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51.
52.
Groundwater warming below cities has become a major environmental issue; but the effect of distinct local anthropogenic sources of heat on urban groundwater temperature distributions is still poorly documented. Our study addressed the local effect of stormwater infiltration on the thermal regime of urban groundwater by examining differences in water temperature beneath stormwater infiltration basins (SIB) and reference sites fed exclusively by direct infiltration of rainwater at the land surface. Stormwater infiltration dramatically increased the thermal amplitude of groundwater at event and season scales. Temperature variation at the scale of rainfall events reached 3 °C and was controlled by the interaction between runoff amount and difference in temperature between stormwater and groundwater. The annual amplitude of groundwater temperature was on average nine times higher below SIB (range: 0·9–8·6 °C) than at reference sites (range: 0–1·2 °C) and increased with catchment area of SIB. Elevated summer temperature of infiltrating stormwater (up to 21 °C) decreased oxygen solubility and stimulated microbial respiration in the soil and vadose zone, thereby lowering dissolved oxygen (DO) concentration in groundwater. The net effect of infiltration on average groundwater temperature depended upon the seasonal distribution of rainfall: groundwater below large SIB warmed up (+0·4 °C) when rainfall occurred predominantly during warm seasons. The thermal effect of stormwater infiltration strongly attenuated with increasing depth below the groundwater table indicating advective heat transport was restricted to the uppermost layers of groundwater. Moreover, excessive groundwater temperature variation at event and season scales can be attenuated by reducing the size of catchment areas drained by SIB and by promoting source control drainage systems. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
53.
Thomas Heymes Patrick Monié Nicolas Arnaud Arnaud Pêcher Jean-Pierre Bouillin Roberto Compagnoni 《Lithos》2010,114(3-4):451-472
This study provides new 40Ar/39Ar geochronological constraints on the age of the Alpine tectonics in the Aspromonte Massif (southern part of the Calabrian–Peloritan belt). This massif exposes the upper units of the Calabride Complex which originated from the European continental margin. The Calabride Complex was incorporated in the Alpine orogenic wedge and then integrated into the Apennines and Maghrebides fold-and-thrust belts. Throughout the Calabride Complex there is evidence for a two stage tectonic history, which remains however rather poorly dated: Alpine nappe stacking is followed by extensional reworking along the former thrust contacts or along new detachment surfaces. Our new ages suggest that exhumation of the uppermost units, which accompanied nappe stacking, probably started at 45 Ma and that the deepest units were almost completely exhumed at 33 Ma. This kinematics probably corresponds to syn-orogenic extension while the end of exhumation is clearly related to the extensional tectonics dated at 28.6 Ma along detachment structures.Our geochronological data reveal a very short lag time between accretional and extensional processes in this part of the Mediterranean Alpine orogenic belt. The direction of extension, when the units are restored to their initial position (i.e. before the opening of the Western Mediterranean basins and the bending of the arc) is NNE–SSW. Such a direction does not fit with the eastward slab-retreat model generally put forward to explain extension in the Western Mediterranean. In contrast, we provide evidence for roughly N–S middle Oligocene extension in the accretionary prism, not previously described in this part of the Mediterranean domain. 相似文献
54.
Hubert Engelbrecht Karl B. Föllmi Ursula Baumer Johann Koller 《Swiss Journal of Geoscience》2010,103(1):3-13
A resin nodule was found in glauconite-rich detrital sediments of the Cretaceous Garschella Formation (Aptian to Albian) outcropping at Langer Köchel (Bavaria, S Germany). Gas chromatographic and mass spectrometric analyses of the fossil resin revealed dealkylation and the total defunctionalisation of its polycyclic constituents. Besides many unspecific components a specific one, agathalene, has survived. Agathalene also presents a strongly degraded product, but may have been derived from its natural precursor agathic acid, which is a very specific constituent (biomarker) of recent and fossil kauri resin. Although agathalene is a far less specific secondary biomarker, it indicates the botanic origin of the fossil resin nodule. Besides other potential producers of agathic acid, precursors of the present-day conifer species Agathis dammara and A. australis were distributed in a wider palaeophytogeographic range than today and might have been the botanical source of kauri resin. In view of the east–west directed Early Cretaceous surface current system of the Tethys ocean, the palaeogeographic provenance of the Werdenfels resin nodule probably was a mainland positioned further to the east or southeast of the Helvetic shelf, to where it was transported probably by driftwood of the resin-producing Agathis sp. 相似文献
55.
