THE DETERMINATION OF TRITIUM IN NATURAL WATERS

Abstract

A study of the tritium content of rain- and sea-water samples collected during the past several years has been made. The tritium in 100–2000 gm. samples was concentrated 2000 to 20000 fold by electrolysis and the final concentrate counted as hydrogen in a Geiger counter. Good counter characteristics were obtained at hydrogen pressures up to one atmosphere by the use of an electronic quench unit of suitable deadtime in addition to the internal quench gas, ethylene. Rain and snow samples collected at Ottawa over the period 1951–1953 were found to range from 17.1 to 42.0 tritium atoms per 1018 hydrogen atoms, averaging 26.6. Tritium values for Ottawa rain-water for 1954 showed marked effects of the thermonuclear tests in the Pacific in the spring of that year, rising 10 to 100 fold during the test period, then gradually returning to normal, demonstrating a half time for washout of 35 days. The average tritium concentration of the year’s rain is estimated to be 260 × 10−18 T/H. Surface sea-water samples collected at widely separated sites in the latter half of 1954 and early 1955 showed tritium concentrations in the range 3.0–4.2 × 10−18 T/H, a value which corresponds with the amount of artificially produced tritium observed in Ottawa rain. Subsurface samples collected at one station off the coast of Nova Scotia in mid-1955 showed an unexpected concentration level and pattern, having a T/H value of 32.4 × 10−18 at the bottom depth of 600 ft., diminishing to a value of 5.4 × 10−18 at the surface. This is not thought to be a result of thermonuclear testing and warrants further investigation.