Modeling Approach to Periphyton and Nutrient Interaction in a Stream

We propose a model of the development of a periphyton community in a stream under the influence of nutrients and light. Coupling the model with a nutrient transport model clarified the longitudinal distribution of both periphyton community and nutrients. The thickness of the periphyton mat, an important factor regulating nutrient exchange between the mat and overflowing water, was determined from water velocity and the periphyton biomass. We compared the results of this study with three observational data sets to overall validate our proposal: (1) a comparison of electrical conductance in two channels with different periphyton biomasses validated the model in the mass exchange between stationary and flowing water zones; (2) a comparison of the temporal variation in periphyton biomass and nutrient concentration in a once-through and a re-circulated water channel, validated the relationships among the periphyton biomass, the nutrient uptake rate, and the nutrient concentrations in the stationary water zone; and (3) a longitudinal distribution of the algal species composition of Stigeoclonium and Chamaesiphon, and the nutrient concentrations of a 140 m reach was reproduced and compared with measured data. The light intensity indirectly controlled the nutrient gradients along the stream by the periphyton biomass in the third application.     

Grazer Control of Stream Algae: Modeling Temperature and Flood Effects

A computer model for epilithic algae and grazer biomass in streams is modified to better predict the effects of temperature and is calibrated for diatoms and mayflies. Mayflies are predicted to maintain low diatom biomass provided that (1) temperatures remain within their preferred range (10–20°C); and (2) mayfly populations are not adversely affected by floods. Algal blooms are predicted to occur in mayfly-dominated streams above 20°C—temperatures common in pasture streams over summer. We hypothesize that mobile bed streams are susceptible to blooms during summer low flows following floods because (1) they usually lack temperature tolerant snail grazers; and (2) mayfly recovery lags behind algal regrowth, and there is a short period when algae escape from “top-down” grazer control.     

Aquifer Response to Sinusoidal or Arbitrary Stage of Semipervious Stream

Analytical expressions for the aquifer responses, viz., groundwater head, rate of flow and cumulative volume of flow, to a generalized sinusoidal stage of semipervious streams considering the stream boundary resistance, are derived. The analytical aquifer responses to a linear stream stage and to a typical analytical flood wave that was used by Cooper and Rorabaugh, are also derived. For a zero-stream resistance, the aquifer responses converge to those for a fully penetrating stream. Also, two analytical methods, a “ramp kernel method” and a “Fourier series method,” for obtaining the aquifer responses to an arbitrary temporal stage of sempervious stream, are developed. The analytical expressions of the ramp kernels for different aquifer responses are developed. The ramp kernel method is found superior to the conventional convolution that uses numerical integration or pulse kernels for obtaining the convolution integral. In the Fourier series method, the aquifer responses to sinusoidal stage are used along with Fourier series. The results obtained using both methods are in close agreement. The new methods are also applicable to fully penetrating streams by assigning a zero value to the stream resistance.     

Effect of Floodwater Extraction on Mountain Stream Morphology

Floodwater is often extracted for consumptive purposes from western mountain streams in the United States. The long-term extraction of floodwater may alter the morphological and ecological balance of such streams. Scale model experiments based on eight mountain gravel-bed streams in Idaho were conducted to test the effects of floodwater extraction on stream morphology. The model channel transported a poorly sorted mix of model “gravel,” as well as copious amounts of model “sand.” The channel had a discontinuous floodplain, developed its own bar morphology, and contained large model colluvium as well as a bedrock platform. A mobile-bed equilibrium was first developed using a repeated hydrograph. The experiment was then repeated using a sliding cutoff discharge. The discharges in the hydrograph that were below a given cutoff discharge were reduced to 30% of bankfull discharge. By raising the cutoff discharge, it was possible to study the effect of increasing severity of floodwater extraction on stream morphology. The experiments indicated an increase in sand content on the bed surface and a decrease in the standard deviation of fluctuations in bed elevation with increasing severity of floodwater extraction.     

Longitudinal effects of conflict behaviors on depressive symptoms in young couples.

