Reservoir sedimentation dynamics were interpreted using Cs-137 activity, particle size and rainfall erosivity analysis in conjunetion with sediment profile coring. Two sediment cores were retrieved from the Changshou ...Reservoir sedimentation dynamics were interpreted using Cs-137 activity, particle size and rainfall erosivity analysis in conjunetion with sediment profile coring. Two sediment cores were retrieved from the Changshou reservoir of Chongqing, which was dammed in 1956 at the outlet of Longxi catchment in the Three Gorges Area using a gravity corer equipped with an aerylie tube with an inner diameter of 6 em. The extracted cores were sectioned at 2 cm intervals. All sediment core samples were dried, sieved （〈2 mm） and weighed. 137Cs activity was measured by y-ray spectrometry. The particle size of the core samples was measured using laser particle size granulometry. Rainfall erosivity was calculated using daily rainfall data from meteorological records and information on soil conservation history was collated to help interpret temporal sedimentation trends. The peak fallout of 137Cs in 1963 appeared at a depth of 84 cm in core A and 56 cm in core B. The peaks of sand contents were related to the peaks of rainfall erosivity which were recorded in 1982, 1989, 1998 and 2005, respectively. Sedimentation rates were calculated according to the sediment profile chronological controls of 1956, 1963, 1982, 1989, 1998 and 2oo5. The highest sedimentation rate was around 2.0 cm·a^-1 between 1982 and 1988 when the Chinese national reform and the Household Responsibility System were implemented, leading to accelerated soil erosion in the Longxi catchment. Since 1990s, and particularly since 2005, sedimentation rates clearly decreased, since a number of soil conservation programs have been carried out in the catchment. The combined use of ^137Cs chronology, particle size and rainfall erosivity provided a simple basis for reconstructing reservoir sedimentation dynamics in the context of both physical processes and soil restoration. Its advantages include avoiding the need for full blown sediment yield reconstruction and the concomitant consideration of core correlation and corrections for autochthonous inputs and reservoir trap efficiency.展开更多
This contribution analyzes the similarities and differences between the measured activities of 137Cs and excess 210Pb(210Pbex) in the cultivated brown and cinnamon soils of the Yimeng Mountain area, discusses the infl...This contribution analyzes the similarities and differences between the measured activities of 137Cs and excess 210Pb(210Pbex) in the cultivated brown and cinnamon soils of the Yimeng Mountain area, discusses the influence of soil texture on the measurement of 210Pbex, and presents differences between the two types of soils. Fields A and B were selected to represent the fields that contain cultivated brown and cinnamon soils, respectively. From either study field, one site of sectioned core and six bulk cores were collected to measure 137Cs levels, 210Pbex levels, and the particle-size composition of soil samples. Three undisturbed soil samples were collected to measure capillary and aeration porosities. The 137Cs inventories for the two study fields are very similar. The 137Cs is a man-made radionuclide, which means that its measured levels for soils are unaffected by soil texture. In contrast, levels of the naturally occurring 210Pbex of soils from Field A were lower than those of Field B by about 50%. In contrast to aquatic sediments, levels of 210Pbex in terrestrial surface soils are affected by the emanation of 222Rn from the soils. It can be assumed that the coarser the soils, the greater the emanation of 222Rn; in addition, the lower the measured 210Pbex, the greater the underestimate of this value. The cultivated brown soils in Field A are coarser than the cultivated cinnamon soils in Field B. As a result, 222Rn in Field A will diffuse more easily into the atmosphere than that in Field B. As a consequence, the measured 210Pbex in soils from Field A is much lower than the actual value, whereas the value measured for Field B is much closer to the actual value.展开更多
To flee the horror of war,these poor people had to move southward.The most excellent craftsmen settled down in the closest Longquan Kiln in Chuzhou(Lishui),who brought new technology and new aesthetic there.Therefore,...To flee the horror of war,these poor people had to move southward.The most excellent craftsmen settled down in the closest Longquan Kiln in Chuzhou(Lishui),who brought new technology and new aesthetic there.Therefore,Longquan Kiln Celadon was the most beautiful with the maximum productivity in the Southern Song Dynasty.展开更多
