Miki Hondzo

A Field Information-based System for Estimating Fish Temperature Tolerances

Abstract In 1979, Biesinger et al. described a technique for spatial and temporal matching of records of stream temperatures and fish sampling events to obtain estimates of yearly temperature regimes for freshwater fishes of the United States. This article describes the state of this Fish and Temperature Database Matching System (FTDMS), its usage to estimate thermal requirements for fishes, some proposed maximum temperature tolerances for several freshwater fish species, and the way these FTDMS-derived values relate to various laboratory test results. Although applicable to all species for which collection records exist, initial development and refinement of FTDMS has focused on estimating the maximum weekly mean temperature tolerance for 30 common fishes of the United States. The method involves extensive use of automated data processing during data incorporation, quality assurance checks, data matching, and endpoint calculation. Maximum weekly mean temperatures derived from FTDMS were always less than ...

Predictive Modeling of Transient Storage and Nutrient Uptake: Implications for Stream Restoration

This study examined two key aspects of reactive transport modeling for stream restoration purposes: the accuracy of the nutrient spiraling and transient storage models for quantifying reach-scale nutrient uptake, and the ability to quantify transport parameters using measurements and scaling techniques in order to improve upon traditional conservative tracer fitting methods. Nitrate ( NO 3− ) uptake rates inferred using the nutrient spiraling model underestimated the total NO 3− mass loss by 82%, which was attributed to the exclusion of dispersion and transient storage. The transient storage model was more accurate with respect to the NO 3− mass loss (±20%) and also demonstrated that uptake in the main channel was more significant than in storage zones. Conservative tracer fitting was unable to produce transport parameter estimates for a riffle-pool transition of the study reach, while forward modeling of solute transport using measured/scaled transport parameters matched conservative tracer breakthrough ...

LABORATORY STUDY OF HEAVY METAL PHYTOREMEDIATION BY THREE WETLAND MACROPHYTES

Detention ponds and constructed wetlands have proven to be effective in reducing peak stormwater runoff volume and flow, and recent interest has extended to utilizing them to improve stormwater runoff quality. A review of stormwater runoff studies indicated that lead, zinc, copper, cadmium, phosphorus, and chloride are contaminants of primary concern. In laboratory settings, the uptake of contaminants by three wetland plant species, Glyceria grandis, Scirpus validus, and Spartina pectinata, was examined and removal rates from nutrient solutions in flow and nonflow reactors were measured. The removal rates varied by plant species and target contaminant, and no one species was the best accumulator of all six contaminants. Belowground tissues of all three species accumulated higher concentrations of the four heavy metals and aboveground tissues accumulated higher concentrations of phosphorus and chloride. Plants grown in flow reactors showed significantly higher accumulation rates than those grown in nonflow reactors. Also, plants grown hydroponically accumulated higher concentrations of the six target contaminants than those grown in sand reactors. However, those grown in sand had a much greater increase of biomass and removed a greater mass of the six target contaminants. Removal rates measured in these experiments can be used to design detention ponds to maximize stormwater remediation.

Dissolved oxygen measurements in aquatic environments: the effects of changing temperature and pressure on three sensor technologies.

Dissolved oxygen (DO) is probably the most important parameter related to water quality and biological habitat in aquatic environments. In situ DO sensors are some of the most valuable tools used by scientists and engineers for the evaluation of water quality in aquatic ecosystems. Presently, we cannot accurately measure DO concentrations under variable temperature and pressure conditions. Pressure and temperature influence polarographic and optical type DO sensors compared to the standard Winkler titration method. This study combines laboratory and field experiments to compare and quantify the accuracy and performance of commercially available macro and micro Clark-type oxygen sensors as well as optical sensing technology to the Winkler method under changing pressure and temperature conditions. Field measurements at various lake depths revealed sensor response time up to 11 min due to changes in water temperature, pressure, and DO concentration. Investigators should account for transient response in DO sensors before measurements are collected at a given location. We have developed an effective model to predict the transient response time for Clark-type oxygen sensors. The proposed procedure increases the accuracy of DO data collected in situ for profiling applications.

Development of a commercial code-based two-fluid model for bubble plumes

Abstract Bubble plume models are applied to study the de-stratification of lake water, aeration of reservoirs, wastewater treatment, and gas injection into liquid metals. Several existing models exemplify numerical modeling as problem-specific art, solve a mixture momentum equation, and have limitations in the availability of documentation, definition of boundary conditions, and post- and pre-processing capabilities. The transfer of problem-specific models to a client or to a multidisciplinary research and development team is a difficult process. The questions addressed in this study were as follows: (a) can one use a commercial code as a basis to develop a user-friendly, efficient model that simulates two-phase flow in bubble plumes? (b) what are the capabilities and limitations of such a model? The two-fluid model developed has flexibility in the definition of the multiphase and viscous models, easily understood definition of boundary conditions, simple definition of spatial dimensionality and time dependency, efficient numerical solution, clear documentation and user-friendly pre- and post-processing capabilities. Water and air phase velocities, water turbulent kinetic energy, and air volume fraction are predicted with accuracy similar to that of existing problem-specific models. A strategy to overcome some under-dispersion and include air–water mass transfer effects through user-defined functions is discussed.

