1 tomsk polytechnic university, tomsk, russian federation; 2 institute of monitoring of climatic and...

1Tomsk Polytechnic University, Tomsk, Russian Federation;

2Institute of Monitoring of Climatic and Ecological Systems SB RAS, Tomsk, RF;

3Kamchatkan Branch Geophysical service, RAS, Petropavlovsk-Kamchatsky, RF

Valentina S. Yakovleva1, Artem V. Vukolov1, Ivan I. Ippolitov1,2,Mikhail V. Kabanov2, Vladimir D. Karataev1, Peter M. Nagorsky1,2,Sergey V. Smirnov1,2, Pavel P. Firstov3

Russian Federation

First results of multifactor experiment on radon transport in

the lithosphere-atmosphere system

The work was fulfilled with financial support of FAP № 02.740.11.0738and project of SB RAS № VII.63.1.1

Natural background radiation is one of the most important elements of atmosphere, and its variations are closely connected with the change of weather parameters of atmosphere, its chemical and aerosol composition.

Registration and further analysis of ionizing radiation fields in the atmosphere is carried out by one radiation type – γ-radiation.

Monitoring of β-radiation in the atmosphere is practically absent.

First results of multifactor experiment on radon transport in the lithosphere-atmosphere system

β- and γ-background in the surface atmosphere is caused by one and the same sources: soil radionuclides and atmosphere decay products of radon and thoron.

Taking this fact into account, one should expect similar behavior of β- и γ-radiation fields in the surface atmosphere.

However, due to large differences in their penetrating power, a legal question arose: how agreed the variations of different types of natural ionizing radiation are.


It is known, that time variability of atmosphere β- and γ-radiation is mainly caused by the influence of RFD from the ground surface.

The attempts to determine RFD value by the γ-dose rate value are known [Szegvary, 2007].

It was found that space variations of γ-background

coincide with RFD variations by 60%. There, it was also found that time variations of γ-background and RFD are in good agreement with each other.


Thus, two problems arose: 1. comparative evaluation of spectrum-time parameters of

β- and γ-radiation fields and detection of their interactions with atmosphere-electrical values of the surface layer.

2. detection of interactions between β- and γ-radiation fields and radon field, with the objective to further research the possibility to investigate radon transport in the “lithosphere-atmosphere” system by β-, γ-radiation.


Tomsk measuring-experimental complex:

The monitoring is performed via automated information measuring system:atmosphere temperature – T,pressure – p, relative humidity – h,wind velocity and direction,surface temperature and subsurface

temperatures at some depths.β-, γ- and α-field characteristics.


Additionally it includes: the detectors of atmosphere electric field intensity E «Field-2», polar electroconductivities L-, L+ of atmosphere air «Electroconductivity-2» gamma radiation dose rate. pyranometer Kipp & Zonen SM-11 and photometer NILU-UV-6T to measure

incoming solar radiation Pr.

The measurements are continuous with 1 minute time step.


Since March 2007 the measurements of electrical, weather and actinometrical values have been transferred to a specially equipped monitoring platform, situated at the IMCES SB RAS building mezzanine at the height of 24 m.

Scheme of the multifactor experiment in Tomsk

А – meteo- and actinometrical sensors;B – sensors of electrical parameters;I – scintillation ZnS α-detector;II – scintillation NaI(Tl) γ-detector;III – STS-6 gas counter of β-radiation;IV – SBT-10 end-window counter of β-radiation;V – line of gas counters of γ-radiation;VI – DGDK-100V semiconducting coaxial germanium detector of γ-radiation, put into Dewar vessel; VII – automated accumulative chamber for radon flux density measurement;APM 2200 – radon decay products radiometer (SARAD GmbH, Germany).

Initial procedure of monitoring of ionizing radiations, meteorological and atmospheric-electric parameters were created to analyze the influence of upper soil layer and ground atmosphere state and dynamics:


a) on radon and thoron fluxes from the ground surface;

b) distribution of radon, thoron and their decay products;

c) vertical distribution of α-, β- and γ-radiation fluxes in the air;

d) ion generation rate due to radon and its decay products.


