The program described herein (LEADAT) serves to calculate sediment date and sedimentation rate using the ^210pb method for the studies of environmental processes and pollution history on a time scale of 100 - 150 a....The program described herein (LEADAT) serves to calculate sediment date and sedimentation rate using the ^210pb method for the studies of environmental processes and pollution history on a time scale of 100 - 150 a. The program written in MATLAB ( Version7.0) permits the user to select the principal models of ^210pb method, i. e. , the constant fluxes of sediment and lead-210 ( CF- SL) model, the constant flux of lead-210 (CFL) model, the constant initial concentration of lead-210 (CICL) model and the twolayer mixing (TLM) model. Although appropriate model selection is essentially based on understanding of the sedimentary processes, the pattern of the excess ^210pb profile is also helpful for model selection. The excess ^210pb profiles for two sediment cores collected from a brackish lake and an embayment respectively are used to demonstrate the application of the program. With a graphical user interface, the program can be easily executed. Not only ASCII but also graphical output can be generated by means of the program. Meanwhile, the code can be modified easily for extension.展开更多
Four sediment cores were collected from Mikawa Bay, Japan, and excess ^210pb and ^137Cs were measured by gamma spectrometry. Sedimentation rates for the four cores were determined by ^210Pb method. The sedimentation r...Four sediment cores were collected from Mikawa Bay, Japan, and excess ^210pb and ^137Cs were measured by gamma spectrometry. Sedimentation rates for the four cores were determined by ^210Pb method. The sedimentation rate range is 0.10-0.70 g/(cm^2.year). The bio-mixing depth for each core is less than 7.0 cm, and was determined by the excess 210^pb profiles as well. Therefore, the bioturbation is slight. The 210^pb-derived dates coincided with the results from ^137Cs geochronology. Acceleration in sedimentation rate due to environmental alteration has been found in cores A2.5 and 05AS8, representing two depocenters due to their topography. Evidence of the Tokal Flood in 2000 was found in core 05AS8 according to the profiles of both radioisotopes and trace metals.展开更多
文摘The program described herein (LEADAT) serves to calculate sediment date and sedimentation rate using the ^210pb method for the studies of environmental processes and pollution history on a time scale of 100 - 150 a. The program written in MATLAB ( Version7.0) permits the user to select the principal models of ^210pb method, i. e. , the constant fluxes of sediment and lead-210 ( CF- SL) model, the constant flux of lead-210 (CFL) model, the constant initial concentration of lead-210 (CICL) model and the twolayer mixing (TLM) model. Although appropriate model selection is essentially based on understanding of the sedimentary processes, the pattern of the excess ^210pb profile is also helpful for model selection. The excess ^210pb profiles for two sediment cores collected from a brackish lake and an embayment respectively are used to demonstrate the application of the program. With a graphical user interface, the program can be easily executed. Not only ASCII but also graphical output can be generated by means of the program. Meanwhile, the code can be modified easily for extension.
基金partially benefited from a scholarship from the Ministry of Education, Culture, Sports, Science and Technology, Japana fellowship from the 21st century COE program, Dynamicsof the Sun-Earth-Life Interactive System , Japan (No. G-4).
文摘Four sediment cores were collected from Mikawa Bay, Japan, and excess ^210pb and ^137Cs were measured by gamma spectrometry. Sedimentation rates for the four cores were determined by ^210Pb method. The sedimentation rate range is 0.10-0.70 g/(cm^2.year). The bio-mixing depth for each core is less than 7.0 cm, and was determined by the excess 210^pb profiles as well. Therefore, the bioturbation is slight. The 210^pb-derived dates coincided with the results from ^137Cs geochronology. Acceleration in sedimentation rate due to environmental alteration has been found in cores A2.5 and 05AS8, representing two depocenters due to their topography. Evidence of the Tokal Flood in 2000 was found in core 05AS8 according to the profiles of both radioisotopes and trace metals.