Study On Relationship Among ¹³⁷Cs,^239+240Pu,Soil Particle Size And Organic Matter In Soil

Soil conservation and erosion control problem is a major environmental problem which is related to sustainable development of human society.The key of the problem is to study the migration process of soil particles and the mechanism of soil erosion.Artificial radioisotopes 137Cs and 239+240Pu are ubiquitous in the environment,and they are mainly from the release of atmospheric nuclear tests and nuclear accidents.Erosion and accumulation of soil is the main reason for the migration and redistribution of 137Cs and 239+240Pu in the soil,so the distribution of 137Cs and 239+240Pu after settling to the earth surface can reflect the erosion and deposition of soil,which makes the 137Cs and 239+24Pu can be used as good tracers of soil erosion and deposition.137Cs and 239+240Pu have been widely used in soil erosion,sediment dating and sediment source resegarching currently.As to the study of tracer technique of 137Cs and 239+240Pu,a key issue is to reveal the redistribution process and mechanism of 137Cs and 239+240Pu in the soil.As adsorbent and redistribution carrier of 137Cs and 239+240Pu,soil particle plays a significant role in the progress of the migration and redistribution of 137Cs and 239+240Pu in the soil.Therefore,in the research of soil erosion adopting the 137Cs and 239+240Pu technique,the particle size effect of 137Cs and 239+240pu absorbed in soil is very important to establish the relationship between the loss(or increase)quantity of 137Cs,239+240Pu and soil erosion(or deposition).Soil organic content also influence the distribution of 137Cs and 239+240Pu in the soil,because it is closely related to the geochemical behavior of 137Cs and 239+240Pu.However,current research about the relationship among 137Cs,239+240Pu,soil particle size and organic matter in soil is still insufficient,and there are clear contradictions between the findings.In this study,Liaodong Bay in Dalian and Lianyungang coastal region were selected as study area,and natural soil collected in the field was study object.Soil samples were graded using wet sieving and centrifugal method.Soil samples and each size fraction were analyzed using ? spectrometry and radiochemical separation combined with inductively coupled plasma mass spectrometry(ICP-MS)respectively for determinations of 137Cs and 239+240Pu.And combined with the physical and chemical characteristics of soil,relationship among 137Cs,239+240Pu,soil particle size and organic matter in soil were studied,then influencing factors of sorption and migration behavior of 137Cs and 239+240Pu in soil were discussed.It provided a theoretical foundation for scientific applications of 137Cs and 239+240Pu in soil erosion tracer studies,while it also provided an important reference for radioactive environmental safety assessment.This study.obtained the following conclusions:(1)Relationships between 137Cs,239+240Pu and soil particle size both both met negative exponential regression equation.The smaller the particle size was,the stronger the adsorption capacity of 137Cs and 239+240Pu was.The adsorption capacity of clay component was significantly stronger than the other components.(2)The distribution of 137Cs and 239+240Pu in soil of different particle sizes had a significant consistency,indicating that the physical digration of 137Cs and 239+240Pu with soil particle had a consistency..(3)The organic matter content was a characteristic parameter that had a great influence on the adsorption of 137Cs and 239+240Pu.There was linear positive relationship between 137Cs,239+240Pu and organic matter.And the correlation between 239+240Pu and organic matter was stronger than 137Cs.