Development of a low-maintenance measurement approach to continuously estimate methane emissions: a case study

The chemical breakdown of organic matter in landfills represents a significant source of methane gas (CH4). Current estimates suggest that landfills are responsible for between 3% and 19% of global anthropogenic emissions. The net CH4 emissions resulting from biogeochemical processes and their modulation by microbes in landfills are poorly constrained by imprecise knowledge of environmental constraints. The uncertainty in absolute CH4 emissions from landfills is therefore considerable. This study investigates a new method to estimate the temporal variability of CH4 emissions using meteorological and CH4 concentration measurements downwind of a landfill site in Suffolk, UK from July to September 2014, taking advantage of the statistics that such a measurement approach offers versus shorter-term, but more complex and instantaneously accurate, flux snapshots. Methane emissions were calculated from CH4 concentrations measured 700 m from the perimeter of the landfill with observed concentrations ranging from background to 46.4 ppm. Using an atmospheric dispersion model, we estimate a mean emission flux of 709 μg m−2 s−1 over this period, with a maximum value of 6.21 mg m−2 s−1, reflecting the wide natural variability in biogeochemical and other environmental controls on net site emission. The emissions calculated suggest that meteorological conditions have an influence on the magnitude of CH4 emissions. We also investigate the factors responsible for the large variability observed in the estimated CH4 emissions, and suggest that the largest component arises from uncertainty in the spatial distribution of CH4 emissions within the landfill area. The results determined using the low-maintenance approach discussed in this paper suggest that a network of cheaper, less precise CH4 sensors could be used to measure a continuous CH4 emission time series from a landfill site, something that is not practical using far-field approaches such as tracer release methods. Even though there are limitations to the approach described here, this easy, low-maintenance, low-cost method could be used by landfill operators to estimate time-averaged CH4 emissions and their impact downwind by simultaneously monitoring plume advection and CH4 concentrations

Methane emissions from oil and gas platforms in the North Sea

Since 1850 the concentration of atmospheric methane (CH4), a potent greenhouse gas, has more than doubled. Recent studies suggest that emission inventories may be missing sources and underestimating emissions. To investigate whether offshore oil and gas platforms leak CH4 during normal operation, we measured CH4 mole fractions around eight oil and gas production platforms in the North Sea which were neither flaring gas nor offloading oil. We use the measurements from summer 2017, along with meteorological data, in a Gaussian plume model to estimate CH4 emissions from each platform. We find CH4 mole fractions of between 11 and 370 ppb above background concentrations downwind of the platforms measured, corresponding to a median CH4 emission of 6.8 g CH4 s−1 for each platform, with a range of 2.9 to 22.3 g CH4 s−1. When matched to production records, during our measurements individual platforms lost between 0.04 % and 1.4 % of gas produced with a median loss of 0.23 %. When the measured platforms are considered collectively (i.e. the sum of platforms' emission fluxes weighted by the sum of the platforms' production), we estimate the CH4 loss to be 0.19 % of gas production. These estimates are substantially higher than the emissions most recently reported to the National Atmospheric Emission Inventory (NAEI) for total CH4 loss from United Kingdom platforms in the North Sea. The NAEI reports CH4 losses from the offshore oil and gas platforms we measured to be 0.13 % of gas production, with most of their emissions coming from gas flaring and offshore oil loading, neither of which was taking place at the time of our measurements. All oil and gas platforms we observed were found to leak CH4 during normal operation, and much of this leakage has not been included in UK emission inventories. Further research is required to accurately determine total CH4 leakage from all offshore oil and gas operations and to properly include the leakage in national and international emission inventories

The air quality impacts of pre-operational hydraulic fracturing activities

Hydraulic fracturing (fracking) is a short phase in unconventional oil and natural gas (O&G) development. Before fracking there is a lengthy period of preparation, which can represent a significant proportion of the well lifecycle. Extensive infrastructure is delivered onto site, leading to increased volumes of heavy traffic, energy generation and construction work on site. Termed the “pre-operational” period, this is rarely investigated as air quality evaluations typically focus on the extraction phase. In this work we quantify the change in air pollution during pre-operational activities at a shale gas exploration site near Kirby Misperton, North Yorkshire, England. Baseline air quality measurements were made two years prior to any shale gas activity and were used as a training dataset for random forest (RF) machine learning models. The models allowed for a comparison between observed air quality during the pre-operational phase and a counterfactual business as usual (BAU) prediction. During the pre-operational phase a significant deviation from the BAU scenario was observed. This was characterised by significant enhancements in NOx and a concurrent reduction in O3, caused by extensive additional vehicle movements and the presence of combustion sources such as generators on the well pad. During the pre-operational period NOx increased by 274 % and O3 decreased by 29 % when compared to BAU model values. There was also an increase in primary emissions of NO2 during the pre-operational phase which may have implications for the attainment of ambient air quality standards in the local surroundings. Unconventional O&G development remains under discussion as a potential option for improving the security of supply of domestic energy, tensioned however against significant environmental impacts. Here we demonstrate that the preparative work needed to begin fracking elevates air pollution in its own right, a further potential disbenefit that should be considered