Gilles Brocard Thierry Adatte Olivier Magand Hans-Rudolf Pfeifer Albedo Bettini Fabien Arnaud Flavio S. Anselmetti Sergio Moran-Ical 《Journal of Paleolimnology》2014,52(3):155-169
Laguna Chichój (Lake Chichój) is the only deep permanent lake in the central highlands of Guatemala. The lake is located in the boundary zone between the North American and Caribbean plates. The lake has been struck by devastating earthquakes and tropical cyclones in historical times. We investigated the imprint of twentieth century extreme events on the sedimentary record of this tropical lake using a bathymetric survey of the lake, coring the lake floor, and providing a chronology of sediment accumulation. The lake occupies a series of circular depressions likely formed by the rapid dissolution of a buried body of gypsum. 210Pb and 137Cs inventories and varve counting indicate high rates of sedimentation (1–2 cm year?1). The annually layered sediment is interrupted by turbidites of two types: a darker-colored turbidite, enriched in lake-derived biogenic constituents, and interpreted as a seismite, and a lighter-colored type, enriched in catchment-derived constituents, interpreted as a flood layer. Comparison of our 137Cs-determined layer ages with a catalog of twentieth century earthquakes shows that an earthquake on the Motagua fault in 1976 generated a conspicuous darker-colored turbidite and slumped deposits in separate parts of the lake. The entire earthquake inventory further reveals that mass movements in the lake are triggered at Modified Mercalli Intensities higher than V. Tropical cyclonic depressions known to have affected the lake area had limited effect on the lake, including Hurricane Mitch in 1998. One storm however produced a significantly thicker flood layer in the 1940s. This storm is reportedly the only event to have generated widespread slope failures in the lake catchment. It is thus inferred that abundant landsliding provided large amounts of concentrated sediment to the lake, through hyperpycnal flows. 相似文献
56.
This article examines the role of coffee in the agriculture of southwest Ethiopian highlands, a context characterized by recent huge private coffee estate developments, coffee certification projects and smallholdings. The analysis shows that smallholder farmers prioritize staple crops, and allocate land and labor to coffee only once food production objectives have been reached. It also underscores the diversity of the local peasantry, often treated as a homogeneous group in development projects designed to boost farmers' income through coffee production. Based on this analysis, the article evaluates the effects of recent coffee-oriented development policies: state forest concessions for coffee investment, and two coffee certification projects (UTZ-Certified and Fair-Trade/Organic). Because they omit the differentiated farmers' strategies, these certification initiatives fail to improve local populations' livelihoods and accelerate incipient socioeconomic inequalities. Moreover, when applied to big private plantations, they participate in farmers' dispossession from critical forest resources essential to households' food self-sufficiency. 相似文献
57.
Luc G. Bulot Jean-Louis Latil Alex Hairabian Arnaud Fournillon 《Proceedings of the Geologists' Association. Geologists' Association》2014
Nolaniceras nolani ( Seunes, 1887) has been widely quoted in the Upper Aptian literature over the years. Re-examination of the holotype of the species shows that it has always been misidentified and that this taxon is represented by a single specimen, the holotype, of uncertain age. As a consequence, its use as an index species for the Upper Aptian should be reconsidered and abandoned. 相似文献
58.
Risk assessment of natural hazards is often based on the actual or forecast weather situation. For estimating such climate-related risks, it is important to obtain weather data as frequently as possible. One commonly used climate interpolation routine is DAYMET, which in its current form is not able to update its database for periods of less than a year. In this paper, we report the construction of a new climate database with a standard interface and implement a framework for providing daily updated weather data for online daily weather interpolations across regions. We re-implement the interpolation routines from DAYMET to be compliant with the data handling in the new framework. We determine the optimal number of stations used in two possible interpolation routines, assess the error bounds using an independent validation dataset and compare the results with a previous validation study based on the original DAYMET implementation. Mean absolute errors are 1°C for maximum and minimum temperature, 28 mm for precipitation, 3.2 MJ/m² for solar radiation and 1 hPa for vapour pressure deficit, which is in the range of the original DAYMET routine. Finally, we provide an example application of the methodology and derive a fire danger index for a 1 km grid over Austria. 相似文献
59.
60.
This paper presents some preliminary measurements of snow spectral reflectance on the tropical Bolivian Zongo glacier. Measurements show a correct agreement with theoretical spectral albedo of pure snow in the near infrared region, but lower values in the visible region (by 10–20%) probably due to aerosols contained in snow. Impurity contents ranged from 10 to 100 ppmw in one‐week‐old snow collected from the Zongo glacier, but measurements are scarce. Large amounts of snowfall partly compensate the proximity of dust sources in mid‐latitude glaciers, whereas on outer‐tropical glaciers precipitations are not abundant and are very seasonal, and sources of aerosols are proximate. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献