Seasonal delivery of the particulate forms of phosphorus to Lake Geneva from the upper Rhone river

Large volume water samples were taken at Porte du Scex and Bouveret at the mouth of the Upper Rhone River as it enters Lake Geneva. Samples were taken every two weeks during 1982 up until August 1983. Water samples were analyzed for total phosphorus (TP), and soluble reactive phosphorus (SRP) and were centrifuged in the field using a continuous flow centrifuge to recover the suspended solids following sieving at 63 µm. The < 63 µm solids were analyzed for total particulate phosphorus (TPP), organic phosphorus (OP), apatite phosphorus (AP) and non apatite inorganic phosphorus (NAIP). The > 63 µm were similarly analyzed and the weight of total solids in both size fractions recorded. Results were compared throughout the period of record to the hydrograph situated at Porte de Scex. The annual cycle of the Rhone can be divided into a low turbidity, low flow winter period (SED 1) and high flow, high turbidity summer season designated (SED 2). Turbidity is well related to discharge. The > 63 µm sediment is mobilized at 200 m³ s^–1 and thereafter increases in concert with, though at a faster rate than, the < 63 µm fraction. The coarse fraction contains significant quantities of phosphorus and in 1982 accounted for 26% of the TPP loading. OP and NAIP are higher in SED 1 than in SED 2 though AP remains constant throughout the year. OP is believed to be driven primarily from point sources whereas NAIP, in addition to point sources, has secondary sources in spring and summer due to sheet erosion from the agricultural soils of the valley. Loadings of phosphorus were calculated by four methods which showed internal consistency though they were higher than previous estimates. Bioavailable phosphorus (BAP) was estimated to account for some 20% of the total phosphorus loading of some 1500 tonnes; BAP is here taken to be the sum of SRP and NAIP and is that portion of the phosphorus load believed to be available to generate phytoplankton growth.     

Radioisotopic evidence of perturbations of recent sedimentary record in lakes: a word of caution for climate studies

The rate of climatic change estimated from the gradient of signals recorded in lake sediments may be erroneous if post-depositional perturbations are overlooked. A smear out of a pulse signal, over a variable thickness of core section, due to physical or biological mixing, is a well known phenomena. Much less attention is paid to a possible overestimation of the rate of change when a part of record is missing due to an erosion event. In this paper we show a few examples of recent lake sediment perturbations and the resulting distortions in the time scale, as documented by short-lived radionuclides.Contribution to Clima Locarno — Past and Present Climate Dynamics; Conference September 1990, Swiss Academy of Sciences — National Climate Program     

Can market mechanisms ameliorate the effects of long-term climate change?

Land prices, insurance rates, future markets, mortgage terms, and other market mechanisms may be expected to guide short-term economic response to climatic change as its effects become apparent to investors. On the other hand, the pervasive influence of discount rates on investment decisions makes it unlikely that the market will give satisfactory guidance to investments that must be undertaken long before the appearance of the climatic effect they are intended to mitigate. For this reason, only government is likely to undertake such long-term investments as large civil works intended to modify hydrology (irrigation, seawall dikes), and research and development in agriculture or other technologies which need to be adapted to new climatic conditions, while the effects of climate change are still distant and uncertain.Decisions regarding very large macroprojects, as well as decisions which determine the siting of installations that have long-term consequences for the environment (e.g., dump sites for disposal of long-term hazardous wastes) should carefully consider the effects of climate change regardless of current market signals. Strategic planners for government and industry should take steps now to identify those decisions for which planning is now beginning, and which need to take into account the effects of long-term climate change.     

Atmospheric trace metals and sulfate in the Greenland Ice Sheet

Chemical analyses of surface snow and dated deep ice core samples from central Greenland suggest that Zn, Pb and sulfate are presently being deposited there at two to three times the natural rates. No recent increases in Cd or V concentrations were observed. Pre-1900 ice shows no measurable effect of the activities of man and represents a good natural aerosol baseline. High enrichment factors relative to average crustal material were observed for Zn, Pb, Cd and sulfate in all samples indicating a natural source other than continental dust is responsible. A high temperature process or vapor phase origin for these enriched elements, possibly volcanism, seems likely.     

Dynamic capillary effects in heterogeneous porous media

In standard multi-phase flow models on porous media, a capillary pressure saturation relationship developed under static conditions is assumed. Recent experiments have shown that this static relationship cannot explain dynamic effects as seen for example in outflow experiments. In this paper, we use a static capillary pressure model and a dynamic capillary pressure model based on the concept of Hassanizadeh and Gray and examine the behavior with respect to material interfaces. We introduce a new numerical scheme for the one-dimensional case using a Lagrange multiplier approach and develop a suitable interface condition. The behavior at the interface is discussed and verified by various numerical simulations.     

Numerical models of convection in the earth's mantle

Calculations on convection in Newtonian fluids at large Rayleigh numbers show behaviour in general agreement with geophysical observations. The calculated values of surface velocities, regional gravity and topographic anomalies all lie within the range of values found at the earth's surface. The sign of the gravity anomaly over rising fluid is positive because the gravitational effect of the surface deformation is greater than that of the density deficit. This result appears to agree with geophysical observations and should permit the flow within the mantle to be followed in some detail.     

