Time‐Lapse Electrical Geophysical Monitoring of Amendment‐Based Biostimulation          下载免费PDF全文

Timothy C. Johnson  Roelof J. Versteeg  Frederick D. Day‐Lewis  William Major  John W. Lane Jr. 《Ground water》2015,53(6):920-932

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 remediation effort conducted at the Department of Defense Reutilization and Marketing Office (DRMO) Yard, in Brandywine, Maryland, United States. Geochemical fluid sampling was used to calibrate a petrophysical relation in order to predict groundwater indicators of amendment distribution. The petrophysical relations were field validated by comparing predictions to sequestered fluid sample results, thus demonstrating the potential of electrical geophysics for quantitative assessment of amendment‐related geochemical properties. Crosshole radar zero‐offset profile and borehole geophysical logging were also performed to augment the data set and validate interpretation. In addition to delineating amendment transport in the first 10 months after emplacement, the time‐lapse ERT results show later changes in bulk electrical properties interpreted as mineral precipitation. Results support the use of more cost‐effective surface‐based ERT in conjunction with limited field sampling to improve spatial and temporal monitoring of amendment emplacement and remediation performance.  相似文献   

1DTempPro V2: New Features for Inferring Groundwater/Surface‐Water Exchange          下载免费PDF全文

Franklin W. Koch  Emily B. Voytek  Frederick D. Day‐Lewis  Richard Healy  Martin A. Briggs  John W. Lane Jr.  Dale Werkema 《Ground water》2016,54(3):434-439

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.  相似文献   

Prescribed‐fire effects on rill and interrill runoff and erosion in a mountainous sagebrush landscape     

Frederick B. Pierson  Corey A. Moffet  C. Jason Williams  Stuart P. Hardegree  Patrick E. Clark 《地球表面变化过程与地形》2009,34(2):193-203

Changing fire regimes and prescribed‐fire use in invasive species management on rangelands require improved understanding of fire effects on runoff and erosion from steeply sloping sagebrush‐steppe. Small (0·5 m²) and large (32·5 m²) plot rainfall simulations (85 mm h^–1, 1 h) and concentrated flow methodologies were employed immediately following burning and 1 and 2 years post‐fire to investigate infiltration, runoff and erosion from interrill (rainsplash, sheetwash) and rill (concentrated flow) processes on unburned and burned areas of a steeply sloped sagebrush site on coarse‐textured soils. Soil water repellency and vegetation were assessed to infer relationships in soil and vegetation factors that influence runoff and erosion. Runoff and erosion from rainfall simulations and concentrated flow experiments increased immediately following burning. Runoff returned to near pre‐burn levels and sediment yield was greatly reduced with ground cover recovery to 40 per cent 1 year post‐fire. Erosion remained above pre‐burn levels on large rainfall simulation and concentrated flow plots until ground cover reached 60 per cent two growing seasons post‐fire. The greatest impact of the fire was the threefold reduction of ground cover. Removal of vegetation and ground cover and the influence of pre‐existing strong soil‐water repellency increased the spatial continuity of overland flow, reduced runoff and sediment filtering effects of vegetation and ground cover, and facilitated increased velocity and transport capacity of overland flow. Small plot rainfall simulations suggest ground cover recovery to 40 per cent probably protected the site from low‐return‐interval storms, large plot rainfall and concentrated flow experiments indicate the site remained susceptible to elevated erosion rates during high‐intensity or long duration events until ground cover levels reached 60 per cent. The data demonstrate that the persistence of fire effects on steeply‐sloped, sandy sagebrush sites depends on the time period required for ground cover to recover to near 60 per cent and on the strength and persistence of ‘background’ or fire‐induced soil water repellency. Published in 2009 by John Wiley & Sons, Ltd.  相似文献   

Small-scale,patchy distributions of infauna in hydrodynamically mobile continental shelf sands: Do ripple crests and troughs support different communities?     

