scholarly journals Temporal variability of methane emissions from a closed landfill at Denmark

2021 ◽  
Author(s):  
Konstantinos Kissas ◽  
Andreas Ibrom ◽  
Peter Kjeldsen ◽  
Charlotte Scheutz
Keyword(s):  
Temporal Variability ◽  
Measurement Techniques ◽  
Barometric Pressure ◽  
Eddy Covariance Method ◽  
Continuous Measurements ◽  
Tracer Dispersion ◽  
Highly Correlated ◽  
Pressure Changes ◽  
The Impact ◽  
Closed Landfill

<p>Methane (CH<sub>4</sub>) emissions from landfills contribute to global warming, impacting significantly the environment and human health. Landfill CH<sub>4</sub> emissions strongly depend on changes in barometric pressure, inducing short-term CH<sub>4</sub> emission variation of several orders of magnitude. Estimating the temporal variability of CH<sub>4</sub> emitted into the atmosphere could help us reducing the uncertainties of annual emission estimates from landfills. In this study, we focus on the temporal variability of CH<sub>4</sub> emissions under the impact of barometric pressure changes.</p><p>CH<sub>4</sub> emissions of a closed landfill (Skellingsted, Western Zealand, Denmark) were measured with two different methods from December 2019 to June 2020; continuously with the eddy covariance method (EC) and discretely with the dynamic tracer dispersion method (TDM). The EC method allows continuous measurements from a confined surface area, with most likely limited representativeness of the whole landfill site due to the considerable horizontal heterogeneity. The TDM method is able to quantify the emission from the whole site insensitive of the topography with the limited representativeness for the temporal variability.</p><p>CH<sub>4</sub> emissions to the atmosphere measured by the TDM and fluxes measured by the EC ranged from to 0 to almost 100 kg h<sup>-1</sup> and from 0 to 10 μmol m<sup>-2</sup> s<sup>-1</sup>, respectively. The CH<sub>4</sub> fluxes measured continuously using the EC method were highly correlated with the emissions from the periodic measurements using the TDM and fluctuated according to the pressure tendency. Under decreasing barometric pressure the highest CH<sub>4</sub> emissions where observed, while increasing barometric pressure suppressed them almost to 0.</p><p>Our results demonstrate the value of implementing two different complementary measurement techniques in parallel that will help to quantify total annual CH<sub>4</sub> emission from a landfill. EC method provides continuous measurements describing accurately the temporal variation of emissions, while TDM method is able to quantify emissions from the whole site.</p>

scholarly journals Pressure effects on methane emissions from landfills

2020 ◽  
Author(s):  
Konstantinos Kissas ◽  
Charlotte Scheutz ◽  
Peter Kjeldsen ◽  
Andreas Ibrom
Keyword(s):  
Measurement Techniques ◽  
Soil Layer ◽  
Barometric Pressure ◽  
Methane Emissions ◽  
Pressure Effects ◽  
Anthropogenic Sources ◽  
Model Concept ◽  
Eddy Covariance Method ◽  
Gas Dispersion ◽  
Pressure Changes

