Water Conductivity Measurements Research Articles

An acoustic sensor transmitter for in situ assessment of water quality and fish behaviour during chemical treatment of a parasite-infected river system: tag design and practical use

BackgroundBehaviour of potential host fish during chemical treatment against the ectoparasite Gyrodactylus salaris is a vital factor in designing treatment strategies, evaluating risk factors and establishing insights into previously failed treatments. The effectiveness of any chemical treatment may be compromised if fish either are forced to, or seek out actively, areas of the river where the water quality is less affected by the chemicals. The aim of this study was to develop and apply an acoustic fish tag for fish localization with sensors for in situ measurement of water conductivity and temperature to investigate fish behaviour before, during and after an aluminium (Al) treatment. The sensor tag allowed discrimination between water qualities, and thereby quantification of exposure to treatment water.FindingsAdult Atlantic salmon and anadromous brown trout from river Lærdalselva were tagged with external conductivity transmitters and followed daily by a network of passive receivers and by manual tracking 1 week ahead of treatment, during a 2-week aluminium (Al) treatment period and one week after an Al treatment. The results show no avoidance behaviour related to the Al treatment and most of the fish exhibited a behaviour during the treatment that did not differ significantly from the behaviour observed before or after the treatment. Data collected from the tags showed that the fish experienced increased conductivity during Al administration, suggesting successful exposure to treatment water. The tag gave verifiable environmental information and functioned well in the turbulent and acoustically demanding river environment, albeit with variable detection range.ConclusionsThe conductivity and temperature tag provided novel data on fish behaviour and exposure during the Al treatment period. Results show that fish exhibit normal behaviour during this period and no avoidance response can be detected in the collected data.

Cross‐borehole geoelectrical time‐lapse monitoring of in situ chemical oxidation and permeability estimation through induced polarization

ABSTRACTWorldwide, soil contamination due to industrial activities is a major issue. One method for remediation of contaminated sites is in situ chemical oxidation, where an oxidizing agent is injected into the contaminated soil. Normally, monitoring wells are established in the remediation area for tracking the oxidizing agent. However, wells only provide point information of the injectant spread. This issue can be addressed using cross‐borehole resistivity and induced polarization tomography, by mapping the electrical properties in the entire remediation volume and by deriving, through petrophysical relations, the hydraulic properties of the medium. Here we present a proof‐of‐concept study, performed over one year as part of a larger remediation project, where resistivity and time‐domain induced polarization data were acquired among 10 boreholes, before and after two rounds of injection of oxidizing agents. The time‐lapse resistivity models, obtained through a focusing inversion scheme that favours compact time‐lapse changes, clearly show the oxidizing agent spread as highly conductive anomalies and confirmed by water conductivity measurements in boreholes. The time‐lapse inversions also show spatial variability in the injectant spread, with some areas not reached. The induced polarization data quality decreased significantly just after the injection rounds, because of the decrease in resistivity and induced polarization signal level, so that induced polarization time‐lapse inversions were not feasible. However, the induced polarization data were used for background characterization and to estimate permeability. In particular, there is a good match between the imaged low‐permeability zones and the areas in which the injectant did not spread, identified by the time‐lapse resistivity inversions. Furthermore, geological samples confirm the presence of fine‐grained sediments in the estimated low‐permeability zones. While time‐lapse resistivity tomography may be used for documenting the injectant spread, induced polarization permeability estimates prior to injection can be used to better tailor the remediation in terms of dimension and location of injection filters.

Estimation of Mineralization Increase in the Under-ice Water Layer of Southern Baikal

Changes in the ionic component of the under-ice mineralization in the southern basin of Lake Baikal in 2001–2016 are analyzed. Data on the under-ice layer mineralization variations derived from water conductivity measurements using the SBE-25 high-precision CTD sonde are compared with the results of calculation of salt separation during the formation and growth of the ice cover. The studies demonstrated that the mineralization increase is affected not only by salinization during ice crystallization but also by the water inflow from the central basin of the lake and from the Selenga River (more than a half of its runoff propagates to Southern Baikal in winter).

Signal Decomposition of Conductivity Sensor Measurements on the Allegheny River, Pennsylvania.

Surface water conductivity measurements were used to evaluate the combined contribution of anions in western Pennsylvania from brines discharged by sources such as oil and gas wastewater treatment, coal-fired power plants, and coal mining activities. Conductivity sensor data were collected in the Allegheny River during a US Environmental Protection Agency and US Fish and Wildlife study that included seven sites covering 256 river km during the fall of 2012. Intermittent discharges, such as oil and gas wastewater, and continuous sources contributing to the conductivity were quantified using constrained and adaptive decomposition of time-series (CADETS) frequency analysis. CADETS was able to quantify the intermittent or short-term component of conductivity at sites where the intermittent fraction was 1 to 22% of the total conductivity. The demonstrated efficacy of the CADETS method for surface water quality analysis suggests it could be widely used to evaluate other water sensor data in rivers with both continuous and intermittent source impacts.

Addressing the challenges of traceable electrolytic conductivity measurements in water

This paper addresses the challenges of making accurate and traceable electrolytic conductivity cell constant calibrations and sensor system calibration measurements over a wide range of conductivity, from 5.5 µS m−1 (ultrapure water) up to 140 000 µS m−1, where stable and reliable commercial certified reference materials (CRMs) are available. The challenges of making electrolytic conductivity measurements in the time domain versus the frequency domain are discussed and the relationship between the two domains is analysed in terms of a Gaver–Stehfest algorithm for inverse Laplace transform. Data from a commercial current-step-pulse-based sensor reader operating in the time domain are compared with accurate and traceable data from a closed-flow-loop electrolytic conductivity measurement system operating in the frequency domain and traceable to the SI length unit. In the high conductivity range, the readouts of the sensor reader are observed to deviate from traceable conductivity values by up to 10 times the estimated standard measurement uncertainty, which is in the range 0.07%–0.17%. If accurate conductivity calibrations are required (<1%), the usual method of calibrating a conductivity sensor system at a high conductivity level, where CRMs are available, and relying on the same calibration for low conductivity measurements is, therefore, risky.

Using neural network techniques in environmental sensing and measurement systems to compensate for the effects of influence quantities

Multiple influence quantities affect environmental sensing and measurement (ESM) systems. Accounting for their variations over time promotes metrological comparability and traceability of measurement results. Using suitable data processing techniques allows identification of the main influence quantities that affect the measurement result of a given quantity and allows evaluation of the associated compensation coefficients. This paper presents several concerns related to implementation of ESM systems, paying particular attention to the impact of the multiple of measuring and influence quantities on system performance. A review of different data processing techniques to compensate for the effects of influence quantities is presented. A case study based on water conductivity measurements is used to illustrate the capability of artificial neural network (ANN) based techniques and to cope with errors due to a low number of measurement values and due to collinear effects between influence quantities.

Thermodynamic study of complex formation of β-cyclodextrin with ibuprofen by conductometric method and determination of ibuprofen in pharmaceutical drugs

The equilibrium constants and the thermodynamic parameters for complex formation of β-cyclodextrin (β-CD) with ibuprofen have been determined by conductivity measurements in water. The inclusion complexation of ibuprofen in β-cyclodextrin (β-CD) has been examined by means of the conductometric method. The results suggest that stable1:1 complex is formed between ibuprofen and β-cyclodextrin. The thermodynamic parameters (ΔHc°,ΔSc°) for this complexation reaction have been determined from temperature dependence of the stability constant using the van’t Hoff plots.Based on the obtained results, a conductometric method for the determination of ibuprofen in the presence of β-CD at 25°C was developed in the range of 10−3–10−5moldm−1. The method was satisfactorily applied to the quantification of ibuprofen in pharmaceutical preparations.

Environmental Geophysical Study of the Groundwater Mineralization in a Plot of the Cotonou Littoral Zone (South Benin)

Geophysical investigations comprising electrical resistivity and electromagnetic conductivities methods were deployed in a 350 m2sector, strewn with 11 wells. Within the framework of an environmental study on a small scale in the south of Benin, the water conductivity of these wells was measured to determine in a direct way mineralization of the coastal water table in the littoral zone. This environmental study aimed to prospect by the geophysical methods the space extension of the water table mineralization obtained by direct measurements of water conductivity in the well and the depth of the fresh water/salted water interface in the coastal aquifer. Electromagnetic measurements of conductivities made it possible to chart a gradient of mineralization in the northwest direction. The logs of vertical electric soundings showed a deepening of the fresh water/salted water interface in the southern part and its rupture in the northern part. The electrical resistivities of the interface are sensitive to the degree of its mineralization. It has been observed that the geophysical methods in electrical and electromagnetic prospection are a great contribution to the environmental study of the water table mineralization in the littoral zone for a sustainable management of the water resource.

A simple conductometric method for trace level determination of brilliant green in water based on β-cyclodextrin and silver nitrate and determination of their thermodynamic parameters

A gravimetric and complexometric titration method based on conductometric technique is presented for the quantitative determination of brilliant green (BG) in water. The equilibrium constants and the thermodynamic parameters for the complex formation of β-cyclodextrin (β-CD) with brilliant green (BG) and precipitation of silver nitrate with BG have been determined by conductivity measurements in water. The results suggest that stable 1:1 complex is formed between BG and β-cyclodextrin and the thermodynamic parameters ( ΔHc°, ΔSc°) for this complexation reaction have been determined from temperature dependence of the stability constant using the van’t Hoff plots. Based on the obtained results, the conductometric method for the determination of BG in the presence of β-CD at 25°C was developed in the range of 10−8–10−3molL−1 and with AgNO3 is 10−3–10−5molL−1.

The Fabrication and Experiment of a Four-Electrode Conductivity Sensor for Fresh Water

In this paper, a new four-electrode sensor for fresh water conductivity measurements is presented.The measurement system includes two parts: a four-electrode conductivity sensor unit and an integrated measuring circuit. The distribution of a four-electrode in electric field and the size of four electrodes are simulated by ANSYS - the MEMS simulation tool. The prototype of the conductivity sensor, with a four-electrode (each electrode is measuring 6mm×2mm or smaller), was fabricated on a PCB. The conductivity of a tested sample could be obtained according to output of the amplifier by calibrating the voltage of the conductivity of the standard liquid. The voltages of the conductivities, in the range from 0.34V to 9.00V, are detected by an oscillograph. This test result proves that it is promising to measure conductivity of fresh water utilizing the sensor based on the four-electrode system.

Waterborne GPR survey for estimating bottom-sediment variability: A survey on the Po River, Turin, Italy

We conducted an integrated geophysical survey on a stretch of the river Po in order to check the GPR ability to discriminate the variability of riverbed sediments through an analysis of the bottom reflection amplitudes. We conducted continuous profiles with a [Formula: see text] GPR system and a handheld broadband EM sensor. A conductivity meter and a TDR provided punctual measurements of water conductivity, permittivity, and temperature. The processing and interpretation of the GEM-2 and GPR data were enhanced by reciprocal results and by integration with the punctual measurements of the EM properties of the water. We used a processing flow that improved the radargram images and preserved the amplitude ratios among the different profiles and the frequency content at the bottom reflection signal. We derived the water attenuation coefficient both from the punctual measurements using the Maxwell formulas and from the interpretation of the GPR data, finding an optimal matching between the two values. The GPR measurements provided maps of the bathymetry and of the bottom reflection amplitude. The high reflectivity of the riverbed, derived from the GPR interpretation, agreed with the results of the direct sampling campaign that followed the geophysical survey. The variability of the bottom-reflection-amplitudes map, which was not confirmed by the direct sampling, could also have been caused by scattering phenomena due to the riverbed clasts which are dimensionally comparable to the wavelength of the radar pulse.

A Four-Terminal Water-Quality-Monitoring Conductivity Sensor

In this paper, a new four-electrode sensor for water conductivity measurements is presented. In addition to the sensor itself, all signal conditioning is implemented together with signal processing of the sensor outputs to determine the water conductivity. The sensor is designed for conductivity measurements in the range from 50 mS/m up to 5 S/m through the correct placement of the four electrodes inside the tube where the water flows. The implemented prototype is capable of supplying the sensor with the necessary current at the measurement frequency, acquiring the sine signals across the voltage electrodes of the sensor and across a sampling impedance to determine the current. A temperature sensor is also included in the system to measure the water temperature and, thus, compensate the water-conductivity temperature dependence. The main advantages of the proposed conductivity sensor include a wide measurement range, an intrinsic capability to minimize errors caused by fouling and polarization effects, and an automatic compensation of conductivity measurements caused by temperature variations.

Direct media exposure of MEMS multi-sensor systems using a potted-tube packaging concept

A packaging concept for Data Storage Tags is presented. A potted-tube packaging concept, using a polystyrene tube and different epoxies as filling material that allows for direct sensor exposure is investigated. The curing temperature, water uptake and the diffusion coefficient for water in the filling material is measured. The packaging concept is used to encapsulate a microfabricated multi-sensor (measuring temperature, water conductivity, pressure and light intensity). The direct exposure of the sensors results in high sensitivity and fast response time. The design of an elongated multi-sensor is described and effectiveness of the packaging is demonstrated with the precise measurement of water conductivity using the packaged multi-sensor. The packaging concept is very promising for high accuracy measurements in harsh environments.

Colloidal properties of benzylpenicillin: Comparison with structurally-related penicillins

The self-association of sodium benzylpenicillin (penicillin G) in aqueous solution as a function of temperature has been examined. Critical concentrations were determined by conductivity measurements in water over the temperature range 288–313 K and by static and dynamic laser light scattering measurements at 298 K. Both techniques indicate the existence of two critical concentrations: the lowest critical premicelle concentration (cpc) and the highest critical micelle concentration (cmc). Aggregation numbers and effective charges of the aggregates were obtained from static light scattering according to the Anacker and Westwell and the Anacker and Jacobs treatments. The thermodynamic properties of the self-association were derived by application of the modified mass action model for systems with low aggregation number. From the analysis of the thermodynamic parameters, a two-step aggregation model has been proposed by which the dimers created at the cpc form micelles at the cmc. A comparative study of the thermodynamics of structurally-related penicillins, ampicillin, oxacillin, cloxacillin, and dicloxacillin has been carried out, including the enthalpy–entropy compensation phenomenon. A compensation temperature of (1/303) K −1 was found for all penicillins.

An experiment on a sand-dune environment in Southern Venetian coast based on GPR, VES and documentary evidence

The internal structures of some surviving sand dunes and the ancient shore-lines along the coast south of Venice have been investigated integrating Ground Probing Radar (GPR) profiles, Vertical Electrical Soundings (VES) and water conductivity measurements in some boreholes. The GPR penetration depth has been limited (4-5 m,using a 400 MHz antenna) by the high conductivity of salt water saturating pores of the shallow sediments. On the other hand, the excellent spatial resolution of the radar survey provided an estimate of internal dune bedding features, such as cross lamination and forwarding ancient covered coast-lines dated in the Thirties. The interpretation of the data, in particular along one line 360 m long intercepting a sizable sand-dune bank, seems to offer clues to the evolutional history of the coast line and the depth of transition from fresh-water to brackish-salt water. The water table was detected with electrical measurements and direct observations in boreholes, whereas the transition between fresh and salt water (brackish water) was pointed out indirectly by the high energy absorption and total back-reflection of the EM waves, encountered at this boundary, and directly by the strong decrease in VES resistivity values.

Self-Association of the Penicillin Sodium Nafcillin in Aqueous Solution

The self-association of the penicillin drug, sodium nafcillin monohydrate, in aqueous solution has been examined as a function of temperature and electrolyte concentration. Critical concentrations determined by conductivity measurements in water over the temperature range 288.15 to 313.15 K indicated a minimum critical concentration at 303 K. Thermodynamic parameters of aggregation were derived from the critical concentration data using a form of mass action model modified for application to systems of low aggregation number. Values for the enthalpy of aggregate formation Δ calculated by this method showed that the aggregation became increasingly exothermic with increase of temperature. The predicted Δ at 298.15 K was in good agreement with the value determined experimentally by calorimetry. Critical concentrations and the size and effective charge of aggregates were determined in the presence of added electrolyte (0.05−0.40 mol kg-1 NaCl) by static light scattering. The interaction between aggregates was interpreted from diffusion data from dynamic light scattering using the DLVO theory. Changes of 1H NMR chemical shift on aggregation suggested stacking of molecules. Application of mass action theory to the concentration dependence of 1H NMR chemical shifts confirmed the aggregation number from light scattering.

Electroosmotic flow and injection: Application to conductimetry

Electroosmotic solution propulsion and sample injection using fused silica tube was investigated. Capillary tube dimensions were 50–100 μm i.d. by 4–7 cm length with a break in the capillary wall near one end through which electrolytic contact with the capillary solution was established. The applied field was typically 150 V/cm. The voltage at the break in the column was monitored by potentiometry with a bridge configuration. Concentrations ranging from 10 μ M to 100 m M were accommodated. The basis for high sensitivity, e.g. 70 mV/μ M, together with low cell volume, e.g. 20 nl, was established. Tap water conductivity measurements were made using CaCl 2 reference solution.

Airborne electromagnetic bathymetry

An experimental airborne electromagnetic (AEM) survey was carried out in the Cape Cod Bay area to investigate the potential of extracting bathymetric information over a shallow ocean. A commercially available Dighem III AEM System was used for the survey without any significant modification. The helicopter-borne system operated at 385 Hz and 7200 Hz, both in horizontal coplanar configurations. A concurrent ground truth survey included extensive included acoustic profiles, as well as spot water conductivity measurements. Because of the lack of knowledge about the absolute system calibration, a postsurvey calibration was made for each flight line, using a small portion of AEM data to derive the zero-level signal, amplitude, and phase calibration factors for each coil pair. The interpreted bathymetric profiles show excellent agreements with corresponding acoustic depth profiles up to one skin depth (possibly more) of the source frequency. It is envisioned that with further improvements in hardware and software, the bathymetric resolution may extend beyond the skin depth. AEM data can also produce (as by-products) conductivity profiles of both seawater and bottom sediments that may find potential applications in various offshore geotechnical engineering works.

Some Yellow Square Planar Complexes of Nickel(II) Chromate with amines

AbstractTetraco‐ordinated complexes of nickel(II) chromate with ammonia, ethylenediamine and propylenediamine have been prepared. Conductivity measurements in water have shown the complexes dissociating in two ions. Magnetic susceptibility and visible absorption spectra suggest square planar configurations.