Simple Resistivity Probe System for Real-Time Monitoring of Injected Reagents     

David Stevenson  Felipe Solano  Yunxiao Wei  Neil R. Thomson  James F. Barker  J. F. Devlin 《Ground Water Monitoring & Remediation》2020,40(4):54-66

In situ treatment usually requires contact between an injected reagent and target contaminant to realize mass removal from source zones and plumes. Despite significant site characterization efforts, unknown heterogeneities that exist at all spatial scales often hinder prediction of the distribution of injected reagents. To provide remediation practitioners with additional information on the distribution of injected reagents, a prototype real-time monitoring probe was designed and tested. This new probe comprises a two-wire resistivity circuit, hence the designation dipole resistivity probe (DRP). The low-cost DRPs were built to be attached as arrays to a central stalk, and installed by direct-push techniques. An installed network of multilevel DRPs can be used to detect the arrival, persistence, and relative concentration of a high-conductivity reagent solution in real-time across a zone of interest. Static cell and sandbox experiments were conducted to test and refine the DRP design before field testing. Static cell experimental results indicated that the DRP was sensitive to solution electrical conductivity (EC), and that the probe response and EC relationship is nonlinear and dependent on the fixed resistor used. The choice of fixed resistor can be adjusted to optimize the DRP response over a critical EC range of interest. Under dynamic conditions in the sandbox, the DRP was able to reproduce breakthrough profiles collected by a commercial EC sensor. The results from two field studies demonstrated the utility of the DRPs to generate information regarding the arrival and persistence of reagents in an efficient and cost-effective manner. The first field study used a network of DRPs to monitor the land application of a sodium sulfate solution, and the second field study employed DRPs to monitor the distribution and longevity of a persulfate solution. While additional field testing is warranted, the results presented are encouraging and suggest that this low-cost system can be used to improve our understanding of the detailed migration of injected reagents in treatment zones.  相似文献   

Reflections from the Editor-in-Chief of Groundwater Monitoring & Remediation     

Neil R. Thomson 《Ground Water Monitoring & Remediation》2020,40(4):15-18

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Recent remote sensing applications for hydro and morphodynamic monitoring and modelling          下载免费PDF全文

Neil Entwistle  George Heritage  David Milan 《地球表面变化过程与地形》2018,43(10):2283-2291

It is not new to recognize that data from remote sensing platforms is transforming the way we characterize and analyse our environment. The ability to collect continuous data spanning spatial scales now allows geomorphological research in a data rich environment and this special issue [coming just eight years after the 2010 special issue of Earth Surface Processes and Landforms (ESPL) associated with the remote sensing of rivers] highlights the considerable research effort being made to exploit this information, for studies of geomorphic form and process. The 2010 special issue on the remote sensing of rivers noted that fluvial remote sensing articles made up some 14% of the total river related articles in ESPL. A similar review of articles up to 2017 reveals that this figure has increased to around 25% with a recent proliferation of articles utilizing satellite‐based data and structure from motion photogrammetry derived data. It is interesting to note, however that many studies published to date are proof of concept, concentrating on confirming the accuracy of the remotely sensed data at the expense of generating new insights and ideas on fluvial form and function. Data is becoming ever more precise and researchers should now be concentrating on analysing these early data sets to develop increased geomorphic insight, to challenge existing paradigms and to advance geomorphic science. The prospect of this occurring is increased by the fact that many of the new remote sensed platforms allow accurate spatial data to be collected cheaply and efficiently, reducing the need for substantial research funding to advance river science. Fluvial geomorphologists have never before been in such a liberated position. As techniques and analytical skills continue to improve it is inevitable that the prediction that remotely sensed data will revolutionize our understanding of geomorphological form and process will prove true, altering our ideas on the very nature of system functioning in the process. © 2018 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.  相似文献   

Through the impact glass: Insight into the evolution of melt at the Mistastin Lake impact structure     

Patrick J. A. Hill  Gordon R. Osinski  Neil R. Banerjee 《Meteoritics & planetary science》2020,55(3):591-621

