In this particular study,99 typical managed small watersheds which representing five water erosion areas in China were selected to study zonality of Runoff Reduction Efficiency(RRE)and of Sediment Reduction Efficiency...In this particular study,99 typical managed small watersheds which representing five water erosion areas in China were selected to study zonality of Runoff Reduction Efficiency(RRE)and of Sediment Reduction Efficiency(SRE).The RRE is the ratio of Effect of Runoff Reduction(ERR)by soil and water conservation measure over management degree in a watershed.And The SRE is the ratio of Effect of Sediment Reduction(ESR)by soil and water conservation measure over management degree in a watershed.First of ah,statistical analysis was applied to test the zonal effects of RRE and SRE between different water erosion regions.The results showed that the mean RRE values in northern regions were significantly greater than those of southern regions;and the mean SRE values in northern regions were significantly greater than those in southern regions.Next,the variation of RRE with runoff depth(H)was studied in direction of both latitude and longitude across regions influenced by East Asian Monsoon.Meanwhile,the variation of SRE with specific sediment yield(Y)was studied in direction of both latitude and longitude across regions influenced by East Asian Monsoon.The results showed that RRE had the inverse variation trend as H in both latitude and longitude direction and SRE had the same variation trend as Y in both latitude and longitude direction.Furthermore,the variation of unit management area Runoff Reduction Rate(RRR)with H and RRE was studied in direction of both latitude and longitude.And the variation of unit management area Sediment Reduction Rate(SRR)with Y and SRE was studied in direction of both latitude and longitude.It was found that RRR had the similar variation trend as H in latitude direction and there was critical point around 37°N greater than which RRR began to be equal to H or even larger;RRR had the similar variation trend as H in longitude direction and there was a critical point around 109°E lees than which RRR began to equal to or greater than H;SRR had the similar variation trend as Y in latitude direction and there was critical point around 36°N greater than which SRR began to be equal to Y or even larger;SRR had the similar variation trend as Y in longitude direction and there was a critical point around 106°E lees than which SRR began to equal to or greater than Y.The zonality of RRE,RRR,SRE and SRR was determined by the combined influence of climate variation and special landform in regions controlled by East Asian Monsoon in China.展开更多
As a case study, refined iron（Fe） speciation and quantitative characterization of the reductive reactivity of Fe（Ⅲ）oxides are combined to investigate Fe diagenetic processes in a core sediment from the eutrophic ...As a case study, refined iron（Fe） speciation and quantitative characterization of the reductive reactivity of Fe（Ⅲ）oxides are combined to investigate Fe diagenetic processes in a core sediment from the eutrophic Jiaozhou Bay.The results show that a combination of the two methods can trace Fe transformation in more detail and offer nuanced information on Fe diagenesis from multiple perspectives. This methodology may be used to enhance our understanding of the complex biogeochemical cycling of Fe and sulfur in other studies. Microbial iron reduction（MIR） plays an important role in Fe（Ⅲ） reduction over the upper sediments, while a chemical reduction by reaction with dissolved sulfide is the main process at a deeper（〉 12 cm） layer. The most bioavailable amorphous Fe（Ⅲ） oxides [Fe（Ⅲ）am] are the main source of the MIR, followed by poorly crystalline Fe（Ⅲ） oxides [Fe（Ⅲ）pc）]and magnetite. Well crystalline Fe（Ⅲ） oxides [Fe（Ⅲ）wc] have barely participated in Fe diagenesis. The importance of the MIR over the upper layer may be a combined result of the high availability of highly reactive Fe oxides and low availability of labile organic matter, and the latter is also the ultimate factor limiting sulfate reduction and sulfide accumulation in the sediments. Microbially reducible Fe（Ⅲ） [MR-Fe（Ⅲ）], which is quantified by kinetics of Fe（II）-oxide reduction, mainly consists of the most reactive Fe（Ⅲ）am and less reactive Fe（Ⅲ）pc. The bulk reactivity of the MR-Fe（Ⅲ） pool is equivalent to aged ferrihydrite, and shows down-core decrease due to preferential reduction of highly reactive phases of Fe oxides.展开更多
The purpose of this study is to investigate the control function and mechanisms of natural river notches. Physical and numerical experiments are analyzed in this study for two representative types of sediment events：...The purpose of this study is to investigate the control function and mechanisms of natural river notches. Physical and numerical experiments are analyzed in this study for two representative types of sediment events： high intensity and short duration Type A sediment disaster events, and low intensity and long duration Type B moderate non-disaster events. Two dimensionless parameters, sediment trapping rate and reduction rate of peak sediment transport, are defined to evaluate the sediment control function of river notches. Study results indicate that the contraction ratio of the notch has a significant influence on sediment control function, with high contraction ratios resulting in both high sediment-trapping and high reduction rates. River notches provide better sediment control during Type A events than Type B events. The sediment control mechanism of river notches is the result of multiple interactions among river flow, sediment transport, and riverbed variation. Analysis of these interactions supports the significant protection role of river notches on sediment control for disaster events.展开更多
基金Financial support was provided by the National Natural Science Foundation of China(Grant No.41271304,Grant No.41001165)Open Foundation of State Key Laboratory of Soil Erosion and Dryland Farming on Loees Plateau(K318009902-1315).
