A portable low-cost device to quantify advective gas fluxes from mofettes into the lower atmosphere: First application to Starzach mofettes (Germany).

In this study, we introduce a portable low-cost device for in situ gas emission measurement from focused point sources of CO, such as mofettes. We assess the individual sensors' precision with calibration experiments and perform an independent verification of the system's ability to measure gas flow rates in the range of liters per second. The results from one week of continuous CO flow observation from a wet mofette at the Starzach site is presented and correlated with the ambient meteorological dynamics.

Fiber Optic Pressure Measurements Open Up New Experimental Possibilities in Hydrogeology.

Fiber-optic (FO) technology is being used increasingly for measurement methods in a variety of environmental applications. However, FO pressure transducers are rarely used in hydrogeological applications. We review the current state of Fabry-Pérot interferometry-based FO pressure transducers, including their advantages and limitations, as another option for high-resolution pressure- or head-change measurements in conventional or advanced aquifer testing.

How to Find Aquifer Statistics Utilizing Pumping Tests? Two Field Studies Using welltestpy.

We present a workflow to estimate geostatistical aquifer parameters from pumping test data using the Python package welltestpy. The procedure of pumping test analysis is exemplified for two data sets from the Horkheimer Insel site and from the Lauswiesen site, Germany. The analysis is based on a semi-analytical drawdown solution from the upscaling approach Radial Coarse Graining, which enables to infer log-transmissivity variance and horizontal correlation length, beside mean transmissivity, and storativity, from pumping test data.

Adaptive observation-based subsurface conceptual site modeling framework combining interdisciplinary methodologies: a case study on advancing the understanding of a groundwater nitrate plume occurrence.

Traditional site characterization and laboratory testing methods are insufficient to quantify and conceptualize subsurface contaminant source-pathway-receptor heterogeneity issues, as they hamper groundwater risk assessment and water resource management using mathematical modeling. To address these issues, we propose an adaptive observation-based conceptual site modeling framework, which emphasizes the need for the iterative testing of hypotheses centered on specific questions with clearly defined objectives using interdisciplinary tools (including, but not limited to, geology, microbiology, hydrogeology, geophysics, and the chemistry of solute fate and transport). Under this framework, we present a case study aimed at a goal-oriented investigation of the source and occurrence of a groundwater nitrate plume previously identified using chemical concentration data from sparsely distributed, conventional, and regional groundwater monitoring wells.

Hydraulic Tomography: Continuity and Discontinuity of High-K and Low-K Zones.

Hydraulic tomography is an emerging field and modeling method that provides a continuous hydraulic conductivity (K) distribution for an investigated region. Characterization approaches that rely on interpolation between one-dimensional (1D) profiles have limited ability to accurately identify high-K channels, juxtapositions of lenses with high K contrast, and breaches in layers or channels between such profiles. However, locating these features is especially important for groundwater flow and transport modeling, and for design and operation of in situ remediation in complex hydrogeologic environments.

Tracer tomography: design concepts and field experiments using heat as a tracer.

Numerical and laboratory studies have provided evidence that combining hydraulic tomography with tomographic tracer tests could improve the estimation of hydraulic conductivity compared with using hydraulic data alone. Field demonstrations, however, have been lacking so far, which we attribute to experimental difficulties. In this study, we present a conceptual design and experimental applications of tracer tomography at the field scale using heat as a tracer.

Where can cone penetrometer technology be applied? Development of a map of Europe regarding the soil penetrability.

Over the past decades, significant efforts have been invested in the development of push-in technology for site characterization and monitoring for geotechnical and environmental purposes and have especially been undertaken in the Netherlands and Germany. These technologies provide the opportunity for faster, cheaper, and collection of more reliable subsurface data. However, to maximize the technology both from a development and implementation point of view, it is necessary to have an overview of the areas suitable for the application of this type of technology.

Delineation of subsurface hydrocarbon contamination at a former hydrogenation plant using spectral induced polarization imaging.

Broadband spectral induced polarization (SIP) measurements were conducted at a former hydrogenation plant in Zeitz (NE Germany) to investigate the potential of SIP imaging to delineate areas with different BTEX (benzene, toluene, ethylbenzene, and xylene) concentrations. Conductivity images reveal a poor correlation with the distribution of contaminants; whereas phase images exhibit two main anomalies: low phase shift values (<5 mrad) for locations with high BTEX concentrations, including the occurrence of free-phase product (BTEX concentrations >1.7 g/l), and higher phase values for lower BTEX concentrations.

Evaluation of combined direct-push methods used for aquifer model generation.

Most established methods to characterize aquifer structure and hydraulic conductivities of hydrostratigraphical units are not capable of delivering sufficient information in the spatial resolution that is desired for sophisticated numerical contaminant transport modeling and adapted remediation design. With hydraulic investigation methods based on the direct-push (DP) technology such as DP slug tests, DP injection logging, and the hydraulic profiling tool, it is possible to rapidly delineate hydrogeological structures and estimate their hydraulic conductivity in shallow unconsolidated aquifers without the need for wells. A combined application of these tools was used for the investigation of a contaminated German refinery site and for the setup of hydraulic aquifer models.

The influence of wellbore inflow on electromagnetic borehole flowmeter measurements.

This paper describes a combined field, laboratory, and numerical study of electromagnetic borehole flowmeter measurements acquired without the use of a packer or skirt to block bypass flow around the flowmeter. The most significant finding is that inflow through the wellbore screen changes the ratio of flow through the flowmeter to wellbore flow. Experiments reveal up to a factor of two differences in this ratio for conditions with and without inflow through the wellbore screen.