Measurement and modelling of pollutant emissions from Hong Kong
Introduction
In 1996 the Hong Kong Environment Protection Department (EPD) commissioned ERM Hong Kong to develop a multi scale, multi species, state of the art modelling system, to be used for investigating the impact of different development and control scenarios in the Special Administrative Region of Hong Kong (SAR). The development of the modelling system (know as PATH — Pollutants in the Atmosphere and their Transport over Hong Kong) was one component of the Territory-Wide Air Quality Modelling Study. Another component was the generation of modelling data sets for eleven case-study days. These case-study days covered a range of meteorological conditions including those conducive to the generation of photochemical smog and aerosols. Daily-average PM10 concentrations from seven of the case-study days were used to generate an estimate of annual average PM10. The case-study days were also used to validate components of PATH, using available near-surface and upper air observations of air quality and meteorology.
In order to provide another level of data in addition to that normally available, EPD also funded an airborne investigation of air pollution within the SAR, the Airborne Inventory Validation Study (AIVS). The AIVS was carried out by CSIRO Energy Technology and its objectives were as follows:
- •
to measure the fluxes of carbon dioxide (CO2), nitrogen oxides (NOx), methane (CH4), non-methane hydrocarbons (NMHC), sulfur dioxide (SO2), particles and volatile organic compounds (VOCs) emitted into the atmosphere of Hong Kong;
- •
to provide windfield data and measurements of selected atmospheric pollutants for the Hong Kong region for comparison with model predictions; and
- •
to provide measurements and speciation (by grab sampling and subsequent chemical analysis) of VOCs in the Hong Kong region.
In the current paper we describe briefly the numerical model developed, the aircraft data obtained and provide a comparison between the aircraft measurements and the model predictions for a day when the aircraft data allowed estimates of the total fluxes of NMHC and NOx from the study area.
Section snippets
Model description
The major role in developing the modelling system was undertaken by CSIRO Atmospheric Research who acted as sub-contractor to ERM. The main modelling approach has been described by Cope et al. (2000). The development of the PATH (Pollutants in the Atmosphere and their Transport over Hong Kong) system included the adaption, coupling and operation of three substantial numerical modules: a numerical weather prediction system (MM5, Dudhia, 1993), an emissions inventory module system (EMS-95,
Measurement of fluxes
A number of workers have used airborne techniques to estimate total fluxes of emissions from distributed sources, such as cities. The basic concept is that by measuring the cross wind concentration distribution in both the vertical and lateral directions the flux of material passing through a plane at right angles to the wind direction can be calculated. The technique requires the concentration and wind fields to be mapped simultaneously by aircraft sensors in sufficient detail to reduce the
Aircraft data
Total fluxes of material entering or leaving the airshed can be estimated from the aircraft measurements by the expression:where Q is the flux of material, u the wind speed at right angles to flight path, χ the concentration of pollutant and x, y and z the downwind, crosswind and vertical dimensions. From a knowledge of the plume concentrations and wind speed, the above expression can be approximated from the aircraft data and estimates of the fluxes of pollutants calculated.
Conclusion
A comparison between modelled and observed fluxes of NMHC and NOx was carried out for aircraft based measurements on 17 November 1997. Air quality modelling of two days with similar overall meteorology to 17 November showed reasonable consistency between the predicted and measured fluxes, suggesting that the NMHC and NOx inventories for Hong Kong are broadly correct.
Acknowledgements
The authors wish to thank EPD Hong Kong for their support of this work and for permission to publish the results. In addition the assistance provided by ERM Hong Kong during the operational phase of the work is gratefully acknowledged. The authors would also like to thank Capt. S Lawrey of Kevron Pty Limited whose flying skills made the measurements possible.
References (12)
- et al.
Emission strengths for primary pollutants as estimated from an aircraft study of Hong Kong air quality
Atmos. Environ.
(1999) - et al.
A comparative study of equilibrium approaches to the chemical characterization of secondary aerosols
Atmos. Environ.
(1986) - Carras, J.N., Thomson, C.J., Williams, D.J., 1991. Measurement of methane fluxes in urban plumes. In: Preprint Volume...
- et al.
A three-dimensional Eulerian acid deposition model: physical concepts and formulation
J. Geophys. Res.
(1987) - Chang, J.S., Jin, S., Li, Y., Beauharnois, M., Lu, C.-H., Huang, H.-C., Tanrikulu, S., DaMassa, J., 1997. The SARMAP...
- Cope, M.E., Burgers, M., Olliff, M., 2000. Application of the SARMAP air quality model (SAQM) to the modelling of air...
Cited by (4)
Aircraft mass budgeting to measure CO<inf>2</inf> emissions of Rome, Italy
2014, Environmental Monitoring and AssessmentVariation-oriented data filtering for improvement in model complexity of air pollutant prediction model
2014, Mathematical Problems in EngineeringLeast squares support vector prediction for daily atmospheric pollutant level
2010, Proceedings - 9th IEEE/ACIS International Conference on Computer and Information Science, ICIS 2010