John Lane

A new version of the computer program 1DTempPro extends the original code to include new capabilities for (1) automated parameter estimation, (2) layer heterogeneity, and (3) time-varying specific discharge. The code serves as an interface to the U.S. Geological Survey model VS2DH and supports analysis of vertical one-dimensional temperature profiles under saturated flow conditions to assess groundwater/surface-water exchange and estimate hydraulic conductivity for cases where hydraulic head is known.

The mass of the canopy of a tree is derived by measuring the resonance frequency of the whole tree as it gently sways in the wind. A low cost, self logging, accelerometer is used to measure the acceleration of the tree canopy as it is rocked by the wind. The resonance frequency of any mass-spring system is related to the (square of the) mass of that system, so the resonance frequency of the tree can be related to the mass of the canopy (including interception). This relation is calibrated by determining the shift in resonance frequency when an object of known mass is hoisted into the canopy. Proof of concept is shown by determining the different resonance frequencies of a tree in full bloom and in leafless situation, and by determining the shift in resonance frequency before and after a rain event.

The bedrock surface contours in Woodbury, Connecticut, were determined downgradient of a commercial zone known as the Middle Quarter area (MQA) using the novel, noninvasive horizontal-to-vertical (H/V) spectral ratio (HVSR) passive seismic geophysical method. Boreholes and monitoring wells had been drilled in this area to characterize the shallow subsurface to within 20 feet (ft) of the land surface, but little was known about the deep subsurface, including sediment thicknesses and depths to bedrock (Starn and Brown, 2007; Brown and others, 2009). Improved information on the altitude of the bedrock surface and its spatial variation was needed for assessment and remediation of chlorinated solvents that have contaminated the overlying glacial aquifer that supplies water to wells in the area.

Educating the next generation of scientists requires new educational methods and unconventional approaches to facilitate the interdisciplinary scholarship required to cope with fast-paced developments in the geosciences. We believe incorporation of field training with active research missions is an effective educational model. By participating in active research and open science dialogue, students are exposed to real-world examples of the principles and processes of complex systems in a manner that allows them to develop a deeper understanding of the subject. We find students are highly motivated by the knowledge that data they collect will advance the research mission; such an environment stokes their passions and imaginations and allows the students to explore the roots of their interest in geoscience. In this context, a two-week educational field course on hydrologic processes and measurements was integrated with ongoing research in Chile to understand the effect of soil shrinkag...

Biostimulation is increasingly used to accelerate microbial remediation of recalcitrant groundwater contaminants. Effective application of biostimulation requires successful emplacement of amendment in the contaminant target zone. Verification of remediation performance requires postemplacement assessment and contaminant monitoring. Sampling-based approaches are expensive and provide low-density spatial and temporal information. Time-lapse electrical resistivity tomography (ERT) is an effective geophysical method for determining temporal changes in subsurface electrical conductivity. Because remedial amendments and biostimulation-related biogeochemical processes often change subsurface electrical conductivity, ERT can complement and enhance sampling-based approaches for assessing emplacement and monitoring biostimulation-based remediation. Field studies demonstrating the ability of time-lapse ERT to monitor amendment emplacement and behavior were performed during a biostimulation re...

ABSTRACT Models of dual-domain mass transfer (DDMT) are used to explain anomalous aquifer transport behavior such as the slow release of contamination and solute tracer tailing. Traditional tracer experiments to characterize DDMT are performed at the flowpath scale (meters), which inherently incorporates heterogeneous exchange processes; hence, estimated “effective” parameters are sensitive to experimental design (i.e., duration and injection velocity). Recently, electrical geophysical methods have been used to aid in the inference of DDMT parameters because, unlike traditional fluid sampling, electrical methods can directly sense less-mobile solute dynamics and can target specific points along subsurface flowpaths. Here, we propose an analytical framework for graphical parameter inference based on a simple petrophysical model explaining the hysteretic relation between measurements of bulk and fluid conductivity arising in the presence of DDMT at the local scale. Analysis is graphical and involves visual inspection of hysteresis patterns to (1) determine the size of paired mobile and less-mobile porosities, and (2) identify the exchange rate coefficient through simple curve fitting. We demonstrate the approach using laboratory column experimental data, synthetic streambed experimental data, and field tracer-test data. Results from the analytical approach compare favorably with results from calibration of numerical models and also independent measurements of mobile and less-mobile porosity. We show that localized electrical hysteresis patterns resulting from diffusive exchange are independent of injection velocity, indicating that repeatable parameters can be extracted under varied experimental designs, and these parameters represent the true intrinsic properties of specific volumes of porous media of aquifers and hyporheic zones.

Near-surface geophysics has throughout its history enjoyed success at both ends of the exploration geophysics evolutionary chart as a benefactor and contributor. Almost all near-surface methods are traceable to or from petroleum exploration. Noteworthy examples are captured in ...

