Argon-39 (39Ar) is necessary for studying fresh water resources. With its half-life of 269 years, it allows determining travel times of 100-2000 years. Measurement of argon, including 39Ar, dissolving from the air to the water is reasonably difficult (and expensive). It is not a routine procedure even in developed countries, and is limited to 3-4 well equipped laboratories in the world. Therefore, our aim is to carry out developments given below.

1. A routine 39Ar sampling method including a sampling device for extracting 60 litres gas (with 1% Ar content) from 1-3 m³ water within 1-2 hours in case of ideal flow rate (50-60 litres/h).
2. A routine separation method allowing separation of argon from 100 litres dissolved gas.

These developments allow us to measure dissolved krypton-85 as well, owing to the similar sampling and sample preparation. The main innovation is the argon separator, which is krypton separator at the same time. Since half-life of 85Kr is 10 years and its atmospheric concentration has been continuously increasing since the 1950’s, it supports the independent dating of young waters. Its measurement is difficult but combining the above mentioned methods, it is possible to give a detailed description of water resources.