Aeolian processes have been studied extensively at low elevations,but have been relatively little studied at high elevations.Aeolian sediments are widely distributed in the Yarlung Zangbo River basin,southern Tibetan ...Aeolian processes have been studied extensively at low elevations,but have been relatively little studied at high elevations.Aeolian sediments are widely distributed in the Yarlung Zangbo River basin,southern Tibetan Plateau,which is characterized by low pressure and low temperature.Here,we comprehensively analyzed the wind regime using data since 1980 from 11 meteorological stations in the study area,and examined the interaction between the near-surface wind and aeolian environment.The wind environment exhibited significant spatial and temporal variation,and mean wind speed has generally decreased on both annual and seasonal bases since 1980,at an average of 0.181 m/(s•10a).This decrease resulted from the reduced contribution of maximum wind speed,and depended strongly on variations of the frequency of sand-driving winds.The drift potential and related parameters also showed obvious spatial and temporal variation,with similar driving forces for the wind environment.The strength of the wind regime affected the formation and development of the aeolian geomorphological pattern,but with variation caused by local topography and sediment sources.The drift potential and resultant drift direction were two key parameters,as they quantify the dynamic conditions and depositional orientation of the aeolian sediments.Wind affected the spatial variation in sediment grain size,but the source material and complex topographic effects on the near-surface wind were the underlying causes for the grain size distribution of aeolian sands.These results will support efforts to control aeolian desertification in the basin and improve our understanding of aeolian processes in high-elevation environments.展开更多
Determination of the threshold shear velocity is essential for predicting sand transport,dust release and desertification.In this study,a wind tunnel experiment was conducted to evaluate the influence of salinity and ...Determination of the threshold shear velocity is essential for predicting sand transport,dust release and desertification.In this study,a wind tunnel experiment was conducted to evaluate the influence of salinity and moisture on the threshold shear velocity of saline sand.Saline sand samples(mean particle size of 164.50–186.08μm and the total silt,clay and salt content of 0.80%–8.25%)were collected from three saline sand dunes(one barchan dune and two linear dunes)in the Qarhan Desert,Qaidam Basin of China.Original saline sand samples were placed in two experimental trays for wet and dry processing to simulate deliquescence and desiccation,respectively.Surface moisture content ranging from 0.30% to 1.90% was generated by the steam method so that the saline sand can absorb water in a saturated water vapor environment.The motion of sand particles was determined by the observers with a solid laser.The laser sheet(0.80 cm thick),which was emitted by the solid laser,horizontally covered the sand surface and was bound to the sand.Results show that the cohesion of saline sand results from a combination of salt and water.The threshold shear velocity increases exponentially with the increase in crust thickness for the linear sand dunes.There is a positive linear correlation between the original moisture content and relative threshold shear velocity.The threshold shear velocity of dewatered sand is greater than that of wet sand with the same original moisture content.Our results will provide valuable information about the sand transport of highly saline soil in the desert.展开更多
雅鲁藏布江位于青藏高原南部,流域内广泛发育着地质历史时期以来的黄土沉积和现代风沙沉积,蕴含着风成过程和环境演化的丰富信息。从风成沉积分布特征、堆积年代、沉积物特征、物源及其可能的形成机制以及风沙活动历史等方面综述了近些...雅鲁藏布江位于青藏高原南部,流域内广泛发育着地质历史时期以来的黄土沉积和现代风沙沉积,蕴含着风成过程和环境演化的丰富信息。从风成沉积分布特征、堆积年代、沉积物特征、物源及其可能的形成机制以及风沙活动历史等方面综述了近些年雅鲁藏布江流域风成沉积的主要研究进展。结果表明:黄土主要发育于河流阶地及部分山体顶部,多形成于末次冰盛期以后且主要发育于深海氧同位素1阶段(约14 ka BP)以来,而风沙沉积集中发育于河流宽谷段,堆积时间相对较短。沉积物颗粒以机械搬运和物理风化为主,化学风化微弱。尽管沉积物理化性质呈现出一定的空间变化,但仍存在明显的局地特征,与附近地表堆积物联系密切。在风成背景下,黄土的近源成因得到了普遍认可,河谷底部地表松散物质是风成沉积发育的主要物源。风沙活动演变较为复杂,除大区域气候变化外,局地环境也是影响风沙活动及其区域差异的重要因素。未来应加强研究区风成沉积物理化性质、全新世以来的气候变化以及粉尘释放对人类生存环境影响等方面的系统研究。展开更多
