中国大陆Cs-137背景值研究

Study of the Cesium-137 Reference Inventory in the Mainland of China

土壤侵蚀是关系人类生存与可持续发展的重大环境问题。20世纪60年代以来,Cs-137作为一种人工放射性示踪核素,被广泛应用于土壤侵蚀及堆积研究。而准确估算区域Cs-137背景值（Cs-137 Reference Inventory,CRI）是应用Cs-137开展土壤侵蚀研究的前提条件,其结果直接影响土壤侵蚀速率结果的准确性和可靠性。基于现有文献资料中获取的中国大陆102个CRI实测数据,以及全球降水气候中心提供的降水量再分析资料（空间分辨率2.5°×2.5°、0.5°×0.5°,1981-2010年）,在借鉴Walling＆He模型（Walling＆He Model,WHM）和Michio Aoyama模型（Michio Aoyama Model,MAM）的基础上,本文建立了中国大陆CRI修正模型（Modified CRI Model for the Mainland of China,MCM）,并利用Kriging/Cokriging插值方法计算了中国大陆CRI的空间分布。模型评估与对比分析表明,MCM模拟值与实测值大致吻合,且总体高于WHM和MAM模拟值,MCM能对中国大陆CRI进行较高分辨率、较高精度的模拟。模拟结果显示,中国大陆CRI的范围为141~12123 Bq/m^2,在东北及新疆局部地区达到最大值,最小值主要集中于25°N以南地带。除新疆局部地区外,中国大陆CRI分布整体呈现自西向东,同纬度地区随降水量增加而增加的特点,而纬向上主要呈现随纬度增加而增加的特点。此外,大尺度大气流场、再悬浮过程、局部核试验等因素增加了中国大陆CRI分布的不均匀性。

Soil erosion is a serious environmental problem closely associated with sustainable development and ultimately the survival of mankind. Cesium-137, a unique artificial radioactive tracer, has been widely applied to the study of soil erosion and deposition since the 1960s. Furthermore, it is a basis for determining a Cesium-137 Reference Inventory （CRI） that employs cesium-137 to measure soil erosion, which can directly influence the accuracy and reliability of the soil erosion rate. This paper references 102 CRI data samples collected from over 80 documents; it also uses the monthly precipitation dataset from the Global Precipitation Climatology Centre from 1981-2010, with spatial resolutions of 2.5°×2.5° and 0.5°×0.5°. The Modified CRI Model for the Mainland of China （MCM） that the paper established is based on incorporating and modifying two previous models, the Walling ＆ He Model （WHM） and the Michio Aoyama Model （MAM）. Then we calculate the geographical distributions of CRI by using Kriging/Cokriging interpolation. The model assessment and comparative analysis demonstrate that MCM simulated values are generally in agreement with the observed values and greater than WHM and MAM simulated values. MCM can be applied to higher resolution and higher precision CRI modeling in the Mainland of China. The results show that the range of CRI in the Mainland of China is between 141 and 12123 Bq/m^2 and the maximum values are found in parts of northeast China and Xinjiang regions. The minimum values generally come from the regions south of 25°N. Except for some parts of Xinjiang, distributions of CRI in the Mainland of China indicate that CRI increases with precipitation from west to east of the same latitude, while zonal distributions of CRI indicate that CRI increases with the increase of the latitude. Besides, other factors such as large-scale atmospheric flow field, re-suspension, and local nuclear testing contribute to the heterogeneity of CRI in the Mainland of China.