H.M. ApSimon

A numerical study of atmospheric pollutant dispersion in different two-dimensional street canyon configurations

Abstract The scope of this paper is to study numerically the dispersion of atmospheric pollutants within different street canyon geometrical configurations and building height scenarios. The microscale model MIMO, designed to take into account pollution dispersion in the vicinity of buildings, is validated against a two-dimensional wind-tunnel experiment for a square (W/H=1) and a deep canyon (W/H=1/2) configuration. It was found that the model performance is satisfactory. Having established this, the study involved the alteration of the building heights bounding the canyon for both square and deep configurations. Furthermore, the effects of different aspect ratios on the pollution dispersion characteristics are investigated. It is demonstrated that, under certain conditions, pollutants disperse more easily, while under others pollutant levels increase, with implications for pedestrian exposure. Furthermore, interaction of air in and above the canyons is investigated under different street geometries. It is found that both street geometry and building height influence the interaction between air inside and above the canyons.

Cost-effective strategies for the abatement of ammonia emissions from European agriculture

Abstract Anthropogenic emissions of ammonia, primarily from agriculture, have been recognised as a significant contributor to overall nitrogen deposition in Europe and are being incorporated within the development of a new international protocol on total nitrogen emissions aimed at protecting natural ecosystems from acidification and eutrophication. In response, the MARACCAS model has been developed to assess the cost-effectiveness of potential abatement measures, mainly relating to the management of livestock wastes, and to assist in the design of efficient abatement strategies. Results indicate that although maximum feasible reductions in emissions are fairly limited, most of the possible abatement can be achieved at relatively low cost. By analysis of the measures which consistently produce cost-effective emissions reductions, a set of guideline measures has been identified which could provide significant reductions at costs competitive with those for NO x abatement measures. Greater inherent uncertainties in the estimation of ammonia emissions and abatement potential as compared to NO x , and practical obstacles to ensuring compliance suggest that a more flexible ‘soft’ protocol may be more appropriate in tackling ammonia.

Space, time and nesting Integrated Assessment Models

Integrated Assessment Modelling in the field of air pollution has advanced greatly since the 1985 Helsinki Protocol on the reduction of Sulphur emissions and their transboundary fluxes. With subsequent protocols and increased understanding of the inter-relationships between local air quality, transboundary air pollution and climate change, a variety of spatio-temporal issues must be addressed in order to model the multi-scalar processes involved and nest Integrated Assessment Models. We describe the state-of-the-art in Integrated Assessment Modelling using a conceptual framework which locates the research activities driving integrated assessment in relation both to each other and to flows of information between activities, and identify inter-relationships with scientific and policy domains beyond the scope of the UN/ECE Convention on Long Range Transboundary Air Pollution, recognising the utility of social science in understanding the effects of policy on socio-cultural behaviours. We discuss how the issues identified are being captured by integrated assessment models, with particular focus on the treatment of non-technical pollution abatement measures, noting current developments at the micro-scale addressing the dynamics of behavioural responses to abatement policies. Finally, we identify three key challenges for issue-driven Integrated Assessment Modelling: (i) capturing the dynamics of behavioural responses to value-driven policy mechanisms designed to promote non-technical abatement measures; (ii) the development of new tools to handle the delay times, inter-dependencies and multi-pollutant effects of abatement measures; and (iii) the identification of boundaries between knowledge domains and the effective transfer of multi-disciplinary scientific and socio-cultural knowledge to an increasingly trans-disciplinary policy domain.

Modelling studies of the atmospheric release and transport of ammonia in anticyclonic episodes

Abstract The TERN model has been developed to simulate the atmospheric release and transport of ammonia. It is a Lagrangian model with detailed vertical resolution to represent pollutant concentration profiles. In this paper it is applied to summer anticyclonic conditions to illustrate the importance of assumptions about emissions, deposition and turbulent mixing and their diurnal variations when considering a reactive gas emitted at ground level, and the implications for the proportions transported over long distances. The paper emphasizes the large uncertainties about emissions of ammonia and their nature, and draws attention to the influence of inhomogeneous nonlinear processes which cannot be fully defined and parameterized in numerical models.

