本文采用严格满足质量守恒的卷积型出口边界条件(uc-D^(c)/x=u integral from 0 to t c0(t-θ)E(L,θ)dθ,x=L),正确描述了闭式模型中纯物理的暂态示踪过程.与[1]类似,这也是一种未知边界问题。本文用传递函数概念给出第二种新解法.结...本文采用严格满足质量守恒的卷积型出口边界条件(uc-D^(c)/x=u integral from 0 to t c0(t-θ)E(L,θ)dθ,x=L),正确描述了闭式模型中纯物理的暂态示踪过程.与[1]类似,这也是一种未知边界问题。本文用传递函数概念给出第二种新解法.结果同样证明:对示踪过程,著名的 Danckwerts出口边界条件(c/x=0,x=L)也仅当模型长度 L→∞时才严格成立,对有限长的模型也是不恰当的。将两种解作了对比.还证明了:模型中示踪物的暂态浓度分布与 L 无关;D→∞时,E(L,t)→δ(t),→0,这与一个=0的全混流模型等价。展开更多
^99Sr concentrations, resulting from the Chernobyl NPP accident, were determined in the salt lakes of the Crimea （Lakes Kiyatskoe, Kirleutskoe, Kizil-Yar, Bakalskoe and Donuzlav）, together with the redistribution be...^99Sr concentrations, resulting from the Chernobyl NPP accident, were determined in the salt lakes of the Crimea （Lakes Kiyatskoe, Kirleutskoe, Kizil-Yar, Bakalskoe and Donuzlav）, together with the redistribution between the components of the ecosystems. The content of mercury in the waters of the studied reservoirs was also established. Vertical distributions of natural radionuclide activities （^238U, ^232Th, ^226Ra, ^210pb, ^40K） and anthropogenic ^137Cs concentrations （as radiotracers） were determined in the bottom sediments of the Koyashskoe salt lake （located in the south-eastern Crimea） to evaluate the long- term dynamics and biogeochemical processes. Radiochemical and chemical analysis was undertaken and radiotracer and statistical methods were applied to the analytical data. The highest concentrations of ^99Sr in the water of Lake Kiyatskoe （350.5 and 98.0 Bq/m^3） and Lake Kirleutskoe （121.3 Bq/m^3） were due to the discharge of the Dnieper water from the North-Crimean Canal. The high content of mercury in Lake Kiyatskoe （363.2 ng/L） and in seawater near Lake Kizil-Yar （364 ng/L） exceeded the maximum permissible concentration （3.5 times the maximum）. Natural radionuclides provide the main contribution to the total radioactivity （artificial and natural combined） in the bottom sediments of Lake Koyashskoe. The significant concentration of ^210pb in the upper layer of bottom sediments of the lake indicates an active inflow of its parent radionuclide-gaseous ^222Rn from the lower layers of the bottom sediment. The average sedimentation rates in Lake Koyashskoe, determined using ^210pb and ^137Cs data, were 0.117 and 0.109 cm per year, respectively.展开更多
Soil erosion, which includes soil detachment, transport, and deposition, is one of the important dynamic land surface processes. The magnetic tracer method is a useful method for studying soil erosion processes. In th...Soil erosion, which includes soil detachment, transport, and deposition, is one of the important dynamic land surface processes. The magnetic tracer method is a useful method for studying soil erosion processes. In this study, five types of magnetic tracers were made with fine soil, fly ash, cement, bentonite, and magnetic powder （reduced iron powder） using the method of disk granulation. The tracers were uniformly mixed with soil and tested in the laboratory using simulated rainfall and inflow experiments to simulate the interrill and rill components of soil erosion, in order to select one or more tracers which could be used to study detachment and deposition by the erosive forces of raindrops and surface flow of water on a slope. The results showed that the five types of magnetic tracers with high magnetic susceptibility and a wide range of sizes had a range of 0.99-1.29 gcm-3 in bulk density. In the interrill and rill experiments, the tracers FC1 and FC2 which consisted of fly ash and cement at ratios of 1：1 and 2：1, respectively, were transported in phase with soil particles since the magnetic susceptibility of sediment approximated that of the soil which was uneroded and the slopes of the regression equations between the detachment of sediment and magnetic tracers FC1 and FC2 were very close to the expected value of 20, which was the original soil/tracer ratio. The detachment and deposition on slopes could be accurately reflected by the magnetic susceptibility differences. The change in magnetic susceptibility depended on whether deposition or detachment occurred. However, the tracer FS which consisted of fine soil and the tracers FB1 and FB2 which consisted of fly ash and bentonite at ratios of 1：1 and 2：1, respectively, were all unsuitable for soil erosion study since there was no consistent relationship between sediment and tracer detachment for increasing amounts of runoff. Therefore, the tracers FC1 and FC2 could be used to study soil erosion by water.展开更多