At the height of 25 m in a standard weather booth there are two gas counters of β+γ-radiation (type STS-6), one of which is worn in aluminum casing for beta-radiation delay. Thus, one counter registers β+γ-radiation and the other one – only γ-radiation. Pure β-background is obtained by registration difference. Data pickup cycle is 2 minutes.

First results of multifactor experiment on radon transport in the lithosphere-atmosphere systemβ+γ-radiation at 10 m;

β+γ-radiation at 5 m;

β-radiation at 0 m;

α-radiation at 0 m;

β-radiation at -0.5 m;

β-radiation at -1 m;

Air temperature, ºC;

Relative humidity, %;

Incoming solar radiation

In some periods a good synchronism was found in dynamics ofα- and β-radiation measured at different height and depth.

In some periods a good synchronism was found in dynamics ofβ-radiation at 0.5 m depth and atmosphere temperature.

β+γ-radiation

β+γ-radiation

β+γ-radiation at 5 m


γ-radiation at 25 m (gas discharge counter-outdoor);

γ-radiation at 24 m (scintillation detector-indoor);

γ-radiation at 24 m (line of gas discharge counters-indoor);

β+γ-radiation at 10 m -outdoor;

β+γ-radiation at 5 m -outdoor;

Horizontal speed of wind, m/s;

Vertical speed of wind, m/s;

Atmosphere air density, kg/m3;

Atmosphere temperature, ºС.

Synchronous spikes were found in γ-radiation dose time series measured at different height and position (indoor or outdoor).

Preliminary results of monitoring data analysis allow to make a conclusion that contributions of β- and γ-radiation into the total level of background atmosphere radiation depend on different meteorological factors and one type of radiation correlates with others not always.

Some examples follow further…


Typical time variations of β- and γ-radiationin summer atmosphere

August, 2009

γ-dose rate, µSv/h

β-flux, m-2 c-1

β-flux, m-2 c-1



August, 2009



β-flux density, m-2 c-1

Pressure


β-flux density

Pressure

On time scales from synoptic to annual the variations of γ–background are appeared to be connected with air pressure change. For instance, air pressure decrease leads

to the increase of γ–background level (and vice versa).



γ– background variations with diurnal period are expressed weakly in comparison with similar β-background variations, however there are

intervals, when they are expressed rather vividly.

γ-dose rate

β-fluxdensity

Beta-background variations appeared to be closely connected with diurnal variations of atmosphere conductivity, its temperature and humidity.

Beta-background variations appeared to be closely connected with diurnal variations of atmosphere temperature and density.

Connection between variations of γ- and β-radiation fields on different time scale


Winter of 2008 and 2009-2010

Summer of 2009 and 2010

Regression relation of variations with 2 days and more periods

Variations with2 hours–2 days periods

(all data)

X-axis - day number of year (beginning from 1.01.2009),Y-axis – time shift (hours).

Normalized crosscorrelation function (NICF) between low-frequency variations of β- and γ-radiations

Summer (4.06.09 – 28.08.09) Winter (21.12.09 – 16.03.10)

Results analysis and Experimental Platform modernization

Conclusion It has been found that:

Variations of beta- and gamma-radiations are weakly connected between each other, however, within some periods of the synoptic scale the correlation between them can be rather high;

The estimations of radon flux variations based only on variations of gamma-radiation can appear to be incorrect;

Beta-background variations appeared to be comparatively weakly connected with variations of synoptic scale pressure and closely connected with diurnal variations of atmosphere conductivity, its temperature, density and steam pressure.

After the first results analysis it was decided to complicate the scheme of the multifactor experiment,

adding 6 gas counters to the existing ones.

Thank you very much for your attention!

Tomsk, Siberia, Russian Federation

1 tomsk polytechnic university, tomsk, russian federation; 2 institute of monitoring of climatic and...

Documents

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