Modelling tracer dispersion from landfills

Several wind tunnel experiments of tracer dispersion from reduced-scale landfill models are presented in this paper. Different experimental set-ups, hot-wire anemometry, particle image velocimetry and tracer concentration measurements were used for the characterisation of flow and dispersion phenomena nearby the models. The main aim of these experiments is to build an extensive experimental data set useful for model validation purposes. To demonstrate the potentiality of the experimental data set, a validation exercise on several mathematical models was performed by means of a statistical technique. The experiments highlighted an increase in pollutant ground level concentrations immediately downwind from the landfill because of induced turbulence and mean flow deflection. This phenomenon turns out to be predominant for the dispersion process. Tests with a different set-up showed an important dependence of the dispersion phenomena from the landfill height and highlighted how complex orographic conditions downwind of the landfill do not affect significantly the dispersion behaviour. Validation exercises were useful for model calibration, improving code reliability, as well as evaluating performances. The Van Ulden model proved to give the most encouraging results

Measuring odours in the environment vs. dispersion modelling: A review

Source characterization alone is not sufficient to account for the effective impact of odours on citizens, which would require to quantify odours directly at receptors. However, despite a certain simplicity of odour measurement at the emission source, odour measurement in the field is a quite more complicated task. This is one of the main reasons for the spreading of odour impact assessment approaches based on odour dispersion modelling. Currently, just a very limited number of reports discussing the use of tracer gas dispersion experiments both in the field and in wind tunnels for model validation purposes can be found in literature. However, when dealing with odour emissions, it is not always possible to identify a limited number of tracer compounds, nor to relate analytical concentrations to odour properties, thus giving that considering single odorous compounds might be insufficient to account for effective odour perception. For these reasons, the possibility of measuring of odours in the field, both as a way for directly assessing odour annoyance or for verifying that modelled odour concentrations correspond to the effective odour perception by humans, is still an important objective. The present work has the aim to review the techniques that can be adopted for measuring odours in the field, particularly discussing how such techniques can be used in alternative or in combination with odour dispersion models for odour impact assessment purposes, and how the results of field odour measurements and model outputs can be related and compared to each other

CH4 emission estimates from an active landfill site inferred from a combined approach of CFD modelling and in situ FTIR measurements

Globally, the waste sector contributes to nearly a fifth of anthropogenic methane emitted to the atmosphere and is the second largest source of methane in the UK. In recent years great improvements to reduce those emissions have been achieved by installation of methane recovery systems at landfill sites and subsequently methane emissions reported in national emission inventories have been reduced. Nevertheless, methane emissions of landfills remain uncertain and quantification of emission fluxes is essential to verify reported emission inventories and to monitor changes in emissions. Here we present a new approach for methane emission quantification from a complex source like a landfill site by applying a Computational Fluid Dynamics (CFD) model to calibrated in situ measurements of methane as part of a field campaign at a landfill site near Ipswich, UK, in August 2014. The methane distribution for different meteorological scenarios is calculated with the CFD model and compared to methane mole fractions measured by an in situ Fourier Transform Infrared (FTIR) spectrometer downwind of the prevailing wind direction. Assuming emissions only from the active site, a mean daytime flux of 0.83 mg m−2 s−1, corresponding to 53.26 kg h−1, was estimated. The addition of a secondary source area adjacent to the active site, where some methane hotspots were observed, improved the agreement between the simulated and measured methane distribution. As a result, the flux from the active site was reduced slightly to 0.71 mg m−2 s−1 (45.56 kg h−1), at the same time an additional flux of 0.32 mg m−2 s−1 (30.41 kg h−1) was found from the secondary source area. This highlights the capability of our method to distinguish between different emission areas of the landfill site, which can provide more detailed information about emission source apportionment compared to other methods deriving bulk emissions

Identification and Quantification of Greenhouse Gas Emissions from Oil and Natural Gas Operations Using an Aircraft-Based Mass Balance Technique

