Determination Of Limestone Erosion Rate With ～(36)Cl AMS Measurement

~36Cl, the long-lived radioactive nuclide distributes abroad in atmosphere and lithosphere. By measuring the concentration of ~36C1 in limestone, the erosion rates and exposure ages of limestone can be determined. In recent years, Accelerator Mass Spectrometry (AMS) is the only effective tool to measure ~36C1 in limestone. It is very significant for science and economy to study the erosion rate of different circumstance .This technology and method can be extended to study the flourishing of the earth's crust and to judge the age of something and even can help to extend the applications of AMS in circumstance science.In the case of ~36C1 in limestone, the most important reactions are the followings:~40Ca(n, 2n3p)~36Cl; ~ 35Cl(n, γ)~36C1; ~40Ca(μ, α)~36ClIn the top meter of the limestone, the reactions of ~40Ca(n,2n3p)~36Cl and ~35Cl(n, γ )~36C1 are dominant. Following the depth increases, the contribution from slow μ capture by ~40Ca becomes progressively more important.As for as a radioactive nuclide ~36C1, its concentration in limestone can be expressed reasonably by the equation:Where, P-the total production of ~36C1; N-the concentration of ~36C1; λ -the decay constant of 36C1; z-the depth of sample; t- exposure age; e- erosion rate. According to this equation , the erosion rate of limestone in Beijing City has been calculated and the erosion rate is (1.33 ± 0.28) × 10~-5m.a~-1.The article is composed of five sections. First, the review about erosion rate. Second, the origin of ~36C1 and the theory about calculation of erosion rate. Third, collecting of limestone samples and making of AgCl. For the AgCl sample preparation, the carrier of Cl is added to the limestone solution and a chemical procedure is used to reduce the abundance of sulfur. Fourth, AMS measurement, it is completed at CIAE-AMS system and Tsukuba university AMS system in Japanese. Fifth, conclusions and discussions.The author mainly do the following work: grasping the mechanism by which the cosmogenic nuclide of chlorine-36 produce, preparing and making the sample of AgCl, as a participant of AMS measurement, last but not least, searching for a reasonable math model and calculating erosion rate.