This study investigated relationship dynamics contributing to gender differences in depression by testing longitudinal associations between observed conflict behaviors and depressive symptoms in young couples. Direct effects of psychological aggression, positive engagement, and withdrawal, as well as indirect effects via relationship satisfaction were considered. Participants were 68 heterosexual couples involving men from the Oregon Youth Study who remained in a stable relationship across at least 2 and up to 10 years from their early 20s to early 30s. Hierarchical linear modeling was used to test both between-couples differences in symptom trajectories predicted by partner behaviors and within-couple covariation between behaviors and depressive symptoms across 5 time points. Higher levels of women’s positive engagement predicted lower symptom levels for both partners, and higher women’s withdrawal predicted higher own symptom levels. Relative increases in couples’ psychological aggression and decreases in positive engagement were additionally associated with increases in women’s symptoms over time. Whereas between-couples behavior effects on women’s symptoms were mediated by relationship satisfaction, within-couple effects proved independent of satisfaction. Implications for mechanisms of depression risk and maintenance in couples are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Estimating Stream Temperature from Air Temperature: Implications for Future Water Quality

This study examines the air temperature/stream temperature relationship at a geographically diverse set of streams. We evaluate the general temperature relationships (both linear and nonlinear) that apply to these streams, and then examine how changes in stream temperature associated with climate variability or climate warming might affect dissolved oxygen levels. The majority of streams showed an increase in water temperature of about 0.6–0.8°C for every 1°C increase in air temperature, with very few streams displaying a linear 1:1 air/water temperature trend. For most of the streams, a nonlinear model produced a better fit than did a simple linear model. Understanding the relationship between air temperature and water temperature is important if people want to estimate how stream temperatures are likely to respond to anticipated future increases in surface air temperature. Surface water temperature in many streams will likely increase 2 to 3°C as air temperature increases 3 to 5°C. At sites with currently low dissolved oxygen content, an increase in summer stream temperatures could cause the dissolved oxygen levels to fall into a critically low range, threatening the health of many aquatic species.     

Spatial-Dynamic Modeling of Algal Biomass in Lake Erie: Relative Impacts of Dreissenid Mussels and Nutrient Loads

Over the past several decades, reductions in phytoplankton stocks and increased water clarity in Lake Erie have resulted from phosphorus load abatement and the introduction of zebra (Dreissena polymorpha) and quagga mussels (D. bugensis). The relative impacts of these developments and their implications for lake management have remained difficult to delineate. To address this issue, we numerically model the complex biophysical interactions occurring in Lake Erie using a two-dimensional hydrodynamic and water quality model that is extended to include dreissenid mussel and zooplankton algorithms. The model reasonably simulates longitudinal trends in water quality as well as the dynamics of central basin hypoxia. Phosphorus is the limiting nutrient through the euphotic zone and its control decreases the algal growth rate and biomass ( ～ 55–60%). Filter feeding by dreissenid mussels also decreases algal biomass ( ～ 25–30%), simultaneously stimulating increased net algae growth through enhanced algal consumption and subsequent phosphorus recycling. Effective recycling implies that algae stocks are ultimately regulated by external phosphorus loads. Returning phosphorus loads to pre-abatement 1960s levels, in the presence of dreissenid mussels, results in a western basin algae concentration of ～ 0.7?mg?dry?weight?L?1 with a potential for nuisance algae growth.     

Vertical Vibration of Full-Scale Pile—Analytical and Experimental Study

This paper presents the results of vertical vibration tests on two full-scale single piles. The diameter of pile and embedded depth were 0.45 and 22 m, respectively. The soil samples were collected from three boreholes located at the site of investigation and it was explored to a depth up to 30.45 m below the ground level. The vertical vibration tests were conducted for different eccentricities to determine the frequency-amplitude response of the pile. Static load tests were also carried out on two single piles. A simple axisymmetric two-dimensional finite-element model was developed to predict the dynamic pile response. Novak’s plane strain model was also used for the prediction of the dynamic response of single pile. It was observed that the finite-element model predicted the natural frequency and peak displacement amplitude of pile reasonably well. However, prediction of dynamic response of the pile was found unsatisfactory by Novak’s plane strain model. Possible reasons for unsatisfactory performance of Novak’s model were investigated and presented.     