文摘本文采用严格满足质量守恒的卷积型出口边界条件(uc-D^(c)/x=u integral from 0 to t c0(t-θ)E(L,θ)dθ,x=L),正确描述了闭式模型中纯物理的暂态示踪过程.与[1]类似,这也是一种未知边界问题。本文用传递函数概念给出第二种新解法.结果同样证明:对示踪过程,著名的 Danckwerts出口边界条件(c/x=0,x=L)也仅当模型长度 L→∞时才严格成立,对有限长的模型也是不恰当的。将两种解作了对比.还证明了:模型中示踪物的暂态浓度分布与 L 无关;D→∞时,E(L,t)→δ(t),→0,这与一个=0的全混流模型等价。
文摘^99Sr concentrations, resulting from the Chernobyl NPP accident, were determined in the salt lakes of the Crimea （Lakes Kiyatskoe, Kirleutskoe, Kizil-Yar, Bakalskoe and Donuzlav）, together with the redistribution between the components of the ecosystems. The content of mercury in the waters of the studied reservoirs was also established. Vertical distributions of natural radionuclide activities （^238U, ^232Th, ^226Ra, ^210pb, ^40K） and anthropogenic ^137Cs concentrations （as radiotracers） were determined in the bottom sediments of the Koyashskoe salt lake （located in the south-eastern Crimea） to evaluate the long- term dynamics and biogeochemical processes. Radiochemical and chemical analysis was undertaken and radiotracer and statistical methods were applied to the analytical data. The highest concentrations of ^99Sr in the water of Lake Kiyatskoe （350.5 and 98.0 Bq/m^3） and Lake Kirleutskoe （121.3 Bq/m^3） were due to the discharge of the Dnieper water from the North-Crimean Canal. The high content of mercury in Lake Kiyatskoe （363.2 ng/L） and in seawater near Lake Kizil-Yar （364 ng/L） exceeded the maximum permissible concentration （3.5 times the maximum）. Natural radionuclides provide the main contribution to the total radioactivity （artificial and natural combined） in the bottom sediments of Lake Koyashskoe. The significant concentration of ^210pb in the upper layer of bottom sediments of the lake indicates an active inflow of its parent radionuclide-gaseous ^222Rn from the lower layers of the bottom sediment. The average sedimentation rates in Lake Koyashskoe, determined using ^210pb and ^137Cs data, were 0.117 and 0.109 cm per year, respectively.
基金Supported by the National Natural Science Foundation of China (No.40701094)the Award Foundation for Excellent Young Scientists of Shandong Province, China (No.BS2009NY025)
文摘Soil erosion, which includes soil detachment, transport, and deposition, is one of the important dynamic land surface processes. The magnetic tracer method is a useful method for studying soil erosion processes. In this study, five types of magnetic tracers were made with fine soil, fly ash, cement, bentonite, and magnetic powder （reduced iron powder） using the method of disk granulation. The tracers were uniformly mixed with soil and tested in the laboratory using simulated rainfall and inflow experiments to simulate the interrill and rill components of soil erosion, in order to select one or more tracers which could be used to study detachment and deposition by the erosive forces of raindrops and surface flow of water on a slope. The results showed that the five types of magnetic tracers with high magnetic susceptibility and a wide range of sizes had a range of 0.99-1.29 gcm-3 in bulk density. In the interrill and rill experiments, the tracers FC1 and FC2 which consisted of fly ash and cement at ratios of 1：1 and 2：1, respectively, were transported in phase with soil particles since the magnetic susceptibility of sediment approximated that of the soil which was uneroded and the slopes of the regression equations between the detachment of sediment and magnetic tracers FC1 and FC2 were very close to the expected value of 20, which was the original soil/tracer ratio. The detachment and deposition on slopes could be accurately reflected by the magnetic susceptibility differences. The change in magnetic susceptibility depended on whether deposition or detachment occurred. However, the tracer FS which consisted of fine soil and the tracers FB1 and FB2 which consisted of fly ash and bentonite at ratios of 1：1 and 2：1, respectively, were all unsuitable for soil erosion study since there was no consistent relationship between sediment and tracer detachment for increasing amounts of runoff. Therefore, the tracers FC1 and FC2 could be used to study soil erosion by water.
