Dissolved organic carbon in the freshwater tidal reaches of the Schelde estuary

To unravel the factors that regulate DOC dynamics in the freshwater tidal reaches of the Schelde estuary, DOC concentration and biodegradability were monitored in the upper Schelde estuary and its major tributaries. Although the Schelde estuary possesses a densely populated and industrialized catchment, our data suggest that the bulk of DOC in the freshwater tidal reaches is not derived from waste water. This was concluded from the low biodegradability of DOC (on average 9%), DOC concentrations that are close to the mean for European rivers (4.61 mg l⁻¹) and the absence of an inverse relationship between DOC and discharge. Most DOC originating from waste water being discharged in tributaries of the estuary appears to be remineralised before these tributaries reach the main estuary. Although dense phytoplankton blooms were observed in the upper estuary during summer (up to 700 μg chl a l⁻¹), these blooms did not appear to produce large quantities of DOC in the freshwater tidal reaches as DOC concentrations were low when phytoplankton biomass was high. The fact that DOC concentrations were high in winter and decreased in summer suggests a predominantly terrestrial source of DOC in the freshwater tidal reaches of the Schelde estuary.     

城中村研究热点及区域差异——基于CiteSpace的文献计量分析

借助可视化工具CiteSpace,以中英文城中村研究文献的关键词为对象进行知识图谱分析,并对我国东、中、西部地区代表性城市城中村研究热点的差异进行深入挖掘。结果表明：“改造”和“住房”是城中村研究绕不开的主题,此领域研究从早期较为重视形成机制和改造模式分析转向对社区治理、社会融合、城市更新等主题的探讨,而在区域层面又呈现差异化的研究倾向,主要包括以北京为代表的人口疏解目标下流动人口聚居区研究、以上海为代表的城市更新背景下社会融合和绅士化研究、以深圳为代表的城市空间重构下制度创新与社区支持研究、以广州为代表的政府主导下多目标可持续研究以及以武汉和西安为代表的城中村改造模式研究。未来城中村研究应树立空间公平的价值取向,强调多元治理的路径选择,重视定量分析的方法创新。在区域扩展上,中西部快速城市化地区潜在的和显现的城中村值得学界关注。     

Organic matter in sediments of canyons and open slopes of the Portuguese,Catalan, Southern Adriatic and Cretan Sea margins

We describe the quantitative and compositional (phytopigment, protein, carbohydrate and lipid) patterns of sedimentary organic matter along bathymetric gradients in seven submarine canyons and adjacent open slopes located at four European regions: one along the NE Atlantic and three along the Mediterranean continental margins. The investigated areas are distributed along a putative longitudinal gradient of decreasing primary production from the Portuguese (northeastern Atlantic Ocean), to the Catalan (western Mediterranean Sea), Southern Adriatic (central Mediterranean Sea) and Southern Cretan (eastern Mediterranean Sea) margins. Sediment concentrations of organic matter differed significantly between the Portuguese margin and the Mediterranean regions and also from one study area to the other within the Mediterranean Sea. Differences in quantity and composition of sediment organic matter between canyons and open slopes were limited and significant only in the eutrophic Portuguese margin, where the differences were as large as those observed between regions (i.e. at the mesoscale). These results suggest that the overall trophic status of deep margin sediments is controlled mostly by the primary productivity of the overlying waters rather than by the local topography. Moreover, we also report that the quantity and nutritional quality of sediment organic matter in canyons and adjacent open slopes do not show any consistent depth-related pattern. Only the Nazaré and Cascais canyons in the Portuguese margin, at depths deeper than 500 m, displayed a significant accumulation of labile organic matter. The results of our study underline the need of further investigations of deep margins through sampling strategies accounting for adequate temporal and spatial scales of variability.     

