The Tibetan Plateau is home to the largest aggregate of glaciers outside the Polar Regions and is a source of fresh water to 1.4 billion people. Yet little is known about the transportation and cycling of Hg in high-e...The Tibetan Plateau is home to the largest aggregate of glaciers outside the Polar Regions and is a source of fresh water to 1.4 billion people. Yet little is known about the transportation and cycling of Hg in high-elevation glacier basins on Tibetan Plateau. In this study, surface snow,glacier melting stream water and lake water samples were collected from the Qiangyong Glacier Basin. The spatiotemporal distribution and transportation of Hg from glacier to lake were investigated. Significant diurnal variations of dissolved Hg（DHg） concentrations were observed in the river water, with low concentrations in the morning（8：00 am–14：00 pm） and high concentrations in the afternoon（16：00 pm–20：00 pm）. The DHg concentrations were exponentially correlated with runoff, which indicated that runoff was the dominant factor affecting DHg concentrations in the river water. Moreover, significant decreases of Hg were observed during transportation from glacier to lake. DHg adsorption onto particulates followed by the sedimentation of particulate-bound Hg（PHg） could be possible as an important Hg removal mechanism during the transportation process. Significant decreases in Hg concentrations were observed downstream of Xiao Qiangyong Lake, which indicated that the high-elevation lake system could significantly affect the distribution and transportation of Hg in the Qiangyong Glacier Basin.展开更多
The Tibetan Plateau（TP） is recognized as ＂Water Tower of Asia＂. Yet our understanding of mechanisms influencing incorporation of mercury（Hg） into freshwater in mountain glaciers on the TP remains quite limited. ...The Tibetan Plateau（TP） is recognized as ＂Water Tower of Asia＂. Yet our understanding of mechanisms influencing incorporation of mercury（Hg） into freshwater in mountain glaciers on the TP remains quite limited. Extensive sampling of environmental matrices（e.g., snow/ice）were conducted on the East Rongbuk glacier on Mt. Everest and Zhadang glacier on Mt.Nyainqentanglha for Hg speciation analysis. Speciated Hg behaved quite different during snowmelt： a preferential early release of DHg（dissolved Hg） was observed at the onset of snowmelt, whereas PHg（particulate-bound Hg） and THg（total Hg） become relatively enriched in snow and released later. Small fraction of Hg in snow was lost during a snowmelt day（18.9%–34.7%） with a large proportion（58.1%–87.3%） contributed by PHg decrease, indicating that the deposited Hg is most likely retained in glacier snow/ice. Furthermore, THg were positively correlated with PHg and crustal major ions（e.g., Ca2＋, Mg2＋） during snowmelt, indicating that Hg is mainly migrated with particulates. The main pathway of Hg loss during snowmelt was most probably associated with release of PHg with meltwater, which was greatly influenced by ablation intensity of snow/ice. This should be paid particular concern as Hg preserved in mountain glaciers will mostly enter aquatic ecosystem as climate warms, impacting on downstream ecosystems adversely. Obvious decrease of THg during the downstream transport from glacier was observed with a large proportion contributed by PHg decrease. The main removal mechanism of Hg was associated with sedimentation of PHg during the transport process.展开更多
Alluvial rivers may experience intense sediment transport and rapid bed evolution under a high flow regime,for which traditional decoupled mathematical river mod-els based on simplified conservation equations are not ...Alluvial rivers may experience intense sediment transport and rapid bed evolution under a high flow regime,for which traditional decoupled mathematical river mod-els based on simplified conservation equations are not applicable. A two-dimen-sional coupled mathematical model is presented,which is generally applicable to the fluvial processes with either intense or weak sediment transport. The governing equations of the model comprise the complete shallow water hydrodynamic equa-tions closed with Manning roughness for boundary resistance and empirical rela-tionships for sediment exchange with the erodible bed. The second-order Total-Variation-Diminishing version of the Weighted-Average-Flux method,along with the HLLC approximate Riemann Solver,is adapted to solve the governing equations,which can properly resolve shock waves and contact discontinuities. The model is applied to the pilot study of the flooding due to a sudden outburst of a real glacial-lake.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 41121001, 41225002, 41571073)the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (No. XDB03030504)
