Asian dust comprises a large portion of the northern hemisphere atmospheric dust load,thereby exerting substantial influence on the Earth’s climate,global biogeochemistry and hydrological cycle through accelerated sn...Asian dust comprises a large portion of the northern hemisphere atmospheric dust load,thereby exerting substantial influence on the Earth’s climate,global biogeochemistry and hydrological cycle through accelerated snow and ice melt.Dust deposited on alpine glaciers encodes information on broad scale atmospheric-environmental processes.The(^(234)U/^(238)U)values of dust fine particulates can reflect the comminuting time and intermediate processes;thus,it provides a new method for the provenance of aeolian dust in the glacial snowpack/cryoconite.Here we present results from a comprehensive survey of uranium isotopic concentrations in dust collected from cryoconites on the glaciers of the northern Tibetan Plateau(TP).These results indicate significant spatial heterogeneity in the(^(234)U/^(238)U)values associated with snowpack/cryoconite dust over a broad range of glaciers in the northern TP.The values of the(^(234)U/^(238)U)ratio in the glaciers of western Qilian Mountains(Qiyi Glacier,Shiyi Glacier,Laohugou Glacier No.12)were the highest,followed by the Tanggula(Dunkemadi Glacier)and Kunlun Mountains(Yuzhufeng Glacier),whereas these values were the lowest in the eastern Qilian Mountains(Jingyangling Snowpack,Dabanshan Snowpack,Lenglongling Glacier).By including the analysis of Sr-Nd isotopic compositions,we find the spatial isotopic distribution reflects a combination of local dust,which is associated with short comminuting times,and dust transported over long ranges.Meteorological data indicate that the dust production in the west and north TP,Alxa arid lands and Gobi Deserts,may have a significant impact on the TP glaciers.Moreover,U-Sr-Nd isotopic composition and end-member mixing models(EMMA)were used in our study to find out the relative contribution of distinct Asian dust sources to the dust budget in the TP glaciers.The results reveal that snowpack/cryoconite dust is derived from both local sources(low comminution signatures)as well as other dust sources in the Asian region.Our study demonstrates the potential of U isotope composition as a dust tracing method.In particular,by investigating this composition on dust collected from glacier snowpack and cryoconite holes,we arrive at a map of the distribution characteristics of(^(234)U/^(238)U)values in different regions of the TP.Our study is the first to deploy uranium comminution age for Tibetan dust source tracing,and the results are important to elucidate the multiple origins and dynamics of dust in the Tibetan Plateau.展开更多
Asian dust has been identified in subtropical soils of China.Neodymium(Nd)and lead(Pb)elemental and isotopic geochemistry of soils in Southeast China were used to assess the significance of local versus extraneous sou...Asian dust has been identified in subtropical soils of China.Neodymium(Nd)and lead(Pb)elemental and isotopic geochemistry of soils in Southeast China were used to assess the significance of local versus extraneous sources.The εNd(0)values were close to the parent rocks(+2.9)in the young soils(NSJ);while their values were always negative(〜—3.7)in the old soils(OMJ),implying dust deposition.The young soils contained less Asian dust contribution(<8%)while the old soils contained more than 50%Asian dust contribution.This implied that dust contributions were gradually increasing with the soil development stage and Asian dust input had become the principal Nd source for the old soils in this area.On the other hand,Pb excesses and low 207Pb/206Pb values(〜0.8503)in near-surface soils indicated a significant anthropogenic Pb addition onto surface soils.The close relationship between the Pb content and isotopic ratios in the soil profile indicated that the excessive lead in the surface soil was exogenous.These results suggested that Asian dust made up a significant fraction in the old soils,but that local sources(i.e.,basalt and anthropogenic)were not trivial in Southeast China.展开更多
根据对昆仑山北麓阿羌地区第四纪风成砂尘沉积物的调查、地层对比和107组古地磁标本(321块样品)的测定结果认为,阿羌地层剖面记录了Brunhes时以来我国极端干旱区最完整的风成砂尘堆积序列;剖面中间冰期形成的生草层1PE和细粒风尘堆积29...根据对昆仑山北麓阿羌地区第四纪风成砂尘沉积物的调查、地层对比和107组古地磁标本(321块样品)的测定结果认为,阿羌地层剖面记录了Brunhes时以来我国极端干旱区最完整的风成砂尘堆积序列;剖面中间冰期形成的生草层1PE和细粒风尘堆积29FGL、31FGL、33FGL、35FGL、37FGL、39FGL、42FGL在形成的地质时代上可依次与黄土高原古土壤S_0、S_1、S_2、S_3、S_4、S_5、S_6、S_7进行对比,而与1PE和细粒风尘堆积29FGL、……、42FGL互为叠覆的冰期气候形成的风成极细砂和粗粒风尘堆积则可与黄土高原黄土L_1、……、L_8进行对比。此外,在阿羌剖面砂尘堆积底部42FGL层中发现有0.7 Ma B P前的宇宙尘埃物质,这对于该地风成砂尘下限年代的确定、研究极端干旱区气候的发展历史和晚新生代地外灾变事件的对比具有重要意义。展开更多
基金funded by the National Natural Science Foundation of China(Grant No.42022002)the State Key Laboratory of Cryosphere Sciences(Grant No.SKLCS-ZZ-2022)+1 种基金funded through NSF Critical Zone Collaborative proposal#2011910the German Research Foundation(DFG)for funding through the Heisenberg Programme“Multiscale Simulation of Earth Surface Processes”.