By analyzing impact glass, the evolution of the impact melt at the Mistastin Lake impact structure was investigated. Impact glass clasts are present in a range of impactites, including polymict breccias and clast‐rich impact melt rock, and from a variety of settings within the crater. From the glass clasts analyzed, three petrographic subtypes of impact glass were identified based on their clast content, prevalence of schlieren, color, texture, and habit. Several alteration phases were also observed replacing glass and infilling vesicles; however, textural observations and quantified compositional data allowed for the identification of pristine impact glass. Although the various types of glasses show significant overlap in their major oxide composition, several subtle variations in the major oxide chemistry of the glass were observed. To investigate this variation, a least‐squares mixing model was implemented utilizing the composition of the glass and the known target rock chemistry to model the initial melt composition. Additionally, image analysis of the glass clasts was used to investigate whether the compositional variations correlated to textural difference in the lithologies. We propose that the textural and compositional dichotomy observed is a product of the evolution, assimilation, and emplacement of the glass. The dichotomy is reflective of the melt either being ballistically emplaced (group 2 glasses: occurring in melt‐poor polymict breccias at lowermost stratigraphic position outside the transient crater) or the result of late‐stage melt flows (group 1 glasses, occurring in melt‐bearing polymict breccias and impact melt rocks at higher stratigraphic positions outside the transient crater).  相似文献   

Petrography and geochemistry of lunar meteorites Dhofar 1673, 1983, and 1984     

Patrick J. A. Hill  Gordon R. Osinski  Neil R. Banerjee  Randy L. Korotev  Sobhi J. Nasir  Christopher D. K. Herd 《Meteoritics & planetary science》2019,54(2):300-320

The Dhofar 1673, Dhofar 1983, and Dhofar 1984 meteorites are three lunar regolith breccias classified based on their petrography, mineralogy, oxygen isotopes, and bulk chemistry. All three meteorites are dominated by feldspathic lithic clasts; however, impact melt rock clasts and spherules are also found in each meteorite. The bulk chemistry of these samples is similar to other feldspathic highland meteorites with the Al₂O₃ content only slightly lower than average. Within the lithic clasts, the Mg # of mafic phases versus the anorthite content of feldspars is similar to other highland meteorites and is found to plot intermediate of the ferroan‐anorthositic suite and magnesian suite. The samples lack any KREEPy signature and have only minor indications of a mare basalt component, suggesting that the source region of all three meteorites would have been distal from the Procellarum KREEP Terrane and could have possibly been the Feldspathic Highland Terrane. All three meteorites were found within 500 m of each other in the Dhofar region of Oman. This, together with their similar petrography, stable isotope chemistry, and geochemistry indicates the possibility of a pairing.  相似文献   

Ice sheets and Late Quaternary environmental change by M. J. Siegert,John Wiley and Sons Ltd,Chichester, 2001. No of pages: 231. ISBN 0 471 98569 4 (paperback); 0 471 98570 8 (hardback).     

Neil Glasser 《Geological Journal》2003,38(2):188-189

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Glacigenic clast fabrics: genetic fingerprint or wishful thinking?     

Matthew R. Bennett  Richard I. Waller  Neil F. Glasser  Michael J. Hambrey  David Huddart 《第四纪科学杂志》1999,14(2):125-135

The interpretation of glacigenic diamictons is a subjective process, for which quantitative support is frequently sought from parameters such as clast shape and fabric. It has been widely suggested that different glacigenic diamicton facies possess distinct clast‐fabric signatures. This paper examines this concept using a data set of 111 clast fabrics, and a synthesis of published results. Eigenvalues are calculated and compared for a variety sedimentary facies. It is concluded that clast fabric alone is not able to discriminate between different glacigenic facies, and it is argued that clast fabric offers little quantitative support in the interpretation of glacigenic sediments. It is suggested, therefore, that although clast fabric may continue to have a role as an indicator of relative strain at specific sites, its use in the discrimination of glacigenic facies is limited. Consequently, we should be much more selective in undertaking such analyses in the future. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Glacial meltwater erosion of the Mid-Cheshire Ridge: implications for ice dynamics during the Late Devensian glaciation of northwest England     

