Air pollution monitoring in Asia
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 ANSTO has 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.
In 2002, the International Atomic Energy Agency (IAEA) established a Regional Co-operative Agreement (RCA) with 14 member countries, 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 systems and have sampled them at the same time twice a week for at least 10 years.
Relevance of study
The data obtained are unique for the region and 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 much higher, and hence the health effects much more significant.
Studying these particles, their sources and their origins will help regulators better tackle air-pollution issues in their respective countries.
What are fine particles?
Fine particles in ambient air are defined as those particles with aerodynamic diameters less than 2.5 µm (approximately 10 times smaller than the width of a human hair). 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.
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 much of the time.
ANSTO’s contribution to this international research effort
ANSTO has analysed each of its exposed filters using four IBA nuclear techniques 1) particle induced X-ray emission (PIXE), particle induced gamma-ray emission (PIGE), particle elastic nuclear scattering analysis (PESA) and Rutherford backscattering (RBS).
These techniques have the sensitivity to identify and measure between 20-30 different chemical species from aluminium to lead at concentrations as low as 1000,000,000th of a gram in a cubic metre of air (ng/m³) which has passed through the filter.
Not just elements but sources
ANSTO also uses a multi-dimensional statistical method known as Positive Matrix Factorisation (PMF) to determine inter-elemental correlation between all of the 20-30 measured elements.
This complex method mathematically identifies key elemental fingerprints, known as factors, which are associated with generic fine-particle pollution sources such soil, cars, industry and smoke.
Long distance transport of fine particles from sources
By combining available wind back trajectory information with the Positive Matrix Factorisation (PMF) analysis, we can determine the likely origins of major pollution sources for a particular site.
For example, 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.
Figure 2 below combines the soil fingerprint obtained from PMF with wind back trajectory data. The squares represent the various dessert regions close to the sampling site in Hanoi.
The symbols in the boxes represent the number of wind trajectory intersections that impacted Hanoi between April 2001 and December 2008 with Soil source levels above 6 µg/m³. A similar example for coal source levels above 30 µg/m³ impacting Hanoi over the same time period is shown in the figure 3.
Clearly, the Gobi and Taklamakan deserts impact the Hanoi site as do several major coal-fired power stations in eastern China. These source sites represent long-range transport of fine-particle pollution some hundreds and even thousands of kilometres into Hanoi.
A subset of the database related to this project has now been released online and can be downloaded at: http://www.rcaro.org/others/articles/view/tableid/pubothers/id/2078
You may be interested to know…
A related ANSTO led research effort known as the Aerosol Sampling Program (ASP) has been running for almost 20 years.
Aerosol samples have be routinely collected in a number of Australian sites as well Asian sites.
The samples are analysed at ANSTO by using IBA techniques and results interpreted and reported every year as a monthly summary sheet.
The following links are provided for the 2011 summary sheets for:
Summaries for several the Australian sites are available here