HR: 0800h
AN: C51B-1033    [Abstracts]
TI: Tritium in Australian Precipitation: a 40 Year Record
AU: * Tadros, C V
EM: ckh@ansto.gov.au
AF: ANSTO Environment, PMB 1, Menai, NSW 2234 Australia
AU: Stone, D J
EM: dms@ansto.gov.au
AF: ANSTO Environment, PMB 1, Menai, NSW 2234 Australia
AU: Hill, D M
EM: dmh@ansto.gov.au
AF: ANSTO Environment, PMB 1, Menai, NSW 2234 Australia
AU: Henderson-Sellers, A
EM: ahssec@ansto.gov.au
AF: ANSTO Environment, PMB 1, Menai, NSW 2234 Australia
AB: Tritium, the radioisotope of hydrogen, directly incorporated into water molecules in the global hydrological system, is the most commonly used radioisotope indicator of groundwater recharge. Tritium in precipitation has been measured in Australia over the past 40 years, as an essential research tool in hydro-climate studies and to contribute to the Global Network for Isotopes in Precipitation (GNIP). Tritium, which as tritiated water (3H 1H O) is very mobile in the environment, delivers the benefit of tracing groundwater systems in a 10 - 20 year timeframe as a result of last century's atmospheric thermonuclear testing. The concentration of tritium in Australian precipitation reached a maximum level of 160 TU in 1963, during one of the most intense periods of nuclear testing. Our data reveal Australia experienced a `minor' bomb pulse compared to the Northern Hemisphere eg. in Ottawa, Canada a value of 6000 TU was recorded in 1963 for tritium in precipitation. From 1963 to 1980 we observe a rapid drop in the concentration of tritium, more than expected from natural decay, mainly due to the wash out of tritium into the oceans and groundwater. Since 1990 the levels of tritium have stabilised globally and regionally. Currently the levels of tritium in Australia have stabilised to 2 to 3 TU latitudinally across the continent, a factor of 10 lower than values observed at stations in the Northern Hemisphere. At present, levels of tritium in Australia appear to have ceased declining and our analyses suggest that today the tritium in precipitation is predominantly natural. We believe that it may be possible that the increased levels observed in the Northern Hemisphere, due to nuclear power generation [1] could `leak' into the Southern Hemisphere. This is important for research in Australia because it could hinder the exploitation of tritium in providing information on the origin and mechanism of recharge of shallow groundwaters and rivers [2]. 1. J.D. Happell, et al. A history of atmospheric tritium gas (HT) 1950-2002. Tellus(2004) 56B, 183-193. 2. D.J.M. Stone, et al. Investigation of Groundwater-Streamflow interactions in the Bega alluvial aquifer using tritium and stable isotopic ratios. ANA 2001, 4th Conference on Nuclear Science and Engineering in Australasia, pp 191-197, Sydney, NSW.
DE: 1854 Precipitation (3354)
DE: 0365 Troposphere--composition and chemistry
DE: 0368 Troposphere--constituent transport and chemistry
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting