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   

Numerical modeling of Maranhão Gulf tidal circulation and power density distribution     

Czizeweski  Anthea  Pimenta  Felipe Mendonça  Saavedra  Osvaldo Ronald 《Ocean Dynamics》2020,70(5):667-682

Ocean Dynamics - Marine resources are outstanding among renewable energy for their wide occurrence and diverse possibilities of exploitation. The tidal resource can be harnessed by the use of both...  相似文献   

Observations of near-inertial oscillations along the Brazilian continental shelf break     

de Freitas  Pedro Paulo  Amorim  Felipe de Luca Lopes  Mill  Guilherme Nogueira  da Costa  Vladimir Santos  Gabioux  Mariela  Cirano  Mauro  Paiva  Afonso de Moraes 《Ocean Dynamics》2019,69(10):1203-1215

Ocean Dynamics - Near-inertial oscillations (NIO) are intermittent motions with a frequency close to the inertial frequency and represent an important fraction of the energy to the currents in the...  相似文献   

Using Mahalanobis Distance to Detect and Remove Outliers in Experimental Covariograms     

Drumond  David Alvarenga  Rolo  Roberto Mentzingen  Costa  João Felipe Coimbra Leite 《Natural Resources Research》2019,28(1):145-152

Experimental variograms are crucial for most geostatistical studies. In kriging, for example, the variography has a direct influence on the interpolation weights. Despite the great importance of variogram estimators in predicting geostatistical features, they are commonly influenced by outliers in the dataset. The effect of some randomly spatially distributed outliers can mask the pattern of the experimental variogram and produce a destructuration effect, implying that the true data spatial continuity cannot be reproduced. In this paper, an algorithm to detect and remove the effect of outliers in experimental variograms using the Mahalanobis distance is proposed. An example of the algorithm’s application is presented, showing that the developed technique is able to satisfactorily detect and remove outliers from a variogram.

  相似文献   

A piecewise curve-fitting technique for vertical oceanographic profiles and its application to density distribution     

Viacheslav G. Makarov  Oleg V. Zaytsev  Valentina D. Budaeva  Felipe Salinas-Gonzalez 《Journal of Oceanography》2008,64(5):675-690

A unified method of approximation, extrapolation, and objective layering is offered for processing vertical oceanographic profiles. The method is demonstrated using seawater density and consists of adjustable splitting of each individual profile into N vertical layers based on tentative, piecewise linear homogeneous approximation with specified accuracy and a final fitting of an N-layered analytical model to data. A set of 3N coefficients of the model includes one density value at the sea surface; N−1 depths of layer interfaces; and N pairs of coefficients that describe a profile shape within the n-th layer—an asymptotic density value (a key parameter for extrapolation) and a vertical scale of maximum density variability (related to vertical gradient). Several distinctive characteristics of the technique are: (1) It can be used for the analysis of the vertical structure of individual profiles when N is an unknown parameter, and spatial interpolation when N should be equal for all profiles. (2) A justified downward extrapolation of incomplete data is possible with the model, especially if historical deepwater profiles are available. (3) Layer interfaces, as well as other coefficients, are derived with only one fitting to the entire profile. (4) The technique, using its general formulation, can serve as a parent for developing various types of models. The simpler step-like (with hyperbolic or exponential approximation) and more complicated smooth (continuous in gradient space) models were designed and tested against a large number of density profiles from the Sea of Okhotsk and the Gulf of California. Comparison of parametric, z-levels and isopycnal averaging was done for the region off the northeastern coast of Sakhalin.  相似文献