Rapid advancements in horizontal drilling and hydraulic fracturing techniques have led to a booming natural gas industry. Natural gas is considered a cleaner fuel alternative to coal, producing less carbon dioxide (CO2) upon combustion per unit energy produced, and therefore has been hailed as a bridge fuel during conversion from fossil fuels to renewable energies for electricity production. The primary component of natural gas is methane (CH4), a potent greenhouse gas with 28 times the global warming potential of CO2 on a 100 year timescale. At oil and natural gas facilities, CH4 leaks are common due to changes in operational modes, scheduled ventings to relieve pressure from equipment, equipment aging, and malfunctions, and it is estimated that a CH4 leak rate of 1.5% of facility throughput is enough to negate the climate benefits incurred by use of natural gas instead of coal. Additionally, the Obama administration has set an aggressive mitigation goal of 26-28% emission reduction by 2025, as compared to 2005 levels. To achieve this target, emission sources must be quickly identified and quantified with high precision and accuracy to best understand where additional controls are required. Here, an aircraft-based measurement technique is used to address this challenge using a high-precision cavity ring-down spectroscopy system to measure atmospheric concentrations of CH4, CO2, and H2O, in conjunction with high-frequency three-dimensional wind measurements and aircraft location tracking from an onboard global positioning and inertial navigation system. Here, an assessment of method accuracy and precision was performed by conducting repeat measurements at a power plant and comparing the calculated CO2 emission rate to the reported hourly emissions measurements made by continuous emissions monitoring systems at the facility. Subsequently, results are presented from a field campaign conducted in the Barnett shale, Texas which quantified CH4 emissions from facilities with atypically large emissions, known as “super-emitters”, and assessed their overall contribution to basin-wide emissions. Calculated emissions were compared to inventory estimates and potential reasons for discrepancies were discussed. Results suggested that super-emitting facilities do not emit at the same rate for extended periods of time, and therefore, their emissions can vary by several orders of magnitude depending on operating conditions. To investigate the degree to which temporal variability of emissions occurs, a separate study was conducted in the Eagle Ford shale, Texas, in which four unique measurement methods were used to conduct repeat measurements at facilities during different operational modes. Results were assessed to suggest potential mitigation strategies that may address this variability to improve national inventories. Finally, a series of measurements were made at natural gas-fired power plants and oil refineries, two facility-types with minimal to no CH4 monitoring requirements due to presumption that they produce negligible CH4 emissions annually. Calculated CH4 and CO2 emission rates were reported and improved emissions factors were presented as an alternative to industry-used emissions factors. Additionally, the source of CH4 emissions was assessed by comparison of CH4 enhancements with combustion- and non-combustion-related enhancements

Proceedings of Abstracts 10th International Conference on Air Quality Science and Application

This 10th International Conference in Air Quality - Science and Application is being held in the elegant and vibrant city of Milan, Italy. Our local hosts are ARIANET and ARPA Lombardia both of whom play a leading role in assessing and managing air pollution in the area. The meeting builds upon the series that began at the University of Hertfordshire, UK in July 1996. Subsequent meetings have been held at the Technical University of Madrid, Spain (1999), Loutraki, Greece (2001), Charles University, Prague, Czech Republic (2003), Valencia, Spain (2005), Cyprus (2007), Istanbul, Turkey (2009) Athens, Greece (2012) and Garmisch-Partenkirchen, Germany (2014). Over the last two decades controls to limit air pollution have increased but the problem of poor air quality persists in all cities of the world. Consequently, the issue of the quality of air that we breathe remains at the forefront of societal concerns and continues to demand the attention of scientists and policy makers to reduce health impacts and to achieve sustainable development. Although urbanisation is growing in terms of population, transport, energy consumption and utilities, science has shown that impact from air pollution in cities is not restricted to local scales but depends on contributions from regional and global scales including interactions with climate change. Despite improvements in technology, users still demand robust management and assessment tools to formulate effective control policies and strategies for reducing the health impact of air pollution. The topics of papers presented at the conference reflect the diversity of scales, processes and interactions affecting air pollution and its impact on health and the environment. As usual, the conference is stimulating cross-fertilisation of ideas and cooperation between the different air pollution science and user communities. In particular, there is greater involvement of city, regional and global air pollution, climate change, users and health communities at the meeting. This international conference brings together scientists, users and policy makers from across the globe to discuss the latest scientific advances in our understanding of air pollution and its impacts on our health and environment. In addition to the scientific advances, the conference will also seek to highlight applications and developments in management strategies and assessment tools for policy and decision makers. This volume presents a collection of abstracts of papers presented at the Conference. The main themes covered in the Conference include: Air quality and impact on regional to global scales Development/application/evaluation of air quality and related models Environmental and health impact resulting from air pollution Measurement of air pollutants and process studies Source apportionment and emission models/inventories Urban meteorology Special session: Air quality impacts of the increasing use of biomass fuels Special session: Air quality management for policy support and decisions Special session: Air pollution meteorology from local to global scales Special session: Climate change and human health Special Session: Modelling and measuring non-exhaust emissions from traffic Special session: Transport related air pollution - PM and its impact on cities and across EuropeFinal Published versio

Emission, dispersion and local deposition of ammonia volatilised from farm buildings and following the application of cattle slurry to grassland