Tsunami flooding extension for coastal zones of Mexico

Abstract

Joint probabilities of runup height due to astronomical tides and tsunamis are calculated for five bays on the Pacific Ocean coast of Mexico. Runup heights equaled or exceeded on the average of once per 100 years, and once per 200 years, for those bays, are evaluated. Calculations are based on wave height probabilities obtained from sets of harmonic constituents and tsunami heights recorded during the last 28 years at tidal stations on each location.

Extension of potential tsunami terrestrial flooding for populated coastal zones around those bays can be determined from the previous results. One case is illustrated showing endangered features in the hazardous zones, and recommendations to prevent casualties and property damages are given.     

胶州湾红岛码头疏浚物质输移扩散数值预测

利用有限元分步杂交法，首先对胶州湾海域潮流场进行了数值模拟，进而建立了胶州湾疏浚物悬浮泥沙的二维输运——扩散模型，并应用于胶州湾红岛拟建码头疏浚区的疏浚物输运扩散数值模拟预测，根据预测结果分析了红岛码头疏浚区施工期间悬浮泥沙对附近水环境的影响。     

Computation of the driving forces of wave-induced currents

For morphological studies in coastal areas the wave-driven currents are often of primary importance. As the computation of the wave-driven current field requires the computation of the driving forces from a wave propagation model, the quality of these forces is basic to the success of the morphological study. It is shown in the paper that, under the common conditions of slowly varying wave fields, the driving force per unit mass is closely proportional to the wave energy dissipation per unit area and that diffraction-related terms give insignificant contributions. This result holds good for wave fields without current refraction. Examples show that formulation of the driving forces in terms of the wave dissipation yields more trustworthy results than those obtained by numerical differentiation of the radiation stress tensor.     

Changes in storminess and surges in western France during the last century

French meteorological data provide some information on wind direction since 1890. Since 1951, wind speed and direction have been digitised every three hours in many stations. The Brest tide gauge has recorded hourly sea levels since 1860, thus enabling hourly surges to be calculated and studied. This set of data has been organised into a data base and analysed in order to recognize evolution and trends. Strong winds are increasing in frequency in the western part of Brittany and decreasing in Normandy and Pays de Loire. Surges associated with these winds do present a slight decreasing trend. A more precise analysis allows to distinguish between southerly winds, which are slightly decreasing, and strong winds from other directions, which display a more or less important increase in frequency. The analysis shows trends that may be linked to the global circulation pattern, and that result in a new spatial distribution of winds on western France.     

The State of the Adriatic Sea Centered on the Small Pelagic Fish Populations

Abstract. The paper provides an overview of the state of the small pelagic fish in the Adriatic Sea. The North Adriatic is reviewed for the 1976–1998 period and the South Adriatic for the 1987–1998 period. First the fluctuations in time and in space of the pelagic biomass, as a whole and per species, are presented. Then the dramatic collapse of anchovy stock and its apparent association with the decrease of surface temperature is discussed. Finally the changes of the anchovy and sardine catches are compared and analysed with respect to their abundances in the sea. The conclusion is that acoustic and satellite methods are able to provide a large amount of information on the variability in the pelagic populations; this is essential for an appropriate management of these resources. There is still a need, however, to refine the methods and to integrate this kind of information with further environmental data (including natural predators).     

铁锰结核结壳生长过程的一种理论假设

铁锰结核成矿物质的直接来源是大洋底层水和沉积物孔隙水，结壳只有底层水，因此，底层水和孔隙水的物理化学特征就成为理解铁锰结核（壳）成矿作用特征与过程的关键。铁锰结核（壳）内部构造的两个明显特征是：①韵律性的环状纹层构造，和②树枝状构造，这两种构造是典型的远离平衡的非线性地质作用的产物。正常情况下，海底水—沉积物界面系统的底层水、孔隙水中Ｍｎ、Ｆｅ是不饱和的。因此，铁锰结核（壳）不可能在平衡状态下连续生长。本文提出铁锰结核（壳）生长的自反馈“振荡式”模型。