Distribution Characteristics Of Pu In The Soil In The Northern Part Of Xining,Qinghai

Plutonium is a kind of radionuclide.Most of the plutonium in nature is man-made.The impact of nuclear accidents on the environment and the harm to human health cannot be ignored.While human beings use nuclear energy to bring convenience,we should also pay attention to protecting against radioactive pollution caused by various nuclides.measuring the isotope of plutonium in the environment can be used to assess the radioactive content of plutonium and infer the source of plutonium.Qinghai Province is located in northwestern China,close to the China Atomic City and the Lop Nor test site.By studying the distribution of plutonium isotopes in the soil in northern Xining,Qinghai Province,it can be inferred whether the study area has been exposed to sources of plutonium other than global fallout,and the migration of plutonium in the soil in this area can also be explored.This article studied three surface soil samples and five soil core samples in the northern part of Xining,Qinghai Province.Inductively Coupled Plasma-Mass Spectrometry（ICP-MS）was used to measure the ^239+240Pu activity and the²⁴⁰Pu/²³⁹Pu atom ratio.Soil core samples measured the content of heavy metal elements（Cr,Co,Ni,Cu,Zn,Cd,Tl and Pb）.In addition,the activities of radionuclides(²³⁸U,²³²Th,²²⁶Ra,²¹⁰Pb and ⁴⁰K)in the soil core samples were measured by a High Purity Germanium Gamma Spectrometer.The research results of this paper show that:（1）The ^239+240Pu activities in the three surface soil samples were obviouly different,with the minimum value was 0.170mBq/g and the maximum value was 1.890mBq/g.The reason is the difference of soil type.Compared with the difference in the ^239+240Pu activities,the ²⁴⁰Pu/²³⁹Pu atom ratio is not much different,and they are all within the range of global fallout.（2）This article compared the vertical distribution trends of ^239+240Pu and¹³⁷Cs activities in five soil core samples.The results showed that the vertical distribution of ^239+240Pu activities and ¹³⁷Cs activities had the same trend:In the soil layers below the maximum value of ^239+240Pu activity and ¹³⁷Cs activity,^239+240Pu activities and ¹³⁷Cs activities showed an exponential decrease trend with the increase of soil depth.（3）The ranges of ^239+240Pu activities in the soil core samples were:0.394-0.010mBq/g,0.481-0.032mBq/g,0.851-0.010mBq/g,1.925-0.015mBq/g,2.196-0.046mBq/g.The ^239+240Pu activities were similar to the values in the same type of soil.The average of ²⁴⁰Pu/²³⁹Pu atom ratio in the soil core samples is0.176±0.010,within the range of global fallout.The inventories of ^239+240Pu in the soil core samples were 291.5Bq/m²,553.8Bq/m²,116.6Bq/m²,147.9Bq/m²and 153.7Bq/m²,which were slightly higher than the values in the same type of soil.This may be due to the fact that the average altitude of the study area is about 3000m,which is above the plateau and the climate is a special plateau climate.（4）The radionuclides(²³⁸U,²³²Th,²²⁶Ra,²¹⁰Pb and ⁴⁰K)in five soil core samples were measured by a High Purity Germanium Gamma Spectrometer.The results showed that:the average activities of the ²³⁸U,²³²Th,²²⁶Ra,²¹⁰Pb and ⁴⁰K in five soil core samples were 25.567mBq/g,39.468mBq/g,28.148mBq/g,15.114mBq/g,and 504.989mBq/g.Slightly lower than the average activity of radionuclides in Chinese soil.From the vertical distribution point of view,the radionuclide activities in the soil core samples do not fluctuate much in each column,and there is almost no obvious trend of increase or decrease,which also shows that the soil core was homogeneous soil.（5）Using Pearson correlation coefficient to explore the relationship between organic matter（OM）,heavy metal elements（Cr,Co,Ni,Cu,Zn,Cd,Tl and Pb）and Pu isotopes in soil core samples.The results showed:Pu isotope is positively correlated with organic matter（OM）and Cd,Cu,Co and Zn.And negatively correlated with Tl,which indicates that Tl in the soil inhibits the adsorption of Pu isotope.From the vertical distribution point of view,the distributions of heavy metal elements in each soil layers are even,which further shows that the study area in this article was not significantly affected by external environmental heavy metal pollution.The results of this study are of great significance for further exploring the sources of radionuclides in the region and recording the environmental impact of plutonium nuclides on the region,thereby expanding the database of specific activities of radionuclides in Chinese soil and the atom ratio of plutonium,and providing future The radiological risk assessment laid the foundation.