The nature and extent of bomb tritium remaining in deep soils

<p>Understanding the movement of water in soils is important for estimating subsurface water reserves. Despite the advances made in understanding water movement, very few tools can directly ‘follow the water’. Tritium, a tracer that decays with time and resides within individual water molecules, is one such tool. Some tritium is produced naturally, others result from the nuclear bomb test era of the 1960s. Since the atmospheric nuclear tests ended following the Partial Nuclear Test Ban Treaty in 1963, however, the amount of tritium in soil water has declined, putting into question the usefulness of the environmental tritium method for tracking water movement in future studies. Our study explores the usefulness of the tritium method. Our results highlight the narrow window of time, over the next 20 years depending on the model used, within which the tritium method may still be applicable. We call on scientists to now take full advantage of the environmental tritium method in places where the tool may still be applicable. A richer understanding of water movement in soils is ultimately critical for ecosystem services and water resources management, particularly in semi-arid environments with deep soils.</p>

Contribution of Isotopic Techniques in the Hydrological Study of the Aquifers of Ica, Villacuri and Lanchas

Ica Aquifer located at the coastal zone of Ica River Valley, supplies 40% of the water to a number of farms of Ica Region which is one of the most productive valley of Peru that covers an area of 30,000 hectares of area, in which a diverse agricultural product are grown for local and external market. In the last 15 years, water-table of the aquifer was lowering at an elevated rate that concerned to farmers and authorities of the Peruvian Government, so a number of studies was carried out to increase the water supply to the agriculture areas.The main purpose of the study using isotope techniques, was to have a first insight of the hydrodynamics of Ica, Villacuri and Lanchas Aquifers and the possible interconnection between them and with Pisco River. For such purpose, 31 wells, lakes, rivers and springs of Ica and Pisco Basin where sampled during the years 2014 to 2016 both in rain and dry seasons, getting 189 samples for isotope and chemical analysis. The sampling schedule didn’t include rain sampling, instead of it, selected springs were sampled and nearby basin rain data was used.18O,2H and 13C stable isotopes and 3H, 14C radioactive isotopes of the water samples were analyzed in the laboratory of “Isotope Tracer Technologies INC”; the results of the stable isotope analysis confirm the hydraulic interconnection of the three aquifers mentioned above; it also was confirmed that the main source of recharge was provided by Ica River and evidences were found about the contribution of Pisco River in the recharge of Villacuri and Lanchas Aquifers.Analysis of 14C reveals that some wells are overexploited. All the results of 3H analysis were out of range, so it was not useful for the conclusions of the study, and a new sampling of water is required; the reason of this out of range result should be the possible contamination of the samples with no environmental Tritium.

ENVIRONMENTAL TRITIUM AROUND A FUSION TEST FACILITY

Deuterium plasma operations using a large fusion test device have been carried out since 2017 at the National Institute for Fusion Science. A small amount of tritium was produced by the fusion reaction, d(d, p)t. Then, a part of the tritium was released into the environment. Thus, monitoring the level of tritium in the environment around the fusion test facility is important. This is done before starting the deuterium plasma experiment. The environmental tritium concentrations indicated that they are at background levels in Japan. After starting the deuterium plasma experiment, the environmental tritium around the fusion test facility was within the range of environmental variation. This suggests that there was no impact of tritium on the environment during the first deuterium plasma experimental campaign.