Pool Quality Index: New Method to Define Minimum Flow Requirements of High-Gradient, Low-Order Streams

High-gradient (>1%), low-order streams, characterized by hydraulically nonuniform and heterogeneous channels, represent a problem for the most widely employed habitat-based in-stream flow methods (IFIM-PHABSIM). In a nonuniform high gradient and turbulent channel, as low-order streams usually are, the classical 1D hydraulic modeling, ordinarily employed by in-stream flow models to simulate the changes in fish habitat with the flow, could be questionable, if not completely inapplicable. Channel morphology in fact plays a major role in association with hydraulics in determining the abiotic environments (biotopes) in which aquatic communities live. Particularly, in low-order river systems, different channel form features shape the biological community that can be hosted in a certain biotope. For this reason, the link between morphology and discharge is important when evaluating possible impacts of flow reduction on aquatic organisms. To represent the relationship between hydraulics and channel morphology quantitatively, a hydraulic diversity concept has been adopted. Studies from the literature have revealed that, in a regulated river, a decrease of the environmental variability including hydraulic diversity quite often resulted in a downstream decrease of the macro-invertebrate diversity, which can consequently affect fish biomass. These considerations create the ground for a hydraulic diversity-discharge–based in-stream flow method with the aim to promote high community diversity in a low-order regulated stream. A statistic ordination technique (correspondence analysis) applied to 370 hydraulic sections helped to identify four main morphological units (pools, deep pools, and slow and fast riffles) in terms of hydraulic diversity. In each morphological unit, the hydraulic diversity-discharge relationship was investigated and modeled by means of best-fit regression curves. Combining the hydraulic diversity-discharge curves from different morphological units (pools and riffles), a simplified model of the stream [pool quality index (PQI)] was obtained. This model has been applied to make recommendations for the minimum flow requirements in six low-order river sites. PQI recommendations were consistent with hydrology and other hydrology-based in-stream flow methodologies. Finally, a multiple regression model indicated that in 12 low-order stream sites a good deal of the variability of macro-invertebrate diversity is explained by the availability of hydraulic environments modeled by means of PQI curves. In conclusion, given the encouraging cues about the ecological meaning of PQI and the possibility to overcome difficulties typically encountered by other methods in the low-order river modeling, PQI can be considered a valid alternative for assessing the in-stream flow needs of low-order streams.     

RiverSpill: A National Application for Drinking Water Protection

RiverSpill is a geographic information system-based software package that calculates time-of-travel and concentration of contaminants in streams and rivers. The purpose of RiverSpill is to serve as a tool for response, planning, and training for the protection of the nation’s surface drinking water from deliberate (homeland security) threats. RiverSpill uses real-time stream flow data, a hydrologically connected stream network, and the locations and populations served by each public, surface drinking water intake. Accidental water contamination events such as spills from transportation infrastructures (highway, railroad, and pipeline), wastewater treatment plants, and hazardous materials storage sites may also be simulated. RiverSpill contains a comprehensive database of potential constituents of concern and their chemical or biological attributes. Spills may be modeled as either instantaneous or continuous events. Times-of-travel and concentration curves calculated with RiverSpill have been compared with those measured in several streams and rivers using dye. The dye measurements have been used to evaluate and calibrate RiverSpill to specific rivers.     

Assessing the Impacts of Nutrient Load Uncertainties on Predicted Truckee River Water Quality

This study examined the effects of uncertain model boundary conditions on dissolved oxygen (DO) predictions for the lower Truckee River, Nevada using an augmented version of the EPA’s Water Quality Analysis Simulation Program Version 5 (WASP5) that included periphyton, or attached algae, in eutrophication kinetics. Uncertainty analyses were performed on selected organic nitrogen (ON) and carbonaceous biochemical oxygen demand boundary conditions using Monte Carlo techniques. The stochastic model was run using boundary concentrations assigned from observed probability distributions. Ranges of simulated values were used to construct confidence intervals, the magnitudes of which indicated the uncertainty associated with model predictions. Uncertainty in agricultural ditch return concentrations had minimal effects on in-stream model predictions, as predicted values of daily minimum and maximum DOs, daily average ON, and periphyton biomass all failed to show significant variability as a result of ditch concentration uncertainty. This result indicates that while ditch return nutrient loads are not trivial, their exact concentrations are not needed to make relatively accurate predictions of in-stream DO. However, uncertainty in the upstream ON boundary did result in significant uncertainty during summer months with regard to in-stream model predictions of ON, periphyton biomass, and DO. The model is clearly more sensitive to changes in this boundary than to changes in agricultural ditch concentrations.     

