Evidence of microphytobenthic roles on coastal shallow water of the Seto Inland Sea,Japan

This study describes the temporal variation of microphytobenthic biomass and its controlling factors, as well as the impact of microphytobenthic activities on coastal shallow sediment in the eastern Seto Inland Sea, Japan. The chlorophyll a (Chl a), phaeopigments and sedimentary biophilic element (C, N, P and Si) contents in surface sediments, as well as nutrient concentrations at the sediment-water interface (overlying water and pore water) were observed monthly during November 2003 to May 2005 at one site in Shido Bay (water depth ca. 7 m) and at one site in Harima-Nada (35 m). No correlation was observed between the sedimentary biophilic elements and other parameters. The maximum chlorophyll a content of 48.2 μg g^–1 was found in surface sediments under the photon flux reaching the seafloor of 537 μmol photon m^–2 s^–1 during the winter period when water transparency was the highest at station S (Shido Bay). Our results suggest that higher chlorophyll a content in surface sediment was due to the fresh microphytobenthic biomass (mainly benthic diatom). We also found a significant negative correlation between Chl a and inorganic nutrients in pore water during the low temperature period, especially silicic acid. This result suggests that the silicic acid was assimilated largely during the increase of microphytobenthic biomass in surface sediment. This study suggests that the microphytobenthic roles may have a great effect on nutrient budgets during the large supply of irradiance (winter periods) for their photosynthetic growth in shallow coastal waters.     

Impact of surface heterogeneity on a buoyancy-driven convective boundary layer in light winds

Land-use practices such as deforestation or agricultural management may affect regional climate, ecosystems and water resources. The present study investigates the impact of surface heterogeneity on the behaviour of the atmospheric boundary layer (ABL), at a typical spatial scale of 1 km. Large-eddy simulations, using an interactive soil–vegetation–atmosphere surface scheme, are performed to document the structure of the three-dimensional flow, as driven by buoyancy forces, over patchy terrain with different surface characteristics (roughness, soil moisture, temperature) on each individual patch. The patchy terrain consists of striped and chessboard patterns. The results show that the ABL strongly responds to the spatial configuration of surface heterogeneities. The stripe configuration made of two patches with different soil moisture contents generates the development of a quasi- two-dimensional inland breeze, whereas a three-dimensional divergent flow is induced by chessboard patterns. The feedback of such small-scale atmospheric circulations on the surface fluxes appears to be highly non-linear. The surface sensible and latent heat fluxes averaged over the 25-km² domain may vary by 5% with respect to the patch arrangement.     

Performance of a steel structure on Ar-Rayyas Sabkha soils

Sabkha deposits cover extensive areas along the Red Sea and the Arabian Gulf shores. They are the site of huge industrial complexes in spite of their low bearing capacity of its upper part. The strength of the Sabkha soil is controlled by several factors, among them are the evaporatic salts that cement the grains. The Standard Penetration Test (SPT) is used extensively in this terrain but its results are misleading. The Sabkha soil that may give high N value will lose most of its strength upon wetting as part of the salts are dissolved. Therefore, the design N value was adjusted for Sabkhas to account for salt migration, by relating the SPT (N) value to the Sabkha moisture and salt content. A steel structure factory that was placed in an eastern Saudi Arabian virgin Sabkha deposits was considered. After a few years of operation fresh water leaked through the ground and caused signi.cant differential collapse settlement which threatened the functional integrity of the superstructure. The differential settlement was con.ned to one area of the structure indicating that localized conditions must have contributed to the observed settlement. The subsurface conditions and the geotechnical properties of the site are presented. A statistical model was developed that quanti.es the effect of the moisture and salt content on SPT (N) values. A simple site procedure is suggested to correct the design N value in similar cases. It was found that the increase in the moisture content could reduce the SPT (N) values by as much as 60, good agreements were found between the measured and predicted N values.     

The influences of various anthropogenic sources of deterioration on meiobenthos (Ostracoda) over the last 100 years in Suo-Nada in the Seto Inland Sea, southwest Japan

This study focuses on the relationships of water and sediment quality with meiobenthos (Ostracoda) over the past 100 years, using a sediment core obtained from Suo-Nada in the Seto Inland Sea, Japan. We compared high-resolution ostracode results with geochemical and sedimentological data obtained from the study core as well as with rich environmental monitoring data that are available. R-mode cluster analysis revealed two bioassociations (BC, KA). Until the1960s, assemblages continued to show high diversity. They changed in approximately 1970, when excessive nutrients and organic matter began to be supplied, and most species decreased in number. All species of bioassociation BC were dominant again by the mid-1990s; however, those of bioassociation KA containing infaunal species did not increase and have been absent or rare since the 1970s because organic pollution of sediments has continued to date. This study provided robust baseline for ostracode-based long-term environmental monitoring in East Asia.     

Luminescence chronology of the inland sand dunes from SE India

Records of past climate changes have been preserved variously on the earth's surface. Sand dunes are one such prominent imprint, and it is suggested that their presence is an indicator of periods of transition from arid to less arid phases. We report inland sand dunes from Andhra Pradesh (SE India) spread over an area of ~ 500 km², ~ 75 km inland from the east coast. The dune sands are examined to understand their provenance, transportation, timing of sand aggradation and their relationship to past climates. The dune distribution, grain morphology and the grain-size studies on sands suggest an aeolian origin. Physiography of the study area, heavy mineral assemblage, and abundance of quartz in the parent rocks indicate that the dune sands are largely derived from first-order streams emanating from hills in the region and from weathering of the Nellore schist belt. It appears that the geomorphology and wind direction pattern both facilitated and restricted the dune aggradation and preservation to a limited area. OSL dating of 47 dune samples ranged from the present to ~ 50 ka, thereby suggesting a long duration of sand-dune aggradation and/or reworking history.     

