The 137Cs vertical distributions in uncultivated and cultivated soils, developed from Quaternary red clay, granite, argillaceous shale, and red sandstone, were studied to develop reliable guidelines for selecting refe...The 137Cs vertical distributions in uncultivated and cultivated soils, developed from Quaternary red clay, granite, argillaceous shale, and red sandstone, were studied to develop reliable guidelines for selecting reference sites in southeastern China, which is dominated by strong acidic and/or clay-textured soils, and examine their reliability by comparing them to the reported 137Cs reference inventory data to see whether they agreed with the global distribution pattern. It was observed that a relatively high proportion of 137Cs was concentrated in the surface layers of soils with relatively high clay content. In the paddy soils developed from granite more 137Cs penetrated to depths below the plow layer (about 45.3%), when compared to those from the other three parent materials. The relatively low soil 137Cs inventories on crests excluded using the crest as the 137Cs reference site; instead the paddy field on the hillock plain was selected. Furthermore, within a specific county characterized by great systematic spatial variations of rainfall and topography across the landscape, a significant (P<0.01) and positive linear relationship (r2=0.81) between local 137Cs inventory and corresponding local annual rainfall was observed. Thus, for areas with large variations in rainfall, a single uniform value of local 137Cs reference inventory should be used with caution.展开更多
Modeling the oxygen-18 in precipitation based on regional topography and meteorological factors is helpful to constrain missing isotopic data in some regions that is required for many paleoclimate,eco-hydrological and...Modeling the oxygen-18 in precipitation based on regional topography and meteorological factors is helpful to constrain missing isotopic data in some regions that is required for many paleoclimate,eco-hydrological and atmospheric circulation studies.Therefore,the relationship betweenδ18Oin precipitation(δ18OPPT)and the affecting factors need to be thoroughly understood.We present a model considering the combined effects of temperature,altitude,and latitude on the spatial variability of annual average of stable isotopes in precipitation across China.This new model performed significantly better(P<0.05)than the widely used Farquhar and Bowen&Wilkinsonmodels.Our model allows modelling the spatial distribution of isotopes in precipitation depending on temperature variation.The residuals of presented model did not significantly correlate with altitude.Based on the model and residuals,a high-resolution map of annual averageδ18Opptacross China was generated.δ18OPPTdecreased from low toward high latitudes and from low towards high altitudes area.The model application provides important information forancient climate,hydrological cycle and water vapor sources studies.展开更多
This paper reports the concentrations of 137Cs, hexaehlorocyclohexane （HCH）, dichlorodiphenyltrichloroethanes （DDT） and its main degradation products, δ3C, and organic carbon in pond sediments （O-210 cm, section...This paper reports the concentrations of 137Cs, hexaehlorocyclohexane （HCH）, dichlorodiphenyltrichloroethanes （DDT） and its main degradation products, δ3C, and organic carbon in pond sediments （O-210 cm, sectioned by 2-20 cm interval） and surface soils （the 0-3 cm horizon） collected in 2OlO from Chenjia catchment, which is located in Yanting county in the hilly central Sichuan of China. α-, β-, and γ-HCH, DDT, and DDD were not detected throughout the sediment profile. Trace concentrations of δ-HCH （0.89-29.31 ng g^-1） and p,p＇- DDE （1.85-6.02 ng g^-1） were detected only in top 40 cm sediment. The 137Cs fallout peak in 1963 （corresponding to the 55-60 cm depth）, the sedimentary signature left by the last year of HCH use in 1989 （an additional indicator at 20-25 cm）, and the obvious original channel bed prior to the construction of the pond in 1956 were used as temporal markers to estimate changes in average sedimentation rate between different periods due to changes in land use. Continuous, marked decrease in average sedimentation rate （i.e., 3.79, 1.35 and 1.07 cm year-1 in 1956-1963, 1963-1989, and 1989-2010, respectively） over time was observed, probably due to the reforestation, abandoning of steep sloping farmland for afforestation and natural re-vegetation （implementation of the Grain for Green Program）, and the conversion of part of gently sloping farmlandterraces to orchard land since the 1980s, especially since the 1990s. This was corroborated by the observed decrease （more negative） in δ3C of sediment towards the surface, which indicates increased relative contribution of eroded soil particles coming from slopes with increased tree cover in sediment source area. Combined use of 137Cs, δ-HCH, and δ3C record in sediments has been demonstrated to be a powerful approach to reconstruction of response in sedimentation rate to historical land use changes.展开更多
