Fine particle pollution in Asia is generally very high compared with internationally accepted health goals. Much of this fine particle pollution is produced by motor vehicles, fossil fuel combustion, industrial processes and even windblown soils from desert regions.
As part of a long-term project in the Asian region we have been using nuclear techniques not only to characterise fine-particle pollution, but also to quantify their sources and origins across 15 countries in the region.
Monitoring air pollution in the Asian region
In 2002, the International Atomic Energy Agency established a Regional Cooperative Agreement project with 14 member states, including Australia, Bangladesh, China, India, Indonesia, Korea, Malaysia, Mongolia, New Zealand, Pakistan, Sri Lanka, Thailand and Vietnam, to monitor, characterise and quantify sources of fine-particle pollution in each of these countries.
This is a unique study as each country uses the same stacked filter samplers and has sampled at the same time twice a week for at least 5 years.
The data obtained are unique for the region and will be picked up by a range of environmental agencies controlling and managing air pollution in each of the member states as well as nongovernment organisations like the World Bank and the Asian Development Bank.
They will be used to correlate medical conditions related to lung disease and heart conditions with high pollution days, with sources of air pollution and with hospital admissions. Even for relatively pollution-free countries like Australia, estimates
show that generally more people are dying each year from air-pollution related issues than are killed on the roads.
In these Asian regions the air-pollution levels are above World Health Organisation (WHO) recommended guidelines most of the time, and hence the health effects are much more significant.
Fig.1 shows the average, media, and distribution of fine-particle air pollution as measured in this IAEA project between 2002-08. In this box and whisker plot the hatched boxes contain 25%- 75% of the measurements for each country, the vertical whiskers from each box cover the 95% confidence interval, the (+) signs are the means and the horizontal bars the median values for each country.
The remaining points outside the box and whiskers represent extreme values. The red horizontal bar at 35 μg/m3 is the current US EPA 24 hour maximum fine particle goal and the green horizontal bar at 15 μg/m3 is annual average goal. Clearly most Asian countries exceed both US EPA goals for fine particles most of the time.
Fine particle characterisation
Fine particles in ambient air are defined as those particles with aerodynamic diameters less than 2.5 μm in diameter. Particles in this size range can be directly absorbed into the blood stream from the lungs, are most efficient at absorbing and scattering visible light and can travel thousands of kilometres from their original source emission points.
A full characterisation of these particles, their sources and their origins will help regulators
better understand air-pollution issues in their countries.
Each filter has been analysed using four nuclear techniques (Particle induced X-ray and gamma ray emission and nuclear scattering and recoil methods) for between 20-30 different chemical species [1].
This broad range of chemical species, together with the long-time series and extensive area covered by the data collection allowed a comprehensive dataset of source fingerprints and source contributions to be compiled across a very broad area of Asia.
The current US EPA (Environmental Protection Agency) fine-particle health goal is 15 μg/m3 (green line) annual average and 35 μg/m3 24 hr maximum (red line).
Clearly many countries exceed these two goals.The current database (established bythe IAEA/RCA project) contains more than 8,400 individual sampling days. Each analysed for more than 20 different elements from hydrogen to lead.
Studying the trajectories of fine particles
Statistical techniques such as Positive Matrix Factorisation [2] can be applied to this database to obtain source fingerprints and their contributions to the total fine-particle mass.
Fig 2 shows the major desert regions and the larger coal-firedpower stations in eastern China, north of Hanoi. It is well known that the Taklamakan and Gobi Desert regions produce large dust storms between March and April each year which may travel across Korea and Japan [3].
By applying standard back trajectory techniques [4] we can determine source ‘fetch regions’ for major Soil and Coal events from the Hanoi site. Figs. 3 and 4 show two such seven-day back trajectories for a high Soil event on 5 March 08 and a high Coal event on 10 Feb 08 at the Hanoi site.
These back trajectory methods can be extended to look at all extreme events (over a long period of time) whose back trajectories intersect with known source regions such as the Taklamakan or Gobi Deserts or the coal-fired power stations in eastern China.
Acknowledgements
We would like to acknowledge the help of staff at the Vietnamese Institute of Nuclear Sciences and Technologies and the International Atomic Energy Agency RCA Program for financial assistance and support throughout this work.
Authors
David Cohen, Eduard Stelcer and Jagoda Crawford
ANSTO
References
- Cohen D.D., Stelcer E., Hawas O., Garton D., IBA Methods for Characterisation of Fine Particulate Atmospheric Pollution: A local, regional and global research problem. Nuclear Instruments and Methods in Physics Research, Section B 219-220, (2004) 145-152.
- Paatero P., Tapper U., Positive Matrix Factorisation: A non-negative factor model with optimal utilisation of error estimates of data values, Environmetrics Vol 5 (1994) 111-126.
- Cohen D.D., Garton D., Stelcer E., Wang T., Poon S., Kim J., Oh S.N., Shin H., Ko M., Uematsu M., 2004a. Multielemental analysis and characterisation of fine aerosols at several key ACE Asia sites. Journal of Geophysical Research, 109 (2004) D19S12, doi:10.1029/2003JD003569.
- Draxler R. R., Rolph G.D, 2003. HYSPLIT (HYbrid Single-Particle Lagrangian Integrated Trajectory) Model access via NOAA ARL READY