The groundwater vulnerability map for the Flemish region: its principles and uses

Fobe, B. and Goossens, M., 1990. The groundwater vulnerability map for the Flemish region: its principles and uses. Eng. Geol., 29: 355–363.

The vulnerability map of the groundwater for the Flemish region demonstrates the possible risk for contamination of the groundwater in the upper aquifer of economical value. The map was ordered by the Flemish government and distributed among the people working in the environmental sector. The vulnerability map, in scale 1/100,000, is based on static factors, like the lithology of the aquifer and its possible coverlayers and the depth of the water table. The map will serve as a tool for proper management of the groundwater. Because of its smaller scale, the document will be used to determine areas where particular regulations and actions for the protection of groundwater are necessary.

Some of the data presented by the map suggest a safer situation than actually present. This is because the compilation followed strictly the principles of the legend. In the future, care should be taken to avoid such ambiguous situations on a map that is available for the public.

Plans exist to start with the compilation of dynamic vulnerability maps. One experimental project is already finished. This study and other recent scientific research gave experience about the influence of topography on the recharge of groundwater. It will be necessary to review the risk of groundwater contamination in some of the areas on the vulnerability map, especially in sandy hill ridges.     

On the use of a modified clean-room optical particle counter for atmosperic aerosols at high relative humidity

This study is devoted to the performance of the CLIMET CI-8060, a white-light optical particle counter (OPC). Designed for clean-room monitoring, the off-the-shelf performance of this instrument is rather poor for outdoor studies. Modifications of this instrument are described turning this low-cost instrument into an OPC with excellent performance. The modifications include a reduction of the flow rate to 1.4 l/min, an altered design of the inlet nozzle, a buffer chamber to assure continuous flow, and a 16-channel pulse height analyzer.The modified version has been checked thouroughly. The counting efficiency is very close to 100% for particle sizes between 0.295 and 0.801 μm. The loss of giant particles is also marginal, as comparative tests with a cascade impactor show. The sizing calibration has been redetermined experimentally, using latex spheres, and theoretically, applying a software package by Jüngert [1988] using the Mie theory. With the help of the established relationship between experimental and theoretical response for latex, calibration tables for any other particle material are obtained (in particular for ambient aerosols and H₂O for fog and cloud condensation studies).The modified counter has been used for monitoring the growth of hygroscopic aerosols in humid conditions, using two different inlet lines, one of them drying the aerosol before entering the OPC, the other one preserving ambient conditions. This system allows to observe haze and fog formation and cloud condensation processes in situ at a one-minute time resolution.     

Supergranular line profile variation of Mg i λ2852

The chromospheric network is barely visible in the Mg i 2852 line. Unlike in plages, where it shows well-defined self-reversed emission structure in the core, the line is an unreversed absorption feature in the network boundaries, exhibiting only a small blue asymmetry. In the network cell interiors, the line is unreversed and symmetrical.     

IV. Stratigraphie Die fazielle Einstufung fossilführender Sedimente

Ohne Zusammenfassung     

Quantitative assessment of intertidal blue mussel (Mytilus edulis L.) stocks: combined methods of remote sensing, field investigation and sampling

The aim of this investigation was to develop appropriate methods for quantitative assessment of blue mussel beds. Combined methods of remote sensing, ground truth investigation and sampling in the field were applied to mature and young intertidal mussel beds. Three variables were measured to obtain reliable quantitative estimates of biomass and abundance: the total area covered by a bed; the cover, i.e. the area of mussel-covered patches in relation to the total mussel bed area; and the proportion, i.e. the area covered by mussels within the patches in relation to the total area of mussel patches. Cover and proportion of intertidal blue mussel beds were measured in the field by the transection method. Aerial photographs enabled the total area of the beds to be determined and large-scale surveys of mussel beds to be carried out synchronously. By examining large-scale aerial photographs it was possible also to determine the cover by remote sensing. The proportion could not be derived from aerial photographs, even from pictures at the largest scale tested during this investigation (scale 1:2500). By statistical methods it was estimated that 12 sub-samples (each covering 177 cm²) from mature beds, and 12 sub-samples (each covering 38 cm²) from young beds are needed to obtain reliable data on biomass and abundance.     

