The relationship between the atmospheric concentration of cosmogenic isotopes, the change of solar activity and hence secondary neutron flux has already been proven. The temporal atmospheric variation of the most studied cosmogenic isotopes shows a significant anti-correlation with solar cycles. However, since artificial tritium input to the atmosphere due to nuclear-weapon tests masked the expected variations of tritium production rate by three orders of magnitude, the natural variation of tritium in meteoric precipitation has not previously been detected. For the first time, we provide clear evidence of the positive correlation between the tritium concentration of meteoric precipitation and neutron flux modulated by solar magnetic activity. We found trends in tritium time series for numerous locations worldwide which are similar to the variation of secondary neutron flux and sun spot numbers. This variability appears to have similar periodicities to that of solar cycle. Frequency analysis, cross correlation analysis, continuous and cross wavelet analysis provide mathematical evidence that the correlation between solar cycle and meteoric tritium does exist. Our results demonstrate that the response of tritium variation in precipitation to the solar cycle can be used to help us understand its role in the water cycle.

Dear Editor,Using an ultrapure 4 He spike in tritium measurements of environmental water samples by the 3 He-ingrowth method The tritium ( 3 H or T, half-life 12.32 years 1 ) concentrations of environmental water samples have already decreased below the level that can be accurately measured by conventional liquid scintillation or proportional counting techniques, even if electrolytic enrichment is used prior to the measurements. [2][3][4] In addition, when the precipitation infiltrates under the soil or ocean surface, the tritium concentration starts to decrease due to radioactive decay. Therefore, tritium concentrations of less than 0.5-1 TU (1 TU corresponds to a 3 H/ 1 H ratio of 10 À18 ) can hardly be measured by counting.He spike aliquots were admitted into the mass spectrometer (note that the uncertainty of the parameters of the exponential function is better than the last digits). The different components of the measured 4 He, i.e. 4 He blank and 4 He spike , have to be determined: the 4 He spike is calculated from the exponential curve, while the blank can be obtained as the difference between 4 He meas and 4 He spike . Figure 6. The results and the IAEA reference values of the TRIC-2008 tritium samples with 1s uncertainties.

This paper describes the procedure followed for noble gas measurements for litres, millilitres and microlitres of water samples in our laboratory, including sample preparation, mass spectrometric measurement procedure, and the complete calibrations. The preparation line extracts dissolved gases from water samples of volumes of 0.2 μ l to 3 l and it separates them as noble and other chemically active gases. Our compact system handles the following measurements: (i) determination of tritium concentration of environmental water samples by the (3)He ingrowth method; (ii) noble gas measurements from surface water and groundwater; and (iii) noble gas measurements from fluid inclusions of solid geological archives (e.g. speleothems). As a result, the tritium measurements have a detection limit of 0.012 TU, and the expectation value (between 1 and 20 TU) is within 0.2 % of the real concentrations with a standard deviation of 2.4 %. The reproducibility of noble gas measurements for water samples of 20-40 ml allows us to determine solubility temperatures by an uncertainty better than 0.5 °C. Moreover, noble gas measurements for tiny water amounts (in the microlitre range) show that the results of the performed calibration measurements for most noble gas isotopes occur with a deviation of less than 2 %. Theoretically, these precisions for noble gas concentrations obtained from measurements of waters samples of a few microlitres allow us to determine noble gas temperatures by an uncertainty of less than 1 °C. Here, we present the first noble gas measurements of tiny amounts of artificial water samples prepared under laboratory conditions.

No abstract