Incorporating both physical and kinetic limitations in quantifying dissolved oxygen flux to aquatic sediments

Traditionally, dissolved oxygen (DO) fluxes have been calculated using the thin-film theory with DO microstructure data in systems characterized by fine sediments and low velocities. However, recent experimental evidence of fluctuating DO concentrations near the sediment-water interface suggests that turbulence and coherent motions control the mass transfer, and the surface renewal theory gives a more mechanistic model for quantifying fluxes. Both models involve quantifying the mass transfer coefficient (k) and the relevant concentration difference (ΔC). This study compared several empirical models for quantifying k based on both thin-film and surface renewal theories, as well as presents a new method for quantifying ΔC (dynamic approach) that is consistent with the observed DO concentration fluctuations near the interface. Data were used from a series of flume experiments that includes both physical and kinetic uptake limitations of the flux. Results indicated that methods for quantifying k and ΔC using the surface renewal theory better estimated the DO flux across a range of fluid-flow conditions.

A Desktop Apparatus for Studying Interactions Between Microorganisms and Small-Scale Fluid Motion

Low levels of kinetic energy dissipation were successfully generated in a reactor using two submersible speakers. A software programme controlled the amplitude and frequency of the signal fed to each speaker and achieved good repeatability of flow conditions. The flow reactor had a near isotropic flow regime with a low mean flow, values were calculated from particle image velocimetry measurements. The flow characteristics compared well with grid turbulence reactors, though as no moving parts are present in this reactor design the strain rates were lower compared to oscillating grid set-ups. The low range of Reynolds numbers based on Taylor microscales (Reλ~0.5–5.9) covered both turbulent and non-turbulent flow regimes. The small-scale fluid motion produced over the entire volume of this reactor makes it suitable for experiments examining the physiological responses of fluid motion on microorganisms.

Three-dimensional lake water quality modeling: sensitivity and uncertainty analyses.

Two sensitivity and uncertainty analysis methods are applied to a three-dimensional coupled hydrodynamic-ecological model (ELCOM-CAEDYM) of a morphologically complex lake. The primary goals of the analyses are to increase confidence in the model predictions, identify influential model parameters, quantify the uncertainty of model prediction, and explore the spatial and temporal variabilities of model predictions. The influence of model parameters on four model-predicted variables (model output) and the contributions of each of the model-predicted variables to the total variations in model output are presented. The contributions of predicted water temperature, dissolved oxygen, total phosphorus, and algal biomass contributed 3, 13, 26, and 58% of total model output variance, respectively. The fraction of variance resulting from model parameter uncertainty was calculated by two methods and used for evaluation and ranking of the most influential model parameters. Nine out of the top 10 parameters identified by each method agreed, but their ranks were different. Spatial and temporal changes of model uncertainty were investigated and visualized. Model uncertainty appeared to be concentrated around specific water depths and dates that corresponded to significant storm events. The results suggest that spatial and temporal variations in the predicted water quality variables are sensitive to the hydrodynamics of physical perturbations such as those caused by stream inflows generated by storm events. The sensitivity and uncertainty analyses identified the mineralization of dissolved organic carbon, sediment phosphorus release rate, algal metabolic loss rate, internal phosphorus concentration, and phosphorus uptake rate as the most influential model parameters.

Enhanced uptake of dissolved oxygen and glucose by Escherichia coli in a turbulent flow

Laboratory experiments were conducted to study the effect of turbulence on Escherichia coli cells in an oscillating grid reactor under conditions of no oxygen transfer to the liquid phase. Fluid flow was quantified at a submillimeter resolution using a particle image velocimetry measuring technique. The root-mean-square estimates of the velocity gradient tensor components indicated the dominance of shear rate deformation in the fluid surrounding E. coli. The E. coli growth rate, dissolved oxygen (DO), and glucose uptake rates were facilitated by fluid-flow energy dissipation in the turbulent fluid. The Kolmogorov length scale (ηK) and velocity (uK) underlined characteristic scales at which enhanced DO and glucose uptake by E. coli were determined in a turbulent flow in comparison to still-water controls. A first-order power–law relation between the mass transport to the cells and the moving fluid is developed. The combined effects of the enhanced rate of strain at ηK scale and uniform velocity at uK determined the facilitated DO and glucose fluxes to E. coli. The mass transport to the E. coli was modeled by the Sherwood (Sh)–Péclet (Pe) number relationship by