Quantifying trace gas emissions from composite landscapes: A mass-budget approach with aircraft measurements

Alfieri, Silvia Maria; Amato, Umberto; Carfora, Maria Francesca; Esposito, Marco; Magliulo, Vincenzo

doi:10.1016/j.atmosenv.2010.02.026

Cited by 16 publications

(18 citation statements)

References 23 publications

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“…Many different sets of assumptions and sampling strategies are employed, but the overall goal is to sample the main dispersion routes of the surface emissions as they make their way into the overlying atmosphere after first accumulating near the surface. The scales that can be addressed by this method are from a few kilometers (Alfieri et al, 2010;Hacker et al, 2016;Hiller et al, 2014;Tratt et al, 2014) to tens of kilometers (Caulton et al, 2014;Karion et al, 2013;Wratt et al, 2001) to even potentially hundreds of kilometers (Beswick et al, 1998;Chang et al, 2014), and this approach has been the focus of recent measurements in natural gas production basins. These basins present a source apportionment challenge in that emissions from multiple sources (agriculture, oil and gas wells, geologic seepage, etc.)…”

Section: Introductionmentioning

confidence: 99%

“…The airborne mass balance flight strategies can be grouped into three basic patterns: a single height transect around a source assuming a vertically uniformly mixed boundary layer , single height upwind/downwind (Wratt et al, 2001) or sometimes just downwind flight legs (Conley et al, 2016;Hacker et al, 2016;Ryerson et al, 1998), multiple flight legs at different altitudes (Alfieri et al, 2010;Gordon et al, 2015;Kalthoff et al, 2002), or just a "screen" on the downwind face of the box Lavoie et al, 2015;Mays et al, 2009). …”

Section: Introductionmentioning

confidence: 99%

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Application of Gauss's theorem to quantify localized surface emissions from airborne measurements of wind and trace gases

et al. 2017

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Abstract. Airborne estimates of greenhouse gas emissions are becoming more prevalent with the advent of rapid commercial development of trace gas instrumentation featuring increased measurement accuracy, precision, and frequency, and the swelling interest in the verification of current emission inventories. Multiple airborne studies have indicated that emission inventories may underestimate some hydrocarbon emission sources in US oil-and gas-producing basins. Consequently, a proper assessment of the accuracy of these airborne methods is crucial to interpreting the meaning of such discrepancies. We present a new method of sampling surface sources of any trace gas for which fast and precise measurements can be made and apply it to methane, ethane, and carbon dioxide on spatial scales of ∼ 1000 m, where consecutive loops are flown around a targeted source region at multiple altitudes. Using Reynolds decomposition for the scalar concentrations, along with Gauss's theorem, we show that the method accurately accounts for the smallerscale turbulent dispersion of the local plume, which is often ignored in other average "mass balance" methods. With the help of large eddy simulations (LES) we further show how the circling radius can be optimized for the micrometeorological conditions encountered during any flight. Furthermore, by sampling controlled releases of methane and ethane on the ground we can ascertain that the accuracy of the method, in appropriate meteorological conditions, is often better than 10 %, with limits of detection below 5 kg h −1 for both methane and ethane. Because of the FAA-mandated minimum flight safe altitude of 150 m, placement of the aircraft is critical to preventing a large portion of the emission plume from flowing underneath the lowest aircraft sampling altitude, which is generally the leading source of uncertainty in these measurements. Finally, we show how the accuracy of the method is strongly dependent on the number of sampling loops and/or time spent sampling the source plume.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Application of Gauss's theorem to quantify localized surface emissions from airborne measurements of wind and trace gases

et al. 2017

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“…The box method expands on the screen method by including multiple screens upwind and surrounding the emissions area (Kalthoff et al, 2002;Alfieri et al, 2010). This analysis is accomplished by flying a square (Alfieri et al, 2010) or a polygon (Kalthoff et al, 2002) pattern around the emissions area and repeating the pattern at multiple heights.…”

