The grain-size characterisation of coastal sand from the Somme estuary to Belgium: Sediment sorting processes and mixing in a tide- and storm-dominated setting

Sand-rich Holocene to modern clastic deposits in the eastern English Channel and the southern North Sea coasts of France and Belgium occur extensively as nearshore-sand bank, estuarine-tidal flat, aeolian dune and beach sub-environments. Sand samples (n = 665) collected from these deposits suggest the presence of three different populations: a largely dominant (83%) medium to fine quartz sand population (“b”), and finer- (14%) and coarser-grained (4%) populations (respectively “c” and “a”). The distribution of these populations among the four sub-environments reflects tide- and storm-dominated sorting and transport processes and a variable degree of mixing. These populations are derived from a mixture of very fine- to very coarse-grained fluvial, outwash and paraglacial sediments deposited on the beds of the eastern English Channel and southern North Sea during the late Pleistocene lowstand. The nearshore-sand bank environment, which also corresponds to the main offshore source area of the coastal deposits, exhibits population heterogeneity reflecting the variability of hydrodynamic conditions and sediment sorting in this zone. The nearshore topography of tidal ridges, banks and troughs in these tidal seas leads to variable bed and tide- and storm-induced shear stress conditions. These conditions only allow for the mobilisation and onshore transport of some of the finer fractions (populations “b” and “c”), leaving an offshore mixture of these finer populations with coarser, less mobilisable sediments (population “a”). Once in the coastal zone, these two finer populations undergo further hydrodynamic sorting and segregation. Variably sorted very fine sands to silts (population “c”) are trapped in the low-energy estuarine-tidal flat sub-environment, while the highly homogeneous population “b” is further sorted in aeolian dune and beach sub-environments. This sorting occurs via a coastal sand transport pathway linking the Somme estuary mouth to the southern North Sea bight where tidal range and wave energy decrease relative to the English Channel. Since this sand transport pathway enables longshore transport of hydrodynamically sorted medium to fine sand derived directly from the immediate nearshore zone, it has further contributed to a net flux of this sand population from the eastern English Channel sea bed to the southern North Sea.     

Calculation of Diversion Ratio of the North Channel in the Yangtze Estuary

The circumfluence around the Jiuduan Sandbank is thoroughly studied by means of the princi-ple of least resistance in fluid dynamics.The diversion ratio of the North Channel for 1998 is calculated,which is almost the same as the field survey data.The normal and minimum diversion ratios of the NorthChannel after stages Ⅰ,Ⅱ and Ⅲ regulation works as well as the future phase are obtained.The numeri-cal results and predicted value are accurate.     

Effects of waterborne nitrite onphase I–II biotransformation in channel catfish(Ictalurus punctatus)

The effects of waterborne nitrite (3 mg/l NO₂) on channel catfish were studied to evaluate changes in hematological parameters and phase I–II biotransformation in liver slices. Nitrite-exposed fish had significantly higher methemoglobin, blood and liver nitrite, and significantly lower pO₂ than control fish. Total phase I-mediated metabolism of 7-ethoxycoumarin (EC) was not altered in nitrite-exposed fish compared with control fish (291±43 and 312±20 pmol/mg/h, respectively). However, phase II glucuronosyltransferase-mediated metabolism of 7-hydroxycoumarin (HC), both as a phase I metabolite of EC and as a parent substrate, was elevated in nitrite-exposed fish (204±17 and 1007±103 pmol/mg/h, respectively) as compared to control fish (149±14 and 735±87 pmol/mg/h) (P<0.05). Sulfotransferase-mediated metabolism of HC (as a metabolite of EC and as a parent substrate) was not notably altered in nitrite-exposed fish (95±16 and 617±33 pmol/mg protein/h, respectively) as compared with control fish (118±24 and 575±55 pmol/mg/h, respectively). These studies indicate that in vivo nitrite exposure and associated changes in hematological parameters do not appear to affect hepatic phase I EC biotransformation in channel catfish. However, subtle but significant changes in phase II glucuronidation, but not sulfation activity, were observed. The mechanism of these alterations is unclear. However, the data suggest that environmentally realistic concentrations of nitrite may affect the dynamics of conjugative metabolism in exposed fish.     

Climate transformation to warm-humid and its effect on river runoff in the source region of the Yellow River

The change characteristics and trends of the regional climate in the source region of the Yellow River, and the response of runoff to climate change, are analyzed based on observational data of air temperature, precipitation, and runoff at 10 main hydrological and weather stations in the region. Our results show that a strong signal of climate shift from warm-dry to warm-humid in the western parts of northwestern China （Xinjiang） and the western Hexi Corridor of Gansu Province occurred in the late 1980s, and a same signal of climate change occurred in the mid-2000s in the source region of the Yellow River located in the eastern part of northwestern China. This climate changeover has led to a rapid increase in rainfall and stream runoff in the latter region. In most of the years since 2004 the average annual precipitation in the source region of the Yellow River has been greater than the long-term average annual value, and after 2007 the runoff measured at all of the hydrologic sections on the main channel of the Yellow River in the source region has also consistently exceeded the long-term average annual because of rainfall increase. It is difficult to determine the prospects of future climate change until additional observations and research are conducted on the rate and temporal and spatial extents of climate change in the region. Nevertheless, we predict that the climate shift from warm-dry to warm-humid in the source region of the Yellow River is very likely to be in the decadal time scale, which means a warming and rainy climate in the source region of the Yellow River will continue in the coming decades.     

