大气成因放射性宇生核素^(10)Be指示土壤演化:机理与进展

Meteoric Cosmogenic Radionuclide ^(10)Be Trace the Soil Evolution:Mechanism and Progress

在全球变化背景下,我国土壤面临严重的污染、侵蚀和退化问题,正在威胁生态系统稳定性和粮食安全性。如何量化土壤的形成演化(时间和速率等)是地球科学领域的重要科学问题。大气成因放射性宇生核素^(10)Be(以下简称大气^(10)Be)是天然示踪剂,其在土壤中的含量受成土时间、地表侵蚀和化学风化等土壤演化过程综合控制,是定量示踪千万年来土壤形成演化过程的有效手段,具有广阔的应用前景。首先系统梳理了^(10)Be在地球大气层的生成、传输、沉降以及在土壤中累积和迁移过程的最新研究进展,指出大气^(10)Be长期沉降速率及其在风化带中迁移性的精确估算,是该研究领域亟待解决的重要难题;其次评述了大气^(10)Be用于估算成土时间、成土速率、指示土壤侵蚀及在坡地运移等方面的方法,提出深入调查区域地质和环境过程并对模型参数和结果进行合理约束,是应用大气^(10)Be技术的关键前提。我国加速器质谱分析技术和能力的快速发展,将有力推动大气^(10)Be技术在土壤演化定量研究中的广泛应用,帮助解决环境生态系统演变预测及耕地土壤保育等难题。

Soil is currently facing serious pollution,erosion,and degradation owing to global change,threatening the ecosystem stability and food security of China.Quantifying soil formation and evolution(time,rate,etc.)is a critical scientific issue in Earth sciences.Meteoric radioactive isotope ^(10)Be(hereinafter referred to as meteoric ^(10)Be)serves as a natural tracer,and its inventory in soil is controlled by soil age,surface erosion,and chemical weathering processes.Therefore,meteoric ^(10)Be is an effective tool for quantitatively tracing soil formation and evolution over ten million years and has broad application prospects.First,this study summarizes and reviews the latest progress in the production,delivery,and deposition of meteoric ^(10)Be in the Earth atmosphere,as well as its accumulation and migration in the soil profile.Reasonable estimation of the long-term deposition rate of meteoric ^(10)Be and its migration to weathering zones are important challenges that urgently require resolution.Second,this study introduces the main methods used by meteoric ^(10)Be to estimate the soil formation(residence)age and formation rate,indicating soil erosion and transportation on hill slopes.The key premise for applying meteoric ^(10)Be technology is an understanding of the geological and environmental processes in the study area and a rational assessment of the calculation model.With the rapid development of accelerator mass spectrometry analysis capabilities in China,the widespread application of meteoric ^(10)Be technology in quantitative research on soil evolution has helped solve problems such as predicting environmental ecosystem evolution and soil conservation on arable land.