Section: Introductionmentioning

confidence: 99%

“…Flight patterns can be grouped into (a) single-height transects, (b) upwind and downwind spirals, (c) single-screen flights, and (d) box flights. In the last case, the box can refer to a cylinder, CO Peischl et al (2013) Single-height transect CO 2 , CH 4 , CO Karion et al (2013) Single-height transect CH 4 Wratt et al (2001) Up and downwind spirals CH 4 Gatti et al (2014) Up and downwind spirals CO, CO 2 Mays et al (2009) Single screen CO 2 , CH 4 Cambaliza et al (2014) Single screen CO 2 , CH 4 Walter et al (2012) Single screen (DOAS) SO 2 Kalthoff et al (2002) Box CO, NO x Alfieri et al (2010) Box CO 2 a rectangular cuboid, or any other prism shape that is uniform with height. The simplest flight pattern, which we refer to as a singleheight transect, is a single flight path at one height perpendicular to the mean wind direction and downwind of the point or area sources (Turnbull et al, 2009;Peischl et al, 2013;Karion et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

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Determining air pollutant emission rates based on mass balance using airborne measurement data over the Alberta oil sands operations

et al. 2015

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Abstract. Top-down approaches to measure total integrated emissions provide verification of bottom-up, temporally resolved, inventory-based estimations. Aircraft-based measurements of air pollutants from sources in the Canadian oil sands were made in support of the Joint Canada-Alberta Implementation Plan for Oil Sands Monitoring during a summer intensive field campaign between 13 August and 7 September 2013. The measurements contribute to knowledge needed in support of the Joint Canada-Alberta Implementation Plan for Oil Sands Monitoring. This paper describes the top-down emission rate retrieval algorithm (TERRA) to determine facility emissions of pollutants, using SO 2 and CH 4 as examples, based on the aircraft measurements. In this algorithm, the flight path around a facility at multiple heights is mapped to a two-dimensional vertical screen surrounding the facility. The total transport of SO 2 and CH 4 through this screen is calculated using aircraft wind measurements, and facility emissions are then calculated based on the divergence theorem with estimations of box-top losses, horizontal and vertical turbulent fluxes, surface deposition, and apparent losses due to air densification and chemical reaction. Example calculations for two separate flights are presented. During an upset condition of SO 2 emissions on one day, these calculations are within 5 % of the industryreported, bottom-up measurements. During a return to normal operating conditions, the SO 2 emissions are within 11 % of industry-reported, bottom-up measurements. CH 4 emissions calculated with the algorithm are relatively constant within the range of uncertainties. Uncertainty of the emission rates is estimated as less than 30 %, which is primarily due to the unknown SO 2 and CH 4 mixing ratios near the surface below the lowest flight level.

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Aircraft mass budgeting to measure CO2 emissions of Rome, Italy

Gioli

Carfora

Magliulo

et al. 2013

Environ Monit Assess

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Aircraft measurements were used to estimate the CO2 emission rates of the city of Rome, assessed against high-resolution inventorial data. Three experimental flights were made, composed of vertical soundings to measure Planetary Boundary Layer (PBL) properties, and circular horizontal transects at various altitudes around the city area. City level emissions and associated uncertainties were computed by means of mass budgeting techniques, obtaining a positive net CO2 flux of 14.7 ± 4.5, 2.5 ± 1.2, and 10.3 ± 1.2 μmol m(-2) s(-1) for the three flights. Inventorial CO2 fluxes at the time of flights were computed by means of spatial and temporal disaggregation of the gross emission inventory, at 10.9 ± 2.5, 9.6 ± 1.3, and 17.4 ± 9.6 μmol m(-2) s(-1). The largest differences between the two dataset are associated with a greater variability of wind speed and direction in the boundary layer during measurements. Uncertainty partitioned into components related to horizontal boundary flows and top surface flow, revealed that the latter dominates total uncertainty in the presence of a wide variability of CO2 concentration in the free troposphere (up to 7 ppm), while it is a minor term with uniform tropospheric concentrations in the study area (within 2 ppm). Overall, we demonstrate how small aircraft may provide city level emission measurements that may integrate and validate emission inventories. Optimal atmospheric conditions and measurement strategies for the deployment of aircraft experimental flights are finally discussed.

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Quantifying trace gas emissions from composite landscapes: A mass-budget approach with aircraft measurements

Cited by 16 publications

References 23 publications

Application of Gauss's theorem to quantify localized surface emissions from airborne measurements of wind and trace gases

Application of Gauss's theorem to quantify localized surface emissions from airborne measurements of wind and trace gases

Determining air pollutant emission rates based on mass balance using airborne measurement data over the Alberta oil sands operations

Aircraft mass budgeting to measure CO2 emissions of Rome, Italy

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