Hydrodynamic evolutions at the Yangtze Estuary from 1998 to 2009

Over the past decade, the Yangtze Estuary has witnessed an unprecedented scale of human interventions and modifications through extensively varied resource utilizations. During the processes, mankind has obtained various resources and benefits via the “golden waterway”, such as navigation channel, harbor, shipping industry, shoreline, reclaimed land, freshwater and fishery resource. At the same time, the estuary and coast have also experienced a series of gradual changes in characteristics, such as sedimentation, erosion, sand hungry, water pollution, intertidal area loss, self-purification capacity decrease, and biological reduction. With the help of measurement data and numerical modeling, this study analyzed the response and feedback mechanisms between hydrodynamic evolutions and morphological processes in the Yangtze Estuary from 1998 to 2009. The results of this study indicate the following. (i) The water level along the main outlet of the Yangtze Estuary increased from 1998 to 2009. This increase was induced by the variation of the whole river regime (including natural geomorphodynamic process and local topography feedbacks from extreme metrological events and human activities). (ii) The decrease of the flow partition ratio at the 3rd bifurcation is directly induced by the Deepwater Navigational Channel (DNC) project and the corresponding morphological changes in the North Passage. (iii) The estuarine environmental gradients (salinity and suspended sediment concentration) were compressed, and the fresh-salt gradient became steeper. This has the indirect effect of backfilling in the waterway, i.e., strengthening the stratification effect near the ETM area and enhancing the tendency of up-estuary sediment transport. The results of this study give insights into explaining other phenomena such as deposition in the middle reach of the DNC, bathymetry evolutions, variations in vertical velocity and sediment concentration profiles, waterway backfilling and delta reclamation.     

浅谈气象频道广西本地插播节目的设计

通过分析目前气象频道广西本地插播节目存在的问题,结合社会需求及实际工作情况,从丰富和加深节目内容．加强地市级的本地化服务,提高气象信息时效性,丰富节目表现形式,加强精细化服务,凸显专业化信息几个方面阐述了气象频道本地插播节目改进的设计思路,以提高插播节目服务水平。     

气象频道省级直播体系的构建与探讨

根据目前广电技术发展的方向,提出气象频道省级本地直播体系的建设思路,从演播室直播系统设计到卫星数字直播车的技术方案,逐步实现气象频道本地插播节目的直播常态化,提升省级气象部门的节目制作及气象应急服务能力。     

Freshwater seepages and ephemeral macroalgae proliferation in an intertidal bay: II. Effect on benthic biomass and metabolism

Intertidal soft-sediments biomass and metabolism are naturally heterogeneous in time and space at different scales. Particular perturbations such as freshwater seepages and seasonal proliferation of ephemeral macroalgae can intermittently and/or locally create additional variability in these systems. Since the impacts of such environmental stresses on natural processes are not well understood, the hypothesis that they would affect the functioning of the benthic system was tested. An intertidal bay whose structure and functioning has been previously described and where a carbon budget has been calculated, was chosen. The results showed that the metabolism of the intertidal sediments was greatly impacted by the above perturbations. Freshwater seepage increased meiofauna and microalgae biomasses and enhanced the total benthic metabolism (increasing community respiration and gross primary production until 4 and 2 fold respectively) without altering its seasonal trend. Ephemeral macroalgae proliferation had a more important effect on the total benthic metabolism, increasing community respiration and gross primary production 8 and 12 fold respectively and leading to a change in the seasonal trend.     

New estimates of annual sea level maxima in the Bristol Channel

Observed sea level maxima in the form of annual extremes have been analysed for 4 ports in the Bristol Channel. The data analysed has been extended to include levels recorded in December 1981, when previous estimates of maximum return levels were exceeded.     

Remote sensing observations of biological material by LANDSAT along a tidal thermal front and their relevancy to the available field data

Two images recorded on two successive summer days by LANDSAT satellite over the western approaches to the English Channel show bright pattern of complex shape the origin of which is puzzling. Among the wavelength bands available on LANDSAT's multispectral scanner, these patterns are apparent only in the green region of the spectrum, and they are located towards the stratified side of a well marked tidal thermal front. Spectral signature analysis and available knowledge on hydrography and plankton in the area are used to derive a proposed interpretation. Phytoplankton would accordingly be the best candidate for being responsible for the observed patterns.