Neil F. Glasser  Gregory H. Sambrook Smith 《第四纪科学杂志》1999,14(7):703-710

Mapping of glacial meltwater channels along the length of the 25-km Mid-Cheshire Ridge reveals evidence for four distinctive channel morphologies, which are used to establish the pattern of meltwater flow during the Late Devensian glaciation. A key characteristic of all channels is an abrupt change in morphology between inception on the Mid-Cheshire Ridge and the downstream continuation on the surrounding Cheshire Plain, with large reductions in channel cross-sectional area at this point. The interpretation of this evidence is that meltwater flowing off the bedrock ridge was absorbed into a layer of permeable sediment beneath the Late Devensian ice sheet. This permeable sediment is significant because it would have acted as a deforming layer beneath the former ice sheet in this area. Reconstruction of the Late Devensian ice sheet based on information from the meltwater channels and using values of shear stresses typical of ice sheets resting on deformable beds (ca. 20 kPa) suggests an ice surface elevation over the Irish Sea of ca. 700 m. This value is considerably less than previous estimates of the vertical extent of the ice sheet of ca. 1000–1200 m and has important implications for the rapidity and mode of deglaciation during the Late Devensian. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Water and salt balance modelling to predict the effects of land-use changes in forested catchments. 2. coupled model of water and salt balances     

Murugesu Sivapalan  Neil R. Viney  John K. Ruprecht 《水文研究》1996,10(3):413-428

A long-term salt balance model is coupled with the small catchment water balance model presented in Part 1 of this series of papers. The salt balance model was designed as a simple robust, conceptually based model of the fundamental salt fluxes and stores in forested and cleared catchments. The model has four interdependent stores representing salt storage in the unsaturated zone, the deep permanent saturated groundwater system, the near-stream perched groundwater system and in a ‘salt bulge’ just above the permanent water-table. The model has performed well in simulations carried out on Salmon and Wights, two small experimental catchments in south-west Western Australia. When applied to Wights catchment the salt balance model was able to predict the stream salinities prior to clearing of native forests, and the increased salinities after the clearing.  相似文献   

Sedimentation within and among mangrove forests along a gradient of geomorphological settings     

María Fernanda Adame  David Neil  Sara F. Wright  Catherine E. Lovelock 《Estuarine, Coastal and Shelf Science》2010

Coastal wetlands provide important ecological services to the coastal zone, one of which is sediment retention. In this study we investigated sediment retention across a range of geomorphological settings and across vegetation zones comprising coastal wetlands. We selected six coastal wetlands dominated by mangroves over a gradient from riverine to tidal settings in Southeast Queensland, Australia. Each site was comprised of three distinct vegetation communities distributed as parallel zones to the coast line: seaward fringe mangroves, landward scrub mangroves and saltmarsh/ cyanobacteria mat of the high intertidal zone. We measured suspended sediment retention and sedimentation rates. Additionally, in order to assess the origin of sediment transported and deposited in the mangroves, glomalin, a novel terrestrial soil carbon tracer, was used. Our results show a mean average sedimentation of 0.64 ± 0.01 mg cm⁻² spring tide⁻¹, which was variable within sites, regardless of geomorphological setting. However, geomorphological setting influenced spatial patterns of sediment deposition. Riverine mangroves had a more homogeneous distribution of sediments across the intertidal zone than tidal mangroves, where most sedimentation occurred in the fringe zone. Overall, the fringe zone retained the majority of sediment entering the coastal wetland during a tidal cycle with 0.90 ± 0.22 mg cm⁻² spring tide⁻¹, accounting for 52.5 ± 12.5% of the total sedimentation. The presence of glomalin in suspended sediments, and thus the relative importance of terrigenous sediment, was strongly influenced by geomorphological setting, with riverine mangroves receiving more glomalin in suspended solids than tidal mangroves. Glomalin was also differentially deposited within the vegetation zones at different geomorphological settings: primarily at the fringe zone of tidal mangroves and within the scrub zone of riverine mangroves. The differences we observed in the spatial distribution of sedimentation and the difference in the origin of the sediment deposited in riverine and tidal mangroves are likely to have an impact on ecological processes.  相似文献