Abstract. Introduction

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1 Concentrations of nitrogen dioxide in the suburban region in and around an international airport D.E. Conlan, D.W. Raper, J.W.S. Longhurst Atmospheric Research and Information Centre, Department of Environmental and Geographical Sciences, Manchester Metropolitan University, Chester Street, Manchester Ml 5GD, UK Abstract Nitrogen dioxide has been monitored for over two years at a number of sites in and around Manchester international airport, UK. At these sites there is a range of activities including major surface communication routes, industrial areas to the north of the airport, aviation activities, and agricultural activities to the south. Aviation is increasing as a transport type and so it is of increasing importance to assess the impact of such areas of intense transport activities. Nitrogen dioxide is measured at two sites on the airport using an Opsis instrument based on a differential optical absorption spectrometry technique. From these data compliance with standards and guidelines have been assessed. In addition further monitoring is undertaken within the airport using diffusion tube samplers and also, in conjunction with the Local Authorities, in the communities surrounding the airport. These data are presented showing a significant spatial variation with highest concentrations around the terminal buildings at the airport and multi storey car parking facilities. The data are also assessed in terms of their input into a proposed local air quality management area. Introduction Aviation is a fast growing, world wide industry which is expected to increase into the next century. During the 1980s there was an unprecedented growth in air traffic. Its economic influence is great and is also on the increase. In addition to the direct and indirect employment opportunities aviation offers it

2 618 Air Pollution Monitoring, Simulation and Control is also the catalyst for many other economic activities [1]. Within the United Kingdom passenger movements have increased at most major airports. For example, at Heathrow Airport, west of London, passenger numbers in 1980 were 27 million which increased to approximately 52 million in 1994 [2]. At Manchester Airport in the North West of England passenger movements were approximately 4 million in 1980 but had grown to 14.6 million in 1995 and is further predicted to increase to 30 million passengers per annum by the year 2005 [3]. Air cargo has also rapidly increased at Manchester Airport over the last decade with 27,659 tonnes handled in 1980 and 81,000 tonnes in 1992 [4], This swift growth in the whole aviation industry has had reprecussions on the surrounding environment at the local airport scale [5]. It is now clear that environmental issues, and air quality in particular, are relatively new challenges that airports, the centre of the aviation industry, are coming to realise. As a consequence of the increased debate within the aviation industry about the strategic importance of air quality a number of major international airports such as Zurich, Heathrow (London), Dusseldorf (Germany) and Schiphol (Netherlands) have developed air quality monitoring and modelling programmes [6]. Manchester International Airport, U.K., is one of the leading European Airports in air quality management. It is the UK's third largest airport and is in the top 20 European airports and within the top rank of world airports for international passengers [7]. Developments at this airport in the last 5 years include construction of a new terminal building, a rail station, a 10 MW Combined Heat and Power plant, prestigious office block and numerous other smaller scale infrastructural developments. In 1994 one of the largest public inquiries in the UK took place assessing the need for a second runway at Manchester Airport. It is therefore useful to investigate air quality at Manchester Airport as this airport is rapidly developing and is located on the edge of a large residential community. With the introduction of the concepts of air quality management incorporated into UK legislation it is imperative that airports and air quality are reviewed as they represent localised sources of relatively high emissions [8]. Air quality monitoring at Manchester Airport Manchester Airport is located on the urban fringe to the south of the city. It is surrounded by an intensive network of communication routes, both rail and road. A large residential area lies to the north of the airport and to the south is the start of a large area of agricultural land in the Cheshire plain.

3 Air Pollution Monitoring, Simulation and Control 619 As part of an on-going air quality monitoring programme there are two OPSIS differential optical absorption spectrometers [9] located between the aprons where most vehicular activity arises and at the northern perimeter of the airport on the boundary of the airport and the surrounding residential community (Figure 1). These instruments measure a range of pollutants, including NC>2, on a 15 minute basis. In addition, a NOg diffusion tube network comprising 15 passive samplers is in operation (Figure 1)[10]. Sampling on the diffusion tube network is on a weekly basis. Within this paper concentrations of NOj will be investigated as this gas is one of the pollutants emitted from air and road traffic which is of great concern to human health. Spatial Variation of Nitrogen Dioxide in the South Manchester/North Cheshire Region. The average weekly concentration of nitrogen dioxide has been recorded at 15 sites at Manchester Airport for some 2 years (Figure 2). Previous to this data were collected at 10 of the above sites for one year (Figure 3). During 1993 highest concentrations of this pollutant were recorded around the Terminal 1 building with declining concentrations towards the south of the airport site. However, in 1994 concentrations of nitrogen dioxide were also significantly elevated around the new Terminal 2 building and the surrounding cargo area. Data collected at Manchester Airport have been combined with those collected by surrounding Local Authorities in south Manchester and north Cheshire. These data enable an assessment of the importance of this airport as a source of air pollution. Sites in all monitoring locations included road side and rural points. Without the full operation of the new Terminal 2 building, and the increase in air traffic and road traffic associated with it, concentrations of NC>2 at Manchester Airport in 1993 were similar to those in the surrounding regions. Those more rural regions, such as Macclesfield, illustrate the lowest concentrations of NOj. However, in 1994, with the full operation of Terminal 2 and the increased development of the Airport there now exists a clear difference in NOa concentrations between the Airport and surrounding communities.

