摘要
7Be是由宇宙射线撞击同温层和对流层大气中氮、氧原子核而生成的天然放射性核素。由于连续沉降、半衰期短（53.3天）以及在土层中分布深度浅（约2 cm）等特点,7Be在示踪单次暴雨或短期强降雨等短时间尺度的侵蚀产沙空间分布研究中具有独特优势。随着气候变化加剧和暴雨等极端天气增多,7Be法应用前景广阔。然而该技术目前处于探索阶段,一些重要基础假设尚未得到有效验证,限制了其在土壤侵蚀研究中的广泛应用。简要回顾了利用7Be法定量土壤侵蚀速率空间分布的历史和现状,介绍了其示踪原理和计算模型及其最新进展;重点评述了7Be法估算土壤侵蚀速率的关键基础假设及其不确定性,以及植被截留、侵蚀分选等对7Be法评价土壤侵蚀速率的影响;并对未来研究趋势进行了展望,包括基础假设的验证及不确定性分析、植被影响的定量评价、示踪时空尺度的扩展以及新模型的开发等方面。
7Be is a naturally occurring cosmogenic radionuclide produced in the stratosphere and troposphere as a result of cosmic ray spallation of nitrogen and oxygen. The constant fallout via precipitation and short half-life （53.3 days）, coupled with shallow depth distribution in soil profile （ -2 cm） provide the unique advantages for its application as a soil and sediment tracer over short timescales, such as a single storm or short period of extreme rainfall. With the climate change and increasing rainfall events, the 7Be tracing method will exhibit wide applica- tion prospect in future. To date, however, this technique is still in its infancy and some important assumptions have not yet been effectively validated. Consequently, the use of 7Be to document soil erosion rates has been limited. This contribution briefly reviews the history and current status relating to this tracing method. In addition, the basic principles and recent research progresses in conversion models for use of 7Be measurements to estimate soil redistri- bution rates are introduced. The key assumptions and uncertainties of the technique, as well as the effects of the vegetation interception and particle size selectivity are discussed. Additionally, some new investigation directions are provided, including the assumption validation and uncertainty analysis, the impact of vegetation interception, the extending of spatial and temporal scales, and the development of new conversion models.
出处
《地球科学进展》
CAS
CSCD
北大核心
2016年第9期885-893,共9页
Advances in Earth Science
基金
国家自然科学基金项目"粒度效应对137Cs
7Be法测算紫色土农耕地土壤流失量的影响"(编号:41301293)
国家重点基础研究发展计划项目"横断山地水土作用失衡机制与灾害风险评价"(编号:2015CB452704)资助~~
关键词
7Be
土壤侵蚀
空间分布
植被截留
颗粒分选
7Be
Soil erosion
Sediment redistribution
Vegetation interception
Particle size selectivity.