Equilibrium Model for Cadmium Adsorption by Green Algae in a Batch Reactor

This paper reports the results of a study on the equilibrium behavior of cadmium adsorption by a tropical, indigenous single-cell algal species, identified as Oocystis sp., in a static reactor. An exponential equation, in the form of Ce/C0 = α?exp(βM/C0), was found to be statistically significant in expressing the relationship between the ratio of equilibrium cadmium (Cd) concentration in solution (Ce) to the initial cadmium concentration (C0) and the ratio of algal biomass (M) to initial cadmium concentration (C0) for both living and dead algal biomass. Based on the above equation and the mass balance of cadmium in the system, another two equations were developed and verified by a series of batch experiments. One equation, in the form of x/m = [1?α?exp(βM/C0)]/(M/C0), describes the relationship between the cadmium content per unit algal biomass (x/m) and the ratio M/C0. The other equation takes the form of x/m = β(1?Ce/C0)/ln(Ce/αC0) and describes the relationship between the ratio of equilibrium cadmium concentration to initial cadmium concentration and cadmium content per unit algal biomass. The above models for Cd adsorption were found to be applicable over a pH range of 4.5–10.5 even though it was found that pH affects the Cd adsorption potential significantly.     

Predicting the evaluation of real stimulus objects from abstract evaluation of their attributes: The case of trout streams.

Studied human judgment behavior in 10 employees of Iowa trout hatcheries. In Phase 1 Ss judged hypothetical trout streams varying in quantity of trout and driving time to stream. In Phase 2 Ss judged real Iowa trout streams and estimated the quantity of trout and the driving time for each stream. These estimates were used in multiple regression equations, derived from the data in Phase 1, to predict the ratings of the real streams in Phase 2. Correlations between predicted and observed judgments ranged from .37 (individual S level) to .85 (group level). Results are consistent with empirical work in the number processing and nonexperimental work in geography and other spatially oriented sciences. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Microalgal Biomass for Greenhouse Gas Reductions: Potential for Replacement of Fossil Fuels and Animal Feeds

Microalgal biomass production offers a number of advantages over conventional biomass production, including higher productivities, use of otherwise nonproductive land, reuse and recovery of waste nutrients, use of saline or brackish waters, and reuse of CO2 from power-plant flue gas or similar sources. Microalgal biomass production and utilization offers potential for greenhouse gas (GHG) avoidance by providing biofuel replacement of fossil fuels and carbon-neutral animal feeds. This paper presents an initial analysis of the potential for GHG avoidance using a proposed algal biomass production system coupled to recovery of flue-gas CO2 combined with waste sludge and/or animal manure utilization. A model is constructed around a 50-MW natural gas-fired electrical generation plant operating at 50% capacity as a semibase-load facility. This facility is projected to produce 216 million k?Wh/240-day season while releasing 30.3 million kg-C/season of GHG-CO2. An algal system designed to capture 70% of flue-gas CO2 would produce 42,400 t (dry wt) of algal biomass/season and requires 880 ha of high-rate algal ponds operating at a productivity of 20?g-dry-wt/m2-day. This algal biomass is assumed to be fractionated into 20% extractable algal oil, useful for biodiesel, with the 50% protein content providing animal feed replacement and 30% residual algal biomass digested to produce methane gas, providing gross GHG avoidances of 20, 8.5, and 7.8%, respectively. The total gross GHG avoidance potential of 36.3% results in a net GHG avoidance of 26.3% after accounting for 10% parasitic energy costs. Parasitic energy is required to deliver CO2 to the algal culture and to harvest and process algal biomass and algal products. At CO2 utilization efficiencies predicted to range from 60–80%, net GHG avoidances are estimated to range from 22–30%. To provide nutrients for algal growth and to ensure optimal algae digestion, importation of 53 t/day of waste paper, municipal sludge, or animal manure would be required. This analysis does not address the economics of the processes considered. Rather, the focus is directed at determination of the technical feasibility of applying integrated algal processes for fossil-fuel replacement and power-plant GHG avoidance. The technology discussed remains in early stages of development, with many important technical issues yet to be addressed. Although theoretically promising, successful integration of waste treatment processes with algal recovery of flue-gas CO2 will require pilot-scale trials and field demonstrations to more precisely define the many detailed design requirements.     