4 620 Air Pollution Monitoring, Simulation and Control s i %? J3

5 Air Pollution Monitoring, Simulation and Control 621 Figure 2: Annual mean concentration of nitrogen dioxide in 1994 monitored by diffusion tube samplers at Manchester Airport, U.K. (fig nv*). Figure 3: Annual mean concentration of nitrogen dioxide in 1993 monitored by diffusion tube samplers at Manchester Airport, U.K. (fig nr*).

6 622 Air Pollution Monitoring, Simulation and Control Table 1: Annual mean concentrations of nitrogen dioxide diffusion tube data collected at Manchester Airport and from surrounding communities Monitoring area and direction relative to Airport Airport south Manchester (N) Trafford (NW) Warrington (W) Congleton (S) Macclesfield (SE) Yearly Variation in Nitrogen Dioxide Concentrations Annual mean concentrations of NC>2 recorded at Manchester Airport between 1991 and 1994 indicate that concentrations have decreased by almost one third since 1991 (Figure 4). For comparison, concentrations recorded at Manchester city centre (measured by chemiluminescence) and adjacent to Heathrow Airport (measured by DOAS) are also presented (Figure 4). Despite this decrease in NC>2 at Manchester Airport, concentrations in 1994 are still the same as those recorded in Manchester city centre, which are amongst the highest concentration in the UK, and about one third more than those recorded in the London Borough of Hillingdon adjacent to Heathrow Airport. Thus, concentrations of this gas at Manchester Airport are representative of a highly urbanised area rather than a suburban area and are unexpectedly higher than those near the larger Heathrow Airport Comparison against standards and guidelines Concentrations of air pollutants in the ambient environment of European Union (formerly EC) States are regulated by statutory air quality limit values. These values have been set by EC directives for nitrogen dioxide (Directive 85/203/EEC). These and other guidelines are given in Table 2. The limit value set by the EC for NO% has never been exceeded during the existing monitoring programme. However, both the 98th and 50th percentile guide values have been exceeded (in 1992 and 1993). While the World Health Organisation (WHO) 1 hour existing guideline has not been exceeded the 24 hour guideline was exceeded on 7 occasions in 1992.

7 Air Pollution Monitoring, Simulation and Control 623 During October 1995 the WHO announced its intention to reduce the 24 hour average air quality guideline for NOj by half due to recent medical evidence on the effects of NOj on human health [11]. This would have lead to 7 exceedences in 1991, 16 in 1992, 1 exceedence in 1993 but no exceedences in The annual mean WHO recommended health guideline and the UNECE vegetation guideline would have been exceeded in each year of monitoring. 1* *o - a Utnohtmr Airport D imtncnottof city 0 London i M2 T MB3 Yeir W4 Figure 4: Annual mean concentration of nitrogen dioxide in at Manchester Airport, Manchester city centre and in the London Borough of Hillingdon adjacent to Heathrow Airport. Conclusion Concentrations of nitrogen dioxide at Manchester Airport are similar to those recorded in the highly urbanised area of Manchester city centre. Although concentrations of NO2 have decreased since 1991 they are in 1994 still higher than those recorded adjacent to the substantially larger Heathrow Airport. Concentrations of NO2 were higher at Manchester Airport than in the surrounding suburban and rural communities and it is clear that guidelines have and probably will continue to be exceeded. On the assumption that Manchester Airport is representative of the average airport, it has been demonstrated that airports are area sources of emission of nitrogen oxides. Recognition must be given to this at the local and regional level in determining air quality management plans. Due to the growth in

8 624 Air Pollution Monitoring, Simulation and Control airports and the general aviation industry it is apparent that this source area will continue be an issue for planners and air quality managers. Table 2: Standards and Guidelines for Nitrogen Dioxide Guideline Set By Description Criteria Based On Value ppb (pgm-3) European Council Limit Value Guide Value Guide Value Calender year of data: 98 %ile of hourly means 98 %ile of hourly means 50%ile of hourly means (200) 70.6 (135) 26.2 (50) World Health Organisation (WHO) Health Guideline Health Guideline Vegetation Guideline Vegetation Guideline 1-hour mean Daily mean Running 4-hour mean Annual Mean 210 (400) 80 (150) 50 (95) 16 (30) Draft WHO Recommended Guideline Health Guideline Health Guideline 1-hour Annual 110(200) (40-50) United Nations Economic Commission for Europe Vegetation Guideline Annual mean 15 (29) The UK government has adopted a strategic policy on air quality, the legal framework of which is provided by the Environment Act Part IV (1995) [12]. This requires Local Authorites to review air quality and to assess whether the air quality standards and objectives are being achieved. A Local Authority, for any area where the air quality standards are not being met, will then be obliged to issue an order designating an air quality management area. The Local Authority will then have a duty to carry out further assessments and draw up an action plan specifying the measures to be carried out and the timescale to bring air quality in the area back within the limits. It therefore seems quite probable, given the air quality data at a leading airport presented here, that airports and their surrounds will become candidates for statutory air quality management areas in the UK. Airports, because of their suburban/rural location represent important area sources of emission on

