High density sensor network system for air quality studies at Heathrow airport

Lead Research Organisation: Imperial College London
Department Name: Civil & Environmental Engineering


Overview The overall scientific objective is to demonstrate the potential of low cost sensor network systems for characterising air quality in the urban environment at an appropriate granularity in order to understand the factors which influence pollutant distributions on local scales. The ultimate aim is develop and demonstrate a sensor network system* methodology which, when appropriately deployed, can contribute to scientific, economic, public policy and regulatory issues, crossing climate change, human (health) responses, as well as air quality on local and regional scales. As well as demonstrating a generic capability, the intention of this application is to address a number of specific scientific and ultimately legislative issues relevant to London Heathrow Airport. We therefore propose to deploy a high-density air quality sensor network system in and around London Heathrow Airport for an extended period. This will use state of the art low cost sensors for selected gases and for size speciated aerosols, providing an unprecedented data-set for use in a range of activities and outcomes. Air Quality and Human Health The World Health Organisation (WHO) reported in 2005 on the effects of air quality on human health and identified the relative contributions to mortality from different components of air pollution. The strongest correlations with health were found to be particulate matter (PM), followed by O3 and NO2; for example it was estimated that a reduction in the PM10 annual mean exposure to 20 ug m-3 would lead to a reduction of 22,000 attributable deaths per year in Europe. The report also identified a substantial reduction in the quality of life for millions of citizens with pre-existing respiratory and/or cardiovascular disease. However, the magnitudes of health impacts per incremental increase in pollutant levels vary between studies, in part due to imperfect knowledge of human exposure particularly within urban locations and complex, multi-source transport infrastructures. The problem lends itself to a high density, long term network of air quality monitoring to refine our understanding of the drivers of the health impacts, and better understand potential mitigation options. London Heathrow Airport There is also a strong political aspect. In 2004 the DfT established technical panels of experts to strengthen and update the assessment of air quality around Heathrow Airport in response to the Airport Transport White Paper 'The Future of Air Transport'. This identified key planning issues with respect to compliance with air quality standards. Deployment of a Sensor Network at London Heathrow Airport Miniaturised low cost measurement methodologies are now available for measurements of a range of chemical species and aerosols at concentrations observed in the urban environment, while infrastructures also exist for GPS (positioning) and GPRS (mobile phone data transfer). The proposed primary sensor network would consist of a series of ~60 sensor units combining NO, NO2, CO, O3, CO2, hydrocarbons, SO2, size speciated aerosols, temperature and RH, allowing deployment along the (14 km) perimeter of Heathrow airport at intervals of a few 100 m. Additional sites would be co-located with static AURN sites in neighbouring Boroughs, and on a campaign basis mobile sensors would be deployed. The project also aims to bring complex mathematical techniques to provide innovative ways of calibrating the sensor network, and sophisticated methods for storing and displaying the data obtained. State of the art computer modelling of pollution levels around Heathrow would also be undertaken, with the aim of producing a more refined tool for assessing the potential impacts, e.g. of airport expansion. The intention is that the sensor network would be developed during the first year of the project, deployed during the second year, with major data analysis during the third year.
Description Imperial's work in this project had two key objectives:

1. To evaluate the performance of models of predicted pollutant emission and dispersion with respect tot the pollutant measurements being taken using a distributed network of pollution sensors at London Heathrow Airport.

2. Identify the extent to which the differences in the predicted and measured values can be explained by uncertainties in the details of aircraft activity.

Several data sources have been combined to model thrust, nitrogen oxides (NOX), carbon monoxide (CO), hydrocarbon (HC) and black carbon (BC) emissions for 8,331 flight data Records. These sources include summary data (supplied by London Heathrow), flight data records (supplied by British Airways), BUCHair engine assignment, ICAO Exhaust Emission Databank and Base of Aircraft Data (BADA). Thrust and emissions have been modelled following the Boeing Fuel Flow Method II and 1 Hz recorded fuel flow rates. Several quality assurance steps have been used to ensure the presence of no erroneous data. Modelled thrust settings and emissions are assigned to the corresponding time series and spatial location using recorded time and positional data, leading to a high-resolution spatial and temporal emission time series for aircraft activity at London Heathrow (up to 3000 ft altitude).

The work undertaken has both highlighted a number of errors in commonly used aggregated aircraft-emission estimation methods and analysed the effect of reduced thrust takeoff and single engine taxi activities on emissions. The corresponding impact of these activities on local air quality has been investigated.
Exploitation Route The practical impacts of this research are two-fold: first, high-resolution spatial and temporal emission sources have been modelled for comparison to monitored air quality concentrations to enable sensor network evaluation; second, tools have been developed to quantify the impact of aircraft-emission reduction strategies as not previous possible, these are ready for adoption by airport/aircraft operators.

The improved understanding of the relationships between air quality sensor network measurements, models of aircraft and the prediction of pollution episodes has the potential to improve the analysis and management of the environmental impact of airports.
Sectors Environment,Healthcare,Transport

Description The results have opened up new possibilities for monitoring the environmental impact of airports. Discussions are ongoing with Heathrow (and other airports), together with equipment manufacturers and modelling service providers regarding the possibility of integrating sensor network based data into existing environmental assessment approaches.
First Year Of Impact 2015
Sector Environment,Transport
Impact Types Policy & public services

Description Heathrow Airport 
Organisation Heathrow Airport Holdings
Department London Heathrow Airport
Country United Kingdom 
Sector Private 
PI Contribution Our research lead to improved understanding of the environment impact of Heathrow airport.
Collaborator Contribution Heathrow Airport provided access to various data (aircraft ground movement, airside ground operations etc.) and facilities (e.g., locations for siting sensor units) that enabled the field data collection part of the research to be successfully completed.
Impact Academic publications, as described elsewhere
Start Year 2011
Description Hounslow 
Organisation London Borough of Hounslow Council
Country United Kingdom 
Sector Public 
PI Contribution Our research improved LBH's understanding of the environmental impact of Heathrow
Collaborator Contribution LBH provided access to local traffic data and to sites that enabled the co-location of instruments. They also participated in workshops and meetings.
Impact Academic publications, as described elsewhere
Start Year 2011