Soil hydraulic parameters θs,α,n,Ks,L and θr of the van Genuchten-Mualem model were estimated using three pedotransfer functions(PTFs) based on soil properties for surface soils of the largest main tributary catchm...Soil hydraulic parameters θs,α,n,Ks,L and θr of the van Genuchten-Mualem model were estimated using three pedotransfer functions(PTFs) based on soil properties for surface soils of the largest main tributary catchment(the Jialing River) of the upper Yangtze River in China.The soil database was from the second national soil survey of China with a spatial 30 × 30 arc-second resolution.According to the statistical analysis of the differences between the continuous-PTFs-estimated values of soil hydraulic parameters for the study catchment and the reference values for a specific texture class provided in the development database of a specific PTF,best estimations were obtained using the W?sten PTF.The Rawls & Brakenssiek PTF was good estimation for parameter θr that was assumed as zero by W?sten PTF.The established higher θr(0.08%) and lower Ks(20 cm/d) and θs(0.43%) in the mid-downstream area relative to the other areas of the catchment could lead to larger amounts of surface runoff andconsequently provide higher energy to erode soil.Thus,these factors provide a supporting explanation for previously reported severe soil erosion occurring in this area.Spatial heterogeneity analysis for estimated hydraulic parameters in terms of semivariogram showed that the spatial correlation distance was in the range of 50-80 km and that the spatial variability(sill) was not large except for parameters Ks and L.The semi-variance with the exponential model at the zero distance(nugget) was 30%-50% of the sill.This study provided a practical PTF approach for estimating soil hydraulic properties from soil survey data at a large watershed scale.The estimation results could provide better insight into the mechanism of surface runoff and soil erosion,which is important to better understand and manage erosion in the catchment.展开更多
基金Project supported by the National Key Basic Research Support Foundation of China (No. G1999011801) the National Natural Science Foundation of China (No. 49973027)and Japan Society for the Promotion of Science (No. P04575).
文摘The 137Cs vertical distributions in uncultivated and cultivated soils, developed from Quaternary red clay, granite, argillaceous shale, and red sandstone, were studied to develop reliable guidelines for selecting reference sites in southeastern China, which is dominated by strong acidic and/or clay-textured soils, and examine their reliability by comparing them to the reported 137Cs reference inventory data to see whether they agreed with the global distribution pattern. It was observed that a relatively high proportion of 137Cs was concentrated in the surface layers of soils with relatively high clay content. In the paddy soils developed from granite more 137Cs penetrated to depths below the plow layer (about 45.3%), when compared to those from the other three parent materials. The relatively low soil 137Cs inventories on crests excluded using the crest as the 137Cs reference site; instead the paddy field on the hillock plain was selected. Furthermore, within a specific county characterized by great systematic spatial variations of rainfall and topography across the landscape, a significant (P<0.01) and positive linear relationship (r2=0.81) between local 137Cs inventory and corresponding local annual rainfall was observed. Thus, for areas with large variations in rainfall, a single uniform value of local 137Cs reference inventory should be used with caution.
基金financially supported by National Natural Science Foundation of China(41790431 and 41471188)the Innovative Talents Promotion Plan in Shaanxi Province(2017-KJXX-74)the CAS “Light of West China” Program
文摘Modeling the oxygen-18 in precipitation based on regional topography and meteorological factors is helpful to constrain missing isotopic data in some regions that is required for many paleoclimate,eco-hydrological and atmospheric circulation studies.Therefore,the relationship betweenδ18Oin precipitation(δ18OPPT)and the affecting factors need to be thoroughly understood.We present a model considering the combined effects of temperature,altitude,and latitude on the spatial variability of annual average of stable isotopes in precipitation across China.This new model performed significantly better(P<0.05)than the widely used Farquhar and Bowen&Wilkinsonmodels.Our model allows modelling the spatial distribution of isotopes in precipitation depending on temperature variation.The residuals of presented model did not significantly correlate with altitude.Based on the model and residuals,a high-resolution map of annual averageδ18Opptacross China was generated.δ18OPPTdecreased from low toward high latitudes and from low towards high altitudes area.The model application provides important information forancient climate,hydrological cycle and water vapor sources studies.