... Page 6. 390 Colette Grégoire, John W. Lane, Jr., and Peter K. Joesten lowest ratio is 0.4). ... The inversion was done in several steps using a Matlab-based inversion tomografic software (Frederick Day-Lewis, US Geological Survey, oral commun., 2003). ...

ABSTRACT Irrigation experiments on twelve instrumented field plots were used to assess the impact of dynamic soil crack networks on infiltration and runoff. During applications of intensity similar to a heavy rainstorm, water was seen being preferentially delivered within the soil profile. However, runoff was not observed until soil water content of the profile reached field capacity and the apertures of surface-connected cracks had closed > 60%. Electrical resistivity measurements suggested that subsurface cracks persisted and enhanced lateral transport, even in wet conditions. Likewise, single-ring infiltration measurements taken before and after irrigation indicated that infiltration remained an important component of the water budget at high soil water content values, despite apparent surface sealing. Overall, though the wetting and sealing of the soil profile showed considerable complexity, an emergent property at the hillslope scale was observed: all of the plots demonstrated a strikingly similar threshold runoff response to the cumulative precipitation amount. This article is protected by copyright. All rights reserved.

A new computer program, 1DTempPro, is presented for the analysis of vertical one-dimensional (1D) temperature profiles under saturated flow conditions. 1DTempPro is a graphical user interface to the U.S. Geological Survey code Variably Saturated 2-Dimensional Heat Transport (VS2DH), which numerically solves the flow and heat-transport equations. Pre- and postprocessor features allow the user to calibrate VS2DH models to estimate vertical groundwater/surface-water exchange and also hydraulic conductivity for cases where hydraulic head is known.

Boreholes drilled through contaminated zones in fractured rock create the potential for vertical movement of contaminated ground water between fractures. The usual assumption is that purging eliminates cross contamination; however, the results of a field study conducted in a trichloroethylene (TCE) plume in fractured sandstone with a mean matrix porosity of 13% demonstrates that matrix-diffusion effects can be strong and persistent. A deep borehole was drilled to 110 m below ground surface (mbgs) near a shallow bedrock well containing high TCE concentrations. The borehole was cored continuously to collect closely spaced samples of rock for analysis of TCE concentrations. Geophysical logging and flowmetering were conducted in the open borehole, and a removable multilevel monitoring system was installed to provide hydraulic-head and ground water samples from discrete fracture zones. The borehole was later reamed to complete a well screened from 89 to 100 mbgs; persistent TCE concentrations at this depth ranged from 2100 to 33,000 microg/L. Rock-core analyses, combined with the other types of borehole information, show that nearly all of this deep contamination was due to the lingering effects of the downward flow of dissolved TCE from shallower depths during the few days of open-hole conditions that existed prior to installation of the multilevel system. This study demonstrates that transfer of contaminant mass to the matrix by diffusion can cause severe cross contamination effects in sedimentary rocks, but these effects generally are not identified from information normally obtained in fractured-rock investigations, resulting in potential misinterpretation of site conditions.

... Risk, 1975; McDowell, 1979; Palacky et al., 1981; Soonawala and Dence, 1981; Taylor, 1982; Mallik et al., 1983; Leonard-Mayer, 1984a ... array have been conducted to detect productive fracture zones in crystalline bedrock for ground-water supply (Darboux-Afouda and Louis ...

... Remote detection of free-phase hydrocarbons within a bedrock fracture requires a method ... to robustly interpret normal-incidence GPR reflection wave forms to identify hydrocarboncontamination. ... frequency EM reflection behavior was simulated in 2-D using GPR2DM (Powers ...

ABSTRACT Electrical resistivity imaging surveys widely used in many environmental and engineering studies have also been conducted in water-covered areas. Surveys in water-covered areas include conventional surveys using multi-electrode resistivity systems where part of the survey line crosses a river or stream, and surveys conducted entirely within a water-covered environment. Surveys that are located entirely within a water-covered environment utilise electrodes mounted on a streamer, towed behind a boat. The streamer can be dragged along the water bottom, or float on the water surface. In this paper, the smoothness-constrained least-squares inversion method commonly used to interpret electrical resistivity imaging data from land surveys is adapted for underwater surveys. To accommodate the water bottom topography, a distorted finite-element grid is used to calculate the apparent resistivity values for the inversion model. The first few rows of elements are used to model the water layer, while the lower part of the grid is used for the sub-bottom resistivity distribution. For robust inversion, the water column resistivity and geometry must be known accurately as a large proportion of the current flows through the water layer. The section of the Earth below the bottom surface is subdivided into a large number of rectangular cells. The water column resistivity and geometry in the earth model is fixed, and the inversion program attempts to determine the resistivity of the cells that would most accurately reproduce the observed resistivity measurements. Implementation of water column resistivity and geometric constraints is demonstrated using numerical simulations and field data. Examples of electrical resistivity imaging surveys conducted on and across water bodies including rivers and near-shore marine environments are shown.

