@article{oai:tsukuba.repo.nii.ac.jp:00025864, author = {戸崎, 裕貴 and 田瀬, 則雄 and 笹, 公和 and Tosaki, Yuki and Tase, Norio and Sasa, Kimikazu and Takahashi, Tsutomu and Nagashima, Yasuo}, journal = {Journal of environmental radioactivity}, month = {Apr}, note = {Essential parameters for the applications of 36Cl as a tracer in groundwater studies include the initial 36Cl/Cl ratio, at the time of recharge, and/or the natural background deposition flux of 36Cl in the recharge area. To facilitate the hydrological use of 36Cl in central Japan, this study aimed to obtain a precise estimate of the long-term average local 36Cl flux and to characterize its seasonal variability. The 36Cl in precipitation was continuously monitored in Tsukuba, central Japan over a period of >5 years. The 36Cl flux showed a clear seasonal variation with an annual peak during the spring, which was attributed to the seasonal variability of tropopause height. The long-term average 36Cl flux (32 ± 2 atoms m−2 s−1), estimated from the measured data, was consistent with the prediction from the 36Cl latitudinal fallout model scaled using the global mean production rate of 20 atoms m−2 s−1. The initial 36Cl/Cl ratio was estimated to be (41 ± 6) × 10−15, which is similar to that of pre-bomb groundwater in the Tsukuba Upland. An observation period covering an 11-year solar cycle would yield more accurate estimates of the values, given the increased 36Cl flux during the solar minimum.}, pages = {73--80}, title = {Measurement of the 36Cl deposition flux in central Japan: natural background levels and seasonal variability}, volume = {106}, year = {2012} }