Role of particle size in till-fabric characteristics: systematic variation in till fabric from Vestari-Hagafellsjökull, Iceland

Till-fabric analysis has often been used to interpret glacier flow directions and subglacial dynamics using vector-based statistics, but recent data suggest that such analysis may also effectively indicate former glacier dynamics. The results of a fabric investigation of subglacially strained till deposited during a surge of Vestari-Hagafellsjökull, Iceland, are presented. Till fabric was collected at four sites within a limited area where ice-flow direction during deposition was known from subglacial bedforms at the site. Analysis was carried out on elongate grains (axial ratio <1.5:1) at seven size fractions, with the a-axis length ranging from 0.25 to 32 mm. The largest grains tend to be parallel to ice flow, whereas smaller grains reflect a mix of parallel and transverse orientations. The implications of these data for the role and validity of till-fabric analysis are discussed, with reference to vector analyses and the compilation of fabric shape envelopes. It is noted that, in contrast to laboratory experimental data, neither March nor Jeffery mechanisms explain the fabric configurations reported. It is concluded that a standardized approach is necessary for collecting fabric data, and in many situations analysis of data populations at a range of particle sizes is desirable.     

Evidence of NAO control on subsurface ice accumulation in a 1200 yr old cave-ice sequence, St. Livres ice cave, Switzerland

Mid-latitude ice caves are assumed to be highly sensitive to climatic changes and thus represent a potentially interesting environmental archive. Establishing a precise chronology is, however, a prerequisite for the understanding of processes driving the cave-ice mass balance and thus allows a paleoenvironmental interpretation. At St. Livres ice cave (Jura Mountains, Switzerland), subfossil trees and organic material are abundant in the cave-ice deposit, therefore allowing the dating of individual ice layers. The dendrochronological analysis of 45 subfossil samples of Norway spruce (Picea abies (L.) Karst.) from the overhanging front of the ice outcrop as well as the dating of seven wood samples with ¹⁴C dating allowed for a reconstruction of the St. Livres cave-ice sequence and for the determination of periods of ice accumulation and ablation. Results suggest a maximal age of 1200 ± 50 ¹⁴C yr BP for the observed ice sequence and indicate the presence of four major deposition gaps dated to the 14th, 15th, mid-19th and late 19th century, which can be related with periods of positive North Atlantic Oscillation anomalies (NAO+) over the winter half-year and/or anthropogenic cave-ice abstraction. Similarly, there is evidence that periods of cave-ice accumulation as observed between AD 1877-1900 and AD 1393-1415 would correspond with phases of negative NAO indices. Cave ice represents therefore an original climate archive for the winter half-year and is complementary to other continental proxies recording preferentially summer conditions (e.g., tree rings, varves).     

激光剥蚀-等离子体质谱技术及其在地球化学宇宙化学和环境研究中的应用

激光剥蚀-等离子体质谱(LA-ICPMS)已成为地球化学、宇宙化学和环境研究领域元素和同位素原位分析最重要的技术之一。文章介绍了多种类型的质谱仪及其使用的激光器。用途最广的LA-ICPMS仪器之一是单接收器扇形磁场质谱仪,配有Nd:YAG激光剥蚀系统(激光波长分为193 nm和213 nm两种),MPI Mainz实验室使用的就是这套系统,文章对此作一详细介绍。文中阐述了数据优化技术及其多种校正过程;介绍LA-ICPMS在痕量元素和同位素分析领域的一些应用,包括参考物质的研制,Hawaiian玄武岩、Martian陨石、生物骨针和珊瑚虫中痕量元素分析及熔融包裹体和富钙-铝碳质球粒陨石中的铅和锶同位素测量。     

Palaeoglaciation of Bayan Har Shan,northeastern Tibetan Plateau: glacial geology indicates maximum extents limited to ice cap and ice field scales

Key locations within an extensive area of the northeastern Tibetan Plateau, centred on Bayan Har Shan, have been mapped to distinguish glacial from non‐glacial deposits. Prior work suggests palaeo‐glaciers ranging from valley glaciers and local ice caps in the highest mountains to a regional or even plateau‐scale ice sheet. New field data show that glacial deposits are abundant in high mountain areas in association with large‐scale glacial landforms. In addition, glacial deposits are present in several locations outside areas with distinct glacial erosional landforms, indicating that the most extensive palaeo‐glaciers had little geomorphological impact on the landscape towards their margins. The glacial geological record does indicate extensive maximum glaciation, with local ice caps covering entire elevated mountain areas. However, absence of glacial traces in intervening lower‐lying plateau areas suggests that local ice caps did not merge to form a regional ice sheet on the northeastern Tibetan Plateau around Bayan Har Shan. No evidence exists for past ice sheet glaciation. Copyright © 2009 John Wiley & Sons, Ltd.