United States tritium rainout and its hydrologie implications

Abstract

Tritium concentrations of precipitation, total rainout, and rainfall amounts for 1964 and 1965 are listed for 15 stations in the conterminous United States, Alaska, and Puerto Rico. These data show that the major increase in tritium rainout observed in 1963 was followed by • decline of about 27% in 1964 compared with 1963, and an additional decline of about 54% in 1965 compared with 1964. Rainout patterns are characterized by increases in tritium rainout with northern latitudes and with distance from the oceans. The total tritium rainout, being a function of both concentration and amount of precipitation, is more random than average tritium concentration. Seasonal, annual, and even ten-year tritium pulses have provided a valuable tag for tracing water in many kinds of hydrological and meteorological investigations. The tritium data now available make it possible to estimate the tritium input to the hydrologic environment at any part of the United States. (Key words: Radioactivity; precipitation; quality of water; tracers) STEWART AND FARNSWORTH To document tritium input to surface and ground waters, the U.S. Geological Survey established a network in 1958 for collecting and testing rainwater samples for tritium activity. Since about January 1963, the network has included 15 stations, collecting bi-weekly samples for tritium analysis. U.S. Geological Survey tritium data from 1958-1963 are published in reports by Thatcher [1962], Thatcher and Ho#man [1963], and Stewart and Ho#man [1966]. This report covers 1964-1965 tritium rainout data with some reference to earlier data for comparison purposes. The primary purpose of this report is to document tritium rainout data, to discuss general observations, and to point out important hydrologic implications. Subsequent reports will list tritium data for 20 United States rivers and will give more detail on the meteorological factors causing observed rainout patterns as well as trends ]ess general than those included here. THE NETWORK To provide bases for natural tritium input to the hydrologic systems of the Nation and yet hold the sample testing volume to a manageab!e level, stations were selected where they could be representative of a large segment of the surrounding country. Where possible, the stations were located in cities where U.S. Geological Survey personnel could collect the samples. In some cases, however, it was advantageous to locate the stations at regular U.S. Weather Bureau stations. The Washington, D.C., and Boston, Massachusetts, stations are operated by U.S. Weather Bureau personnel. Other stations, operated by the Geological Survey, include:

Distribution of tritium in precipitation and surface water in California

“…The tritium data are reported in picocuries per liter (pCi/L), a non-SI unit of radioactivity equivalent to 0.037 Becquerels per liter (Bq/L) or approximately 0.3125 TU (Stewart & Farnsworth, 1968 The water isotope data from the NGMS and LWIA were calculated by linear bestfit between the raw measurements and the known standards. The six values for each sample were then averaged.…”

“…The authors found that tritium content in precipitation generally increased with latitude and was higher at inland than coastal sites, even though coastal areas had a greater amount of rain. Within California, tritium was shown to generally increase inland, especially to the northeast (Stewart & Farnsworth, 1968). (Stewart & Farnsworth, 1968).…”

“…Within California, tritium was shown to generally increase inland, especially to the northeast (Stewart & Farnsworth, 1968). (Stewart & Farnsworth, 1968). Robert Michel, also of the USGS, performed a follow-up study to that of Stewart and Farnsworth in 1989.…”

Hydrology and geochemistry of thermal springs of the Appalachians

“…As figure (Stewart and Farnsworth, 1968;Stewart and Wyerman, 1970). The line may therefore be taken to represent the approximate tritium content of shallow, recently recharged ground waters at these latitudes.…”

Study and interpretation of the chemical characteristics of natural water

“…Concentrations of tritium in water can be determined, but extensive concentration and highly sensitive detection procedures are required, because the tritium concentration in normal rainwater is only about 10 tritium atoms per 1018 normal hydrogen atoms. Stewart and Farnsworth (1968) presented detailed data on tritium in rainfall in the United States in the period 1963-65. The half life of tritium is 12.3 years, and it can, therefore, be used as a means of determining how long a particular water may have been stored out of contact with fresh supplies of tritium.…”