The use of magnetic susceptibility anisotropy for estimating the ferromagnetic mineral fabrics of metamorphic rocks

Some fabrics of ferromagnetic minerals of metamorphic rocks have been studied by means of the magnetic susceptibility anisotropy; amphibolites from West Moravian crystallinicum were used as an example. These studies have shown that besides the differences in metamorphism and tectonics of the two main fabric units of that area (Moldanubicum, Moravicum) there exist differences in the content and fabric of ferromagnetic minerals as well.The fabric of ferromagnetic minerals in amphibolites of Moravicum originated probably simultaneously with the fabric of rock-forming minerals. On the other hand some of the ferromagnetic minerals in amphibolites from Moldanubicum are younger and their fabric originated later. The different character of the premetamorphic material of ortho-amphibolites has also been reflected in the intensity and the type of preferred orientation of ferromagnetic minerals.The results of our research show that the amphibolites of West Moravian crystallinicum can be put into different petrogenetic and geological-structural units through studies of their magnetic anisotropy.

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Zusammenfassung Einige Gefüge der ferromagnetischen Mineralien der metamorphen Gesteine wurden am Beispiel der Amphibolite des westmÄhrischen Kristallins mit Hilfe der Anisotropie der magnetischen SuszeptibilitÄt untersucht. Es wurde festgestellt, da\ au\er den Unterschieden in Metamorphose und Tektonik der beiden geologischen Haupteinheiten dieses Gebietes (d. h. Moldanubikum und Moravikum) auch Unterschiede im Gehalt und im Gefüge der ferromagnetischen Mineralien deutlich sind.Das Gefüge der ferromagnetischen Mineralien in den Amphiboliten des Moravikums ist wahrscheinlich gleichzeitig mit dem Gefüge der gesteinsbildenden Mineralien entstanden, wÄhrend im Moldanubikum ein Teil der ferromagnetischen Mineralien offensichtlich jünger ist und ihr Gefüge spÄter entstand. Der andere Charakter des prÄmetamorphen Materials in den Orthoamphiboliten kommt auch in der IntensitÄt und im Typ der Vorzugsorientierung der ferromagnetischen Mineralien zum Ausdruck.Aus den Ergebnissen ergibt sich, da\ die Kenntnis der magnetischen Anisotropie die Einordnung der Amphibolite zu unterschiedlichen petrogenetischen und geologisch-strukturellen Einheiten im westmÄhrischen Kristallin ermöglicht.

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Résumé Plusieurs «Gefüge» des minéraux ferromagnétiques des roches métamorphiques ont été étudiées à l'aide de l'anisotropie de la susceptibilité magnétique sur l'exemple d'amphibolites du cristallin de la Moravie de l'Ouest. On a constaté qu'à part des différences de métamorphisme et de tectonique des deux unités principales de cette région (Moldanubique et Moravique), il y a aussi des différences dans le volume et la «Gefüge» des minéraux ferromagnétiques.On a constaté que la «Gefüge» des mineraux ferromagnétiques dans des amphibolites du Moravique s'était produite probablement en mÊme temps que la structure des minéraux formant les roches, tandis qu'une partie des minéraux ferromagnétiques dans le Moldanubique pourrait Être plus jeune, sa «Gefüge » s'étant produite plus tard. Un caractère différent des matériaux prémetamorphiques dans les orthoamphibolites, s'est révélé, en mÊme temps, par l'intensité et le genre de l'orientation dominante de minéraux ferromagnétiques.Des résultats on peut déduire qu'à l'aide d'une étude de l'anisotropie magnétique, il est possible de classer les amphibolites dans les différents ensembles de petrogénese et de structures géologiques.

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Spatial and temporal dynamics of suspended particles and E. coli in a complex surface-water and karst groundwater system as a basis for an adapted water protection scheme,northern Vietnam

Karst aquifers in subtropical regions are characterized by high variability of water availability and quality due to changes associated with rainy and dry seasons. An additional challenge for water management is the combination of surface-water and karst groundwater systems since high spatiotemporal dynamics cause high variability of water quality. In these cases, adapted protection strategies are required. In this study, a protection approach for the catchment of a river-water diversion point in a rural area in northern Vietnam is developed. The variability of water quality was evaluated by rainy and dry season synoptic surveys of suspended particles and microbial contamination at 49 sites and time series at three sets of paired sites under constant hydraulic conditions. The anthropogenic land-use activities in the catchment were mapped to identify potential contamination sources and to highlight the challenging combination of surface-water and karst groundwater management. The analyzed data indicate differences in water quality between the dry and rainy seasons and a higher influence on water quality from land use than from hydrologic conditions. Furthermore, the results suggest a high risk of contamination resulting from residential areas, agriculture, and livestock farming, and reveal the necessity of implementation of appropriate measures such as restricted farming and the hook-up of buildings to municipal sewage disposal. Finally, the data show that water quality can be improved by adjusting water withdrawals by the time of day. The applied methods can be transferred to other surface-water and karst groundwater systems in similar subtropical environments.