Organization(s):

Australian Science and Technology Organization (ANSTO) Institute for Nuclear Geophsiology

What does this program measure?

Hourly radon concentrations are measured in air samples from an intake of 40m elevation. The units are mBq m-3 (millibecquerels per cubic meter)

How does this program work?

The radon monitor uses a continuously flowing air sample from the top of the 40m tower. The radon is collected on a filter. The radioactivity of the filter is monitored and air stream radon concentrations are calculated. The system is under computer control. Radon is recorded at MLO using an ANSTO-built detector. The radon detector is of dual flow loop two filter type.

For details, see Whittlestone, S. and Zahorowski, W. 1998. Baseline radon detectors for shipboard use: Development and deployment in the First Aerosol Characterization Experiment (ACE 1). Journal of Geophysical Research, 103(D13), 16,743-16,751.

Why is this research important?

Radon is a very useful passive tracer of air masses having been in recent contact with land. The purpose of this project is to carry out continuous radon concentration monitoring at MLO using techniques developed at ANSTO. Variations in radon concentration show variations in air mass transport to MLO from Asian and North American continental areas and also local influences from the island of Hawaii.

Are there any trends in the data?

There are distinctive trends on both seasonal and diurnal time scales. The former reflect the Asian continental outflow to the Pacific that occurs within the troposphere as the result of rapid westerly advection within the jet stream, the latter reflect the local island influence.

How does this program fit into the big picture?

What is it's role in global climate change?

Radon ( 222Rn ) is a gaseous decay product of uranium, which is ubiquitous in most rock and soil types. It has a relatively short half-life (T 0.5 » 3.8days), and since terrestrial radon fluxes are 2-3 orders of magnitude greater than oceanic fluxes, there is a large contrast between radon concentrations in continental and aged oceanic air masses. Consequently, radon monitoring at island or coastal sites provides insight into air mass history including the extent of recent land contact. This is a desirable characteristic since most anthropogenic atmospheric pollutants are also of terrestrial origin. Radon is inert, and relatively unsusceptible to wet or dry atmospheric removal processes, so its predominant atmospheric sink is radioactive decay. Since its half-life is comparable to the lifetimes of short-lived atmospheric pollutants (e.g. NO, SO2, CO, O3), the residence times of water and aerosols, and the time scale of many important aspects of atmospheric dynamics, radon is a particularly useful tracer at local, regional or global scales.