Dec 2008, Volume 2 Issue 4
    

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  • CAO Jianfeng, YE Xueyan, JIANG Jiyi, WANG Kaijun
    Frequent flow cutoff has a serious effect on the eco-environment of the region along the Lower Yellow River. The authors study the impact on lateral seepage quantity and groundwater cycling caused by cutoff of the Yellow River and compare it with that of the year 1999 through the numerical simulation model of groundwater flow system of the affected zone. The lateral seepage quantity decreased 53.8% on flow cutoff stage from Huayuankou to the river entrance and breaking time of 300 d. The lateral seepage quantity will decrease 46.3% if flow cutoff is from Jiahetan to the river entrance and breaking time is 300 d, and it will decrease 75.2% if flow cutoff occurs throughout the year. The lateral seepage quantity will decrease 19.8% if flow cutoff is from Luokou to the river entrance and breaking time is 300 d, and it will decrease 25.1% if flow cutoff occurs throughout the year. The lateral seepage quantity will decrease 4.7% if flow cutoff is from Lijin to the river entrance and flow cutoff occurs throughout the year. Flow cutoff of the Yellow River has a minor effect on the shape of groundwater flow domain of the affected zone. Thus, the boundary condition of the shallow groundwater system will not change. Although flow cutoff has a major influence on the riverside source fields in the Lower Yellow River, it will not have a significant effect on groundwater resources macroscopically in the affected zone of the Yellow River due to its large storage capacity.
  • Khan Sirajur Rahman, Islam Md Badrul
    Major part of the Holocene Ganges-Brahmaputra delta occupies the southern and southwestern part of Bangladesh with a smaller part extending beyond the international boundary in the west. Five facies assemblages are documented in the lower deltaic plain in five different depositional environments: levee or levee complex, bil or depression, abandoned meander belt, interdistributary plain and estuarine plain. The thickness of the Holocene sediments ranges from 30 m to 70 m in the deltaic plain, usually floored by the Pleistocene stiff clays, with the exception of the abandoned meander belt deposit where Holocene channel sand deposited directly on the Pleistocene sand. Radiocarbon dates indicate that low-rate sedimentation has occurred in the northern part, where 4–6 m thick sediments were deposited since the mid-Holocene, whereas 10–30 m thick sediments were deposited in the southern part during the same span of time. In addition, significant coastal subsidence (3 mm/a on average), added by sea-level rise (1.5 mm/a, conservative rate) occurs in the study area, which serves as a negative factor in degrading the coastal plain of Bangladesh in the future, while taking into consideration the weaker sedimentation in the area.
  • GUO Zhengfu, CHEN Xiaoyu, LIU Jiaqi
    Based on the determination of composition of volcanic volatiles and petrologic estimation of the total mass of volatiles erupted, we showed important advances in the study of the impact of Mesozoic and Cenozoic volcanic activities on paleo-environmental changes in China. The volcanic activities include western Liaoning and Zhangjiakou Mesozoic intermediate-acidic explosive eruptions, southern Tibet and Shanwang Cenozoic volcanism, and Mt. Changbai volcanic eruption around one thousand years ago. The paper predominantly discusses the earth’s surface temperature changes, ozone depletion, acidic rain formation and mass mortalities of vertebrate induced by the Mesozoic and Cenozoic volcanism in China.
  • SHEN Mingjie, YAN Haitao, HU Shouyun, BLAHA Uli., RÖSLER Wolfgang., APPEL Ewin., HOFFMANN Viktor.
