Contributions of gas flaring to a global air pollution hotspot:spatial and temporal variations, impacts and alleviation

Studies of environmental impacts of gas flaring in the Niger Delta are hindered by limited access to official flaring emissions records and a paucity of reliable ambient monitoring data. This study uses a combination of geospatial technologies and dispersion modelling techniques to evaluate air pollution impacts of gas flaring on human health and natural ecosystems in the region. Results indicate that gas flaring is a major contributor to air pollution across the region, with concentrations exceeding WHO limits in some locations over certain time periods. Due to the predominant south-westerly wind, concentrations are higher in some states with little flaring activity than in others with significant flaring activity. Twenty million people inhabit areas of high flare-associated air pollution, which include all of the main ecological zones of the region, indicating that flaring poses a substantial threat to human health and the environment. Model scenarios demonstrated that substantial reductions in pollution could be achieved by stopping flaring at a small number of the most active sites and by improving overall flaring efficiency

ADMS-AIRPORT: MODEL INTER-COMPARISIONS AND MODEL VALIDATION

The functionality of ADMS-Airport and details of its use in the Model Inter-comparison Study of the Project for the Sustainable Development of Heathrow Airport (PSDH) have previously been presented, Carruthers et al (2007). A distinguishing feature is the treatment of jet engine emissions as moving jet sources rather than averaging these emissions into volume sources as is the case in some other models. In this presentation two further studies are presented which each contribute to the overall evaluation of the model. In the Heathrow study on adding capacity (third runway) further comparisons have been made between the measured NOx, NO2 and PM10 concentrations from the large number of automatic monitoring sites located in the neighbourhood of Heathrow Airport and the ADMS-Airport predictions. A range of tools is employed with which to present the comparisons including the BOOT validation toolkit and concentration wind roses. In the CAEPport study a fictional but realistic airport was ‘constructed’ for a model inter-comparison study the purposes of which were (i) to determine that air quality airport models put forward for CAEP (ICAO’s Committee on Environmental Aviation Protection) analysis are ‘sufficiently robust, rigorous and transparent’ for forthcoming CAEP analyses and (ii) to explain differences in the models. The study included consideration of both emissions and air pollution concentrations however the focus here will be on the modelled concentrations. Results for ADMS-Airport from this study will be presented along with those of the other participating models – EDMS, LASPORT and ALAQS

A study of pollutant concentration variability in an urban street under low wind speeds

The short time‐scale variability in pollutant concentrations in an urban street under very low wind speed conditions and short source–receptor distance has been investigated using the inert tracer sulfur hexafluoride (SF6) as a continuous point‐source (release times ≥ 5 min), and fast detection using separation by gas chromatography coupled with a μ‐electron capture detector (ECD). The results are complex but can be broadly interpreted in terms of horizontal wind speed and direction coherence. Comparisons with a simple dispersion model suggest that observed time‐averaged maximum concentrations approach predicted values, whilst instantaneous maximum concentrations vary greatly and would therefore be difficult to predict