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Publication Open Access Comparison of the mechanistic AGDISP ground boom spray model with experimental data(The New Zealand Plant Protection Society Inc., 2012) Connell, Robert J.; Schou, W. C.; Nuyttens, D.; Wolf, T.; Praat, J.-P.Since work reported in 2008, developments on the AGDISP ground boom model have improved results against New Zealand field trial drift data and also compare better with ground boom drift data sets from Belgium and Canada. The model still predicts more drift than the experimental data in most cases, especially for smaller droplet sizes, but does predict less drift for larger droplets at large distances downwind. The original AGDISP ground model was calibrated from Spray Drift Task Force data from the United States. The experimental methods need to be developed to improve collection efficiency and mass balance. The physics behind the model are discussed and proposed methods for improvement are suggested, including air velocities in the spray jet below the nozzle, the dispersion of the spray plume cloud at ground level due to atmospheric turbulence and wakes from the spraying equipment. © 2012 New Zealand Plant Protection Society (Inc.).Publication Open Access Evaluation of the AGDISP ground boom spray drift model(The New Zealand Plant Protection Society Inc., 2008) Woodward, Simon; Connell, Robert J.; Zabkiewicz, J. A.; Steele, K. D.; Praat, John-PaulAGDISP is a well-established spray drift model that has been validated for aerial spraying of forests. Recently a prototypical ground boom option has been added to AGDISP. This was evaluated in the current study by collecting data from spray trials over a grass sward using a ground boom sprayer and representative application parameters. Spray solutions were made up of water, sticker adjuvant and a metal cation, which was changed for each spray application. Deposition from spray drift was measured by analyses of the cation deposits on artificial targets (plastic tapes) placed on the grass surface. Measured deposition was compared with profiles calculated using AGDISP. AGDISP overpredicted deposition from spray drift by a factor of 3.5-100 outside the spray block. Possible reasons for these discrepancies are given. Options are to improve measured deposition and the algorithms for the deposition on the downwind swath of the spray block and evaporation of droplets.Publication Restricted The Lektraspray Nozzle: A novel ultra low volume spray applicator for the greenhouse industry(Lincoln University, 1995) May, William A.A novel electrostatic spray nozzle, termed the Lektraspray Nozzle, was evaluated to assess its suitability for pesticide application in the greenhouse industry. The nozzle is based on the vortical nozzle principle, releasing the spray liquid into a low pressure/high volume airstream through a flexible emitter tube. The encompassing airstream shatters the liquid into small droplets and transports them to the target. The experimental work identified that the nozzle could deliver a droplet spectra with a Volume Median Diameter (VMD) of approximately 75 μm for a range of liquids and viscosities. Charging the droplets had a minor effect on the VMD, although typically improved the droplet spectra. The nozzle could be operated satisfactorily with or without electrostatically charging the droplets. The VMD could be changed simply by increasing/decreasing the liquid flow rate and/or adjusting the air pressure of the encompassing airstream. Small adjustments to the air pressure (4.5 to 14 kPa) will allow the production of an acceptable droplet spectra over a large range of liquid flow rates (30 to 1000 ml/min). The results of a limited number of tests using the Lektraspray nozzle on plants indicated that electrostatic charging could significantly influence the deposition of droplets on the underside of the leaves, providing the foliage was not "dense". However no significant increase in the total amount deposited on the plant was noted when the droplets were charged. The results from spraying a "dense" foliage plant (Pittosporum eugenioides) indicated the need to adjust the charge/air pressure relationship of the spray nozzle to increase underleaf deposition and improve droplet penetration into the plant canopy. After evaluating the experimental work on the Lektraspray nozzle, and considering the simplicity and ruggedness of the nozzle, the conclusion was that it should be seriously considered as an alternative spray application technique for use where controlled environment spraying is required. In particular - the greenhouse industry.Publication Open Access Optimising MICREDOX to accurately report the BOD of sewage samples(Lincoln University. Lincoln Ventures., 2004) Webber, Judith; Hay, Joanne; Noonan, M.; Pasco, NeilPublication Open Access Scale-dependent dispersivity: a velocity fluctuation model(Modelling and Simulation Society of Australia and New Zealand, 2003-07) Verwoerd, WS; Post, DAIn the previous paper, it was shown that the cumulative effect of multiple one-dimensional velocity fluctuations can explain qualitative features of the observed scale dependent dispersivity in natural aquifers, but not the magnitude of the effect. It is plausible that in real systems the enhancement of dispersion caused by a single fluctuation may be larger than that derived for the 1-dimensional stepped fluctuation, because for example there are additional enhancement mechanisms in 2- and 3-dimensional systems. However this paper