This paper presents a detailed study on the textural and geochemical characteristics of the proglacial sediments near the edge of modern Nelson Ice Cap, Antarctica. The grain size distributions of the proglacial sedim...This paper presents a detailed study on the textural and geochemical characteristics of the proglacial sediments near the edge of modern Nelson Ice Cap, Antarctica. The grain size distributions of the proglacial sediments are characteristic of glacigenic deposits, but very different from those of aeolian and lacustrine sediments. Moreover, the grain size distributions of the proglacial sediments are fractal with a dimension of about 2.9, and the fractal dimensions can be used as another summary statistical parameter for quantifying the relative amounts of coarse and fine materials. Correlations between the absolute element abundances of the proglacial sediments are very weak due to mineral partitioning and other effects of glacial processes, but correlations between the element/Rb ratios are statistically significant. This finding indicates that element/Rb ratios can be used to reduce or eliminate the effects of glacial processes, evaluate geochemical data and determine the sediment provenance in the foreland of Antarctic glacier. Comparisons on the element concentrations among different environments suggest that the proglacial sediments are derived predominantly from local bedrocks and appear to be natural in origin. Thus these natural sediments can be used to study chemical weathering in the proglacial foreland of modern glacier.展开更多
The preliminary measurements of nitrous oxide fluxes from the ornithogenic soils on tropical Xi-sha atoll were made using a closed chamber technique for the first time. N_2O fluxes from the ornithogenic soils ranged f...The preliminary measurements of nitrous oxide fluxes from the ornithogenic soils on tropical Xi-sha atoll were made using a closed chamber technique for the first time. N_2O fluxes from the ornithogenic soils ranged from 1 8 to 40 3 μg/(m^2\5h) on Dong Island and 3 2 to 20 4 μg/(m^2·h) on Yongxing Island and their flux averaged 11 0 μg/(m^2·h) and 8 3 μg/(m^2·h), respectively. N_2O fluxes from two wetland sites in salt marsh of Dong Island were approximately one order of magnitude lower than those from the ornithogenic soils and averaged 2 1 μg/(m^2·h) and 2 4 μg/(m^2·h). The diurnal variation cycle in the fluxes was obtained at the observation sites; the N_2O flux increased with the increase in soil temperature. The sudden increase in soil moisture greatly stimulated N_2O emission from the ornithogenic soils on Dong Island due to the heavy rainfall. The undisturbed soils showed the lower N_2O fluxes and the average was 4 8 μg/(m^2·h) and the soils via the reclamation showed the higher N_2O fluxes and the average was 16 6 μg/(m^2·h) on Yongxing Island, suggesting that the changes of land use have an important effect on N_2O fluxes from the ornithogenic soils. In addition, the N_2O fluxes at the different sites showed high spatial variations. The fluxes were positively correlated with the concentrations of NO^-_3, PO~ 3- _4 and Mn in the soils. The negative correlation between the fluxes and total S concentration in the ornithogenic soils was also found for the first time. Coastal soils or sediments constitute an important source of global atmospheric N_2O and the increases in nitrogen loading from seabird guanos will lead to significant increases in the flux of this atmospherically active gas.展开更多
基金The work was supported by the Nationa1 Natural ScienceFoundation of China(Grant No．40231002 and 40076032)the project of Chinese Academy of Sciences(Grant No．KZCX2-303)
文摘This paper presents a detailed study on the textural and geochemical characteristics of the proglacial sediments near the edge of modern Nelson Ice Cap, Antarctica. The grain size distributions of the proglacial sediments are characteristic of glacigenic deposits, but very different from those of aeolian and lacustrine sediments. Moreover, the grain size distributions of the proglacial sediments are fractal with a dimension of about 2.9, and the fractal dimensions can be used as another summary statistical parameter for quantifying the relative amounts of coarse and fine materials. Correlations between the absolute element abundances of the proglacial sediments are very weak due to mineral partitioning and other effects of glacial processes, but correlations between the element/Rb ratios are statistically significant. This finding indicates that element/Rb ratios can be used to reduce or eliminate the effects of glacial processes, evaluate geochemical data and determine the sediment provenance in the foreland of Antarctic glacier. Comparisons on the element concentrations among different environments suggest that the proglacial sediments are derived predominantly from local bedrocks and appear to be natural in origin. Thus these natural sediments can be used to study chemical weathering in the proglacial foreland of modern glacier.
文摘The preliminary measurements of nitrous oxide fluxes from the ornithogenic soils on tropical Xi-sha atoll were made using a closed chamber technique for the first time. N_2O fluxes from the ornithogenic soils ranged from 1 8 to 40 3 μg/(m^2\5h) on Dong Island and 3 2 to 20 4 μg/(m^2·h) on Yongxing Island and their flux averaged 11 0 μg/(m^2·h) and 8 3 μg/(m^2·h), respectively. N_2O fluxes from two wetland sites in salt marsh of Dong Island were approximately one order of magnitude lower than those from the ornithogenic soils and averaged 2 1 μg/(m^2·h) and 2 4 μg/(m^2·h). The diurnal variation cycle in the fluxes was obtained at the observation sites; the N_2O flux increased with the increase in soil temperature. The sudden increase in soil moisture greatly stimulated N_2O emission from the ornithogenic soils on Dong Island due to the heavy rainfall. The undisturbed soils showed the lower N_2O fluxes and the average was 4 8 μg/(m^2·h) and the soils via the reclamation showed the higher N_2O fluxes and the average was 16 6 μg/(m^2·h) on Yongxing Island, suggesting that the changes of land use have an important effect on N_2O fluxes from the ornithogenic soils. In addition, the N_2O fluxes at the different sites showed high spatial variations. The fluxes were positively correlated with the concentrations of NO^-_3, PO~ 3- _4 and Mn in the soils. The negative correlation between the fluxes and total S concentration in the ornithogenic soils was also found for the first time. Coastal soils or sediments constitute an important source of global atmospheric N_2O and the increases in nitrogen loading from seabird guanos will lead to significant increases in the flux of this atmospherically active gas.