基金the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(2019QZKK0602)the Open Foundation of MOE Key Laboratory of Western China's Environmental System,Lanzhou University and the Fundamental Research Funds for the Central Universities(lzujbky-2020-kb01)。
文摘Aeolian processes have been studied extensively at low elevations,but have been relatively little studied at high elevations.Aeolian sediments are widely distributed in the Yarlung Zangbo River basin,southern Tibetan Plateau,which is characterized by low pressure and low temperature.Here,we comprehensively analyzed the wind regime using data since 1980 from 11 meteorological stations in the study area,and examined the interaction between the near-surface wind and aeolian environment.The wind environment exhibited significant spatial and temporal variation,and mean wind speed has generally decreased on both annual and seasonal bases since 1980,at an average of 0.181 m/(s•10a).This decrease resulted from the reduced contribution of maximum wind speed,and depended strongly on variations of the frequency of sand-driving winds.The drift potential and related parameters also showed obvious spatial and temporal variation,with similar driving forces for the wind environment.The strength of the wind regime affected the formation and development of the aeolian geomorphological pattern,but with variation caused by local topography and sediment sources.The drift potential and resultant drift direction were two key parameters,as they quantify the dynamic conditions and depositional orientation of the aeolian sediments.Wind affected the spatial variation in sediment grain size,but the source material and complex topographic effects on the near-surface wind were the underlying causes for the grain size distribution of aeolian sands.These results will support efforts to control aeolian desertification in the basin and improve our understanding of aeolian processes in high-elevation environments.
基金funded by the National Natural Science Foundation of China(41601002,41871008)
文摘Determination of the threshold shear velocity is essential for predicting sand transport,dust release and desertification.In this study,a wind tunnel experiment was conducted to evaluate the influence of salinity and moisture on the threshold shear velocity of saline sand.Saline sand samples(mean particle size of 164.50–186.08μm and the total silt,clay and salt content of 0.80%–8.25%)were collected from three saline sand dunes(one barchan dune and two linear dunes)in the Qarhan Desert,Qaidam Basin of China.Original saline sand samples were placed in two experimental trays for wet and dry processing to simulate deliquescence and desiccation,respectively.Surface moisture content ranging from 0.30% to 1.90% was generated by the steam method so that the saline sand can absorb water in a saturated water vapor environment.The motion of sand particles was determined by the observers with a solid laser.The laser sheet(0.80 cm thick),which was emitted by the solid laser,horizontally covered the sand surface and was bound to the sand.Results show that the cohesion of saline sand results from a combination of salt and water.The threshold shear velocity increases exponentially with the increase in crust thickness for the linear sand dunes.There is a positive linear correlation between the original moisture content and relative threshold shear velocity.The threshold shear velocity of dewatered sand is greater than that of wet sand with the same original moisture content.Our results will provide valuable information about the sand transport of highly saline soil in the desert.
文摘雅鲁藏布江位于青藏高原南部,流域内广泛发育着地质历史时期以来的黄土沉积和现代风沙沉积,蕴含着风成过程和环境演化的丰富信息。从风成沉积分布特征、堆积年代、沉积物特征、物源及其可能的形成机制以及风沙活动历史等方面综述了近些年雅鲁藏布江流域风成沉积的主要研究进展。结果表明:黄土主要发育于河流阶地及部分山体顶部,多形成于末次冰盛期以后且主要发育于深海氧同位素1阶段(约14 ka BP)以来,而风沙沉积集中发育于河流宽谷段,堆积时间相对较短。沉积物颗粒以机械搬运和物理风化为主,化学风化微弱。尽管沉积物理化性质呈现出一定的空间变化,但仍存在明显的局地特征,与附近地表堆积物联系密切。在风成背景下,黄土的近源成因得到了普遍认可,河谷底部地表松散物质是风成沉积发育的主要物源。风沙活动演变较为复杂,除大区域气候变化外,局地环境也是影响风沙活动及其区域差异的重要因素。未来应加强研究区风成沉积物理化性质、全新世以来的气候变化以及粉尘释放对人类生存环境影响等方面的系统研究。
