Variations of ⁷Be concentration in plants and its significance for ⁷Be in soil on the Loess Plateau, China: Based on three-year monitoring data

Aims: With the wide application of ⁷Be (Beryllium-7) in soil erosion investigations, retention and interception of ⁷Be by vegetation plays an important role in documenting soil ⁷Be redistribution, with a large impact on the interpretation of ⁷Be measurements. However, the dynamic and temporal changes in plants and the relationship with soil ⁷Be concentration remain unclear, and the significance of dead plants in ⁷Be interception is under-researched. Methods: The samples of single plants (6 different species), compositive plants (including living and dead plants), along with soil reference on the Loess Plateau were collected individually to analyze the variations of ⁷Be concentration during the growth period from 2010 to 2012. Results: The accumulation of ⁷Be per mass is significantly higher in leaves than stems. The ⁷Be activity per mass and per area in living plants with seasonal trends ranged from 173.9 to 703.1 Bq kg^–1 and 21.5 to 190.1 Bq m^–2, respectively, and in dead plants ranged from 381.8 to 964.5 Bq kg^–1 and 30.4 to 285.7 Bq m^–2. Precipitation accounted for the largest contribution to the accumulation of ⁷Be in plants, followed by plant growth, species and parts. Plants accounted for ⁷Be interception on slope up to 66% (living plants accounted for 7% ~ 31% and dead plants accounted for 6% ~ 44%). The interception of living plants is low at first, then increases with the accumulation of rainfall and biomass together. Conclusions: Our results highlight that ⁷Be in plants (especially for the dead plants) is of great significance for ⁷Be in soil on the slope, and is controlled by precipitation, growth status and plant characteristics. The reference information obtained in this work will contribute to improving the accuracy of ⁷Be tracing technology, and broadening its scope.