基金funded by the Chinese Academy of Sciences(Grant No.KZCX2-XB3-09)the Ministry of Science and Technology of China(Grant No.2011BAD31B03)the National Natural Science Foundation of China(Grant Nos.41101259,41102224 and 41201275)
文摘Reservoir sedimentation dynamics were interpreted using Cs-137 activity, particle size and rainfall erosivity analysis in conjunetion with sediment profile coring. Two sediment cores were retrieved from the Changshou reservoir of Chongqing, which was dammed in 1956 at the outlet of Longxi catchment in the Three Gorges Area using a gravity corer equipped with an aerylie tube with an inner diameter of 6 em. The extracted cores were sectioned at 2 cm intervals. All sediment core samples were dried, sieved （〈2 mm） and weighed. 137Cs activity was measured by y-ray spectrometry. The particle size of the core samples was measured using laser particle size granulometry. Rainfall erosivity was calculated using daily rainfall data from meteorological records and information on soil conservation history was collated to help interpret temporal sedimentation trends. The peak fallout of 137Cs in 1963 appeared at a depth of 84 cm in core A and 56 cm in core B. The peaks of sand contents were related to the peaks of rainfall erosivity which were recorded in 1982, 1989, 1998 and 2005, respectively. Sedimentation rates were calculated according to the sediment profile chronological controls of 1956, 1963, 1982, 1989, 1998 and 2oo5. The highest sedimentation rate was around 2.0 cm·a^-1 between 1982 and 1988 when the Chinese national reform and the Household Responsibility System were implemented, leading to accelerated soil erosion in the Longxi catchment. Since 1990s, and particularly since 2005, sedimentation rates clearly decreased, since a number of soil conservation programs have been carried out in the catchment. The combined use of ^137Cs chronology, particle size and rainfall erosivity provided a simple basis for reconstructing reservoir sedimentation dynamics in the context of both physical processes and soil restoration. Its advantages include avoiding the need for full blown sediment yield reconstruction and the concomitant consideration of core correlation and corrections for autochthonous inputs and reservoir trap efficiency.
基金financially supported by the National Natural Science Foundation of China(Nos.41102224,41101259 and 41101206)
文摘This contribution analyzes the similarities and differences between the measured activities of 137Cs and excess 210Pb(210Pbex) in the cultivated brown and cinnamon soils of the Yimeng Mountain area, discusses the influence of soil texture on the measurement of 210Pbex, and presents differences between the two types of soils. Fields A and B were selected to represent the fields that contain cultivated brown and cinnamon soils, respectively. From either study field, one site of sectioned core and six bulk cores were collected to measure 137Cs levels, 210Pbex levels, and the particle-size composition of soil samples. Three undisturbed soil samples were collected to measure capillary and aeration porosities. The 137Cs inventories for the two study fields are very similar. The 137Cs is a man-made radionuclide, which means that its measured levels for soils are unaffected by soil texture. In contrast, levels of the naturally occurring 210Pbex of soils from Field A were lower than those of Field B by about 50%. In contrast to aquatic sediments, levels of 210Pbex in terrestrial surface soils are affected by the emanation of 222Rn from the soils. It can be assumed that the coarser the soils, the greater the emanation of 222Rn; in addition, the lower the measured 210Pbex, the greater the underestimate of this value. The cultivated brown soils in Field A are coarser than the cultivated cinnamon soils in Field B. As a result, 222Rn in Field A will diffuse more easily into the atmosphere than that in Field B. As a consequence, the measured 210Pbex in soils from Field A is much lower than the actual value, whereas the value measured for Field B is much closer to the actual value.
文摘To flee the horror of war,these poor people had to move southward.The most excellent craftsmen settled down in the closest Longquan Kiln in Chuzhou(Lishui),who brought new technology and new aesthetic there.Therefore,Longquan Kiln Celadon was the most beautiful with the maximum productivity in the Southern Song Dynasty.