文摘Asian dust comprises a large portion of the northern hemisphere atmospheric dust load,thereby exerting substantial influence on the Earth’s climate,global biogeochemistry and hydrological cycle through accelerated snow and ice melt.Dust deposited on alpine glaciers encodes information on broad scale atmospheric-environmental processes.The(^(234)U/^(238)U)values of dust fine particulates can reflect the comminuting time and intermediate processes;thus,it provides a new method for the provenance of aeolian dust in the glacial snowpack/cryoconite.Here we present results from a comprehensive survey of uranium isotopic concentrations in dust collected from cryoconites on the glaciers of the northern Tibetan Plateau(TP).These results indicate significant spatial heterogeneity in the(^(234)U/^(238)U)values associated with snowpack/cryoconite dust over a broad range of glaciers in the northern TP.The values of the(^(234)U/^(238)U)ratio in the glaciers of western Qilian Mountains(Qiyi Glacier,Shiyi Glacier,Laohugou Glacier No.12)were the highest,followed by the Tanggula(Dunkemadi Glacier)and Kunlun Mountains(Yuzhufeng Glacier),whereas these values were the lowest in the eastern Qilian Mountains(Jingyangling Snowpack,Dabanshan Snowpack,Lenglongling Glacier).By including the analysis of Sr-Nd isotopic compositions,we find the spatial isotopic distribution reflects a combination of local dust,which is associated with short comminuting times,and dust transported over long ranges.Meteorological data indicate that the dust production in the west and north TP,Alxa arid lands and Gobi Deserts,may have a significant impact on the TP glaciers.Moreover,U-Sr-Nd isotopic composition and end-member mixing models(EMMA)were used in our study to find out the relative contribution of distinct Asian dust sources to the dust budget in the TP glaciers.The results reveal that snowpack/cryoconite dust is derived from both local sources(low comminution signatures)as well as other dust sources in the Asian region.Our study demonstrates the potential of U isotope composition as a dust tracing method.In particular,by investigating this composition on dust collected from glacier snowpack and cryoconite holes,we arrive at a map of the distribution characteristics of(^(234)U/^(238)U)values in different regions of the TP.Our study is the first to deploy uranium comminution age for Tibetan dust source tracing,and the results are important to elucidate the multiple origins and dynamics of dust in the Tibetan Plateau.
基金the China Natural Science Foundation(Nos.41877006 and 41930862)we also express great thanks to Hailong Wang for his assistance in language polishing.
文摘Asian dust has been identified in subtropical soils of China.Neodymium(Nd)and lead(Pb)elemental and isotopic geochemistry of soils in Southeast China were used to assess the significance of local versus extraneous sources.The εNd(0)values were close to the parent rocks(+2.9)in the young soils(NSJ);while their values were always negative(〜—3.7)in the old soils(OMJ),implying dust deposition.The young soils contained less Asian dust contribution(<8%)while the old soils contained more than 50%Asian dust contribution.This implied that dust contributions were gradually increasing with the soil development stage and Asian dust input had become the principal Nd source for the old soils in this area.On the other hand,Pb excesses and low 207Pb/206Pb values(〜0.8503)in near-surface soils indicated a significant anthropogenic Pb addition onto surface soils.The close relationship between the Pb content and isotopic ratios in the soil profile indicated that the excessive lead in the surface soil was exogenous.These results suggested that Asian dust made up a significant fraction in the old soils,but that local sources(i.e.,basalt and anthropogenic)were not trivial in Southeast China.
文摘根据对昆仑山北麓阿羌地区第四纪风成砂尘沉积物的调查、地层对比和107组古地磁标本(321块样品)的测定结果认为,阿羌地层剖面记录了Brunhes时以来我国极端干旱区最完整的风成砂尘堆积序列;剖面中间冰期形成的生草层1PE和细粒风尘堆积29FGL、31FGL、33FGL、35FGL、37FGL、39FGL、42FGL在形成的地质时代上可依次与黄土高原古土壤S_0、S_1、S_2、S_3、S_4、S_5、S_6、S_7进行对比,而与1PE和细粒风尘堆积29FGL、……、42FGL互为叠覆的冰期气候形成的风成极细砂和粗粒风尘堆积则可与黄土高原黄土L_1、……、L_8进行对比。此外,在阿羌剖面砂尘堆积底部42FGL层中发现有0.7 Ma B P前的宇宙尘埃物质,这对于该地风成砂尘下限年代的确定、研究极端干旱区气候的发展历史和晚新生代地外灾变事件的对比具有重要意义。
