Seasonal and spatial variations of tritium in precipitation in Northeast Asia (Korea) over the last 20 years

Abstract

Several studies have documented the characteristics of seasonal, decadal, and spatial variations of tritium in different regions including North America, Australia, and Europe. However, long-term data such as these studies were not yet reported for Northeast Asia. In this study, we document the extensive spatial-temporal monitoring data of tritium levels in precipitation measured at 16 stations in Korea over the last 20 years, including the long-term trend since 1961 by using measured and estimated data. The long-term variation of tritium concentrations in the Korean precipitation follows the global trend, reaching the maximum in 1963 owing to nuclear bomb testing, followed by a consistent level since the late 1990s. Tritium concentrations in precipitation from 1998 to 2017 were maximum in spring (April) due to tropopause folding and minimum in summer (July) due to the dominant inflows of marine air. The tritium concentrations in precipitation were lower toward the coastal stations, due to the influence of marine moisture for all seasons. Our results characterize the differences in tritium levels in groundwater recharging areas for different periods in this region. These results will serve as important tritium reference data for hydrology studies in Northeast Asia, which is an important region for understanding global hydrological cycles.