<p>Landfills are one of the major anthropogenic sources of methane (CH<sub>4</sub>) emissions to the atmosphere, even years after being inactive. Model-based estimates of CH<sub>4</sub> emission from landfills are inaccurate due to uncertainties in the underlying assumptions regarding gas generation rates, oxidation and recovery parameters. In-situ measurement techniques are more reliable in quantifying CH<sub>4</sub> emissions, with the tracer gas dispersion method (TDM) being one of the best-validated methods. The TDM does however not allow for continuous estimation unless a higher sampling frequency for longer measurement campaigns is being used. Field studies report short-term CH<sub>4</sub> emission variation of several orders of magnitude, which are being driven by changes in meteorological conditions, with changes in barometric pressure being the most important. This variation makes discontinuous measurements more uncertain. In this presentation, we focus on CH<sub>4</sub> emission dynamics under the influence of barometric pressure changes and develop a model that can explain the dynamics.</p><p>Landfill methane emissions were measured continuously with the eddy covariance method over several months in an inactive landfill (Skellingsted, Western Zealand, Denmark). The landfill is covered with an 80 cm thick soil layer and vegetated with grassland. Screenings of the site indicate a considerable horizontal heterogeneity of the emissions, which needs to be considered when interpreting continuously measured fluxes.</p><p>Measured methane fluxes ranged from 0 to 10 μmol∙m<sup>-2</sup>∙s<sup>-1</sup>. Periods with decreasing barometric pressure showed highest flux rates, while increasing barometric pressure suppressed the methane flux almost to 0 μmol∙m<sup>-2</sup>∙s<sup>-1</sup>. However, this dependency had a complex dynamic nature. In most of the cases, the responses of CH<sub>4</sub> fluxes to pressure changes were delayed by 0 to 4 hours. We developed a model concept that is able to explain this behavior, including the pressure gradient driven advective CH<sub>4</sub> transports through the porous soil layer above the source and diffusion between fronts of background air and landfill gas.</p><p>The general implications from this work are an estimation of the uncertainty and possibly correction of point CH<sub>4</sub> emission measurements, e.g. with the TDM. Additionally, the increased understanding of gas transport dynamics through terrestrial landfill covers will help to evaluate the efficiency of methane emission mitigation methods that aim at increasing methane oxidation by the establishment of biocovers.</p>

Anodic Bond Quality and impact on Pressure Sensor Long-Term Stability

2001 ◽  
Vol 681 ◽  
Author(s):  
Henry Allen ◽  
Kamrul Ramzan ◽  
Jim Knutti ◽  
Carl Ross ◽  
Tim Milliman ◽  
...  
Keyword(s):  
Pressure Sensor ◽  
Pressure Sensors ◽  
Barometric Pressure ◽  
Absolute Pressure ◽  
Glass Wafer ◽  
Bond Quality ◽  
Long Term Stability ◽  
Pressure Changes ◽  
The Impact

ABSTRACTSilicon pressure sensors have historically been fabricating by bonding a glass wafer to a micro-machined silicon wafer. The sensor may be sealed as an absolute pressure sensor by using planar glass and can then be used for detection of barometric pressure changes.It has generally been assumed that as long as the glass and silicon are reasonable clean, then the silicon-glass seal is good and the part becomes a reliable, stable sensor. This paper addresses a low-level drift that was identified in such an absolute pressure sensor. A Zero drift in the range of 0.1% FS was detectable under humidity stresses. The stress always caused drift in the same direction, indicating an effective increased pressure in the sealed cavity.The impact of various cleaning processes in reducing drift are reported. The improved process assure reliable product for applications such as automotive and altimeter applications.

scholarly journals Research on HAR-Based Floor Positioning

2021 ◽  
Vol 10 (7) ◽  
pp. 437
Author(s):  
Hongxia Qi ◽  
Yunjia Wang ◽  
Jingxue Bi ◽  
Hongji Cao ◽  
Shenglei Xu
Keyword(s):  
Barometric Pressure ◽  
Air Pressure ◽  
Location Based Services ◽  
Sensor Data ◽  
Reference Station ◽  
Position Change ◽  
Radio Signals ◽  
Positioning Method ◽  
Pressure Changes

Floor positioning is an important aspect of indoor positioning technology, which is closely related to location-based services (LBSs). Currently, floor positioning technologies are mainly based on radio signals and barometric pressure. The former are impacted by the multipath effect, rely on infrastructure support, and are limited by different spatial structures. For the latter, the air pressure changes with the temperature and humidity, the deployment cost of the reference station is high, and different terminal models need to be calibrated in advance. In view of these issues, here, we propose a novel floor positioning method based on human activity recognition (HAR), using smartphone built-in sensor data to classify pedestrian activities. We obtain the degree of the floor change according to the activity category of every step and determine whether the pedestrian completes floor switching through condition and threshold analysis. Then, we combine the previous floor or the high-precision initial floor with the floor change degree to calculate the pedestrians’ real-time floor position. A multi-floor office building was chosen as the experimental site and verified through the process of alternating multiple types of activities. The results show that the pedestrian floor position change recognition and location accuracy of this method were as high as 100%, and that this method has good robustness and high universality. It is more stable than methods based on wireless signals. Compared with one existing HAR-based method and air pressure, the method in this paper allows pedestrians to undertake long-term static or round-trip activities during the process of going up and down the stairs. In addition, the proposed method has good fault tolerance for the misjudgment of pedestrian actions.