shows that to achieve the observed magnitude, it is not enough to increase the size of enhancement factor but in addition the rate at which the effect of a single fluctuation changes with fluctuation length and with position along the fluctuation sequence need to be modified. Several variations are explored. Simple assumptions are shown to lead to dispersivity formulas in terms of purely algebraic power laws, while more elaborate assumptions yield expressions that are still analytic but contain non-elementary functions. In either case it is possible to find the required variation of the dispersivity over 3 or more orders of magnitude and with curve shapes that are consistent with historical observations Moreover, this is achieved with plausible parameter values, leading for example to the conjecture that in the observed systems the porous medium could not have been homogeneous on a scale of more than centimeters. The model presented is schematic in the sense that it contains some detail assumptions not derived from first principles, but is believed to capture the essentials of the mechanism that causes scale dependent dispersivity. It sets some boundaries for viable detail models, but within those boundaries the final predictions are not very sensitive to the detail assumptions. A key merit of the treatment is that it identifies crucial variables that need to be measured or controlled in experimental studies.Publication Open Access Using a simple 2D steady-state saturated flow and reactive transport model to elucidate denitrification patterns in a hillslope aquifer(Modelling and Simulation Society of Australia and New Zealand, 2011-12) Woodward, S; Stenger, R; Bidwell, VIn the last 50 years, agricultural intensification has resulted in increasing nutrient losses that threaten the health of the lakes on the volcanic plateau of New Zealand’s North Island. As part of our efforts to understand the transport and transformations of nitrogen in this landscape, the 2D vertical groundwater transport model AquiferSim 2DV was used to simulate water flow, nitrate transport, denitrification, and discharge to surface waters in a hillslope adjacent to a wetland and stream discharging into Lake Taupo, Australasia’s largest lake. AquiferSim 2DV is a steady state model using the finite-difference stream function method for flow modelling and finite-volume mixing cell method for contaminant transport modelling. The ratio of horizontal to vertical hydraulic conductivity must be specified within the aquifer domain, as must effective porosity and denitrification rates. Boundary conditions consist of recharge fluxes and contaminant concentrations, as well as the assumed zone of discharge. Hydrodynamic dispersion is simulated through numerical dispersion, which depends on grid resolution. Denitrification reactions within each computational cell may include both zero-order and first-order rates. All parameters may be spatially heterogeneous. Previous applications of this model have been to essentially horizontal aquifer systems. By contrast, this hillslope system has sloping material layers and a dynamic and sloping water table. Extensions were made to AquiferSim 2DV, including representation of converging/diverging flow, which allowed a 2D steady-state model of this system to be developed. Comparison of model predictions with detailed water level and hydrochemical data from the site, however, showed that the model’s attractive simplicity in this case precluded adequate characterisation of what is essentially a 3D, transient system. While the model produced reasonable agreement with the concentration patterns under an average water table profile, predictions of oxygen and nitrate concentrations under low summer and high spring water table conditions were poor. The seasonal changes reflected an annual recharge pulse of fresh, oxidised water followed by gradual oxygen depletion till the next recharge pulse occurs in the following year, an essentially transient phenomenon which could not be represented using a steady state model. This in itself has provoked fresh thinking about the dynamic nature of flow and chemistry at the site.Publication Open Access Optimisation of monitoring data for increased predictive reliability of regional water allocation models(Modelling and Simulation Society of Australia and New Zealand, 2011-12) Moore, CR; Wöhling Th,; Wolf, LThis paper discusses the optimization of monitoring data for the increased reliability of regional groundwater models and the predictions that depend on them. The significant costs of commissioning and maintaining groundwater monitoring networks are such that there is great benefit in being able to assess where data gathering has the greatest impact on improving predictive reliability. This optimization assessment can be made on the basis of existing networks or prior to any data acquisition efforts. Various data acquisition strategies, for quite disparate data types, can be compared in terms of their ability to increase the reliability of model based predictions; data collection strategies which provide the greatest return for investment can then be selected for implementation. Similarly the relative merits of making measurements at different locations and times can be assessed. Using the Lockyer Valley ground water model (RPS 2010) we demonstrate how predictive uncertainty analysis can provide a powerful foundation for optimizing both existing monitoring networks and future data acquisition strategies to support