中国干旱内陆流域水体 N、P负荷特征与动态变化——以黑河流域为例

以黑河流域中游地区为研究区域，通过11年在不同河流断面的长期监测和区域内各类水体如地下水、泉水、水库和河流的空间选点取样分析，研究了干旱内陆流域水体 N、P等植物营养元素的负荷与时空分布及动态变化特征。浅层地下水与河水中NO₃-N含量普遍较高，含量超过 1．1 m g／L，大部分平原水库水中NH₄-N含量超过 0．3 m g／L；河水与浅层地下水TP、NH₄-N与NO₃-N含量均呈现沿流域从出山口至下游的显著递增变化，同时还具有明显的随时间递增趋势，其中NH₄-N含量在河流出山口及下游断面平均年增加幅度分别为 0．11 m g／L和 0．114 m g／L；流域水体 N、P含量的季节变化明显，黑河流域春季及春夏之交的枯水期大部分河段NH₄-N、NO₃-N和TP等要素含量为全年最高并出现水质超标污染。控制干旱内陆流域水域尤其是枯水期的 N、P污染，应成为干旱内陆流域水资源保护问题中值得关注的关键内容。     

Mapping small wetlands of Kenya and Tanzania using remote sensing techniques

Although wetlands in Tanzania and Kenya have great potentials for agricultural production and a multitude of uses, many of them are not even documented on official maps. Lack of official recognition has done little in preventing there over utilization. As the wetlands continue to play remarkable roles in the movement of people and terrestrial species in the region, it is important that they are monitored and properly managed. This study was undertaken in Usambara highlands and the Pangani floodplain in Tanzania, the Mount Kenya highlands and Laikipia floodplain in Kenya to map the different types of wetlands in terms of their size, density, spatial distribution and use patterns. Remote sensing techniques and field surveys were adopted, and 51 wetlands were identified in flood plains within the semi-arid and sub-humid lowlands, and inland valleys in the region. The detailed maps generated showed the intensity of wetland use, inland valleys being the most intensively used, and are useful in monitoring changes in wetlands for their effective management. The use of multispatial resolution imagery, combined with field survey and GIS produced satisfactory results for the delineation and mapping of small wetlands and their uses.     

The effect of a tidal cycle on the dynamics of nutrients in a tidal estuary in the Seto Inland Sea, Japan

A 24 hour time series survey was carried out during a spring tide (tidal range ca.2 m) of May 1995 on a tidal estuary in the Seto Inland Sea, Japan, in the context of an integrated program planned to quantify the dynamics of biophilic elements (carbon, nitrogen and phosphorus) and the roles played by the macrobenthos on the processes. Three stations were set along a transect line of about 1.4 km, which linked the river to the rear to the innermost part of the subtidal zone. Every hour, at each station, measurements were made of surface water temperature, salinity and dissolved oxygen concentration, and surface water was collected for the determination of nutrients [NH₄ ⁺−N, (NO₃ ⁻+NO₂ ⁻)−N, PO₄ ³⁻−P and Si (OH)₄−Si]. During the ebb flow, riverine input of silicate and nitrate+nitrite significantly increased the concentrations of both the intertidal and the subtidal stations. Conversely, during the high tide, river nutrient concentrations were lowered by the mixing of fresh water with sea water. As a result, best (inverse) correlations were found at the river station for salinity against silicate (y=-2.9 Sal.+110.7,r ²=0.879) and nitrate+nitrite (y=-1.3 Sal.+48.4,r ²=0.796). In contrast, ammonium nitrogen concentrations were higher at intermediate salinities. Indeed, no significant correlation was found between salinity and ammonium. The effect of the macrobenthos, which is abundant on the intertidal flat, is discussed as a biological component that influences the processes of nutrient regeneration within the estuary. The effect of the tidal amplitude is an important one in determining the extent of the variations in nutrient concentrations at all three stations, which were stronger between the lower low tide and the higher high tide.     

舞阳盆地内陆沙布哈—盐湖环境和有机质聚集

舞阳盆地是一个早第三纪的陆相拗陷。在核桃园组沉积了碎屑和蒸发岩。为了重建沉积环境,研究了该盆地WK1井1222—1253m及1401—1405m段岩心。它们属核桃园组,由几套沉积韵律组成。硬石膏泥岩代表含盐泥坪环境,石盐岩代表盐湖环境。该类泥岩发育泥裂。WK1井内陆沙布哈沉积有机质的含量和类型变化大。在泥裂泥岩中,总有机碳低到0.24—0.34％,有机质多为Ⅲ型,纹层状泥岩的有机碳高到2.52—3.10％,有机质多为Ⅱ型。这类内陆沙布哈岩石有机质的丰度明显受沉积环境控制。该盆地WK1井内陆沙布哈沉积具有中等生油潜力。     

美国大尺度综合环境观测站网计划介绍及其相关研究

大尺度综合环境观测站网(CLEOs) 是研究大尺度流域水资源环境问题的国家观测站网计划,是美国国家科学基金委员会正在策划的前瞻性、基础性的战略部署之一。强调在实验观测网的基础上、实现在流域尺度学科的综合与集成,寻求水问题解决方案。通过全面介绍该计划的背景、设计框架、核心和实施步骤,结合我国流域尺度水文水资源研究现状,指出我国在西北内陆河流域建立大尺度综合环境观站网的可能性。