Comparison of environmental tracers including organic micropollutants as groundwater exfiltration indicators into a small river of a karstic catchment     

Clarissa Glaser  Marc Schwientek  Tobias Junginger  Benjamin Silas Gilfedder  Sven Frei  Martina Werneburg  Christian Zwiener  Christiane Zarfl 《水文研究》2020,34(24):4712-4726

Understanding groundwater–surface water (GW–SW) interactions is vital for water management in karstic catchments due to its impact on water quality. The objective of this study was to evaluate and compare the applicability of seven environmental tracers to quantify and localize groundwater exfiltration into a small, human-impacted karstic river system. Tracers were selected based on their emission source to the surface water either as (a) dissolved, predominantly geogenic compounds (radon-222, sulphate and electrical conductivity) or (b) anthropogenic compounds (predominantly) originating from wastewater treatment plant (WWTP) effluents (carbamazepine, tramadol, sodium, chloride). Two contrasting sampling approaches were compared (a) assuming steady-state flow conditions and (b) considering the travel time of the water parcels (Lagrangian sampling) through the catchment to account for diurnal changes in inflow from the WWTP. Spatial variability of the concentrations of all tracers indicated sections of preferential groundwater inflow. Lagrangian sampling techniques seem highly relevant for capturing dynamic concentration patterns of WWTP-derived compounds. Quantification of GW inflow with the finite element model FINIFLUX, based on observed in-stream Rn activities led to plausible fluxes along the investigated river reaches (0.265 m³ s⁻¹), while observations of other natural or anthropogenic environmental tracers produced less plausible water fluxes. Important point sources of groundwater exfiltration can be ascribed to locations where the river crosses geological fault lines. This indicates that commonly applied concepts describing groundwater–surface water interactions assuming diffuse flow in porous media are difficult to transfer to karstic river systems whereas concepts from fractured aquifers may be more applicable. In general, this study helps selecting the best suited hydrological tracer for GW exfiltration and leads to a better understanding of processes controlling groundwater inflow into karstic river systems.  相似文献   

Analyzing relationship between user‐generated content and local visual information with augmented reality‐based location‐based social networks     

Chengbi Liu  Sven Fuhrmann 《Transactions in GIS》2020,24(3):704-718

Location‐based social networks (LBSNs) have become an important source of spatial data for geographers and GIScientists to acquire knowledge of human–place interactions. A number of studies have used geotagged data from LBSNs to investigate how user‐generated content (UGC) can be affected by or correlated with the external environment. However, local visual information at the micro‐level, such as brightness, colorfulness, or particular objects/events in the surrounding environment, is usually not captured and thus becomes a missing component in LBSN analysis. To provide a solution to this issue, we argue in this study that the integration of augmented reality (AR) and LBSNs proves to be a promising avenue. In this first empirical study on AR‐based LBSNs, we propose a methodological framework to extract and analyze data from AR‐based LBSNs and demonstrate the framework via a case study with WallaMe. Our findings bolster existing psychological findings on the color–mood relationship and display intriguing geographic patterns of the influence of local visual information on UGC in social media.  相似文献   

On the efficient analysis of shallow tunnels     

G. Beer  G. Swoboda 《Computers and Geotechnics》1985,1(1):15-31

The numerical analysis of shallow tunnels using a combined Finite Element-Boundary Element method is discussed. The theory of coupling the Boundary and Finite Element discretisation is presented and solutions obtained by the method compared with analytical results for near surface circular excavations. The coupled method is then applied to a practical problem in tunneling.  相似文献   

Combination of multi-mission altimetry data along the Mekong River with spatio-temporal kriging     

Eva Boergens  Sven Buhl  Denise Dettmering  Claudia Klüppelberg  Florian Seitz 《Journal of Geodesy》2017,91(5):519-534

River water-level time series at fixed geographical locations, so-called virtual stations, have been computed from single altimeter crossings for many years. Their temporal resolution is limited by the repeat cycle of the individual altimetry missions. The combination of all altimetry measurements along a river enables computing a water-level time series with improved temporal and spatial resolutions. This study uses the geostatistical method of spatio-temporal ordinary kriging to link multi-mission altimetry data along the Mekong River. The required covariance models reflecting the water flow are estimated based on empirical covariance values between altimetry observations at various locations. In this study, two covariance models are developed and tested in the case of the Mekong River: a stationary and a non-stationary covariance model. The proposed approach predicts water-level time series at different locations along the Mekong River with a temporal resolution of 5 days. Validation is performed against in situ data from four gauging stations, yielding RMS differences between 0.82 and 1.29 m and squared correlation coefficients between 0.89 and 0.94. Both models produce comparable results when used for combining data from Envisat, Jason-1, and SARAL for the time period between 2002 and 2015. The quality of the predicted time series turns out to be robust against a possibly decreasing availability of altimetry mission data. This demonstrates that our method is able to close the data gap between the end of the Envisat and the launch of the SARAL mission with interpolated time series.  相似文献   

Book reviews     

Charles A. S. Hall  Joseph D. Cornell  Jill Jäger  Tom Beer 《Climatic change》1990,16(1):141-151

The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献