文摘The Tibetan Plateau is home to the largest aggregate of glaciers outside the Polar Regions and is a source of fresh water to 1.4 billion people. Yet little is known about the transportation and cycling of Hg in high-elevation glacier basins on Tibetan Plateau. In this study, surface snow,glacier melting stream water and lake water samples were collected from the Qiangyong Glacier Basin. The spatiotemporal distribution and transportation of Hg from glacier to lake were investigated. Significant diurnal variations of dissolved Hg（DHg） concentrations were observed in the river water, with low concentrations in the morning（8：00 am–14：00 pm） and high concentrations in the afternoon（16：00 pm–20：00 pm）. The DHg concentrations were exponentially correlated with runoff, which indicated that runoff was the dominant factor affecting DHg concentrations in the river water. Moreover, significant decreases of Hg were observed during transportation from glacier to lake. DHg adsorption onto particulates followed by the sedimentation of particulate-bound Hg（PHg） could be possible as an important Hg removal mechanism during the transportation process. Significant decreases in Hg concentrations were observed downstream of Xiao Qiangyong Lake, which indicated that the high-elevation lake system could significantly affect the distribution and transportation of Hg in the Qiangyong Glacier Basin.
基金supported by the National Natural Science Foundation of China (Nos.41421061,41671074)the Foundation of State Key Laboratory of Cryosphere Science (No.SKLCS-ZZ-2015-01-10)
文摘The Tibetan Plateau（TP） is recognized as ＂Water Tower of Asia＂. Yet our understanding of mechanisms influencing incorporation of mercury（Hg） into freshwater in mountain glaciers on the TP remains quite limited. Extensive sampling of environmental matrices（e.g., snow/ice）were conducted on the East Rongbuk glacier on Mt. Everest and Zhadang glacier on Mt.Nyainqentanglha for Hg speciation analysis. Speciated Hg behaved quite different during snowmelt： a preferential early release of DHg（dissolved Hg） was observed at the onset of snowmelt, whereas PHg（particulate-bound Hg） and THg（total Hg） become relatively enriched in snow and released later. Small fraction of Hg in snow was lost during a snowmelt day（18.9%–34.7%） with a large proportion（58.1%–87.3%） contributed by PHg decrease, indicating that the deposited Hg is most likely retained in glacier snow/ice. Furthermore, THg were positively correlated with PHg and crustal major ions（e.g., Ca2＋, Mg2＋） during snowmelt, indicating that Hg is mainly migrated with particulates. The main pathway of Hg loss during snowmelt was most probably associated with release of PHg with meltwater, which was greatly influenced by ablation intensity of snow/ice. This should be paid particular concern as Hg preserved in mountain glaciers will mostly enter aquatic ecosystem as climate warms, impacting on downstream ecosystems adversely. Obvious decrease of THg during the downstream transport from glacier was observed with a large proportion contributed by PHg decrease. The main removal mechanism of Hg was associated with sedimentation of PHg during the transport process.
基金the National Basic Research and Development Program of China (973 Program) (Grant No 2007CB14106)the National Natural Science Foundation of China (Grant No 50459001)the Key Project of Chinese Academy of Sciences (Grant No KZCX3-SW-357-02)
文摘Alluvial rivers may experience intense sediment transport and rapid bed evolution under a high flow regime,for which traditional decoupled mathematical river mod-els based on simplified conservation equations are not applicable. A two-dimen-sional coupled mathematical model is presented,which is generally applicable to the fluvial processes with either intense or weak sediment transport. The governing equations of the model comprise the complete shallow water hydrodynamic equa-tions closed with Manning roughness for boundary resistance and empirical rela-tionships for sediment exchange with the erodible bed. The second-order Total-Variation-Diminishing version of the Weighted-Average-Flux method,along with the HLLC approximate Riemann Solver,is adapted to solve the governing equations,which can properly resolve shock waves and contact discontinuities. The model is applied to the pilot study of the flooding due to a sudden outburst of a real glacial-lake.
