Cosmogenic radionuclide 22Na in the Lake Biwa system (Japan): residence time, transport and application to the hydrology

The Effect of Land Use on Availability of Japanese Freshwater Resources and Its Significance for Water Footprinting

“…Considering the above, the availability of groundwater recharge and surface flow is obviously different. Even though the range of residence time in groundwater and lakes is wide because of site specific conditions, the results of previous studies support that residence time in groundwater and lakes is generally longer than one year in Japan [20][21][22]. Given the temporal resolution of the present study (one year), freshwater in groundwater and surface flow discharge into lakes has sufficiently long residence times for availability within one year.…”

Cosmogenic 22Na as an index of the residence time of water in freshwater basins: a review

“…For the past two decades, only cosmogenic 22 Na has been present in freshwater basins, and its concentrations are stationary in the limits of natural variations. According to the published data, during this steady-state period the cosmogenic 22 Na has been used in the hydrological studies of the largest lake of Europe, Lake Ladoga (Blinov et al, 2003; and of the largest lake of Japan, Lake Biwa (Ohtsuka et al, 2002;Sakaguchi et al, 2005).…”

“…Unfortunately, in the modern textbooks on the use of environmental radionuclides in hydrology (e.g., Aggarwal et al, 2005;Kazemi et al, 2006;Kendall and McDonnell, 1998;Mook, 2001), 22 Na is not mentioned even as a potential marker for dating freshwaters although Kazemi et al (2006, p. 16) cited, without mention of 22 Na, the paper of Sakaguchi et al (2005) where cosmogenic 22 Na was applied for the determination of the residence time of water in the Lake Biwa system in Japan.…”

Opportunities for Decay Counting of Environmental Radioisotopes Using Ultra-low-background Detection Systems

“…Next, studies from the 1980s demonstrated that the bomb produced 22 Na, consistent with predictions, had decayed significantly below the cosmogenic concentration by the mid 1980s. Since the steady state cosmogenic level has been reached, a number of papers reported 22 Na dating including results for young water from the largest lake in Europe, Lake Ladoga, as well as for the largest lake in Japan, Lake Biwa (Sakaguchi, Ohtsuka et al 2005). Most recently, results have been reported for waters in the Caucasus Mountains (Nevinskii, Tsvetkova et al 2004) and for ground water from Daisen Volcano, Japan (Inoue and Komura 2007).…”

“…To begin, we calculate the counting time for a sodium sample obtained from a 500 L volume of water with a 22 Na concentration of 30 µBq/L[H 2 O] characteristic of the values recently measured in the Lake Biwa system (Sakaguchi, Ohtsuka et al 2005). We define the counting time as the time required to measure the sample concentration with 10% precision.…”