Seasonal and Spatial Distribution of Atmospheric Tritiated Water Vapor in Mainland China

Abstract

To reveal the distribution of atmospheric tritium water (HTO) vapor and provide a baseline for tritium pollution control, a subnational survey was conducted in mainland China. As the largest study on HTO vapor in China that has ever been formally reported, this study provides a macroimpression of the atmospheric HTO specific activity from March 2017 to March 2018. A total of 102 passive samplers were deployed at 34 sites in 30 provinces to determine the seasonal and spatial distributions of HTO vapor. In general, the HTO specific activity in the atmosphere ranged from lower than the minimum detectable activity (0.18 Bq·L–1) to 5.5 Bq·L–1. Spatially, the specific activity of HTO was positively correlated to the latitude and the distance to proximal coastline. Seasonally, significantly higher HTO specific activities were observed in spring and relatively lower in summer. Based on correlation analysis, the atmospheric HTO distributions were considered to be the consequence of combined factors of the stratospheric–tropospheric net mass flux, the distance from the tropopause to the ground, the fraction of air mass that originated from ocean re-evaporation and long-distance transport from high-latitude continents.

Levels and behavior of environmental tritium in East Asia

“…As indicated in Table 2, tritium in the atmosphere, precipitation, and water bodies was mainly measured in the form of HTO. This reflects both the importance of HTO and relative convenience of the HTO measurements [5,19,27]. For tritium in soil and living organisms, even though the measurements were relatively difficult and time-consuming, the data still accounted for 36% of the total in the vicinity of nuclear facilities.…”

“…To assess the large-scale and long-term effects of anthropogenic tritium release on the environment, surveys on atmospheric HTO have been conducted in areas without nuclear facilities for many years in both China and Japan. Figure 1 plots the pooled concentrations of atmospheric tritium [27, by latitude and distance from the proximal coastlines in China and Japan over the past three decades.…”

“…Consequently, East Asia is considered a region with high tritium emission densities both now and in the future. On the other hand, the extensive latitudinal and longitudinal spans and significant altitude differences induce differences in the natural sources of tritium distributed in East Asia [27]. Furthermore, the remarkable climatic differences resulting from such geographical differences can exacerbate the spatial and temporal variances in natural tritium profiles [27].…”

“…On the other hand, the extensive latitudinal and longitudinal spans and significant altitude differences induce differences in the natural sources of tritium distributed in East Asia [27]. Furthermore, the remarkable climatic differences resulting from such geographical differences can exacerbate the spatial and temporal variances in natural tritium profiles [27]. Therefore, East Asia is regarded as an ideal region for studies on tritium behavior.…”

Cryogenic vacuum extraction scarcely changes low-level tritium (3H) concentrations in free water extracted from environmental samples

“…Naturally produced 3 H occurs mainly because of the cosmogenic activities of nitrogen and oxygen in the upper layer of the atmosphere, resulting in the wide distribution of 3 H in environments without nuclear facilities. In terrestrial environments distant from nuclear facilities, seasonal variations in 3 H activity concentrations in environmental water (En-water), such as atmospheric, precipitation, and river water, are generally up to 1 Bq L −1 [5][6][7]. This suggests that minimum detectable activity concentration of at least within 1 Bq L −1 is necessary for precisely evaluating the contribution of nuclear facilities to environmental seasonal variation in 3 H concentrations.…”