model based environmental management. Such analyses are efficient yet robust. The particular characterization of model predictive variance in the problem formulation employed (Moore and Doherty, 2005), ensures that the contributions to predictive uncertainty by both measurement errors and environmental heterogeneity that cannot be captured by the calibration process is accounted for in the analysis. Efficiency is gained via a linearity assumption in the equation used in the analysis, which allows the calculation to be made sufficiently rapidly, so that it can be repeated at many alternative existing or proposed monitoring sites and times. Furthermore, this analysis has no cost barriers, as the software for such analyses is in the public domain (Doherty, 2011a and b). These are particularly important benefits in the large scale regional model context, where monitoring is typically a significant effort and is subject to public scrutiny in terms of both cost and rigour.Publication Open Access Dual-domain mixing cell modelling and uncertainty analysis for unsaturated bromide and chloride transport(Modelling and Simulation Society of Australia and New Zealand, 2011) Wöhling Th,; Dann, R; Wall, A; Moorhead, B; Clague, J; Vrugt, JA; Barkle, GF; Bidwell Vince, JLand use intensification is considered the main reason for early signs of deterioration in the water quality of Lake Taupo, New Zealand. Little is understood, however about the origin, and governing flow paths of the contaminants and their respective transformation processes that affect the water quality of Lake Taupo. In this study we investigate contaminant transport and its small-scale variability in the volcanic vadose zone surrounding the Lake. Lateral and preferential solute transport is analysed to better understand the risks of diffuse groundwater pollution from contaminant sources at the land surface. As part of the investigations into this problem the Spydia experimental facility has been installed under a pastoral agriculture land use in the Lake Taupo region, New Zealand (Barkle et al. 2011). A multiple tracer experiment was conducted at the site and vadose zone drainage volumes were measured using Automated Equilibrium Tension Plate Lysimeters (Figure 1). The chemical composition of the drainage samples was analysed in the laboratory. A dual-domain mixing cell model was set up to simulate the unsaturated advective-dispersive tracer transport at selected monitoring sites for two different bromide-chloride (Br⁻, Cl⁻) tracers that were applied at the land surface at two different regions (Figure 1). Some model parameters were constrained by mixing calculations of the measured total Br⁻ and Cl⁻ load, whereas others were calibrated using the measured Br⁻ and Cl⁻ breakthrough curves and drainage volumes. Multi-objective inverse modelling using the AMALGAM evolutionary search method (Vrugt & Robinson, 2007) showed a significant trade-off between simulated transient Br⁻ and Cl⁻ breakthrough curves and corresponding drainage volumes, but also a compromise solution that fits both objective functions reasonably well. Estimates of parameter and model predictive uncertainty were subsequently derived using the differential evolution adaptive metropolis, DREAMZS adaptive Markov chain Monte Carlo algorithm (Vrugt et al., 2011) with a formal Bayesian likelihood function (Wöhling & Vrugt, 2011). Uncertainty bounds derived by this MCMC method simultaneously capture the observed Br⁻ and Cl⁻ breakthrough curves and corresponding drainage volumes. Our results demonstrate that (1) flow and transport in the vadose zone is highly variable, and (2) contaminants at the land surface can travel rapidly through the soil to larger depths and this cannot be described with the classical advection-dispersion equation.Publication Open Access An object-oriented software framework for the farm-scale simulation of nitrate leaching from agricultural land uses – IRAP FarmSim(Modelling and Simulation Society of Australia and New Zealand, 2005-12) Good, J; Bright, JThe purpose of this project is the creation of a framework that will allow the prediction of drainage flux and nitrate leaching from a whole farm taking into account a full range of agricultural activities. Ultimately, the simulation framework will be used to provide nitrate and drainage flux input values for a regional groundwater model. In addition, the project aims to provide a highly effective and adaptable farm-scale simulation framework that has application well beyond the scope of nitrate leaching prediction. It is being implemented as a component-based simulation, utilising models produced by research collaborators within the Integrated Research for Aquifer Protection (IRAP) programme and from the public domain. The simulation framework consists of a variable number of individual paddock simulations controlled by a detailed farm-scale management component. When complete, FarmSim will be able to represent a wide range of agricultural activities including pasture-based grazing (sheep and dairy farming) and cropping using a wide range of cropping models applicable in New Zealand.Publication Open Access The benefits and practicalities of using Extensible Markup Language (XML) for the interfacing and control of object-oriented simulations(Modelling and Simulation Society of Australia and New Zealand., 2005-12) Good, JTraditionally simulation software has been custom built for its particular purpose with input and output file formats as well as control interfaces