Environmental hydrogeology of the southern sector of the Samborombon Bay wetland,Argentina

The Samborombon Bay wetland is located on the west margin of the Rio de la Plata estuary, in the Province of Buenos Aires, Argentina. This paper analyses the geological, geomorphologic, soil and vegetation characteristics of the southernmost sector of this wetland and their influence on surface water and groundwater. The study area presents three hydrologic units: coastal dunes, sand sheets and coastal plain. Coastal dunes and sand sheets are recharge zones of high permeability with well-drained, non-saline soils, and a few surface water flows. Changes in the water table are related to rainfall. Groundwater in coastal dunes is Ca–Mg–HCO₃ to Na–HCO₃, and of low salinity (590 mg/l). Groundwater in sand sheets is mainly Na–HCO₃ with a salinity of about 1,020 mg/l. The coastal plain exhibits medium to low permeability sediments, with submerged saline soils poorly drained. Groundwater is Na–Cl with a mean salinity of 16,502 mg/l. A surface hydrological network develops in the coastal plain. Surface water levels near the shoreline are affected by tidal fluctuations; far from the shoreline water accumulates because of poor drainage. Both sectors have Na–Cl water, but the former is more saline. Human intervention and sea level rise may affect the wetland severely.     

手掘式顶管在市政排水工程中的应用

从混凝土管材的选定、工作坑的设计及施工、顶管顶进中若干关键问题入手,介绍了手掘式顶管施工技术在成都市中心城水环境综合整治工程G标段管道排水工程中的应用。     

Isotopic variation of fishes in freshwater and estuarine zones of a large subtropical coastal lagoon

We used stable C and N isotope ratios of tissues from 29 fish species from a large subtropical lagoon in southern Brazil to examine spatial variability in isotopic composition and vertical trophic structure across freshwater and estuarine habitats. Nitrogen isotope ratios indicated a smooth gradation in trophic positions among species, with most fishes occupying the secondary and tertiary consumer level. Fish assemblages showed a significant shift in their carbon isotopic signatures between freshwater and estuarine sites. Depleted carbon signatures (from −24.7‰ to −17.8‰) were found in freshwater, whereas more enriched signatures (from −19.1‰ to −12.3‰) were obtained within the estuarine zone downstream. Based on our survey of the C₃ and C₄ plants and isotopic values for phytoplankton and benthic microalgae reported for ecosystems elsewhere, we hypothesized that the observed δ¹³C differences in the fish assemblage between freshwater and estuarine sites is due to a shift from assimilating organic matter ultimately derived from C₃ freshwater marsh vegetation and phytoplankton at the freshwater site (δ¹³C ranging from −25‰ to −19‰), to C₄ salt-marsh (e.g. Spartina) and widgeon grass (Ruppia maritima), benthic microalgae and marine phytoplankton at the estuarine sites (from −18‰ to −12‰). Our results suggested that fish assemblages are generally supported by autochthonous primary production. Freshwater fishes that likely were displaced downstream into the estuary during periods of high freshwater discharge had depleted δ¹³C values that were characteristic of the upper lagoon. These results suggest that spatial foodweb subsidies can occur within the lagoon.     

RTK技术在杭州湾跨海大桥桥位地形测绘中的应用

介绍了RTK技术在杭州湾跨海大桥桥位地形测绘中的应用,并对其定位结果进行了精度比较与分析,结果表明:RTK定位测量的点位精度可达厘米级,各点位之间不存在误差积累,与全站仪等测量手段取得的结果符合得较好,可以用来代替二三级导线控制测量和等外水准等测量方法;流动站与基准站的距离在10km范围以内时,应用RTK技术对近岸水下地形进行测量具有方便、快捷、精度高等特点,但当此距离超过10km时,其精度则难以保证。杭州湾跨海大桥施工时应用RTK技术进行定位、高程测量,可提高工作效率和成果的质量。     

青岛胶州湾地区重大工程建设项目设计的地质基础

本文以青岛胶州湾地区的基本地质条件为基础，分析研究了该地区地质基础对重大工程建设项目设计的影响，提出了青岛市重大工程项目设计的基本原则和对城市整体规划的具体建议。     

1998年春深圳湾环节环沟藻赤潮及其发生原因的探讨

1998年4月23日至29日深圳湾发生了较大规模的环节环沟藻赤潮,面积逾200km2,细胞密度高达3.8×106 个/L。赤潮发生于大量降雨之后 ,高峰期水体盐度在20以下。在深圳河河口海域 ,虽然富营养化程度也较高 ,但由于悬浮物含量过高 ,浮游植物及环节环沟藻数量较少。赤潮期间 ,深圳湾没有发生死鱼现象 ,养殖牡蛎的大量死亡估计与赤潮无关     

大鹏湾潮流数值计算

应用分步杂交方法建立了大鹏湾边界潮流数值模型，并对其进行了模拟计算，重现了该区域潮波及潮流的分布规律，并根据实测资料对其进行了验证，从而可系统地了解这一海区的潮波系统及潮流场等海洋要素的分布情况。     

南极冰退与深圳湾北岸海平面变化的地质记录

南极冰层的冰量为２４．５×１０６ｋｍ３，占地球总冰量的９０％以上，南极冰川进退控制着全球海平面变化和气候波动。酉部南极乔治王岛第四纪冰碛与湖积剖面记录了近１２０００ａ来南极曾于距今１１０００ａ，９０００ａ和６１００ａ出现过３次快速的冰消过程，近６０００ａ来是一小幅度冷暖交替的气候波动过程。深圳湾北岸潮间带堆积是在近６０００ａ以来发育的，堆积物的环境记录表明，海平面呈周期性升降变化，波动周期平均为６７０ａ，低海面时期发生于距今５５００—４９００ａ，３９００—３６００ａ，２４００—２２００ａ和１３００—１２００ａ。相邻低海面间则是海面上升时期，每一升降周期的海平面变化幅度为８０ｃｍ左右，近１００ａ的现代增温，海平面处于上升阶段，上升速率为２—３ｍｍ·ａ（－１）。     

象山港,三门湾潮间带生态学研究：Ⅱ.数量组成与分布

象山港、三门湾软相潮间带底栖动物数量的水平分布与港湾的屏蔽性程度有一定的关系，生物量是三门湾（１８０．９５ｇ／ｍ２）高于象山港（９４．４７ｇ／ｍ２），生物密度是象山港（８１６个／ｍ２）高于三门湾（３４７个／ｍ２）。决定所面生物数量变化的主要底栖动物种类数随着港湾屏蔽性程度的提高而相应地减少。生物数量的垂直分布主要受潮汐作用的影响，以中潮区为最高。生物量以６月份最大，密度是４月份最大。     

Marine Ecology - A Century of Changes

Abstract. The major changes within the concepts of marine ecology are investigated, with the aim to design this new journal's scientific format. Four phases of marine sciences are distinguished: the phase of seafarers, of oceanographic expeditions, of marine stations, and of field research. The changes in the latter two are discussed in detail. The changes are described as occurring along three axes. First, as a movement towards the object; accomplished by fieldwork, scientific diving, remote controlled equipment, and by underwater experimentation. Second, the cooperation between several disciplines that led towards bridging gaps. And lastly, how the discovery of unifying principles in ecology (the development of an ecological theory) led the approach in marine ecology towards increasing complexity.