Isotope analysis

Overview

CSIRO's Land and Water team provides isotope, noble gas and trace gas analyses for hydrological and environmental purposes. We have an analytical facility for noble gases and radioactive noble gas isotopes. We provide special expertise in multi-tracer interpretation in groundwater hydrology.

Established in 1984, we undertake several thousand different analyses per year for over 100 customers in Australia and overseas.

The major strengths of our service include:

• the provision of quality analyses for over 25 years
• backed by Australia's premier scientific research organisation
• ongoing research and development of new analytical techniques
• only facility for noble gas measurements in water samples in the southern hemisphere
• reliable turnaround and support
• one-stop-shop for the coordination of other environmental tracers not available in-house
• collaboration with universities and Australian federal and state government departments.

Analyses provided

Noble Gas analyses

Noble gases are the most versatile natural tracers for surface and subsurface waters.

We operate the only facility in the southern hemisphere to measure noble gases in water samples. At present these comprise the light noble gases helium, neon and argon. A new facility to measure all noble gas concentrations (He, Ne, Ar, Kr, Xe) with higher accuracy and precision in fully automated mode was made operational in 2017.

Noble gas analyses can provide the infiltration conditions (temperature, pressure, salinity) of a groundwater sample at the time of recharge. They can indicate the amount of excess air that is trapped during infiltration at amounts indicative of the infiltration process (e.g. flood infiltration, infiltration through an unsaturated soil zone or riverbank infiltration).

They can also provide information on residence time of water in the subsurface (groundwater and aquitard pore water) by the accumulation of helium from the decay of naturally occurring uranium and thorium in the rock matrix.

²²²Rn and ²²⁶Ra analyses

²²²Rn and ²²⁶Ra form part of the decay chain for uranium bearing minerals. They are often found in higher concentrations in groundwater than in surface water because groundwater has more contact with uranium and radium bearing rocks than surface water. ²²²Rn and ²²⁶Ra can be used to identify areas of input of groundwater into streams and rivers.

We use the PET method (developed by CSIRO) which allows more accurate measurements of ²²²Rn and ²²⁶Ra concentrations in surface water samples. This method is often used in groundwater-surface water interaction studies.

Other analyses

We also serve as a one-stop shop for other analyses that we outsource to cooperating laboratories with the most reliable measurement techniques and a known record of quality control and quality assurance.

These services include:

• Analyses of the stable isotopes of water (¹⁸O and ²H) in water samples, plant material and soil. For groundwater we also provide analysis of the stable isotopes of nitrate (¹⁸O and ¹⁵N on NO₃) and sulfate (¹⁸O and ³⁴S on SO₄).
• Through our co-operators we also provide analysis of tritium (³H). Tritium is more reliable for characterising young groundwater.
• Through our collaborating laboratories we provide Accelerator Mass Spectrometric (AMS) analysis of ¹⁴C, ¹³C and ³⁶Cl to assess time scales of old groundwater.
• We can provide large volume gas sampling from groundwater, sample preparation to extract the Ar and Kr fraction, and through collaborating overseas laboratories also the analysis of the radioactive noble gas isotopes ⁸⁵Kr, ³⁹Ar and ⁸¹Kr. These provide the most reliable tracer system to assess time scales of decades, centuries and millions of years in groundwater.