被动大陆边缘对于深海侵蚀作用及陆坡后退的挠曲响应：海平在上对变化中的

我们认为根据层序地层学所测的早一－晚渐新世全球海平面降落的幅度过高，因为存在晚新世到早渐新世的侵生去负荷作用所产生的陆缘曲性反弹作用，在深海侵蚀及陆坡后退过程中，大边缘的去负荷作用将伴随某种型式的挠曲反弹作用，这种反弹作用的幅度及型式受控于（１）沉积物被侵蚀的数量，和（２）沉积物被侵蚀时的岩石圈强度。在具有狭窄大架的陆级，这种反弹作用将导致海同相对降落，使海岸线向盆地方向迁移，所预测的体系均将类似     

Spatial distribution of intertidal sandy beach polychaeta along an estuarine and morphodynamic gradient in an eutrophic tropical bay

The spatial distribution of polychaeta along pollution gradients often reflects different degrees of disturbance. In order to evaluate polychaeta fauna of an organically polluted tropical bay, 20 sandy beaches distributed in five areas were sampled. The relationship between community structure, slope, beach index, exposure, sediment and water quality parameters were analysed. Multivariate analysis of variance (PERMANOVA) showed differences among areas and beaches. Scolelepis chilensis dominated at mouth of bay beaches whereas Streblospio gynobranchiata and Capitella capitata complex, at inner beaches. Highest polychaete density was recorded at areas 3 and 5 with the dominance of Saccocirrus sp. and the organic indicator species C. capitata complex and Polydora sp. The most important factors obtained from canonical analysis were sorting, slope, mud and organic matter percentage. Marine biotic index (AMBI) showed that areas 3 and 5 were highly affected by anthropogenic factors, given that a poor polychaeta fauna, dominated by opportunistic species, were found. Polychaete assemblages were affected by eutrophication along an estuarine gradient as well as by morphodynamic condition of the beaches.     

如何提高产层深度预测的准确度？

如何提高产层深度预测的准确度？ＪｏｈｎＡＷａｒｄ三维地震资料已经迅速成为寻找西得克萨斯州古生界碳酸盐岩中隐蔽圈闭的主要工具。在成熟油田中,三维地震资料提供一种机会,采用二维资料办不到的方法研究时深转换关系。令人惊讶的是,在利用三维地震资料进行开发井...     

佛罗里达和大巴哈马滩上新世—更新世低水位大气成岩作用的限制条件:海平面变动模型的意义

业已证实，潜水大气透镜体内更新世浅水碳酸盐岩中广泛发育成岩作用．且有人推测在更新世大规模低水位期间连续发生这种交代作用，其根据来自出现广布的埋藏洞穴（大于5000m；Spencer，1967），但是，所有的这些洞穴发现在浅水岩相中，在沉积作用之后不久开始重复地出露，因此，洞穴形成的原始深度仍然存在问题．为了正确确定大规模低水位期间出现的大气水成岩作用，蓄意在沉积作用时期存在一个未重复的与大气流体接触的层段，并且目前存在于海面之下80－120m，这样的一个较深水岩相上覆有浅水岩相，在佛罗里达南部和大巴哈马滩前积边缘（C…     

Metal speciation and toxicity of Tamar Estuary water to larvae of the Pacific oyster, Crassostrea gigas

As part of the PREDICT Tamar Workshop, the toxicity of estuarine waters in the Tamar Estuary (southwest England) was assessed by integration of metal speciation determination with bioassays. High temporal resolution metal speciation analysis was undertaken in situ by deployment of a Voltammetric In situ Profiling (VIP) system. The VIP detects Cd (cadmium), Pb (lead) and Cu (copper) species smaller than 4?nm in size and this fraction is termed 'dynamic' and considered biologically available. Cadmium was mainly present in the dynamic form and constituted between 56% and 100% of the total dissolved concentration, which was determined subsequently in the laboratory in filtered discrete samples. In contrast, the dynamic Pb and Cu fractions were less important, with a much larger proportion of these metals associated with organic ligands and/or colloids (45-90% Pb and 46-85% Cu), which probably reduced the toxicological impact of these elements in this system. Static toxicity tests, based on the response of Crassostrea gigas larva exposed to discrete water samples showed a high level of toxicity (up to 100% abnormal development) at two stations in the Tamar, particularly during periods of the tidal cycle when the influence of more pristine coastal water was at its lowest. Competitive ligand-exchange Cu titrations showed that natural organic ligands reduced the free cupric ion concentration to levels that were unlikely to have been the sole cause of the observed toxicity. Nonetheless, it is probable that the combined effect of the metals determined in this work contributed significantly to the bioassay response.     

The Lisse effect revisited

The Lisse effect is a rarely noted phenomenon occurring when infiltration caused by intense rain seals the surface soil layer to airflow, trapping air in the unsaturated zone. Compression of air by the advancing front results in a pressure increase that produces a water-level rise in an observation well screened below the water table that is several times as large as the distance penetrated by the wetting front. The effect is triggered by intense rains and results in a very rapid water-level rise, followed by a recession lasting a few days. The Lisse effect was first noted and explained by Thal Larsen in 1932 from water-level observations obtained in a shallow well in the village of Lisse, Holland. The original explanation does not account for the increased air pressure pushing up on the bottom of the wetting front. Analysis of the effect of this upward pressure indicates that a negative pressure head at the base of the wetting front, psi(f), analogous to that postulated by Green and Ampt (1911) to explain initially rapid infiltration rates into unsaturated soils, is involved in producing the Lisse effect. Analysis of recorded observations of the Lisse effect by Larsen and others indicates that the water-level rise, which typically ranges from 0.10 to 0.55 m, should be only slightly larger than psi(f) and that the depth of penetration of the wetting front is no more than several millimeters.     

Time should be considered in developmental ecotoxicity test

Developmental toxicity tests are often used for the hazard assessment of chemicals and environmental media. One of the most widely used is the oyster embryo larval test (OEL), in which the development of oyster larvae is arrested at a single fixed time (e.g. 24 or 48 h) of toxic exposure, and the proportion of normal larvae measured. However, a major problem with this conventional approach is the lack of information on temporal trends in development. In this study, Pacific oyster Crassostrea gigas embryos were exposed to nominal concentrations of copper (CuSO₄) of <0.001 (control), 0.60, 1.25, 2.5, 5.0, 10.0 and 20.0 μg l⁻¹ (at 20 °C, salinity 35‰ and pH 8.1). Three replicates from each group were arrested and examined every 8 h during 24–72 h of exposure, and the number of viable larvae developed to D-shape was determined. The results revealed that the number of viable D-shape larvae in the control increased rapidly and reached an optimum at 32 h, before declining gradually due to starvation. Analysis of covariance (ANCOVA) showed that larval developmental rates during 0–32 h were significantly inhibited by Cu at all concentrations. This paper demonstrates that arrest and measurement at different time periods are important and should be incorporated into the OEL test. This would maximise the sensitivity of the test in detecting developmental effects in spiked or environmental samples.