9 Air Pollution Monitoring, Simulation and Control 625 the edge of conurbations and may therefore be designated as a complete air quality management area. Alternatively, airports may be included in a more wider designation of an air quality management area which encompasses industrial, commercial and residential areas. However, it is clear that as a consequence of this new duty of Local Authorites a liaison has to develop between the airport officials and the Local Authority representatives to devise a mechanism behind the establishment of any future air quality management. If economic benefit is to be retained for the airport and the surrounding region then air quality plans will have to be developed by airports setting stringent air quality targets. These air quality targets will have to address emissions from aircraft, airside and landside road transportation and power plants and boilers. With the introduction of more Chapter 3 aircraft it is anticipated that emissions from aircraft are forecast to decrease [13]. Airside transportation at the majority of airports are diesel fuelled. Developments need to be made to establish viable alternatives such as the use of low emission fuels, introduction of electrified or gas fuelled vehicles to reduce emissions from this sector. Public transportation should be encouraged both for the passenger and the staff who work at airports. Car sharing schemes, for example, could be established which potentially could significantly reduce emissions from airports and their surrounds. Technological emission controls could be fitted to power plant to ensure low emissions. The strong liklihood that the aviation industry will retain its current growth curve well into the next century is, in general, not disputed. However, what has become the challenge for airport operators, scientists and air quality managers is the reconciliation between this growth and meeting the new air quality standards and guidelines which will be established by the Expert Panel on Air Quality Standards in the UK and also by the new framework directive on Air Quality [14]. References 1. KLM 'Position regarding aviation and the environment*. Amstelveen Local Government Management Board, Local Agenda 21, LGMB, Luton British Airports Authority. 'Heathrow Terminal 5. Statement of Case'. BAA/1. December Stevenson, K.J., Stacey, B. and Willis, P. 'Air quality at Heathrow Airport Annual Report for 1994'. AEA Technology, Oxfordshire, UK. May Manchester Airport. 'Development strategy to 2005'. Manchester, UK. May Raper, D.W., Longhurst, J.W.S. and Conlan, D.E. 'The impact of airport operations on urban air quality'. In Baldasano, J.M., Brebbia, C.A., Power, H. and Zannetti, P. (Eds.) Pollution Control and Monitoring, Air Pollution 11 Volume 2, Computational Mechanics Publicaions, Southampton, pp 91-97,

10 626 Air Pollution Monitoring, Simulation and Control Owen, B., Raper, D.W., Longhurst, J.W.S. and Conlan, D.E. 'Air quality management at European Airports'. In Air Pollution 96, Toulouse, France Computational Mechanics Publicaions, Southampton, August Manchester Airport. 'Development strategy to 2005'. Manchester, UK. May Pratt, M.S. 'Environmental Modelling - Air Quality'. Presented at Computaport '96, Nice, France 5-8 March Sandroni, S., Cerutti, C., Noreiega, A. Palmgren, F. 'Air quality measurements in Brussels ' Report EUR EN. Joint Research Group, European Commission Environment Institute Atkins, D.H.F., Sandalls, J., Law, D.V., Hough, A.M., and Stevenson, K. 'The measurement of nitrogen dioxide in the outdoor environment using passive diffusion tubes samplers.' Report AERE - R 12133, United Kingdom Atomic Energy Authority, Harwell, UK National Society for Clean Air. Clean Air and Environmental Protection Winter 1995 Volume 25 number Longhurst, J.W.S., Lindley, S.J., Watson, A.F.R. and Conlan, D.E. 'The introduction of Local Air Quality Management in the United Kingdom: A review and Theoritical Framework'. Atmospheric Environment, in press. 13. Raper, D.W., Longhurst, J.W.S. and Conlan, D.E. 'The impact of airport operations on urban air quality'. In Baldasano, J.M., Brebbia, C.A., Power, H. and Zannetti, P. (Eds.) Pollution Control and Monitoring, Air Pollution 11 Volume 2, Computational Mechanics Publicaions, Southampton, pp 91-97, Department of Environment. 'Air Quality: Meeting the Challenge. The Government's strategic Policies for Air Quality Management'. D.E., UK