排序方式： 共有6条查询结果，搜索用时 15 毫秒
1
1.
Groundwater mixing between different aquifer types in a complex structural setting discerned by elemental and stable isotope geochemistry 
下载免费PDF全文
下载免费PDF全文 Karst aquifers are well known for their intricate stratigraphy and geologic structures, which make groundwater characterization challenging because flowpaths and recharge sources are complex and difficult to evaluate. Geochemical data, collected from ten closely spaced production wells constructed in two karst aquifers (Bangor Limestone (Mb) and Tuscumbia Limestone/Fort Payne Chert (Mftp)) in Trussville, north‐central Alabama, illustrate two distinctive groundwater end‐members: (1) higher major ion, dissolved inorganic carbon, conductivity, alkalinity concentrations, heavier δ13C ratios (max: −10.2 ± 0.2‰ Vienna Pee Dee Belemnite (PDB)) and lower residence times (mean: 19.5 ± 2 years, n = 2) of groundwater in the Mb aquifer and (2) lower constituent concentrations, lighter δ13C ratios (min: −13.4 ± 0.2‰ PDB) and longer residence times of groundwater (mean: 23.6 ± 2 years, n = 4) in the Mftp aquifer. Summer and fall data and the binary mixing model show aquifer inter‐flow mixing along solution fractures and confirms the distinctive groundwater geochemistry of the two aquifers. Lowering of static water levels over the summer (drawdown from 2 to 5.2 m) leads to more reducing groundwater conditions (lower Eh values) and slightly enriched δ18O and δD ratios during the fall [δ18O: −4.8 ± 0.1 to −5.4 ± 0.1‰ Vienna Standard Mean Oceanic Water (VSMOW), n = 9; δD: −25.4 ± 1 to −27.4 ± 1‰ VSMOW, n = 9] when compared with summer season samples (δ18O: −5.1 ± 0.1 to −5.7 ± 0.1‰ VSMOW, n = 11; δD: −25.0 ± 1 to −30.6 ± 1‰ VSMOW, n = 11). GIS analyses confirm the localized origin of recharge to the investigated aquifers. The combination of GIS, field parameters and geochemistry analyses can be successfully used to identify recharge sources, evaluate groundwater flow and transport pathways and to improve understanding of how groundwater withdrawals impact the sustainability and susceptibility to contamination of karst aquifers. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
2.
Liviu?Mihai?Irimia Cristian?Valeriu?PatricheEmail author Hervé?Quenol Lucian?Sf?c? Chris?Foss 《Theoretical and Applied Climatology》2018,131(3-4):1069-1081
Climate change is causing important shifts in the suitability of regions for wine production. Fine scale mapping of these shifts helps us to understand the evolution of vineyard climates, and to find solutions through viticultural adaptation. The aim of this study is to identify and map the structural and spatial shifts that occurred in the climatic suitability for wine production of the Cotnari wine growing region (Romania) between 1961 and 2013. Discontinuities in trends of temperature were identified, and the averages and trends of 13 climatic parameters for the 1961 to 1980 and 1981 to 2013 time periods were analysed. Using the averages of these climatic parameters, climate suitability for wine production was calculated at a resolution of 30 m and mapped for each time period, and the changes analysed. The results indicate shifts in the area’s historic climatic profile, due to an increase of heliothermal resources and precipitation constancy. The area’s climate suitability for wine production was modified by the loss of climate suitability for white table wines, sparkling wines and wine for distillates; shifts in suitability to higher altitudes by about 67 m, and a 48.6% decrease in the area suitable for quality white wines; and the occurrence of suitable climates for red wines at lower altitudes. The study showed that climate suitability for wine production has a multi-level spatial structure, with classes requiring a cooler climate being located at a higher altitude than those requiring a warmer climate. Climate change has therefore resulted in the shift of climate suitability classes for wine production to higher altitudes. 相似文献
3.
The present study tests the usefulness of SoLIM software and GIS techniques for the reconstruction of large vegetation formations from the mid-Holocene period in Romania. We used current reference climate data (temperature, precipitation) and the current extent of ecological regions in Romania to derive climate optimality functions for each vegetation formation. The optimality functions were used to simulate current and past distributions of vegetation. The results showed that the current and mid-Holocene simulated spatial distributions of vegetation are quite similar. Changes were found for about 14% of the Romanian territory (33 946 km2), the most important being the retreat of coniferous forests in favor of mixed forests and of mixed forests in favor of forest steppe. The former is validated by previous pollen-based studies showing the transition from coniferous forests to mixed forests that occurred in several areas of the country after the mid-Holocene. The study demonstrates the potential of this methodological approach to reconstruct past vegetation formations, and at the same time that it is a straightforward and expert knowledge-based method. Although our application uses only climate factors, the results can be further refined by incorporating additional drivers (soil and landform information, site-specific pollen and fossil data, wildfire data) for a more accurate inference of paleovegetation. 相似文献
4.
5.
Paolo Soleri Valeriu Tudose Rob Fender Michiel van der Klis Peter G. Jonker 《Monthly notices of the Royal Astronomical Society》2009,399(1):453-464
We present the results of simultaneous X-ray and radio observations of the peculiar Z-type neutron star X-ray binary Cir X-1, observed with the Rossi X-ray Timing Explorer satellite and the Australia Telescope Compact Array in 2000 October and 2002 December. We identify typical Z-source behaviour in the power density spectra as well as characteristic Z patterns drawn in an X-ray hardness–intensity diagram. Power spectra typical of bright atoll sources have also been identified at orbital phases after the periastron passage, while orbital phases before the periastron passage are characterized by power spectra that are typical neither of Z nor of atoll sources. We investigate the coupling between the X-ray and the radio properties, focusing on three orbital phases when an enhancement of the radio flux density has been detected, to test the link between the inflow (X-ray) and the outflow (radio jet) to/from the compact object. In two out of three cases, we associate the presence of the radio jet to a spectral transition in the X-rays, although the transition does not precede the radio flare, as detected in other Z sources. An analogous behaviour has recently been found in the black hole candidate GX 339-4. In the third case, the radio light curve shows a similar shape to the X-ray light curve. We discuss our results in the context of jet models, considering also black hole candidates. 相似文献
6.
Patriche Cristian Valeriu Irimia Liviu Mihai 《Theoretical and Applied Climatology》2022,148(3-4):1035-1056
Theoretical and Applied Climatology - Climate change affects the viticulture sector worldwide in different ways, some countries reporting negative impacts, other positive effects, depending on the... 相似文献
1