Patricia A. Ramey  Judith P. Grassle  J. Frederick Grassle  Rosemarie F. Petrecca   《Continental Shelf Research》2009,29(18):2222-2233

Spatial variability of infauna with respect to distribution of topographic habitat features was examined in hydrodynamically mobile sandy sediments on the inner continental shelf off New Jersey, USA (39° 27.69′ N, 74° 15.81′W). Sediment cores for infauna were taken by SCUBA divers at multiple spatial scales over time at 12-m depth in the LEO-15 research area on Beach Haven Ridge. Crests, troughs and less consistently flanks of sand ripples 5–15-cm in height, were characterized by different infaunal community patterns at spatial scales of centimeters to kilometers on several sampling dates. Overall, infaunal community differences among ripple crests, troughs, and/or flanks within areas <1-m² were greater than those found for each of these habitats (i.e., either crests, troughs, or flanks) that were separated by distances of 2 m–4 km. Infaunal density and species richness were consistently higher in troughs compared to crests. Indirect measures of food resources such as particulate organic carbon, chl a, and pheophytin were associated with ripple crests and troughs. Troughs contained significantly higher levels of particulate organic carbon (~1.2 times higher) associated with finer sediments, compared with crests and flanks. Various combinations of taxa had higher densities in either crests or troughs of sand ripples depending on date, and the relative abundances of three taxa, the deposit-feeding polychaete Polygordius jouinae, the suspension-feeding surfclam Spisula solidissima, and predatory nemerteans were important in distinguishing between crests and troughs on most dates. Thus, a priori knowledge of whether a benthic sample comes from a crest or trough helped to explain small-scale infaunal patchiness in relatively homogeneous, subtidal sandy sediments. Consideration of such topographic features in sampling designs can help in explaining variation in species’ distributions at several spatial and temporal scales.  相似文献   

Benefits and Cautions in Data Assimilation Strategies: An Example of Modeling Groundwater Recharge     

Allen M. Shapiro  Frederick D. Day-Lewis 《Ground water》2024,62(3):405-416

Assimilating recent observations improves model outcomes for real-time assessments of groundwater processes. This is demonstrated in estimating time-varying recharge to a shallow fractured-rock aquifer in response to precipitation. Results from estimating the time-varying water-table altitude (h) and recharge, and their error covariances, are compared for forecasting, filtering, and fixed-lag smoothing (FLS), which are implemented using the Kalman Filter as applied to a data-driven, mechanistic model of recharge. Forecasting uses past observations to predict future states and is the current paradigm in most groundwater modeling investigations; filtering assimilates observations up to the current time to estimate current states; and FLS estimates states following a time lag over which additional observations are collected. Results for forecasting yield a large error covariance relative to the magnitude of the expected recharge. With assimilating recent observations of h, filtering and FLS produce estimates of recharge that better represent time-varying observations of h and reduce uncertainty in comparison to forecasting. Although model outcomes from applying data assimilation through filtering or FLS reduce model uncertainty, they are not necessarily mass conservative, whereas forecasting outcomes are mass conservative. Mass conservative outcomes from forecasting are not necessarily more accurate, because process errors are inherent in any model. Improvements in estimating real-time groundwater conditions that better represent observations need to be weighed for the model application against outcomes with inherent process deficiencies. Results from data assimilation strategies discussed in this investigation are anticipated to be relevant to other groundwater processes models where system states are sensitive to system inputs.  相似文献   

Implications of rate-limited mass transfer for aquifer storage and recovery     

Culkin SL  Singha K  Day-Lewis FD 《Ground water》2008,46(4):591-605

Pressure to decrease reliance on surface water storage has led to increased interest in aquifer storage and recovery (ASR) systems. Recovery efficiency, which is the ratio of the volume of recovered water that meets a predefined standard to total volume of injected fluid, is a common criterion of ASR viability. Recovery efficiency can be degraded by a number of physical and geochemical processes, including rate-limited mass transfer (RLMT), which describes the exchange of solutes between mobile and immobile pore fluids. RLMT may control transport behavior that cannot be explained by advection and dispersion. We present data from a pilot-scale ASR study in Charleston, South Carolina, and develop a three-dimensional finite-difference model to evaluate the impact of RLMT processes on ASR efficiency. The modeling shows that RLMT can explain a rebound in salinity during fresh water storage in a brackish aquifer. Multicycle model results show low efficiencies over one to three ASR cycles due to RLMT degrading water quality during storage; efficiencies can evolve and improve markedly, however, over multiple cycles, even exceeding efficiencies generated by advection-dispersion only models. For an idealized ASR model where RLMT is active, our simulations show a discrete range of diffusive length scales over which the viability of ASR schemes in brackish aquifers would be hindered.  相似文献   

A New R Program for Flow-Log Analysis of Single Holes (FLASH-R)     

Marcos B. Barbosa  Neil Terry  Frederick D. Day-Lewis  Reginaldo Bertolo  John W. Lane Jr 《Ground water》2020,58(6):987-992