being unique to the simulation. This leads to considerable difficulties in preparing simulation data, utilising output data in other applications and using the simulation as a component of larger simulations. This paper presents an alternative method for the interfacing and control of simulations. This method uses an industry standard language for the implementation of interfaces and the representation of data and metadata. The use of this technique facilitates the interoperability of simulation components and provides flexibility for the development of user interfaces. It also greatly simplifies connection to external data sources such as database applications and GIS systems. This paper illustrates the benefits of using XML and XSDL using the example of the FarmSim application produced as part of the Integrated Research for Aquifer Protection (IRAP) programme. This has provided great flexibility in handling the large quantities of data associated with the simulation. The implementation of this technology has enabled an external company to develop a user interface for the paddock-level component that specifically addresses their operational requirements without any knowledge of the internal operation of simulation component. Should the user simulation component change, the user interface automatically incorporates the changes by utilising the data in the XML and XSDL structures.Publication Open Access State-space mixing cell model of unsteady solute transport in unsaturated soil(Modelling and Simulation Society of Australia Inc., 1997-12) Bidwell, Vince JThe purpose of this model is to enable implementation of the theory of linear systems control in operational management of waste and fertiliser applications onto land, so that the underlying groundwater is protected from pollution by leachate. The state-space form of the model enables use of the extensive theory and available software on stochastic linear systems. In particular, the Kalman filter is relevant to the imperfectly understood and highly variable processes of solute transport and transformation in field soils. The series of mixing cells was selected as a linear system model of one-dimensional, vertical, advective-dispersive transport, and based on cumulative soil water drainage as the index variable for application to unsteady flow in unsaturated soil. For each cell, solute transfer between mobile and immobile soil water, as well as equilibrium and nonequilibrium linear adsorption, are represented as lumped processes by two fractions linked by rate-limited transfer. The resident solute concentrations in the cell fractions are the states of the system. The complete model of solute transport and transformation for a uniform soil has four parameters, and can be described in MATLAB® with about ten lines of code. The software library can then be used to produce the discrete form of the model, which is unconditionally stable for any drainage interval as well as to implement state estimation and control algorithms. A demonstration of the model is reported for ³⁵S-labelled sulphate leached from five replicated lysimeters (800 mm diameter, l100 mm depth) of an undisturbed field soil (a free-draining silt loam) under pasture receiving rainfall and irrigation, The results show satisfactory one-step-ahead forecasts with the Kalman filter for the period of record, and a forecast is given of the complete response to the solute pulse application beyond the data record.Publication Open Access CFD modelling of kiwifruit vines and leaves: a method of handling multiple thin surfaces(Modelling and Simulation Society of Australia and New Zealand, 2011-12) Connell, RJ; Endalew, AM; Verboven, P; Chan, F; Marinova, D; Anderssen, RSModelling air flow through vegetation is important in many areas of horticulture both for air quality monitoring and for calculating spray drift from agrichemical spraying operations. Modelling vegetation in computational fluid dynamics (CFD) has traditionally been carried out using the porous media properties of the leaves and branches. This entails an extra sink term in the momentum equations for the drag force of the leaves and branches; an extra source term for the turbulent kinetic energy generated by the vegetation; and the corresponding sink term for the turbulent dissipation. More complex models have been developed by Katholic University Leuven that have branching included into the CFD model with the leaves, small branches and petioles modelled using the porous media approach. The kiwifruit vine model developed here took this one step further to include details of the leaves but omitted the smaller branches and petioles, due to their small scales/sizes. The leaves were generated from the output of a model of a kiwifruit vine developed using the L-system-based plant modelling platform, L-studio. The output was converted into a suitable format for CFD using a conversion program, C4W. The leaf model developed did not include the leaf edges in the mesh as this would have created cells that were too small to run the model. The ANSYS workbench can include thin-surfaces in the model domain but it was impractical to handle that many leaves. The model was developed using the standard meshing in CFX version 12.1 to create a leaf with no edge. This was done by giving the leaf its normal width of about 200 μm and specifying a minimum cell size of 4.5 mm. The resultant leaf had a surface on either side, with about 35 faces each side to simulate the curved surface of the leaf. The