scholarly journals Clinical Epidemiology of Systolic and Diastolic Orthostatic Hypotension in Patients on Peritoneal Dialysis

2021 ◽  
Vol 10 (14) ◽  
pp. 3075
Author(s):  
Claudia Torino ◽  
Rocco Tripepi ◽  
Maria Carmela Versace ◽  
Antonio Vilasi ◽  
Giovanni Tripepi ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Peritoneal Dialysis ◽  
Orthostatic Hypotension ◽  
Clinical Epidemiology ◽  
Hemodialysis Patients ◽  
Excess Death ◽  
Death Risk ◽  
Standardized Protocol ◽  
Pressure Changes ◽  
The Impact

Blood pressure changes upon standing reflect a hemodynamic response, which depends on the baroreflex system and euvolemia. Dysautonomia and fluctuations in blood volume are hallmarks in kidney failure requiring replacement therapy. Orthostatic hypotension has been associated with mortality in hemodialysis patients, but neither this relationship nor the impact of changes in blood pressure has been tested in patients on peritoneal dialysis. We investigated both these relationships in a cohort of 137 PD patients. The response to orthostasis was assessed according to a standardized protocol. Twenty-five patients (18%) had systolic orthostatic hypotension, and 17 patients (12%) had diastolic hypotension. The magnitude of systolic and diastolic BP changes was inversely related to the value of the corresponding supine BP component (r = −0.16, p = 0.056 (systolic) and r = −0.25, p = 0.003 (diastolic), respectively). Orthostatic changes in diastolic, but not in systolic, BP were linearly related to the death risk (HR (1 mmHg reduction): 1.04, 95% CI 1.01–1.07, p = 0.006), and this was also true for CV death (HR: 1.08, 95% CI 1.03–1.12, p = 0.001). The strength of this association was not affected by further data adjustment (p ≤ 0.05). These findings suggest that independent of the formal diagnosis of orthostatic hypotension, even minor orthostatic reductions in diastolic BP bear an excess death risk in this population.

scholarly journals The Influence of Trading Locations on Equity Returns

2016 ◽  
Vol 12 (12) ◽  
pp. 188
Author(s):  
Nguyen N.T. Vo
Keyword(s):  
Risk Premium ◽  
Stock Price ◽  
Listed Companies ◽  
Equity Returns ◽  
Stock Exchanges ◽  
Home Market ◽  
Trade Effect ◽  
Market Index ◽  
Highly Correlated ◽  
The Impact

This paper evaluates the impact of trading locations on equity returns by examining the stock price behaviour of three Anglo-Dutch dual-listed companies which result from mergers where two corporations agree to function as a single operating business, but maintain separate identities. The shares of these stocks are traded not only in their home market but also on several US stock exchanges in the form of American Depository Receipts. Regressing the return differentials on these dual-listed and cross-listed stocks on the relative market index returns and currency changes provides evidence of an apparent violation of the Law of One Price. The regression results show that the return on each part of dual-listed companies is highly correlated with the market on which it is most intensively traded. Similarly, returns on cross-listed stocks have considerably higher co-movement with US market indices and considerably lower co-movement with home-market indices than their home-market counterparts. Market risk premium is not a significant explanatory variable of the location of trade effect.

scholarly journals Air Movement in Snow Due to Windpumping

1989 ◽  
Vol 35 (120) ◽  
pp. 209-213 ◽  
Author(s):  
S.C. Colbeck
Keyword(s):  
Pore Space ◽  
Barometric Pressure ◽  
Surface Flows ◽  
Wind Speeds ◽  
Compression And Expansion ◽  
Strong Winds ◽  
Pressure Changes ◽  
Low Amplitude ◽  
Pressure Perturbations ◽  
Rapid Pressure

