EGU22-3270
https://doi.org/10.5194/egusphere-egu22-3270
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Microscale spatial variability of 7Be inventory at a reference site and its implications for soil erosion estimation

Zhonglin Shi, Yi Long, and Anbang Wen
Zhonglin Shi et al.
  • Institute of Mountain Hazards and Environment, CAS, Chengdu, China (shizl@imde.ac.cn)

Quantitative assessment of soil erosion and deposition rates using fallout radionuclides, including Beryllium-7 (7Be), requires reliable reference inventory, a crucial parameter in the conversion models. However, little information is currently available on the microscale spatial variabilities of 7Be inventory at reference locations, producing less confidence in the accuracy of the estimated soil redistribution rates with 7Be measurements.

To address this need, 44 soil cores were sampled extensively at 1 m intervals on a 5×12 m2 bare flat reference plot in each year of 2019 and 2021 in Southwestern China. Surface soil samples were collected using a stainless steel cylinder with an internal diameter of 10 cm and a height of 3 cm. The soils are purple soils characterised by a silt loam texture. 7Be activity concentrations in <2 mm particles were measured to explore potential variability of fallout inventory at the microscale within the reference area. To determine possible causes of 7Be variation in soils, physicochemical characteristics including organic matter content (OM), pH, cation exchange capacity (CEC) and grain size compositions were also analysed. 

In the case of 2019, 7Be mass activities in soil samples ranged from 2.5 to 10.9 Bq kg-1 and the areal activities ranged from 82.7 to 417.6 Bq m-2. The deposition of 7Be was higher in 2021, with mass activities ranged between 5.6 and 22.1 Bq kg-1 and the areal activities between 213.9 and 775.6 Bq m-2. The higher inventory of 7Be in 2021 (211.1 ± 66.2 Bq m-2, mean ± 1SD) than that of 2019 (456.1 ± 145.5 Bq m-2) can be explained by higher rainfall amounts of 384.0 mm in 2021 (January 1 - May 18) 2021, compared with 225.4 mm for 2019 (January 1 - May 15). The coefficient of variation (CV) analysis indicated that soil pH and CEC were the most stable properties at the study site with CVs ranged from 1.3 to 5.1%. In contrast, 7Be contents in soils, in terms of both mass and areal activities, exhibited almost the strongest variation with CVs around 30%. No significant correlations were noted between 7Be activities and the measured soil properties. The high degree of spatial viability in 7Be areal activities at the reference site indicates that the simple assumption of uniform distribution of 7Be across the reference site needs detailed examination. A spatially-integrated sampling design is recommended to improve the accuracy of reference inventory estimates and thus soil erosion assessment with 7Be technique.

How to cite: Shi, Z., Long, Y., and Wen, A.: Microscale spatial variability of 7Be inventory at a reference site and its implications for soil erosion estimation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3270, https://doi.org/10.5194/egusphere-egu22-3270, 2022.