oxides, particle number concentration (PN), and black
carbon, the calculated EFs were characteristic of a relatively clean vehicle
fleet dominated by light-duty vehicles (LDV). Our fleet-average EF for BC (median:
25 mg kgfuel-1; interquartile range, IQR:
10–76 mg kgfuel-1) suggests that overall vehicular
emissions of BC have decreased over time. However, the distribution of EFs
indicates that a small proportion of high-emitters continue to contribute
disproportionately to total BC emissions. We report the first fleet-average
EF for HNCO (median: 2.3 mg kgfuel-1, IQR:
1.4–4.2 mg kgfuel-1) and HCN (median:
0.52 mg kgfuel-1, IQR:
0.32–0.88 mg kgfuel-1). The distribution of the estimated
EFs provides insight into the real-world variability of HNCO and HCN
emissions and constrains the wide range of literature EFs obtained from
prior dynamometer studies. The impact of vehicle emissions on urban HNCO
levels can be expected to be further enhanced if secondary HNCO formation
from vehicle exhaust is considered.
Large-scale oil production from oil sands deposits in Alberta, Canada has raised concerns about environmental impacts, such as the magnitude of air pollution emissions. This paper reports compound ...emission rates (E) for 69–89 nonbiogenic volatile organic compounds (VOCs) for each of four surface mining facilities, determined with a top-down approach using aircraft measurements in the summer of 2013. The aggregate emission rate (aE) of the nonbiogenic VOCs ranged from 50 ± 14 to 70 ± 22 t/d depending on the facility. In comparison, equivalent VOC emission rates reported to the Canadian National Pollutant Release Inventory (NPRI) using accepted estimation methods were lower than the aE values by factors of 2.0 ± 0.6, 3.1 ± 1.1, 4.5 ± 1.5, and 4.1 ± 1.6 for the four facilities, indicating underestimation in the reported VOC emissions. For 11 of the combined 93 VOC species reported by all four facilities, the reported emission rate and E were similar; but for the other 82 species, the reported emission rate was lower than E. The median ratio of E to that reported for all species by a facility ranged from 4.5 to 375 depending on the facility. Moreover, between 9 and 53 VOCs, for which there are existing reporting requirements to the NPRI, were not included in the facility emission reports. The comparisons between the emission reports and measurement based emission rates indicate that improvements to VOC emission estimation methods would enhance the accuracy and completeness of emission estimates and their applicability to environmental impact assessments of oil sands developments.
PDF
