氡填图中土壤氡测量与氡潜势分类方法研究

In order to reduce the risk of lung cancer to the public due to exposure of radon and its daughters and to decrease the disease burden of the national medical insurance, many developed countries have drawn up the geogenic radon potential maps. Radon hazard can be identified using radon potential mapping and/or site investigation. Indoor radon concentration could be decreased to the Action Level (200 Bq/m3) by radon protection and treatment. Radon potential mapping in China is still in its infancy stage. The soil radon concentration is a key parameter in radon potential mapping, and the accuracy of measured data is premise to ensure the radon potential classification reliable..Aiming at the problems of sampling device being sealed and larger deviation from the measurement accuracy, researches will be systematically carried out from sampling device, instrument calibration, and the measuring procedures. Meanwhile, the distribution of Rn-220 and its interference to the determination of radon concentration in soil gas will be studied. After that, techniques for soil radon measurements will be improved greatly. . Based on the researches on the characteristics and distributions of geogenic radon potential in the typical Yanshanian granite areas in southern China (Shenzhen City, Guangdong), using the Bayesian theory and methods, we will focus on the integration of point data (soil radon concentration, soil uranium content) and polygons and lines (lithology, structure and geological units), multivariate modeling of geogenic radon, as well as classification approach of radon potential based on the GIS environment. This research will provide effective methods and techniques for geogenic radon mapping in a large scale in China.

为降低氡及其子体导致公众患肺癌的几率，降低国家医疗保障的疾病负担，许多发达国家都编制了氡潜势图。氡灾害可通过氡潜势图或场所调查确定，通过氡的防护与治理，可将室内氡降低到行动水平以下。我国氡潜势填图工作尚处于刚刚起步阶段。土壤氡浓度是氡潜势填图中的关键参数，测量结果的准确性是保证氡潜势分类可靠的前提。针对我国目前土壤氡测量中采样系统不够密封和测量准确度存在较大误差的问题，从采样装置、仪器校准到现场测量开展系统研究。同时研究土壤钍射气的分布规律及其对土壤氡测量结果的影响，全面提升我国的土壤氡测量技术水平。通过研究中国南方（广东深圳市）典型燕山期花岗岩地区氡地质潜势特征及分布规律，采用贝叶斯理论和方法，研究基于GIS环境下点数据（土壤氡浓度、铀含量等）与线和面积数据（岩性、构造等地质资料）整合与集成方法及氡潜势分类数学模型。建立氡潜势图分类方法，为我国大面积开展氡地质潜势填图提供有效方法技术。

为降低氡及其子体导致公众患肺癌的几率，降低国家医疗保障的疾病负担，许多发达国家都编制了氡潜势图，以圈定氡灾害或氡风险高潜势地区。我国氡潜势填图工作起步较晚，至今尚没有编制全国的氡潜势图。.开展了野外对比实验，包括型连续测氡仪和不同土壤气体采样装置及取气探管对测量结果准确性及测量效率影响,以及不同类型测氡仪之间与国外校准测氡仪的现场对比测量。发现不同的土壤气体采样装置和取气探管密封程度土壤氡测量结果准确性影响很大。取气探管直径越大，测量结果的不确定度越大。综合考虑野外工作效率及地表以下土壤层分布情况得出土壤氡测量深度以地下80 cm为宜。仪器校准和现场采样是关键技术环节。在广东深圳实施了面积性土壤氡-220浓度测量，基本了解了土壤氡-220浓度平面和垂直方向的变化规律，为中国南方地区氡潜势填图中增加新的评价参数提供了参考数据。.在广东深圳实施了土壤氡浓度、土壤气体渗透率、土壤氡析出率和地面伽马能谱测量的联合观测, 面积约1800km2，查明了深圳不同岩石和不同土壤中放射性核素钾、铀和钍的活度浓度以及土壤氡浓度水平。我们还调查了深圳地表水、地下水中氡浓度。结果发现梧桐山地表水和马峦山郊野公园水样中氡浓度超过了美国环保署规定的上限值（11 Bq/L）。.采用氡潜势指数法编制了广东中山和广东深圳氡潜势图, 其中风化花岗岩是高氡潜势地质单元，而砂岩、火山岩为低氡潜势地质单元。.此外，我们在国内创新性开展了多元贝叶斯概率统计氡潜势分类方法的研究。建立并完善了低本底、可有效消除土壤湿度和钍射气影响的实验室土壤样品氡析出率测量方法，为有效地解决野外现场测量耗时长、工作量大、土壤湿度影响等问题提供了新的方法技术。.综上，土壤氡测量方法研究对规范我国土壤氡测量的程序和方法提供了技术依据。广东中山市和深圳氡潜势填图为我国开展大面积氡填图提供了应用范例。