A new version of the computer program FLASH (Flow-Log Analysis of Single Holes) is presented for the analysis of borehole vertical flow logs to estimate fracture (or layer) transmissivities and far-field hydraulic heads. The program is written in R, an open-source environment. All previous features have been retained and new features incorporated including more rigorous parameter estimation, uncertainty analysis, and improved data import. The program has a dynamic user interface compatible with most operating systems.  相似文献   

Resolving the contributing factors to Mississippi Delta subsidence: Past and Present     

Bruce C. Frederick  Michael Blum  Richard Fillon  Harry Roberts 《Basin Research》2019,31(1):171-190

To date, quantification of individual components that contribute to shallow and deep‐seated subsidence in passive margin deltas worldwide has proven problematic. A new, regional gridded chronostratigraphic dataset for the Lower Mississippi Delta region, derived from 80,928 well reports across the northern Gulf of Mexico (GOM), has bridged the disparity between geodetic mean rates measuring total land surface subsidence across annual‐to‐decadal timescales and the deep‐seated stratigraphic subsidence rates that record isostatic response over timescales of >10⁴ years. Through a quantitative assessment of gridded chronostratigraphic surfaces, sections, and subsidence rates extending from the Middle Pleistocene (0.58 Ma) to the Late Pliocene (3.85 Ma), we identify both temporal and spatial variability in deep‐seated subsidence across the northern GOM. Targeted deep‐seated subsidence data extracted across prior GOM Holocene sea‐level sample locations have revealed more than an order of magnitude greater rates of isostatic compensation in the Mississippi depocentre versus similar GOM sea‐level control sites in Florida and Alabama, casting doubt on efforts towards a representative Holocene sea‐level curve. Spatial variability in subsidence was also assessed locally in both the strike and dip directions to assess the contributions of growth faults. Fault throw displacement magnitude was discovered to decrease with depth, accounting for less than half of the total deep‐seated subsidence record of the Middle Pleistocene. Temporal subsidence complexities were also revealed including a direct, inverse logarithmic relationship between subsidence rate and time indicating variable subsidence component controls across different timescales. Despite the spatial and temporal complexities, this dataset serves as the first regional baseline for deep‐seated subsidence rates across the northern GOM.  相似文献   

A high temperature superconductor notch filter for the Sardinia Radio Telescope     

Pietro Bolli  Luca Cresci  Frederick Huang  Sergio Mariotti  Dario Panella 《Experimental Astronomy》2018,45(2):165-176

A High Temperature Superconductor filter operating in the C-band between 4200 and 5600 MHz has been developed for one of the radio astronomical receivers of the Sardinia Radio Telescope. The motivation was to attenuate an interference from a weather radar at 5640 MHz, whose power level exceeds the linear region of the first active stages of the receiver. A very sharp transition after the nominal maximum passband frequency is reached by combining a 6th order band-pass filter with a 6th order stop-band. This solution is competitive with an alternative layout based on a cascaded triplet filter. Three units of the filter have been measured with two different calibration approaches to investigate pros and cons of each, and data repeatability. The final performance figures of the filters are: ohmic losses of the order of 0.15–0.25 dB, matching better than ?15 dB, and ?30 dB attenuation at 5640 MHz. Finally, a more accurate model of the connection between external connector and microstrip shows a better agreement between simulations and experimental data.  相似文献   

Spatial and temporal aspects of the lake effect on the southern shore of Lake Superior   总被引：1，自引：0，他引：1  

Kenneth M. Hinkel  Frederick E. Nelson 《Theoretical and Applied Climatology》2012,109(3-4):415-428

A climate-monitoring network was implemented in a large private preserve along the southern shore of Lake Superior. The network uses a dense sampling design to assess the spatial and temporal influence of a large, cold body of water on adjacent terrestrial surfaces. Based on a 3-year record, near-shore sites are 1–2°C cooler than sites 5?km inland in spring and summer, and 1°C warmer in winter. Near the shore, winds are from the NNW most of the year, and are much stronger in winter. Inland, southwesterly flow is typical and overall wind velocity is lower and more consistent. This decoupling is attributable to the influence of the Huron Mountains, a topographic barrier that restricts the lake effect to a narrow coastal zone. A 2-year record of hourly air temperature measurements from 26–30 sites across the study area demonstrates that the mean daily temperature can differ by as much as 11°C, but the average difference is 2.5–3.0°C.  相似文献