基金supported by the National Key Technology R&D Program of the Ministry of Science and Technology of China (Grant No. 2011BAC09B05)the National Natural Science Foundation of China (Grant No. 41171372)+2 种基金International Atomic Energy Agency (15521/RO)the Hundred Talents Program of the Chinese Academy of Sciences and Sichuan Provincethe CAS-SAFEA International Partnership Program for Creative Research Team (Grant No. KZZD-EWTZ-06)
文摘This paper reports the concentrations of 137Cs, hexaehlorocyclohexane （HCH）, dichlorodiphenyltrichloroethanes （DDT） and its main degradation products, δ3C, and organic carbon in pond sediments （O-210 cm, sectioned by 2-20 cm interval） and surface soils （the 0-3 cm horizon） collected in 2OlO from Chenjia catchment, which is located in Yanting county in the hilly central Sichuan of China. α-, β-, and γ-HCH, DDT, and DDD were not detected throughout the sediment profile. Trace concentrations of δ-HCH （0.89-29.31 ng g^-1） and p,p＇- DDE （1.85-6.02 ng g^-1） were detected only in top 40 cm sediment. The 137Cs fallout peak in 1963 （corresponding to the 55-60 cm depth）, the sedimentary signature left by the last year of HCH use in 1989 （an additional indicator at 20-25 cm）, and the obvious original channel bed prior to the construction of the pond in 1956 were used as temporal markers to estimate changes in average sedimentation rate between different periods due to changes in land use. Continuous, marked decrease in average sedimentation rate （i.e., 3.79, 1.35 and 1.07 cm year-1 in 1956-1963, 1963-1989, and 1989-2010, respectively） over time was observed, probably due to the reforestation, abandoning of steep sloping farmland for afforestation and natural re-vegetation （implementation of the Grain for Green Program）, and the conversion of part of gently sloping farmlandterraces to orchard land since the 1980s, especially since the 1990s. This was corroborated by the observed decrease （more negative） in δ3C of sediment towards the surface, which indicates increased relative contribution of eroded soil particles coming from slopes with increased tree cover in sediment source area. Combined use of 137Cs, δ-HCH, and δ3C record in sediments has been demonstrated to be a powerful approach to reconstruction of response in sedimentation rate to historical land use changes.
基金supported by the“Hundred Talents Program”of the Chinese Academy of Sciences and Sichuan Province,the National Basic Research Program of the Ministry of Science and Technology of China(Grant No.2012CB417101)the National Natural Science Foundation of China(Grant Nos.41171372 and 41471268)the CASSAFEA International Partnership Program for Creative Research Team(Grant No.KZZD-EWTZ06)
文摘Soil hydraulic parameters θs,α,n,Ks,L and θr of the van Genuchten-Mualem model were estimated using three pedotransfer functions(PTFs) based on soil properties for surface soils of the largest main tributary catchment(the Jialing River) of the upper Yangtze River in China.The soil database was from the second national soil survey of China with a spatial 30 × 30 arc-second resolution.According to the statistical analysis of the differences between the continuous-PTFs-estimated values of soil hydraulic parameters for the study catchment and the reference values for a specific texture class provided in the development database of a specific PTF,best estimations were obtained using the W?sten PTF.The Rawls & Brakenssiek PTF was good estimation for parameter θr that was assumed as zero by W?sten PTF.The established higher θr(0.08%) and lower Ks(20 cm/d) and θs(0.43%) in the mid-downstream area relative to the other areas of the catchment could lead to larger amounts of surface runoff andconsequently provide higher energy to erode soil.Thus,these factors provide a supporting explanation for previously reported severe soil erosion occurring in this area.Spatial heterogeneity analysis for estimated hydraulic parameters in terms of semivariogram showed that the spatial correlation distance was in the range of 50-80 km and that the spatial variability(sill) was not large except for parameters Ks and L.The semi-variance with the exponential model at the zero distance(nugget) was 30%-50% of the sill.This study provided a practical PTF approach for estimating soil hydraulic properties from soil survey data at a large watershed scale.The estimation results could provide better insight into the mechanism of surface runoff and soil erosion,which is important to better understand and manage erosion in the catchment.