present model was adequate only up to 200 leaves due to the large number of leaf surface boundaries that the CFD model cannot handle at present. Methods to reduce this are currently being investigated. The resultant CFD model was developed so it did not need sink/source terms for the vegetation and gave the main properties of the kiwifruit vine including the drag from the branches and leaves, as shown by the velocity field in Figure 1. This allows detailed modelling of droplet deposition on to the leaf, consideration of turbulence intensity and the inclusion of a droplet retention/deposition model. The problem of the change in drag created by movements or leaf fluttering is to be the subject of future research. The model will be validated using turbulence and wind data from a series of sonic anemometers sited within and above the plant canopy.Publication Open Access Linear system model of water flow and oxygen-18 transport on a steep hillslope(Modelling and Simulation Society of Australia Inc., 1997-12) Bidwell, Vince J; Stewart, MKThe purpose of this model was to assist with the determination of the nature of water flow processes on steep (≈35°) hillslopes in a 3.8 ha forested catchment. The soils are sufficiently permeable that, for most rainstorms, streamflow responds rapidly without significant surface runoff occurring. Scientific debate had focused on whether "old water" held within the soil could be rapidly mobilised by incoming "new water" from storm rainfall. A linear system approach was taken to the analysis of the dynamic response of water flow and concentration of the natural isotope oxygen-18 in the stream to the input series of rainfall and associated oxygen-18 content from one storm. The candidate system components were bounded and unbounded water storages with first-order water flow dynamics, and bounded storages with zero-order dynamics. The upper limits on the bounded storages allow for nonlinearities in flow processes. The dynamic effect on transport of the isotopic tracer was assumed to be due to perfect mixing within each of the water storage components. The model was implemented on spreadsheet software in the form of difference equations and logical expressions. Analysis of the rainfall and streamflow data showed that the hydrometric response could be simulated with one bounded (8.5 mm) zero-order storage to account for initial rainfall loss, followed by a bounded (25.6 mm) and an unbounded first-order storage in parallel. However, this model provided insufficient attenuation of the oxygen-18 signal. Satisfactory simulation of oxygen-18 in the stream was achieved by including a bounded zero-order storage (250 mm) of specified oxygen-18 concentration. The same model structure was fItted to additional data from measurement of subsurface flow conected by troughs at four locations on the hillslopes. The results support the hypothesis that mobilisation of old water is an important component of water flow on the hillslopes. However, the degree of mixing within the old water storage has not been conclusively determined on the basis of the one storm event.Publication Open Access The importance of farmer behaviour: an application of Desktop MAS, a multi-agent system model for rural New Zealand communities(New Zealand Agricultural and Resource Economics Society, 2012-08) Schilling, C.; Post, Elizabeth A.; Rains, Scott T.; Kaye-Blake, W.This paper describes a multi-agent system (MAS) model, Desktop MAS, designed for New Zealand‟s pastoral industries. Desktop MAS models the strategic decisions and behaviours of individual farmers in response to changes in their operating environment. Farmer responses determine production, economic and environmental outcomes. Each farmer has a profit-maximising or cost-minimising objective that governs their decision-making, and a social network with whom they interact. Information transfer between farmers occurs through this social network. We consider a simple scenario analysis that investigates the impact of emissions prices on industry mix and farming intensity. We then investigate the importance of farmer behaviours and interaction. We find that farmer social networks and objectives impact particularly on farming intensity decisions within land-use industries. Land-use change between industries becomes more sensitive to farmer attitudes as the profitability differential between land-uses narrows.Publication Open Access Hydrogeological support for the Orari environmental flow and water allocation plan(Environment Canterbury, 2011-02) Burbery, LeeAn environmental flow and water allocation plan is being developed for the Orari River, South Canterbury. In 2006/07, an integrated field study of surface water shallow - groundwater was undertaken of the region. As part of the study, shallow groundwater levels started to be monitored throughout the catchment. These levels provide a useful data series from which the dynamic properties of the shallow Orari aquifer can be studied and information gained on probable aquifer recharge mechanisms. The hydrodynamics of the shallow Orari aquifer were characterised, based on analysis of daily time series hydrograph data available from 10 shallow monitoring wells. A Groundwater Data Analysis tool that is built around the mathematical Eigen-model, and which has recently been developed by Lincoln Venture Ltd was applied for this purpose.Publication Open Access Efficient and reasonable use of water for irrigation.