The Researching For Natural γ Radiation Field Of Chengdu Plain’s Air-ground Interface

The radiation source around the ray species, with a range of differences betweenthe different sizes rays affect the space, called the radiation field. Various physicalfield, the γ radiation field is the electromagnetic field composed by a number ofmoving photons, particle movement as the main feature. Study of the regional naturalconditions, topography, soil distribution and geological characteristics as the researchfoundation, through to the natural radioactive gamma ray source analysis, usinggamma radiation field basic theory, studies the natural radioactive series of gammaenergy spectrum characteristics and natural gamma radiation field measurementprinciple, has established the air-ground interface geological body gamma radiationfield mathematical model; the use of natural radionuclides in the soil of uranium,thorium, potassium content data to calculate the corresponding environmentalradiation effect evaluation parameters, evaluation in the study area the air-groundinterface natural gamma radiation field and the basic characteristics of the radiationenvironment.The conclusions of the paper is as follows：1. In the studied area, the content of238U is0.94⁶.87×10^-6g/g, the average valueis2.559×10^-6g/g, the mean square deviation is0.596×10^-6g/g;238U content basically in4.645×10^-6g/g, only a few, very small area is higher than4.645×10^-6g/g; the uraniumcontent in interval3.155×10^-6g/g⁴.645×10^-6g/g,2.410×10^-6g/g³.155×10^-6g/g andthe following2.410×10^-6g/g each accounted for about1/3;Specific activity of238Uvalue is11.61⁸4.84Bq/Kg, average value is31.599Bq/Kg, variance is7.357Bq/Kg;specific activity of238U in the study area are basically in the66.65Bq/Kg below, onlya very few, very small area is higher than75.83Bq/Kg;238U activity in48.30Bq/Kgbelow the region accounted for about4/5; specific activity of238U mean value is lowerthan the national average; 2. In the studied area, the content of232Th is4.57³1.10×10^-6g/g, the averagevalue is14.008×10^-6g/g, the mean square deviation is3.819×10^-6g/g;232Th contentbasically in24.45×10^-6g/g below; wherein the thorium content in the interval14.48×10^-6g/g²4.45×10^-6g/g and14.48×10^-6g/g data about each half.Specific activity of232Th value is18.56¹26.27Bq/Kg, the average value is56.873Bq/Kg, the meansquare is15.504Bq/Kg.Specific activity of232Th generally in the86.00Bq/Kg below,only a very few, very small area is higher than that of86.00Bq/Kg;232Th activity in59.00Bq/Kg above the region accounted for about2/5, is less than45.5Bq/Kg regionaccounted for about1/5;232Th BQ average and the average level of the whole nationbasically the same;3. In the studied area, the content of40K is0.96⁴.07×10^-2g/g, the average valueis2.108×10^-2g/g, the mean square deviation is0.448×10^-2g/g;40K content basically in2.904×10^-2g/g below; in addition to a small part area values in the interval2.904×10^-2g/g⁴.07×10^-2g/g, the rest of the region, potassium content in the2.904×10^-2g/g below.The Specific activity of40K value is300.48¹273.91Bq/Kg,theaverage value is659.845Bq/Kg, mean square deviation is140.146Bq/Kg;the specificactivity of40K generally in the1031.00Bq/Kg below, in which specific activity of40Kin543.80Bq/Kg following the region accounted for about1/5.The Specific activity of40K average value slightly higher than the national average; Combined with thegeological conditions, Chengdu Plain potassium activity is slightly higher than thenational average may be the cause of Chengdu Plain in eastern Longquan mountaintectonic fracture zone and Pujiang Xinjin fracture zone in the sediments of theinfluence result, also has the possibility is the Chengdu Plain developed surface watersystem makes the Chengdu Plain has an area of extensive of potassium content inhigh river flows through the valley quaternary alluvial and diluvial deposits of clayand humus clay layer;4. In the studied area,the air-ground interface gamma-ray exposure rate is11.87³9.84×10^-4C/（Kg.s）, the average value is22.850×10^-4C/（Kg.s）, the mean squaredeviation is3.870×10^-4C/（Kg.s）; the air-ground interfacethe of the study area,gamma-ray exposure rate basically in20×10^-4C/（Kg.s） to35×10^-4C/（Kg.s）, normaldistribution;5. In the studied area, the air gamma absorbed dose rate range from41.10nGy/h¹40.74nGy/h, the average value is79.516nGy/h, the mean square deviation is13.792nGy/h, normal distribution; In the study area, the air gamma absorbed dose rateaverage is79.516nGy/h, that with national and worldwide air gamma absorbed dose rate consistent basically; in the studied area, only a few regions of the airborne gammaabsorbed dose rate data is higher than116nGy/h, the vast majority of regional airgamma absorbed dose rate data belong to the normal range of values;6. In the studied area, internal exposure index is in the range of0.06⁰.42, theaverage value is0.158, the mean square deviation is0.037; external exposure index isin the range of0.24⁰.81, the average value is0.461, the mean square deviation is0.079; in the studied area, internal, external exposure index all belong to the normalrange of values;7. In the studied area, indoor annual effective dose range of0.005⁰.017mSv, theaverage value is0.01mSv, the mean square deviation is0.0017mSv; outdoor annualeffective dose range of0.02⁰.069mSv, the average value is0.039mSv,the meansquare deviation is0.0068mSv; in the studied area, the annual effective dose to thenormal range of values;In conclusion, on the air-ground interface natural gamma radiation field andradiation environment research must be closely linked to the geologic conditions,comprehensive analysis.The paper can provide ecological environment regulation toprovide reference and basis for the city, measurement of radioactivity in theenvironment and the sustainable development of the city and provide basic data andscientific basis for decision making.