MODFLOW 2000 head uncertainty,a first-order second moment method

A computationally efficient method to estimate the variance and covariance in piezometric head results computed through MODFLOW 2000 using a first-order second moment (FOSM) approach is presented. This methodology employs a first-order Taylor series expansion to combine model sensitivity with uncertainty in geologic data. MODFLOW 2000 is used to calculate both the ground water head and the sensitivity of head to changes in input data. From a limited number of samples, geologic data are extrapolated and their associated uncertainties are computed through a conditional probability calculation. Combining the spatially related sensitivity and input uncertainty produces the variance-covariance matrix, the diagonal of which is used to yield the standard deviation in MODFLOW 2000 head. The variance in piezometric head can be used for calibrating the model, estimating confidence intervals, directing exploration, and evaluating the reliability of a design. A case study illustrates the approach, where aquifer transmissivity is the spatially related uncertain geologic input data. The FOSM methodology is shown to be applicable for calculating output uncertainty for (1) spatially related input and output data, and (2) multiple input parameters (transmissivity and recharge).     

The loss of the chemical tanker Ievoli Sun in the English Channel,October 2000

A chemical product tanker, The Ievoli Sun, was abandoned and later sank approximately 11 miles NW of Alderney in the English Channel in October 2000. The vessel carried a mixed cargo comprising 4000 tonnes of styrene, and 1000 tonnes each of methyl ethyl ketone and isopropyl alcohol. These chemicals are of low to moderate toxicity to aquatic life, are not persistent and have a low potential for bio-accumulation. Both of the solvents are miscible in water, whilst styrene is practically insoluble and, following release, it will rise to the sea surface and rapidly evaporate. More than 1000 tonnes of styrene are believed to have been lost to sea during the incident, resulting in an aerial plume of vapour which crossed Alderney and episodic contamination of air and water in the immediate vicinity of the wreck site. Analysis of edible tissues using coupled gas chromatography/mass spectrometry demonstrated low-level styrene contamination of crabs recovered from pots laid very close to the wreck site prior to the incident. These concentrations posed no risks to human consumers, and no fishery controls were implemented. The remainder of the styrene and the ship's main bunker fuel were recovered from the wreck on the seabed, whilst the two chemical solvents were released to the water column in a slow, controlled manner.     

Polycyclic aromatic musk compounds in sewage treatment plant effluents of Canada and Sweden--first results

Polycyclic musk fragrances (PMF) are widely used fragrances for cosmetics and other personal and household care products. Quantitative data on PMF (HHCB-Galaxolide, AHTN-Tonalide, ATTI-Traseolide, AHMI-Phantolide, ADBI-Celestolide, and DPMI-Cashmeran) and the most prominent nitro musks (Musk Xylene-MX, and Musk Ketone-MK) in different wastewater treatment effluents in Canada and Sweden are presented to provide preliminary information on the variations within the emission pattern of these compounds. In all samples HHCB and AHTN were detected at concentrations of up to 1300 and 520 ngl(-1), respectively. ADBI, AHMI were also present, but close to the detection limit. The other PMF DPMI, ATTI, and more surprisingly musk ketone and musk xylene were not detected in any sample analysed. In comparison the samples from Canada were contaminated at a higher level than the Swedish samples, by a maximum factor of ca 10 for HHCB and AHTN.     

可扩展性的公路空间数据库方案设计

以开放、通用为指导思想，提出了建立一个具有良好可扩展性公路空间数据库的建议，阐述了公路实体网络和分析公路数据库结构数据实体的关系；使用数据字典设计了专题属性标准数据表，从而实现公路管理专题的扩展；提出了灵活可变的图形的属性结构，实现公路实体属性扩展；运用动态分段理论完成网络图的建立和维护，实现了核心层图形数据的动态更新。     

成都标准基线场的设计及光干涉测量

本文较详尽地阐述了成都标准基线场的设计特点及其理论依据，并介绍了光干涉测量及其配合的EDM测量、光干涉测量计算结果和精度分析。     

参考数据集的数据质量管理

地理信息团体习惯于使用现有的数据集,元数据(关于数据的数据)也随之日渐重要,数据质量正是元数据的一个重要方面。为广泛使用地理信息,出现了包括全球空间基础设施、欧洲的 INSPIRE以及国家空间数据基础设施(澳大利亚、美国)等项目。开放地理信息系统联盟 (OGC)已推出在不同应用程序间的数据转换方     

盐湖沉积物的穆斯堡尔效应研究

对青海柴达木盆地察尔汗、昆特依盐湖以及新疆罗布泊盐湖一系列沉积物样品进行了穆斯堡尔效应的研究。对全部样品做了常温下的穆斯堡尔谱学测量,并对部分样品做了低温下的测量。从穆斯堡尔谱的解析结果可知,盐湖沉积物黏土矿中含二价铁的主要矿物是绿泥石,在察尔汗盐湖样品中有少量菱铁矿;三价铁存在于多种矿物和非晶态的氢氧化物中;某些样品中含有少量的赤铁矿,它在常温下即出现磁有序。不同盐湖的沉积物样品和同一盐湖不同深度样品的含铁矿物组成及相对含量不同,Fe2+/Fe3+的比值也不同。这些结果可以反映出盐湖沉积过程中地球化学和环境及气候的变化。     

地震滑动时空分布的合成孔径雷达干涉测量、全球定位系统、远震和强震数据的联合反演：在1999年伊兹米特主震中的应用（二）

图11和图12分别给出了对地表位移未作约束和有约束时由实际数据分别反演和联合反演得到的滑动分布。它们有共同的特征：(1)在模型西部的深处缺少滑动；(2)在模型的中部，从格尔居克以西约10km到萨潘贾湖的东邻区，存在高滑动值(4～8m)；(3)在最东段滑动显著。没有地表位     

由GPS测量确定的2002年阿拉斯加迪纳利断层Mw7．9级地震的同震滑动分布

2002年11月3日，阿拉斯加中部发生了一次Mw7．9级的地震。该地震使部分苏西特纳冰川断层、迪纳利断层及托茨春达断层发生破裂。反演GPS测量的位移场表明，该事件以沿迪纳利断层复杂的右旋走滑破裂占优势。最靠近震中的GPS测点显示出苏西特纳冰川断层有逆冲运动的影响。优选的Mw7．9级地震同震滑动模型表明，在破裂的西段滑动相对较小，而在震中以东约60km至在迪纳利断层和托茨春达断层的交汇处滑动相对较大。我们发现大多数浅层滑动从地表至深15km，但反演却表明在震中以东110km有一大的深部滑移层。我们的模型预示地表滑动与地表地质观测非常一致，模型分辨率也非常好。