ISMC2021-33
https://doi.org/10.5194/ismc2021-33
3rd ISMC Conference ─ Advances in Modeling Soil Systems
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Tracer vertical movement and its affecting factors in karst soil profiles using the simulated leaching method

Jianghu He, Keli Zhang, Zihao Cao, and Qihua Ke
Jianghu He et al.
  • State Key Laboratory of Earth Surface Processes and Resources Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China (keli@bnu.edu.cn)

Soil erosion is a severe issue in Southwest China due to complex karst geomorphology and excessive farming activities. It is also difficult to observe and evaluate using traditional research methods. Fortunately, as a supplement to traditional methods, the 137Cs tracing technique has strong potential to monitor and evaluate soil loss in karst regions. However, 137Cs might move downward with tiny particles under adequate rainfall conditions. This is critical because it directly affects accuracy of using the 137Cs conversion model to evaluate soil erosion. Thus, in our study, in order to explore whether tracers actually moved vertically and to evaluate the movement distance and the factors influencing the movement, magnetic powder (Fe3O4) and rare earth oxides (CeO2 and La2O3) were used as the substitute tracers under different conditions (rainfall and leaching area) of a simulated leaching experiment, which possess similar properties as 137Cs and have no toxicity problems in humans and the environment. The results showed that tracers moved downward 6 cm when water was added to simulate 1-10-year rainfall conditions and 8 cm when water was added to simulate 15-20-year rainfall conditions. The movement distance of tracers increased slowly with increasing water input, and the concentration of the tracers that moved related indirectly to the leaching area. Tracer movement at the edge of the simulated profile was affected by tracer type and concentration since there was no transition layer between soil and plastic column. Our field observations in two karst watersheds showed that ignoring the vertical movement of tracer can cause the overestimation of soil loss amount by 6.90% and 22.22% respectively. This study proved that in the karst area of Southwest China with abundant rainfall, 137Cs would move vertically, and the soil loss will be overestimated if the vertical movement distance of the tracer is ignored.

How to cite: He, J., Zhang, K., Cao, Z., and Ke, Q.: Tracer vertical movement and its affecting factors in karst soil profiles using the simulated leaching method, 3rd ISMC Conference ─ Advances in Modeling Soil Systems, online, 18–22 May 2021, ISMC2021-33, https://doi.org/10.5194/ismc2021-33, 2021.