Radionuclide evaluation of postextrasystolic potentiation of left ventricular function induced by atrial and ventricular stimulation

Postextrasystolic potentiation of left ventricular function induced by ventricular and atrial stimulation was compared in 10 patients using radionuclide ventriculography. After insertion of pacing wires, a preliminary radionuclide ventriculogram was obtained and then ventricular and atrial trigeminy was induced in random order, each with identical R-R coupling intervals, each for 6 to 10 minutes. During the stimulation studies, radionuclide data were acquired in electrocardiographic gated list mode format. Left ventricular ejection fraction and relative end-diastolic and end-systolic volume changes were measured for each reformatted composite sinus, atrial and ventricular premature beat and potentiated beat. The volume changes were normalized to the count-based values obtained for the sinus beat of the appropriate study. Postextrasystolic potentiation induced by either ventricular or atrial stimulation was characterized by similar significant increases in left ventricular ejection fraction (mean +/- standard deviation 7 +/- 3 percent, p < 0.01 versus 7 +/- 5 percent, p < 0.01; difference not significant [NS]) and decreases in relative end-systolic volume (-12 +/- 12 percent, p < 0.01 versus -12 +/- 8 percent, p < 0.01; NS) but little change in relative end-diastolic volume (+5 +/- 10 percent, NS versus +4 +/- 7 percent, NS; NS). This was despite a longer compensatory pause (1,120 +/- 220 versus 1,050 +/- 190 ms, p < 0.01) after the ventricular premature beat. It is concluded that there is no difference in the postextrasystolic potentiation induced by atrial or ventricular premature stimulation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23931/1/0000177.pd

The development and trial of an unmanned aerial system for the measurement of methane flux from landfill and greenhouse gas emission hotspots

This paper describes the development of a new sampling and measurement method to infer methane flux using proxy measurements of CO2 concentration and wind data recorded by Unmanned Aerial Systems (UAS). The flux method described and trialed here is appropriate to the spatial scale of landfill sites and analogous greenhouse gas emission hotspots, making it an important new method for low-cost and rapid case study quantification of fluxes from currently uncertain (but highly important) greenhouse gas sources.We present a case study using these UAS-based measurements to derive instantaneous methane fluxes from a test landfill site in the north of England using a mass balance model tailored for UAS sampling and co-emitted CO2 concentration as a methane-emission proxy. Methane flux (and flux uncertainty) during two trials on 27 November 2014 and 5 March 2015, were found to be 0.140 kg s−1 (±61% at 1σ), and 0.050 kg s−1 (±54% at 1σ), respectively. Uncertainty contributing to the flux was dominated by ambient variability in the background (inflow) concentration (>40%) and wind speed (>10%); with instrumental error contributing only ∼1–2%. The approach described represents an important advance concerning the challenging problem of greenhouse gas hotspot flux calculation, and offers transferability to a wide range of analogous environments. This new measurement solution could add to a toolkit of approaches to better validate source-specific greenhouse emissions inventories – an important new requirement of the UNFCCC COP21 (Paris) climate change agreement

Assessing London CO2, CH4 and CO emissions using aircraft measurements and dispersion modelling

We present a new modelling approach for assessing atmospheric emissions from a city, using an aircraft measurement sampling strategy similar to that employed by previous mass balance studies. Unlike conventional mass balance methods, our approach does not assume that city-scale emissions are confined to a well-defined urban area and that peri-urban emissions are negligible. We apply our new approach to a case study conducted in March 2016, investigating CO, <span classCombining double low lineCH4 and <span classCombining double low lineCO2 emissions from a region focussed around Greater London using aircraft sampling of the downwind plume. For each species, we simulate the flux per unit area that would be observed at the aircraft sampling locations based on emissions from the UK national inventory, transported using a Lagrangian dispersion model. To reconcile this simulation with the measured flux per unit area, assuming the transport model is not biased, we require that inventory values of CO, <span classCombining double low lineCH4 and <span classCombining double low lineCO2 are scaled by 1.03, 0.71 and 1.61, respectively. However, our result for <span classCombining double low lineCO2 should not be considered a direct comparison with the inventory which only includes anthropogenic fluxes. For comparison, we also calculate fluxes using a conventional mass balance approach and compare these to the emissions inventory aggregated over the Greater London area. Using this method we derive much higher inventory scale factors for all three gases, as a direct consequence of the failure to account for emissions outside the Greater London boundary. That substantially different conclusions are drawn using the conventional mass balance method demonstrates the danger of using this technique for cities whose emissions cannot be separated from significant surrounding sources

