Dalveen (Queensland) – Gross Alpha Activity
2023/24: Dalveen (Queensland)
Total Alpha Activity 0.8* Bq/L (max), 0.53 Bq/L (mean), 0.4 Bq/L (low)
Total Beta Activity 0.5 Bq/L (max), 0.3 Bq/L (mean), 0.1 Bq/L (low)
*0.80 Bq/L on 12/02/24 in Bore B untreated sample. Follow up radium testing in the combined corrected (Bore A and B) was 0.103 mSv/yr which is under
the ADWG guideline limit of 0.30 mSv/yr. Treated sample was 0.40 Bq/L in DAL 1 Pumphouse.
Radium-226 and Radium-228 should be determined if the gross alpha radioactivity in drinking water exceeds 0.5 Bq/L, or the gross beta activity (with the contribution of potassium-40 subtracted) exceeds 0.5 Bq/L.
GENERAL DESCRIPTION
Radium isotopes are formed as a result of radioactive decay of uranium-238 and thorium-232, both of which occur naturally in the environment. The two most significant isotopes in this process, in terms of radiological health, are radium-226 (uranium series) and radium-228 (thorium series), which have half-lives of 1620 years and 5.8 years, respectively.
Radium-226 is an alpha emitter. It has been used, separated from its parent uranium, in cancer therapy.
Of the radionuclides that comprise the natural thorium and uranium series, radium-226 and radium-228 are those most likely to be found in drinking water, and this occurs more commonly in supplies derived from groundwater. Concentrations in surface water are likely to be extremely low. Concentrations of radium isotopes in groundwater vary according to the type of aquifer minerals and dissolved anions such as chloride, carbonate, and sulfate anions, which tend to increase the mobility of radium.
Radium is widespread in the environment and trace amounts are found in many foods. The average dietary intake is estimated to be 15 Bq per year (UNSCEAR 2000).
TYPICAL VALUES IN AUSTRALIAN DRINKING WATER
In supplies derived from groundwater sources, radium-226 and radium-228 concentrations vary
considerably depending on the aquifer, and it is not uncommon in small supplies to find concentrations up to, or exceeding, 0.5 Bq/L. Radium concentrations in Australian surface water supplies are generally below 0.02 Bq/L.