Kansu （KS） profile is located in the east of Yili basin, western Xinjiang, where typical loess sediments are distributed. The magnetic parameters （such as IRM, SIRM SOFT, and M） and grain size in the KS profile we...Kansu （KS） profile is located in the east of Yili basin, western Xinjiang, where typical loess sediments are distributed. The magnetic parameters （such as IRM, SIRM SOFT, and M） and grain size in the KS profile were analyzed in the study. The results showed that the magnetic property of KS loess is dominated by ferrimagnetic minerals, such as magnetite and maghemite. Antiferromagnetic and superparamagnetic minerals also exist in the profile, but had less impact on magnetic susceptibility. Compared with the typical loess sediments of the central Loess Plateau in China, the strata of Kansu profile contained more magnetic minerals and hard magnetic minerals. The analysis of grain size for magnetic minerals indicated that the properties of loess and paleosol were respectively dominated by PSD/MD and coarse SSD magnetite. The research found that the contents of magnetic minerals in loess and paleosol sequences in Kansu profile were similar, but the proportion of fine grained magnetite and soft magnetic minerals were varying, which implies a positive relationship between the value of magnetic susceptibility and intensity of pedogenesis.展开更多
The aim of this study was to investigate the benthic bacterial communities in different depths of an urban river sediment accumulated with high concentrations of nutrients and metals. Vertical distributions of bacteri...The aim of this study was to investigate the benthic bacterial communities in different depths of an urban river sediment accumulated with high concentrations of nutrients and metals. Vertical distributions of bacterial operational taxonomic units （OTUs） and chemical para- meters （nutrients： NH4＋, NO3, dissolved organic carbon, and acid volatile sulfur; metals： Fe, Zn, and Cu） were characterized in 30 cm sediment cores. The bacterial OTUs were measured using the terminal restriction fragment length polymorphism analysis. Biodiversity indexes and multivariate statistical analyses were used to characterize the spatial distributions of microbial diversity in response to the environmental parameters. Results showed that concentrations of the nutrients and metals in this river sediment were higher than those in similar studies. Furthermore, high microbial richness and diversity appeared in the sediment. The diversity did not vary obviously in the whole sediment profile. The change of the diversity indexes and the affiliations of the OTUs showed that the top layer had different bacterial community structure from deeper layers due to the hydrological disturbance and redox change in the surface sediment. The dominant bacterial OTUs ubiquitously existed in the deeper sediment layers （5-27 cm） corresponding to the distributions of the nutrients and metals. With much higher diversity than the dominant OTUs, the minor bacterial assemblages varied with depths, which might be affected by the sedimentation process and the environmental competition pressure.展开更多
The calculation accuracy of the suspended sediment transport rate relies on that of the vertical distribution of the particle concentration,the particle velocity distribution and the reference concentration.In view of...The calculation accuracy of the suspended sediment transport rate relies on that of the vertical distribution of the particle concentration,the particle velocity distribution and the reference concentration.In view of the limitations of the previons formulas for both the velocity and the concentration distributions,general expressions are introduced to the calculation of sus- pended sediment transport rate.Based on these analyses,a simple and practical calculation model is given in the present paper.展开更多
Coastal salt marshes represent an important coastal wetland system. In order to tmderstand the differences between boundary layer parameters of vegetated and unvegetated areas, as well as the mechanisms of sediment tr...Coastal salt marshes represent an important coastal wetland system. In order to tmderstand the differences between boundary layer parameters of vegetated and unvegetated areas, as well as the mechanisms of sediment transport, several electromagnetic current meters （AEM HR, products of Alec Electronics Co. Ltd.） were deployed in coastal wetlands in Quanzhou Bay, China, to measure current velocity. During the low tide phase, the surficial sediment was collected at 10 m intervals. In situ measurements show that the current velocities on the bare flat were much higher than those in the Spartina alterniflora marsh. Current velocity also varied with distance from marsh edge and plant canopy height and diameter. Around 63% of the velocity profiles in the tidal creek can be described by a logarithmic equation. Over the bare flat and Spartina alterniflora marsh, a logarithmic profile almost occurs during the flood tide phase. Sediment analysis shows that mean grain size was 6.7 Ф along the marsh edge, and surface sediments were transported from bare fiat to marsh; the tidal creeks may change this sediment transport pattern. The hydrodynamics at early flood tide and late ebb tide phases determined the net transport direction within the study area.展开更多
基金funded by the National 973 Project (2009CB421308)the Natural Science Foundation of China (40871080 and 90502008)
文摘Kansu （KS） profile is located in the east of Yili basin, western Xinjiang, where typical loess sediments are distributed. The magnetic parameters （such as IRM, SIRM SOFT, and M） and grain size in the KS profile were analyzed in the study. The results showed that the magnetic property of KS loess is dominated by ferrimagnetic minerals, such as magnetite and maghemite. Antiferromagnetic and superparamagnetic minerals also exist in the profile, but had less impact on magnetic susceptibility. Compared with the typical loess sediments of the central Loess Plateau in China, the strata of Kansu profile contained more magnetic minerals and hard magnetic minerals. The analysis of grain size for magnetic minerals indicated that the properties of loess and paleosol were respectively dominated by PSD/MD and coarse SSD magnetite. The research found that the contents of magnetic minerals in loess and paleosol sequences in Kansu profile were similar, but the proportion of fine grained magnetite and soft magnetic minerals were varying, which implies a positive relationship between the value of magnetic susceptibility and intensity of pedogenesis.