9th Annual Seminar on Legal Issues for Financial Institutions

Outline of speakers\u27 presentations from the 9th Annual Seminar on Legal Issues for Financial Institutions held by UK/CLE on March 10-11, 1989

Assessing the value of intangible benefits of property level flood risk adaptation (PLFRA) measures

© 2015, Springer Science+Business Media Dordrecht. Studies in the UK and elsewhere have identified that flooding can result in diverse impacts, ranging from significant financial costs (tangible) to social (intangible) impacts on households. At the same time, it is now clear that large-scale flood defence schemes are not the panacea to flood risk, and there is an increasing responsibility on property owners to protect their own properties. Hence, there is an emerging expectation for homeowners to take action in the form of investing in property level flood risk adaptation (PLFRA) measures to protect their properties. However, hitherto the level of uptake of such measures remains very low. The tangible financial benefits of investing in PLFRA measures are generally well understood and have been demonstrated to be cost beneficial for many properties at risk from frequent flooding. Importantly, these estimates tend to take little account of the value of the intangible benefits of PLFRA measures and therefore may be under estimating their full benefits. There remains a need to develop an improved understanding of these intangible benefits, and this research sets out to bridge this knowledge gap. Based on a synthesis of the literature, the contingent valuation method was selected as a means to value intangible impacts of flooding on households. A questionnaire survey of homeowners affected in the 2007 flooding was employed to elicit willingness to pay (WTP) values to avoid the intangible impacts of flooding on their households. The analysis of the questionnaire survey data revealed that the average WTP per household per year to avoid intangible flood impacts was £653. This therefore represents the value of the intangible benefits of investing in PLFRA measures and is significantly higher than previously estimated. This research builds on previous research in suggesting a higher value to the intangible impacts of flooding on households by assessing wider range of intangible impacts and focussing on more experienced individuals. Furthermore, the research indicates that factors which influence the WTP values were principally stress of flood, worrying about loss of house values, worrying about future flooding and age of respondents, with income showing a weak correlation. The establishment of a new value for the intangible impacts of flooding on households in the UK is helpful in the domain of flood risk management when evaluating the total benefits (tangible and intangible) of investing in flood protection measures, thus providing a robust assessment for decision-making on flood adaptation measures at an individual property level

Value of percutaneous transluminal coronary angioplasty after unsuccessful intravenous streptokinase therapy in acute myocardial infarction

The effect of sequential high-dose intravenous streptokinase (SK) (1.5 million units) followed by emergency percutaneous transluminal coronary angioplasty (PTCA) on preserving left ventricular function was assessed prospectively in 34 patients with acute myocardial infarction (AMI). Intravenous SK therapy was initiated 2.6 +/- 1.3 hours (mean +/- standard deviation) after the onset of chest pain. Urgent coronary angiography showed persistent total occlusion in 13 patients, significant diameter stenosis (70 to 99%) in 18 patients and a widely patent artery (less than 50% stenosis) in 3 patients. Emergency PTCA was performed in 29 patients 5.0 +/- 2.1 hours after symptom onset. Successful recanalization was achieved in 33 of the 34 patients (97%) treated with sequential therapy. Repeat contrast ventriculograms recorded 7 to 10 days after intervention in 23 patients showed that the left ventricular ejection fraction increased from 53 +/- 12% to 59 +/- 13% (area-length method, p &lt; 0.002). Regional wall motion of the infarcted segments improved from - 2.7 +/- 1.1 to - 1.5 +/- 1.7 SD/chord (centerline method, p &lt; 0.003). In the subgroup of patients with an occluded artery on initial angiography (group A, N = 10), both global left ventricular ejection fraction (49 +/- 12% vs 59 +/- 12%, p &lt; 0.002) and regional wall motion (-3.2 +/- 1.0 vs -1.9 +/- 1.7 SD/chord, p &lt; 0.002) improved significantly. In contrast, no significant improvement was seen in patients with a patent artery on initial angiography (n = 13). Thus, sequential intravenous SK and emergency PTCA is efficacious in achieving coronary reperfusion and in improving both global and regional left ventricular function. When thrombolytic therapy fails, successful recanalization can be achieved by emergency PTCA, resulting in significant myocardial salvage.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26031/1/0000104.pd