密度差随深度变化的不规则截面二度体的重力异常

本文是将Hubbert(1948)的线积分法用于求得密度差随深度呈线性变化的任意截面二度体的重力异常。以N边的多边形代替物体截面,利用任一边的两个顶点坐标来求其相应的重力异常,然后再对各边产生的重力异常进行求和得出总的重力效应。在这里我们还研究了密度差随深度呈指数变化的情况。利用这个方法求得了美国加州San Jacinto地堑的构造,在该地堑内充填的沉积物其密度差是随深度呈指数增加的。     

Analysis-Prediction Experiments over Indian Region Using Primitive Equation Barotropic Model

The impact of initial guess and grid resolutions on the analysis and prediction has been investigated over the Indian region. For this purpose, an univariate objective analysis scheme and a primitive equation barotropic model have been used. The impact of initial guess and the resolutions on analysis and prediction is discussed.     

亚洲城市平衡化、空间一体化及经济发展的政策和规划

对亚洲许多城市规划专家和政策分析家们来说,城市化至今仍是一件高深莫测的事。过去的三十年里,迅速发展的东亚和东南亚的城市化,被描绘成经济增长的促进因素、现代化的产物、严重社会问题的根源以及阻碍财富合理分配的绊脚石。     

Challenges in global ballast water management

Ballast water management is a complex issue raising the challenge of merging international regulations, ship's specific configurations along with ecological conservation. This complexity is illustrated in this paper by considering ballast water volume, discharge frequency, ship safety and operational issues aligned with regional characteristics to address ecological risk for selected routes. A re-estimation of ballast water volumes gives a global annual level of 3500 Mton. Global ballast water volume discharged into open sea originating from ballast water exchange operations is estimated to approximately 2800 Mton. Risk based decision support systems coupled to databases for different ports and invasive species characteristics and distributions can allow for differentiated treatment levels while maintaining low risk levels. On certain routes, the risk is estimated to be unacceptable and some kind of ballast water treatment or management should be applied.     

Water quality and presence of pesticides in a tropical coastal wetland in southern Mexico

The water quality of the Pozuelos-Murillo lagoon system in southern Mexico was evaluated during three periods between March and October 2002, with particular emphasis on the detection of organochlorine and organophosphorous pesticide residues in water and sediments. Physicochemical and microbiological parameters of water were also measured and integrated in a water quality index (WQI). Multivariate analysis was used to regionalise the lagoon system as a function of the behaviour of all measured parameters. Solid phase micro-extraction followed by gas chromatography (SPME-GC) was used for pesticide analysis. The concentration of phosphorous was found to be higher than that of nitrogenous compounds. This, besides a deficiency in dissolved oxygen and a high organic matter concentration (as COD), reflects eutrophication processes in some areas of the system. Measured levels of faecal coliforms and oils and greases were above the limits established by Mexican law and comparable to the concentrations reported for other highly polluted systems in Mexico. Residues of DDD (2.0 microg L(-1)) in water and DDE (247 ng g(-1)) and endosulfan I (814 ng g(-1)) sediments were detected by SPME-GC. The spatial distribution of these contaminants implies major potential risks because the most polluted sites were found to be those with the highest fishing activity. Although in general the WQI is on acceptable levels (65-80%), some contamination problems are evident.     

Sediment disturbance off the Tagus Estuary, Western Portugal: chronic contamination, sewage outfall operation and runoff events

Sediment disturbance patterns in the coastal area off the Tagus Estuary (Portugal) have been assessed using a set of combined techniques. The potential sources of disturbance in the area include chronic contamination of the fine sediments originating from the estuary, a local input from a long-sea sewage outfall and occasional high runoff episodes following torrential rain. The Sediment Quality Triad approach, combining environmental chemistry (namely organic contaminants), macrofaunal benthic communities and laboratory sediment toxicity assays, was performed on sediment samples from 20 sites. The samples were collected before the outfall commenced operation and four years after commissioning, in order to evaluate the relative magnitudes of the three potential sources of disturbance. The sediment contamination created by the estuary was identified as the most important cause of reduced sediment quality, as disturbance in all three components of the Sediment Quality Triad were only found in a site located near the estuary.     

Concentration and subcellular distribution of trace elements in liver of small cetaceans incidentally caught along the Brazilian coast

Concentrations of trace elements (V, Cr, Mn, Fe, Co, Cu, Zn, Ga, As, Se, Rb, Sr, Mo, Ag, Cd, Sb, Cs, Ba, T-Hg, Org-Hg, Tl and Pb) were determined in liver samples of estuarine dolphin (Sotalia guianensis; n = 20), Franciscana dolphin (Pontoporia blainvillei; n = 23), Atlantic spotted dolphin (Stenella frontalis; n = 2), common dolphin (Delphinus capensis; n = 1) and striped dolphin (Stenella coeruleoalba; n = 1) incidentally caught along the coast of Sao Paulo State and Parana State, Brazil, from 1997 to 1999. The hepatic concentrations of trace elements in the Brazilian cetaceans were comparable to the data available in literature on marine mammals from Northern Hemisphere. Concentrations of V, Se, Mo, Cd, T-Hg and Org-Hg increased with increasing age in liver of both estuarine and Franciscana dolphins. Very high concentrations of Cu (range, 262-1970 microg/g dry wt.) and Zn (range, 242-369 microg/g dry wt.) were observed in liver of sucklings of estuarine dolphin. Hepatic concentrations of V, Se, T-Hg, Org-Hg and Pb were significantly higher in estuarine dolphin, whereas Franciscana dolphin showed higher concentrations of Mn, Co, As and Rb. Ratio of Org-Hg to T-Hg in liver was significantly higher in Franciscana dolphin than estuarine dolphin, suggesting that demethylation ability of methyl Hg might be lower in liver of Franciscana than estuarine dolphins. High hepatic concentrations of Ag were found in some specimens of Franciscana dolphin (maximum, 20 microg/g dry wt.), and 17% of Franciscana showed higher concentrations of Ag than Hg. These samples with high Ag concentration also exhibited elevated hepatic Se concentration, implying that Ag might be detoxified by Se in the liver. Higher correlation coefficient between (Hg+0.5 Ag) and Se than between Hg and Se and the large distribution of Ag in non-soluble fraction in nuclear and mitochondrial fraction of the liver also suggests that Ag might be detoxified by Se via formation of Ag2Se in the liver of Franciscana dolphin.