| Stable daughter lead will be formulated after α and β particles irradiated by radon. New method for the passive and cumulative chemical sampling of radon will be established here based on lead. And new determination method for catalytic spectrophotometric of radon will be made based upon the catalytic kinetics characteristics of lead ion. The radioactive hazard can be avoided through newly built sampling method and quantitative detection method. The sampling solution can be directly detected without any treatment. The method has the advantage of simple equipment, convenient operation and high sensitivity.In the chapter 2, taking HNO3 as the absorber, radon radiation entered into the sampling device through the membrane, radiative decay would form lead. Lead was oxidized into Pb2+ ions after dissolving HNO3.In the Na OH medium(p H=11), phenolphthalein solution was faded because of the oxidization of H2O2. Pb2+ ion had strong sensitive catalytic on this reaction.The fading degree of reaction system(ΔΑ value) was linearly correlated with the concentration of lead ion. And there was a linear quantitative relationship between the ΔΑ value and exposure time(t). The calculation of passive accumulative content of radon could be conducted by applying the ΔΑ value or the concentration of lead ion.The research shows that, the catalytic fading reaction is a pseudo first order reaction, and apparent activation energy Ea=83.606 k J/mol. The determination wavelength of reaction system is λmax=553 nm. The concentration of lead ion is ρ= 7.7~200.0 ng·m L-1, the linear regression equation is DA=0.0021ρ(ng·m L-1)+0.32 with a detection limit of lead was 2.31 ng·m L-1, r=0.9995.The spectral information(ΔA value) of this oxidation reaction system is linearly correlated with the radon exposure time(or sampling time, t). When t=3~9h, ΔA = 0.0272 t + 0.2883,r = 0.9948, and t=9~48h, ΔA = 0.0022 t + 0.5115, r = 0.9949. All these tests help build mathematical model for the site determination for the passive and cumulative concentration of radon(CRn) based on the ΔA value and t value: ΔA=FCRnt +a,CRn=(ΔA-a)/(Ft), F is a constant.In the chapter 3, a new fluorescence method was established to measure the radiation dose of radon on the basis of lead ion catalyzing the oxidation reaction of dichloride fluorescence.In alkaline medium, trace Pb2+ play an important role in catalyzing the reaction between dichloride fluorescence element and hydrogen peroxide and it also helps to clearly observe fluorescence intensity being weak. Under certain conditions, there is a good linear relation between the fluorescence value decreased in chemical reaction and lead ion concentration in solution, which means after getting the value of dichloride fluorescence decreased, trace Pb2+ can be determined and further figure out radon radiation dose value. Therefore, a new way to measure radon has been found. What’s more,the reaction conditions were optimized and a standard curve was established, that is, the data are more precise.While activating wavelength 504nm(λex=504nm) maximum, the fluorescence value of dichlorofluorescein decreased. And at the point of 526 nm, dichloride fluorescent value has a good linear relation with Pb2+ during the range of 11~120μg·L-1. The linear regression equation was DF =3063.6ρ(μg·m L-1)+9.95, the regression coefficient was 0.9988. In the chapter 4, a new method based on the suppression of trace Pb2+ catalytic kinetic spectrophotometric determination was established to measure the radiation dose of radon on the basis of lead ion.In ammonia medium, trace Cu(II) play an important role in catalyzing the reaction between alizarin red S and hydrogen peroxide, and Pb2+ has obvious inhibitory effect to the fading reaction. Under certain conditions, we determined the absorbance value A1 and A2 of not obstructed solution and inhibitory reaction solution, then calculating lg(A2/A1). There is a good linear relation between lg(A2/A1) and lead ion concentration in solution, which means trace Pb2+ can be determined and further figure out radon radiation dose value. Therefore, a new way to measue radon has been found.At the Maximum absorption wavelength of 525 nm, lg(A2/A1) has a good linear relation with Pb2+ during the range of 0.025~0.36μg·m L-1. The linear regression equation was lg(A2/A1)=0.0341+0.5604 ρ(μg·m L-1), the regression coefficient was 0.9991. |
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