(Environment Canterbury., 2002-05) McIndoe, IanEnvironment Canterbury (ECan) is currently preparing a Natural Resources Regional Plan (NRRP) to manage the natural and physical resources of the Canterbury region. The NRRP sets out detailed objectives and policies for setting and managing water allocation. A major part of the available water resource is allocated for irrigation. How efficiently that water is used impacts on how water is allocated and what potential adverse environmental effects could arise. The purpose of this report is to define irrigation efficiency, recommend a reasonable and desirable level of irrigation application efficiency for use in allocating water for irrigation, and to review conditions of water use. The information will be used to develop and promote policy in the NRRP, be incorporated in a reasonable use test for setting water permits, and assist in the fair allocation of water resources with the least environmental effect. Fourteen definitions of efficiency have been described and evaluated.Publication Open Access Delineation of the Rangitata riparian zone.(Environment Canterbury., 2012-06) Burbery, LeeA riparian zone aquifer is a groundwater system that is closely related to a surface water body. Water resource management rules within a riparian zone might be tailored differently from rules outside such a zone, to account for the strong surface water/groundwater connection. The riparian aquifer zone of the lower section of the Rangitata River which divides the Mayfield-Hinds groundwater allocation zone (GWAZ) and Rangitata-Orton GWAZ has been delineated based on the review of available geological, hydrological and water chemistry data. The Rangitata riparian aquifer zone is conceived to include both shallow and deep groundwater that underlies the margin of land between the Rangitata River and Kapunatiki Creek (encompassing Rangitata Island and the Rangitata South Branch). The historic flood plain on the north side (true-left) of the Rangitata, directly south of Coldstream, is also considered to be part of the riparian zone. Covering 17,388 hectares, the riparian aquifer zone is approximately three times the area of the active Rangitata River channel. 61 million m3 of groundwater is currently consented to be pumped from the riparian aquifer zone, annually. This is four times more than what can conceivably be supplied by rainfall recharge, the deficit of which must be made up from river water flow losses. Consequently, groundwater abstractions from within the riparian zone have potential to significantly impact flows in the Rangitata River system and in particular the spring-fed McKinnons Creek. McKinnons Creek and Ealing Springs constitute features of the Rangitata River system that are protected under the Rangitata River Conservation Order for their salmon spawning properties and cultural significance to Ngāi Tahu. Elevated nitrate levels in these surface waters pose a potential environmental risk to the ecological qualities for which these spring-fed water systems are recognised. There is technical merit in defining a riparian aquifer zone for the Rangitata River, although the resource management implications of doing so are not clear, particularly given the Rangitata River is already subject to a conservation order. The relatively small spring-fed McKinnons Creek would likely stand to benefit the most from the establishment of a riparian aquifer management zone on the Rangitata. There is an obvious need for further field investigation work to be undertaken that would assist in the technical refinement of the Rangitata riparian zone, and is required before any changes to groundwater allocation resource management in the Rangitata region might be made.Publication Open Access The spectroscopic impedance of cellophane(International Society for Electromagnetic Aquametry (ISEMA)., 2003) Christie, JH; Sylvander, SR; Woodhead, Ian M; Irie, KenjiThe electrical impedance of cellophane has been measured as a function of moisture content and temperature in the frequency range 10⁻³ – 10⁵ Hz. The data show a very strong dependence on moisture content, which is a typical characteristic of hygroscopic solids, and at low frequencies, remarkable constant phase angle spectra were obtained. Making use of the hopping model of conduction in non-crystalline solids, we explain the measured spectra. The model treats absorbed water as an impurity in the cellophane and conduction is predicted to occur by temperature-activated proton hopping between water molecules. We also propose that this model is widely applicable to prediction of the low frequency dielectric properties of hygroscopic solids.Publication Open Access Rapid toxicity assessment: a new method based on quantifying mediated microbial respiration at a microelectrode(2002) Webber, Judith; Tizzard, A. C.; Pasco, N. F.; Hay, J.; Gooneratne, R.; John, R.Lincoln Technology has developed a rapid biosensor-based assay called MICREDOX®. While MICREDOX® was originally developed for BOD monitoring, here we report how this rapid assay has been extended to ascertain the impact of toxic chemicals on biological materials resident in the environment.Publication Open Access MICREDOX® - advantages derived from an immobilised biocomponet for a rapid BOD biosensor(2004) Webber, Judith; Pasco, Neil; Baronian, Keith; Hay, JoanneMICREDOX® is a novel rapid microbial technique for monitoring environmental contaminants, including biological oxygen demand (BOD). The advantages of an immobilised biocomponent are explored for the MICREDOX® process in this poster.