Abstract Strong winds can disrupt the thermal regime in seasonal snow because of the variation in surface pressure associated with surface features like dunes and ripples. Topographical features of shorter wavelengths produce stronger surface flows, but the flow decays rapidly with depth. Longer-wavelength features produce weaker surface flows but the flow decays more slowly with depth. The flow may only be strong enough to disrupt the temperature field for features of wavelengths on the scale of meters or tens of meters at wind speeds of 10 m/s or more. Other possible causes of windpumping have been examined but they do not appear to be as significant. Rapid pressure perturbations due to turbulence produce very little displacement of the air because of the high frequency and low amplitude. Barometric pressure changes cause compression and expansion of the air in the pore space, but the rate is too low to have much effect.

scholarly journals The influence of riparian woodland on the spatial and temporal variability of stream water temperatures in an upland salmon stream

2004 ◽  
Vol 8 (3) ◽  
pp. 449-459 ◽  
Author(s):  
I. A. Malcolm ◽  
D. M. Hannah ◽  
M. J. Donaghy ◽  
C. Soulsby ◽  
A. F. Youngson
Keyword(s):  
Thermal Regime ◽  
Temporal Variability ◽  
Heat Budget ◽  
Riparian Forest ◽  
Stream Water ◽  
Spatial And Temporal Variability ◽  
Substantial Impact ◽  
Site Specific ◽  
The Impact ◽  
Riparian Woodland

Abstract. The spatio-temporal variability of stream water temperatures was investigated at six locations on the Girnock Burn (30km2 catchment), Cairngorms, Scotland over three hydrological years between 1998 and 2002. The key site-specific factors affecting the hydrology and climatology of the sampling points were investigated as a basis for physical process inference. Particular emphasis was placed on assessing the effects of riparian forest in the lower catchment versus the heather moorland riparian zones that are spatially dominant in the upper catchment. The findings were related to river heat budget studies that provided process detail. Gross changes in stream temperature were affected by the annual cycle of incoming solar radiation and seasonal changes in hydrological and climatological conditions. Inter-annual variation in these controlling variables resulted in inter-annual variability in thermal regime. However, more subtle inter-site differences reflected the impact of site-specific characteristics on various components of the river energy budget. Inter-site variability was most apparent at shorter time scales, during the summer months and for higher stream temperatures. Riparian woodland in the lower catchment had a substantial impact on thermal regime, reducing diel variability (over a period of 24 hours) and temperature extremes. Observed inter-site differences are likely to have a substantial effect on freshwater ecology in general and salmonid fish in particular. Keywords: temperature, thermal regime, forest, salmon, hydrology, Girnock Burn, Cairngorm

scholarly journals Exploiting correlated molecular-dynamics networks to counteract enzyme activity–stability trade-off

2018 ◽  
Vol 115 (52) ◽  
pp. E12192-E12200 ◽  
Author(s):  
Haoran Yu ◽  
Paul A. Dalby
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Active Site ◽  
Dynamic Networks ◽  
Aromatic Aldehydes ◽  
Active Site Residues ◽  
Trade Off ◽  
Highly Correlated ◽  
Dynamics Simulations ◽  
The Impact

The directed evolution of enzymes for improved activity or substrate specificity commonly leads to a trade-off in stability. We have identified an activity–stability trade-off and a loss in unfolding cooperativity for a variant (3M) of Escherichia coli transketolase (TK) engineered to accept aromatic substrates. Molecular dynamics simulations of 3M revealed increased flexibility in several interconnected active-site regions that also form part of the dimer interface. Mutating the newly flexible active-site residues to regain stability risked losing the new activity. We hypothesized that stabilizing mutations could be targeted to residues outside of the active site, whose dynamics were correlated with the newly flexible active-site residues. We previously stabilized WT TK by targeting mutations to highly flexible regions. These regions were much less flexible in 3M and would not have been selected a priori as targets using the same strategy based on flexibility alone. However, their dynamics were highly correlated with the newly flexible active-site regions of 3M. Introducing the previous mutations into 3M reestablished the WT level of stability and unfolding cooperativity, giving a 10.8-fold improved half-life at 55 °C, and increased midpoint and aggregation onset temperatures by 3 °C and 4.3 °C, respectively. Even the activity toward aromatic aldehydes increased up to threefold. Molecular dynamics simulations confirmed that the mutations rigidified the active-site via the correlated network. This work provides insights into the impact of rigidifying mutations within highly correlated dynamic networks that could also be useful for developing improved computational protein engineering strategies.

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