The abatement strategies assessment model—ASAM: Applications to reductions of sulphur dioxide emissions across Europe

Abstract In May 1991 the 34 nations of the UN ECE region agreed that strategies for the abatement of SO 2 and NO x should be designed in the most cost-effective way, and that the concept of critical loads should serve as a guideline to formulate these strategies where science has provided the necessary information. The ASAM model has been developed in this context, as a computer tool to aid in guiding policy through investigation of the effectiveness of potential abatement strategies in Europe. In evaluating the environmental consequences, it takes into account the geographical distribution of emissions and the patterns of atmospheric transport and deposition; with the introduction of costs of reducing the different emissions, it provides a stepwise optimized approach to attaining specified target loads or critical loads for deposition across Europe, subject to flexible constraints in different countries. This paper describes the ASAM model, and work undertaken to establish the robustness of the model with regard to the assumptions made and uncertainties in the data used; and explores a range of scenarios currently being addressed.

Long-range atmospheric dispersion of radioisotopes—i. The MESOS model

Abstract The Lagrangian puff trajectory model, MESOS, was initiated in 1976 to simulate the atmospheric transport and dispersal of radionuclides over distances of several hundred km or more. Extensive meteorological data bases have since been constructed from routine reports from European synoptic stations and ships, and used with the model to study large numbers of notional releases from various West European sites. Probability distributions of different levels of contamination have been deduced at several receptor points for hypothetical accidental releases of selected nuclides. Patterns of air contamination and ground deposition have been predicted for continuous releases and used for calculations of collective dose to the population of the EEC countries arising from routine emissions from nuclear installations. In part I of this paper the basic MESOS model is described, together with a comparison study of model predictions and measurements made following the Windscale release in 1957. In part II results obtained with the model for different European sources are presented and discussed.

Transboundary air pollution in Europe

Abstract Under the Convention on Transboundary Air Pollution the UN Economic Commission for Europe has produced a series of international agreements to reduce emissions of pollutants contributing to acidification, eutrophication and formation of tropospheric ozone. This includes the Second Sulphur Protocol signed in Oslo in 1994, which took into account maps of critical loads as those levels of annual deposition which are deemed sustainable without adverse effects. This paper describes scientific and technical work undertaken in the course of development of this protocol, and how the approach might be extended in future as attention turns to new protocols on NO x and VOCs.

Uncertainties in integrated assessment modelling of abatement strategies: illustrations with the ASAM model

Abstract Following the signing of the Second Sulphur Protocol in 1994 under the 1979 Convention on Long-range Transboundary Air Pollution, preparations are now underway for a new multi-pollutant multi-effects protocol, under the auspices of the United Nations Economic Commission for Europe (UN ECE). A number of scientific models have been used to provide policy makers involved in these preparations with sound scientific information. These include the Abatement Strategies Assessment Model (ASAM). ASAM has recently been extended to cover abatement strategies for NH 3 and NOx as well as SO 2 , in order to address the amelioration of acidification and eutrophication in the ECE region. It is important to be able to demonstrate that the scientific information provided to policy makers is robust to uncertainties, and hence there is a need for a thorough sensitivity analysis. In this study ASAM is used to demonstrate a large degree of robustness of derived abatement strategies to uncertainties in critical loads, meteorological data and cost information. This is based on a comparison of strategies at the same overall abatement cost. Systematic changes in data are shown to influence model results more profoundly than random changes.

The UK Integrated Assessment Model, UKIAM: A National Scale Approach to the Analysis of Strategies for Abatement of Atmospheric Pollutants Under the Convention on Long-Range Transboundary Air Pollution

Integrated assessment modelling aims to bring together information on emissions, atmospheric transport between sources and exposed areas or populations, criteria for environmental protection, and potential emission control measures and their costs, in order to explore effective abatement strategies. We describe the development of a new UK scale Integrated Assessment Model which can be used to investigate strategies for the attainment of national emission ceilings. The model optimises abatement strategies in relation to acidification, eutrophication, and/or human-exposure to particulate PM10, with reference to the deposition of sulphur and nitrogen (oxidised and reduced), and concentrations of primary and secondary particles. The model combines sector specific emissions, atmospheric transport and deposition, ecosystem specific critical load exceedances, and pollution abatement costs to determine optimised abatement strategies using benefit and, where applicable, recovery functions.

Modelling long-range transport of primary particulate material over Europe

This paper uses a simple model of atmospheric transport and an emissions inventory prepared by TNO to estimate the contribution of primary particulate material to PM10 and PM2.5 concentration across Europe. The resulting population exposure is compared with that of secondary particulates, and it is noted that both primary and secondary contributions will be significantly reduced with the implementation of new protocols under the Convention on Long-Range Transboundary Air Pollution (CLRTAP). Since concentrations of primary PM10 can become elevated in episodic situations, when long-range transport of particulate could, on its own, exceed 24 h average targets of 50 μg m−3 over large areas of Europe, such reduction is important for achievement of current air quality standards to control exposure to atmospheric particulate PM10.