Merged with duplicate record 10026.1/570 on 15.02.2017 by CS (TIS)Emissions of ammonia (NH3) into the atmosphere, principally from agricultural sources, have been implicated in the pollution of forests, moorlands and grasslands, through the subsequent deposition of reduced nitrogen (NHx -N). Consequently, legislation has been implemented to control both the transboundary transport and local environmental impacts of NHx. This thesis investigates the emission, dispersion and local deposition of NH3 from two sources that are major components of national NH3 emissions inventories, slurry applied to grassland and naturally ventilated cattle buildings. A N balance method was identified for determining the time-average deposition of NH3 downwind of a farm building, whilst an adapted micrometeorological flux-gradient technique was developed for estimating local deposition downwind of slurry spreading. This method used an analytical atmospheric dispersion model to provide advection corrections to the standard flux-gradient method. The UK-ADMS model, which incorporates a reasonably detailed treatment of building effects, was identified for use in determining the near-field dispersion from naturally ventilated farm buildings. Eight field experiments were conducted to determine the emission, dispersion and local deposition of NH3 volatilised from slurry applications. Emission fluxes during the initial runs following slurry spreading were found to depend on friction velocity, relative humidity and rainfall. Local deposition, at sufficient rates to affect local deposition budgets, was not found to occur during near-freezing conditions or following the application of fertilisers. Local deposition velocities during other periods were found to depend on the latent heat flux, temperature and the roughness length. During such periods, 14 - 18 % of the emitted NH3 was estimated to deposit within 50 m of the source. Experiments were also conducted at two naturally ventilated farm buildings, the Silsoe Research Institute Structures Building and a working dairy farm. Ammonia emission factors were determined for the main building and slurry lagoon at the dairy farm. A novel application of a model back-calculation method was applied to determine the emission from the lagoon. Dispersion of NH3 from both sites was found to be adequately modelled using UK-ADMS. Approximately 2 % of the emitted NH3 deposited within 100 - 150 m of each building. Time averaged deposition velocities calculated from the farm building studies confirmed that NH3 was deposited to the leaf surfaces and uptaken across the leaf cuticle. Temperature dependent exchange rates were also indicated by the results of the farm building experiments, with NH3 uptake being regulated by the assimilation potential of the plant. The experimental results demonstrated that deposition around both sources could lead to local critical load exceedances. These were only estimated to occur within a few tens of metres downwind of slurry spreading whilst critical load exceedances were predicted at distances of up to 100 m or more downwind of the farm building. The temporal variability in local recapture found in these experiments, particularly for farm buildings, suggests that seasonal variability in the treatment of NH3 emission and deposition should be included in atmospheric transport models. Furthermore, it is possible that transboundary transport of NHx may increase during winter periods with peak housing emissions.The Institute of Grassland and Environmental Researc

Detection, attribution and quantification of methane emissions using mobile measurement techniques in European cities

Global actions are required to reduce Greenhouse Gas (GHG) emissions, and thus mitigate global warming. On the 4th of November 2016 the Paris agreement between 196 countries entered into force which aims to limit global warming to less than 2 °C. Methane (CH4) has a relatively short atmospheric lifetime (≈10 years) which makes it an effective mitigation target to slow down global warming on the short to medium term. The CH4 mitigations can be implemented faster and have less severe economic effects than reduction of carbon dioxide (CO2) emissions because CO2 emission is directly proportional to energy consumption. Despite the attractiveness of CH4 reduction, on the longer term also CO2 emission will need to be reduced to zero around the middle of this century to reach the goals of the Paris agreement. Among all the CH4 sources, emission mitigation in the energy sectors seems to be the most time efficient and cost effective compared to emission reduction from other sectors. CH4 emissions from the energy sector, particularly from production, storage, transportation, distribution and end-use of fossil fuels (oil, gas and coal) contribute 19% to total anthropogenic CH4 emissions in Europe. This contribution can increase to more than 60% in fossil fuel producing countries. Fossil fuel related emission have been identified as an interesting target within the CH4 reduction strategy of the EU. The emissions from these activities are mainly estimated using Emission Factors (EFs) and Activity Data (AD) in inventories. The EFs are the ratio of emission rate per activity unit, e.g. kg of CH4 emitted per amount of gas produced. The EFs are tabulated in reports from national or international agencies, and standard EFs for emission reporting have been tabulated by the Intergovernmental Panel on Climate Change (IPCC). However, the EFs can vary temporally and spatially which increases the uncertainty in the estimated emissions. To reduce the uncertainty, independent measurement campaigns are required to update or verify these EFs, some of which are outdated or are possibly affected by sampling and / or emission rate biases. Detailed information is required on where and how large the emissions are, for effective mitigation policies. This thesis was carried out within the MEMO2 (MEthane goes MObile, MEasurements and MOdelling) project, with the objective to use mobile measurement techniques to improve our understanding of CH4 emissions. The main focus was on emissions in the energy sector. In this thesis, we provide detailed results from detection, quantification and attribution of CH4 emissions from extensive measurement campaigns focusing on emissions from the gas distribution networks in cities. These measurements showed that the contribution of CH4 emissions from natural gas leaks, microbial or combustion sources are different from one city to another, thus dedicated emission mitigation policies are required for different cities