Groundwater-surface water interactions (GSI) connect rivers and streams with riparian areas and the adjacent aquifer. Although these interactions exert a substantial control of quantity and quality of both groundwater and surface water, knowledge on GSI along rivers at the regional scale, particularly for inland waterways, is still limited. We investigated GSI along the river Moselle, an important federal inland waterway in Germany, by using radon and tritium to identify gaining (water flux from the aquifer to the surface water) and losing (water flux from the surface water to the aquifer) stream conditions, respectively. Gaining stream conditions were identified by continuously measuring radon along the river during boat surveys with a high spatial resolution (every 2 km) during intermediate (October 2020) and near low flow conditions (August/September 2021). The tritium concentrations in surface water and groundwater and the resulting tritium inventories were used to characterize losing stream conditions Monthly tritium inventories from 2017 to 2022 revealed a mean loss for the whole period of 20.3 % and a mean gain of 21.8%. Both were probably triggered by a combination of losing stream conditions and flood-induced mass transfer of water from the aquifer back into the river as well as discharge fluctuations. At the investigated site Lehmen there were direct indications of an influence of surface water due to elevated tritium concentrations in the groundwater (up to 13.3 Bq L−1). Using radon mass balance modelling, good agreements of simulated versus measured radon data with respect to two groundwater end-member scenarios were obtained during intermediate flow (Spearman's ρ: 0.97 and 0.99; MAE: 10.1 and 3.4 Bq L−1) and near low flow (Spearman's ρ: 0.97 and 0.99; MAE: 11 and 6.5 Bq L−1). Considerable groundwater inflow was limited to the meander of Detzem, where cumulated groundwater inflow of about 19 m3 s−1 (9.5% of total discharge) and 4.2 m3 s−1 (3.8% of total discharge) was simulated during intermediate and near low flow, respectively. However, the groundwater inflow was relatively low compared to alpine streams, for example. The study will help to better identify and quantify GSI at the regional scale and provide methodological guidance for future studies focusing on inland waterways. 相似文献
The quantification of percolation processes and deep drainage rates in cracking clays is challenging due to the existence of multiple flow pathways, including desiccation crack networks, and the effect of variability in antecedent soil moisture and rain event properties. While most previous research on this topic focuses on long-term average rates, this study focusses on inter-event dynamics. The study uses data from soil moisture sensors distributed vertically down 4 m profiles of Vertosol and Chromosol soils across 13 sites over an area of approximately 20 km2. The objectives were to estimate the temporal and spatial variability of deep drainage rates and to investigate the effect of antecedent soil moisture conditions and rain event properties on deep drainage rates and percolation dynamics. 35 deep drainage events over a 40-month period contributed 78 % of the total deep drainage of 254 mm at 4 m depth. Average deep drainage estimates were about 15 % (ranging from 0 – 80 % between sites) of total rainfall and irrigation in the Vertosol and 8% (0 – 24 %) in the Chromosol. The event water travel times at 4 m depth were 0.25 – 38 hr and 14 – 39 hr in the Vertosol and Chromosol respectively. The event deep drainage rates averaged across sites were associated with event rainfall volumes (linear regression R2 = 0.40), with the effect of antecedent conditions evident only when looking at inter-site differences. The percolation response time was strongly associated with higher rainfall intensities (R2 = 0.33) with no evidence from the linear regression of an antecedent moisture effect. 相似文献
Long-term field experiments at Abisko, Sweden, and Toolik Lake, Alaska, reveal both similarities and differences in response of contrasting Arctic ecosystems to changes in temperature, light, and nutrient availability. Five different ecosystems were manipulated for 5–15 years by increasing air temperature with greenhouses, by decreasing light with shading, and by increasing available N and P with fertilizers. The ecosystems at Abisko included evergreen-dominated heath and fellfield sites; at Toolik Lake they included wet sedge tundra, moist tussock tundra, and dry heath tundra. In all ecosystems, fertilizer treatment increased plant growth, production, and/or biomass. Plant responses to warming were smaller and occasionally nonsignificant, Responses to shading were generally nonsignificant after 3–6 years, although after 9 years the tussock tundra showed significant decreases in biomass. In general, the ecosystems at Abisko were less responsive to nutrients and more responsive to temperature than the ecosystems at Toolik Lake. Overall, though, the sites were quite similar in their responses to the perturbations, increasing our confidence in predictions of response to climate change over large areas based on small-area studies. 相似文献