Groundwater discharge locations along the upper Delaware River, both discrete bank seeps and diffuse streambed upwelling, may create thermal niche environments that benefit the endangered dwarf wedgemussel (Alasmidonta heterodon). We seek to identify whether discrete or diffuse groundwater inflow is the dominant control on refugia. Numerous springs and seeps were identified at all locations where dwarf wedgemussels still can be found. Infrared imagery and custom high spatial resolution fiber-optic distributed temperature sensors reveal complex thermal dynamics at one of the seeps with a relatively stable, cold groundwater plume extending along the streambed/water-column interface during midsummer. This plume, primarily fed by a discrete bank seep, was shown through analytical and numerical heat-transport modeling to dominate temperature dynamics in the region of potential habitation by the adult dwarf wedgemussel.

ABSTRACT Water-borne continuous resistivity profiling (CRP), also called marine or streaming resistivity, increasingly is used to support hydrogeophysical studies in freshwater and saltwater environments. CRP can provide resistivity tomograms for delineation of focused ground-water discharge, identification of sediment types, and mapping the near-shore freshwater/saltwater interface. Data collection, performed with a boat-towed electrode streamer, is commonly fast and relatively straightforward. In contrast, data processing and interpretation are potentially time consuming and subject to pitfalls. Data analysis is difficult due to the underdetermined nature of the tomographic inverse problem and the poorly understood resolution of tomograms, which is a function of the measurement physics, survey geometry, measurement error, and inverse problem parameterization and regularization. CRP data analysis in particular is complicated by noise in the data, sources of which include water leaking into the electrode cable, inefficient data collection geometry, and electrode obstruction by vegetation in the water column. Preliminary modeling has shown that, as in other types of geotomography, inversions of CRP data tend to overpredict the extent of and underpredict the magnitude of resistivity anomalies. Previous work also has shown that the water layer has a strong effect on the measured apparent resistivity values as it commonly has a much lower resistivity than the subsurface. Here we use synthetic examples and inverted field data sets to (1) assess the ability of CRP to resolve hydrogeophysical targets of interest for a range of water depths and salinities; and (2) examine the effects of CRP streamer noise on inverted resistivity sections. Our results show that inversion and interpretation of CRP data should be guided by hydrologic insight, available data for bathymetry and water layer resistivity, and a reliable model of measurement errors.

Submarine ground-water discharge (SGD) is an important source of nutrients and pollutants to ecologically sensitive estuaries. We observe SGD and the movement of freshwater/saltwater interfaces by measuring two physical properties that differ between the coastal aquifer and estuarine waters - temperature and electrical resistivity. SGD from the fresh coastal aquifer is colder in the summer than estuarine waters, and warmer

ABSTRACT In both field and laboratory settings, time-lapse electrical measurements have indicated rate-limited mass transfer of ionic tracer between mobile and immobile (or less mobile) domains in porous media over a range of flow rates and time scales. In previous work, a simple bicontinuum extension of Archie's Law was used to relate direct-current bulk conductivity and fluid conductivity assuming that the mobile and immobile domains contribute as conductors in parallel with weights given by porosity fraction; however, other petrophysical models may account for the effect of internal connectivity of each domain on its relative contribution to bulk conductivity. Additional work is required to (1) evaluate the bicontinuum Archie formulation relative to these other models for bulk conductivity of multiphase (i.e., multidomain) media with application to mass-transfer problems, and (2) characterize the geoelectrical signature of mass transfer for porous media with different pore geometries and electrical properties. To address this long standing problem, we developed a coupled fluid flow, electrical conduction, and solute transport simulator for two-dimensional pore networks. The pore space is modeled as a pipe lattice where pipes are square in cross section with widths drawn from random distributions. Pipe conductances for the fluid flow problem are assigned according to Hagen-Pouseuille flow, and the conservation problem is solved. Alternative to computationally intensive simulation of transient advective-dispersive transport, we adopt a more efficient but approximate two-step approach. First, we find the zeroth and first temporal moments throughout the network by solving sequentially two steady-state transport problems; from these results we calculate mean arrival time for each node in the network. Second, we convert the calculated mean arrival times to mass-transfer rates for input to a semi-analytical multi-rate mass transfer model to simulate gross transport through a synthetic core. For electrical conduction, pipes are segregated into classes of mobility based on mass-transfer rates and assigned concentrations, and thus fluid conductivities, based on the output of the multi-rate model. Electrical conductances are calculated according to Ohm's law and the direct-current electrical problem is solved. Ongoing work focuses on identification of an appropriate, robust petrophysical relation between bulk and fluid conductivity that holds over range of pore network geometries and accounts for the hysteretic nature of bulk/fluid conductivity in the presence of mass transfer.