全国土壤中天然放射性核素含量调查研究(1983—1990年)

INVESTIGATION OF NATURAL RADIONUCLIDE CONTENTS IN SOIL IN CHINA

中国土壤中天然放射性核素含量调查(1983—1990年)是中国环境天然放射性水平调查研究的一部分。本文作为分报告之一,系根据全国29个省、市、自治区(不包括台湾省,海南省包括在广东省内)的调查结果整理编写而成,主要报告这项调查的方法和结果。本调查在全国按均匀网格布点,并区分不同成土母岩母质、土壤类型进行加密布点,在天然γ辐射剂量率局部异常地区以及部分核企业和放射性伴生矿等对环境可能产生放射性污染的地区,也作了加密布点。本调查布点区域复盖面积约占全国总面积的80%。采样点基本与陆地γ辐射剂量率测点同位布设,土壤采样与陆地γ辐射剂量率测量同步进行。全国共采集土壤样品13866份;分析测量了11216份,其中网格点样品9114个,加密点样品2102个。本报告主要结果由7777个25×25和50×50 km 的基本网格点分析数据统计得到。本调查主要结果如下:(1)全国土壤中天然放射性核素^(238)U、^(226)Ra、^(232)Th、^(40)K 含量按面积加权平均值(±单次测量标准差)分别为39.5(±34.4)、36.5(±22.0)、49.1(±27.6)、580.0(±202.0)Bq·kg^(-1),范围值分别为1.8—520.0、2.4—425.8、1.0—437.8、11.5—2185.2 Bq·kg^(-1)。(2)土壤中天然放射性核素含量与成土母岩母质类型明显相关。由1552个不同成土母岩?

The survey of natural radionuclide contents in soil in China（1983—1990）is a part of in-vestigation of environmental natural radioactivity level on China.This paper,as one of the sub-report,is writtern based on the investigation results for 29 provinces,cities and autonomous regions（Taiwaiprovince is not included,Hainan province is included in Guangdong province）,which mainly reportsthe investigation methods and results.The monitoring points were uniformly set up by net-checking method and were also added on thebasis of different soil-forming parent rock and material and the type of soil.The added points were alsoset up in following areas:the areas in which the natural γ radiation dose rate is locally abnormal andparts of nuclear facilitres and associated radioactive mines which might result in radioactive contamina-tion to environment.The area cover by this investigation amounts for some 80% of total area of Chi-na.The sampling points were selected as the same points as that for measuring terrestrial γ radiationlevel. The soil sampling was simultaneously carried out as terrestrial γ radiation level measurement.13866 soil samples were collected and 11216 samples measured,of which 9114 were net-checkingsamples,2102 additional ones.The main results of this report were obtained through analysis andstatistics for 7777 basic net-checking with 25×25 and 50×50 km.The investigation has more com-plete quality assurance system.The strict quality assurance measures were adopted during whole processof investigation.The results of the investigation are as follows:（1）The average content of natural radionuclides 238U,226Ra,232Th and 40K（area weighted）andits standard deviation for single measurement is 39.5 and 34.4,36.5 and 22.0,49.1 and27.6,580.0 and 202.0 Bq·kg-1within the range of（1.8—520.0）,（2.4—425.8）,（1.0—437.8）,（11.5—2185.2）Bq·kg-1,respectively.（2）The content of natural radionuclides is apparently correlated to the types of soil-formingrock.The analysis results from 1552 soil samples of soil-forming rock show that:the con-tent of 238U,226Ra,232Th and 40K for magmatic rock type is the highest,238U,226Ra and232Th of metamorphic rock type higher,sedimentary rock type the lowest.However,thecontent of 40K of sedimentary rock type is more higher,magmatic rock type the lowest,inmagmatic rock type,the content of 238U,226Ra,232Th of granite and acidic magmatic rocktype,and the content of 40K of acidic and alkaline magmatic rock type is higher.（3）The analysis results from 9613 various types of soil samples show that for crimson soil offerralsol wind soil of rock soil-forming order at northern part is lower.For frigid dessert soil of alpine soil order,alpine dessert soil,and the burozem,dark burozem and drab soil ofalfisol order and semialfisol order,the content of 40K is shown to be higher,and it is lowerfor latosol of ferralsol order,crimson soil,yellow soil and various lime soil.（4）The geographical distribution of the matural radionuclide content in soil appears apparentlyregional.For 238U,226Ra and 232Th,their content at south part of China is higher than thenorth part.The content of 40K is shown to be lower in the south and higher in the north ateast part of China,it is almost not changed in middle of China and is shown to be higher inthe south and lower in the north of western China.