Spatial decision-making in time-critical situations requires effective and usable two-dimensional and three-dimensional (3D) cartographic products. Holographic displays allow decision makers to work with auto-stereoscopic maps without the hassle of interacting with complex user interfaces or additional vision hardware. Holographic production processes have advanced greatly in a short period and now support timely and full integration of digital 3D models in geospatial holograms. George Mason University’s and Zebra Imaging’s research on interactive holographic motion displays showcases the leadership in moving cartography and geovisualization research in the US forward. In close cooperation with academic researchers, decision makers, and domain experts, the usability and usefulness of these cartographic products is tested and design guidelines for effective geospatial holograms are being developed. 相似文献
The initial accumulation of primary magma occurs just after the mantle has become permeable. The accumulation is caused by the compaction of the residuum, which either may be controlled by the rate of creep, or by the rate of flow of the interstitial melt. Experimental results suggest that the rate of compaction is controlled by the permeability, and a model for the accumulation process is worked out on this basis. The compaction causes the formation of a lower compaction boundary and an upper layer of melt. The ascending mantle of plumes and convection currents will form layers of melt situated 20–100 m apart. The type of partial melting for this accumulation is critical melting. 相似文献
Crustal xenoliths from basanitic dikes and necks that intruded into continental sediments of the Cretaceous Salta Rift at
Quebrada de Las Conchas, Provincia Salta, Argentina were investigated to get information about the age and the chemical composition
of the lower crust. Most of the xenoliths have a granitoid composition with quartz-plagioclase-garnet-rutile ± K-feldspar
as major minerals. The exceedingly rare mafic xenoliths consist of plagioclase-clinopyroxene-garnet ± hornblende. All xenoliths
show a well equilibrated granoblastic fabric and the minerals are compositionally unzoned. Thermobarometric calculations indicate
equilibration of the mafic xenoliths in the granulite facies at temperatures of ca. 900 °C and pressures of ca. 10 kbar. The
Sm-Nd mineral isochron ages are 95.1 ± 10.4 Ma, 91.5 ± 13.0 Ma, 89.0 ± 4.2 Ma (granitoid xenoliths), and 110.7 ± 23.6 Ma (mafic
xenolith). These ages are in agreement with the age of basanitic volcanism (ca. 130–100 and 80–75 Ma) and are interpreted
as minimum ages of metamorphism. Lower crustal temperature at the time given by the isochrons was above the closure temperature
of the Sm-Nd system (>600–700 °C). The Sm-Nd and Rb-Sr isotopic signatures (147Sm/144Nd = 0.1225–0.1608; 143Nd/144Ndt0 = 0.512000–0.512324; 87Rb/86Sr = 0.099–0.172; 87Sr/86Srt0 = 0.708188–0.7143161) and common lead isotopic signatures (206Pb/204Pb = 18.43–18.48; 207Pb/204Pb = 15.62–15.70; 208Pb/204Pb = 38.22 –38.97) of the granitoid xenoliths are indistinguishable from the isotopic composition of the Early Paleozoic metamorphic
basement from NW Argentina, apart from the lower 208Pb/204Pb ratio of the basement. The Sm-Nd depleted mantle model ages of ca. 1.8 Ga from granitoid xenoliths and Early Paleozoic
basement point to a similar Proterozoic protolith. Time constraints, the well equilibrated granulite fabric, P-T conditions and lack of chemical zoning of minerals point to a high temperature in a crust of nearly normal thickness at ca.
90 Ma and to a prominent thermal anomaly in the lithosphere. The composition of the xenoliths is similar to the composition
of the Early Paleozoic basement in the Andes of NW Argentina and northern Chile. A thick mafic lower crust seems unlikely
considering low abundance of mafic xenoliths and the predominance of granitoid xenoliths.
Received: 21 July 1998 / Accepted: 27 October 1998 相似文献
Ultramafic dikes with carbonatitic affinities (“damtjernites”) in southern Norway were generated during two magmatic events separated by about 275 Ma. The older event is late Proterozoic and the younger is mid Carboniferous.
More than 50 satellitic damtjernite intrusions occur within a 1500 km2 large region surrounding the Fen Central Complex. Phlogopite macrocrysts from 10 of these satellites yield a Rb---Sr isochron age of 578±24 Ma (2σ expanded errors). This demonstrates that the late Proterozoic carbonatitic magmatism centered at the Fen Central Complex occurred on a regional scale. This region is termed “the Fen Province”. The emplacement of the magmas in the Fen Province most likely occurred in connection with minor extensional tectonic activity on the Baltic platform during the drift-phase after the Proto-Atlantic opening.
Sr-isotopic data also show that a dike mineralogically and chemically similar to the Fen damtjernites was emplaced at 324±4 Ma (mid Carboniferous). This dike very likely dates the initiation of magmatism in the Oslo rift. Consequently very similar carbonate-bearing ultramafic magmas were generated within the south Norwegian mantle during the relatively minor Fen event and in the initial extensional period when the magma production in the Oslo rift was still low. 相似文献