基金Acknowledgements This work was partly supported by grants from the National Natural Science Foundation of China （Grant Nos. 51039007 and 511792t2）, the Mega-projects of Science Research for Water Environment Improvement （No. 2009ZX07211-002-01） and the Research Fund Program of Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology （No. 2013K0011）.
文摘The aim of this study was to investigate the benthic bacterial communities in different depths of an urban river sediment accumulated with high concentrations of nutrients and metals. Vertical distributions of bacterial operational taxonomic units （OTUs） and chemical para- meters （nutrients： NH4＋, NO3, dissolved organic carbon, and acid volatile sulfur; metals： Fe, Zn, and Cu） were characterized in 30 cm sediment cores. The bacterial OTUs were measured using the terminal restriction fragment length polymorphism analysis. Biodiversity indexes and multivariate statistical analyses were used to characterize the spatial distributions of microbial diversity in response to the environmental parameters. Results showed that concentrations of the nutrients and metals in this river sediment were higher than those in similar studies. Furthermore, high microbial richness and diversity appeared in the sediment. The diversity did not vary obviously in the whole sediment profile. The change of the diversity indexes and the affiliations of the OTUs showed that the top layer had different bacterial community structure from deeper layers due to the hydrological disturbance and redox change in the surface sediment. The dominant bacterial OTUs ubiquitously existed in the deeper sediment layers （5-27 cm） corresponding to the distributions of the nutrients and metals. With much higher diversity than the dominant OTUs, the minor bacterial assemblages varied with depths, which might be affected by the sedimentation process and the environmental competition pressure.
文摘The calculation accuracy of the suspended sediment transport rate relies on that of the vertical distribution of the particle concentration,the particle velocity distribution and the reference concentration.In view of the limitations of the previons formulas for both the velocity and the concentration distributions,general expressions are introduced to the calculation of sus- pended sediment transport rate.Based on these analyses,a simple and practical calculation model is given in the present paper.
基金supported by the National Natural Science Foundation of China (Grant Nos. 40606012,40576040 and 41076035)
文摘Coastal salt marshes represent an important coastal wetland system. In order to tmderstand the differences between boundary layer parameters of vegetated and unvegetated areas, as well as the mechanisms of sediment transport, several electromagnetic current meters （AEM HR, products of Alec Electronics Co. Ltd.） were deployed in coastal wetlands in Quanzhou Bay, China, to measure current velocity. During the low tide phase, the surficial sediment was collected at 10 m intervals. In situ measurements show that the current velocities on the bare flat were much higher than those in the Spartina alterniflora marsh. Current velocity also varied with distance from marsh edge and plant canopy height and diameter. Around 63% of the velocity profiles in the tidal creek can be described by a logarithmic equation. Over the bare flat and Spartina alterniflora marsh, a logarithmic profile almost occurs during the flood tide phase. Sediment analysis shows that mean grain size was 6.7 Ф along the marsh edge, and surface sediments were transported from bare fiat to marsh; the tidal creeks may change this sediment transport pattern. The hydrodynamics at early flood tide and late ebb tide phases determined the net transport direction within the study area.