    An expressway-side soil profile 22 cm long was sampled from the grassland of the expressway linking Beijing and the Capital International Airport. Magnetic measurements, geochemical and multivariate statistic analyses were performed on the soil samples. The results reveal that the soil profile can be divided into two parts with significant difference in magnetic proxies and heavy metal concentration. The uppermost soil horizon (0–8 cm) represents the pollution-rich layer with higher concentration of ferrimagnetic phases and metallic elements. The values of ? are very high with an average of 141.60 × 10-8 m3·kg-1 in the layer. We explain that the anthropogenic dust input from traffic is the predominant cause for strong signals of magnetic phases and heavy metals. Below the profile depth of 8 cm, there is minor pollution in the soil with lower concentration of magnetic minerals and heavy metals compared to the natural background values. ? remains quite stable and relatively low with an average of 49.44 × 10-8 m3·kg-1. S-ratio also generally decreases with depth, and it changes from 0.93 in the 0–8 cm layer to 0.87 below the depth of 8 cm. It indicates that the soil samples are overwhelmingly predominated by ferrimagnetic minerals in the upper part soil, while the contribution of imperfect antiferromagnetic components is stronger in the lower part. Rock magnetic experiments show MD magnetite as the main magnetic carrier both in the upper and lower parts. The magnetic grain size in the upper part is, however, a bit coarser than that in the lower part. Cluster analysis shows a positive correlation between magnetic properties (?, ARM, SIRM) and heavy metal pollutants of Pb, Zn, Cu. Fuzzy C-means cluster analysis can clearly help divide the soil profile into two different layers and distinguish their characteristics. It can be concluded that these magnetic concentration-related parameters can be used as proxies for pollution investigation in a fast, sensitive, low-cost and highly efficient approach to screening heavy metal pollution.
  • YIN Yong, ZOU Xinqin, ZHU Dakui, HUANG Jiaxiang
    A unique radial tidal sand ridge system (RTSRS) has developed under a complex tidal current field on the eastern China coast between the Yangtze River delta to the south and the abandoned Yellow River (Huanghe) delta to the north. The present study examines the sedimentary evolution of a ridge-channel pair in the central RTSRS. Three cores, with two on the ridges and one in the channel, were drilled to reveal the late Pleistocene-Holocene deposits of the system. Five sedimentary facies were distinguished, i.e. ridge-shallow subtidal facies, ridge-deep subtidal facies, near-surface channel bottom facies, middle tidal flat facies and low tidal flat facies. The ridge-shallow subtidal facies consists of sandy strata with ripple cross beddings, horizontal lamina, and massive beddings. Bioturbation seldom occurs. The ridge-deep subtidal facies is primarily characterized by sandy and muddy interlayers with common flaser and lenticular bedding structures. Bioturbation appears abundantly. Massive and graded sediment sequences of storm origin are present as characterized by rich shell fragments. The near-surface channel bottom facies consists of loose, soft, clayey silt deposits with deformed sedimentary layers. This facies occurs in the deeper part of the active channels. The middle tidal flat and lower tidal flat facies composed of silt-clay couplets prevailed primarily in the tidal flats. Incomplete sedimentary successions show that coastal plain deposits dominate in the study area during 12–13 ka B.P. The sandy ridge and channel facies became dominant during 4–6 ka B.P. when the sea level receded temporarily. Tidal ridge and channel in the study area became active during the last four decades. Sediment reworking due to typhoon and sandy ridge migration plays a key role in shaping the present radial ridge system.
  • QU John, WANG Wanting, DASGUPTA Swarvanu, HAO Xianjun
    Wildland fire is both one of the major natural hazards and a natural process for ecosystem persistence. Accurate assessment of fire danger potential and timely detection of active fires are critical for fire fighting and fuel management. Space-borne measurements have become the primary approaches for these efforts. Many research works have been conducted and some data products have been generated for practical applications. This paper presents a review of the major sensors and algorithms for active fire monitoring and fire danger potential detection from space. Major sensors and their characteristics, physical principles of the major algorithms are summarized. Limitations of these algorithms and future improvements are also discussed.
  • HUANG Bormin, HUANG Hunglung
    Ultraspectral sounders provide an enormous amount of measurements to advance our knowledge of weather and climate applications. The use of robust data compression techniques will be beneficial for ultraspectral data transfer and archiving. This paper reviews the progress in lossless compression of ultraspectral sounder data. Various transform-based, prediction-based, and clustering-based compression methods are covered. Also studied is a preprocessing scheme for data reordering to improve compression gains. All the coding experiments are performed on the ultraspectral compression benchmark dataset collected from the NASA Atmospheric Infrared Sounder (AIRS) observations.