文摘In this particular study,99 typical managed small watersheds which representing five water erosion areas in China were selected to study zonality of Runoff Reduction Efficiency(RRE)and of Sediment Reduction Efficiency(SRE).The RRE is the ratio of Effect of Runoff Reduction(ERR)by soil and water conservation measure over management degree in a watershed.And The SRE is the ratio of Effect of Sediment Reduction(ESR)by soil and water conservation measure over management degree in a watershed.First of ah,statistical analysis was applied to test the zonal effects of RRE and SRE between different water erosion regions.The results showed that the mean RRE values in northern regions were significantly greater than those of southern regions;and the mean SRE values in northern regions were significantly greater than those in southern regions.Next,the variation of RRE with runoff depth(H)was studied in direction of both latitude and longitude across regions influenced by East Asian Monsoon.Meanwhile,the variation of SRE with specific sediment yield(Y)was studied in direction of both latitude and longitude across regions influenced by East Asian Monsoon.The results showed that RRE had the inverse variation trend as H in both latitude and longitude direction and SRE had the same variation trend as Y in both latitude and longitude direction.Furthermore,the variation of unit management area Runoff Reduction Rate(RRR)with H and RRE was studied in direction of both latitude and longitude.And the variation of unit management area Sediment Reduction Rate(SRR)with Y and SRE was studied in direction of both latitude and longitude.It was found that RRR had the similar variation trend as H in latitude direction and there was critical point around 37°N greater than which RRR began to be equal to H or even larger;RRR had the similar variation trend as H in longitude direction and there was a critical point around 109°E lees than which RRR began to equal to or greater than H;SRR had the similar variation trend as Y in latitude direction and there was critical point around 36°N greater than which SRR began to be equal to Y or even larger;SRR had the similar variation trend as Y in longitude direction and there was a critical point around 106°E lees than which SRR began to equal to or greater than Y.The zonality of RRE,RRR,SRE and SRR was determined by the combined influence of climate variation and special landform in regions controlled by East Asian Monsoon in China.
基金The National Natural Science Foundation of China under contract Nos 41576078 and 41276069the Shandong Province Natural Science Foundation of China under contract No.ZR2015DM006the National Key Research and Development Program of China under contract No.2016YFA0601301
文摘As a case study, refined iron（Fe） speciation and quantitative characterization of the reductive reactivity of Fe（Ⅲ）oxides are combined to investigate Fe diagenetic processes in a core sediment from the eutrophic Jiaozhou Bay.The results show that a combination of the two methods can trace Fe transformation in more detail and offer nuanced information on Fe diagenesis from multiple perspectives. This methodology may be used to enhance our understanding of the complex biogeochemical cycling of Fe and sulfur in other studies. Microbial iron reduction（MIR） plays an important role in Fe（Ⅲ） reduction over the upper sediments, while a chemical reduction by reaction with dissolved sulfide is the main process at a deeper（〉 12 cm） layer. The most bioavailable amorphous Fe（Ⅲ） oxides [Fe（Ⅲ）am] are the main source of the MIR, followed by poorly crystalline Fe（Ⅲ） oxides [Fe（Ⅲ）pc）]and magnetite. Well crystalline Fe（Ⅲ） oxides [Fe（Ⅲ）wc] have barely participated in Fe diagenesis. The importance of the MIR over the upper layer may be a combined result of the high availability of highly reactive Fe oxides and low availability of labile organic matter, and the latter is also the ultimate factor limiting sulfate reduction and sulfide accumulation in the sediments. Microbially reducible Fe（Ⅲ） [MR-Fe（Ⅲ）], which is quantified by kinetics of Fe（II）-oxide reduction, mainly consists of the most reactive Fe（Ⅲ）am and less reactive Fe（Ⅲ）pc. The bulk reactivity of the MR-Fe（Ⅲ） pool is equivalent to aged ferrihydrite, and shows down-core decrease due to preferential reduction of highly reactive phases of Fe oxides.
基金financial support were provided by the Disaster Prevention Research Center, National Cheng Kung University
文摘The purpose of this study is to investigate the control function and mechanisms of natural river notches. Physical and numerical experiments are analyzed in this study for two representative types of sediment events： high intensity and short duration Type A sediment disaster events, and low intensity and long duration Type B moderate non-disaster events. Two dimensionless parameters, sediment trapping rate and reduction rate of peak sediment transport, are defined to evaluate the sediment control function of river notches. Study results indicate that the contraction ratio of the notch has a significant influence on sediment control function, with high contraction ratios resulting in both high sediment-trapping and high reduction rates. River notches provide better sediment control during Type A events than Type B events. The sediment control mechanism of river notches is the result of multiple interactions among river flow, sediment transport, and riverbed variation. Analysis of these interactions supports the significant protection role of river notches on sediment control for disaster events.