Calculation of Bed Changes in Mountain Streams

Simulation of flow and sediment transport in mountain streams is complicated by the presence of high gradients, abrupt changes in geometry, variations in regime of flow, and large roughness elements. Most of the numerical models to predict aggradation and degradation in alluvial channels have been developed for low-gradient rivers. This paper is devoted to the development of a numerical model to calculate bed elevation and grain size distribution changes in mountain streams where the maximum bed material size is in the range of boulders. An attempt is made to validate the model by using observed field data collected upstream from a small retention dam in a Venezuelan stream. After calibration of the sediment transport equation, reasonable agreement is obtained for the variations in the grain size distribution of the bed-surface material. An additional application is presented in the Cocorotico River, a small mountain stream located in the northwest region of Venezuela, which illustrates the adaptability of the model to handle a case of coarsest-bed-material removal from the active channel and to simulate the armoring process.     

BOT Viability Model for Large-Scale Infrastructure Projects

The key to a successful implementation of a build-operate-transfer (BOT) infrastructure project is in-depth analysis of all aspects related to economic, environmental, social, political, legal, and financial feasibility of the project. For these reasons, the analysis of the project feasibility decision needs a technique to include the qualitative decision factors that have a strong impact on the project. This paper aims to introduce a decomposed evaluation model developed to assess the most common significant decision factors that strongly affect the feasibility of BOT projects. The paper describes the viability decision factors that were identified and screened with the assistance of a group of industry experts. This analysis yielded 21 significant factors that would have a certain impact on the feasibility of any BOT project. These factors were classified into three relative categories forming the structure of the suggested project viability model. This model presents a new approach, based on the analytical hierarchy process technique, to evaluate the relationships between decision factors related to project feasibility determination. The new approach has been validated by information obtained from three case studies of BOT projects. The proposed approach to project feasibility evaluation aims to increase the decision maker’s ability to determine the factors contributing the most to the viability to the BOT project at hand.     

It takes two to tango: How parents’ and adolescents’ personalities link to the quality of their mutual relationship.

According to J. Belsky’s (1984) process model of parenting, both adolescents’ and parents’ personality should exert a significant impact on the quality of their mutual relationship. Using multi-informant, symmetric data on the Big Five personality traits and the relationship quality of mothers, fathers, and two adolescent children, the current study set out to test this prediction. Adolescents’ agreeableness and parents’ extraversion emerged as predictors of relationship warmth, whereas parents’ openness emerged as a predictor of low restrictive control. In addition, some gender-specific effects emerged. Overall, parents’ and adolescents’ traits equally predicted the amount of relationship warmth, whereas adolescents’ unique personality more strongly predicted the amount of restrictive control. The predictive power of adolescents’ personality increased with age. Personality characteristics that affected relationship quality were partly shared between parents and their adolescent children. Findings support Belsky’s (1984) notion that both parents’ and children’s personality predict the quality of their mutual relationship, though the relative predictive power of children and parents depends on the type of outcome variable and the age of the children. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Removal of a Volatile Organic Compound in a Hybrid Rotating Drum Biofilter

A hybrid bioreactor, combining an activated sludge process (ASP) and a rotating drum biofilter (RDB), was developed and evaluated for the treatment of volatile organic compounds (VOCs) in waste gas streams. The effects of the influent VOC concentration and the organic loading rate on the VOC removal efficiency and on the pattern of biomass accumulation were investigated. Toluene was used as the model VOC, the flow rate of the waste gas stream was 0.59 L/s, and the empty-bed retention time (EBRT) in the ASP portion was 46 s with an actual retention time of about 2 s. The EBRT in the RDB portion was 38 s based on the drum volume. When the VOC feed concentration increased from 221 to 884 mg toluene/m3 (from 57.2 to 229 ppm), correspondingly the organic loading rate of the hybrid bioreactor increased from 1.58 to 6.32 kg chemical oxygen demand/m3/day (from 0.505 to 2.02kg?toluene/m3/day) based on the drum volume, both the ASP and RDB decreased, and the overall toluene removal efficiency declined from 99.8 to 74.1%. Biomass accumulation at different medium depths became more even when the organic loading rate was increased. Part of the applied VOC was biodegraded by the ASP, which suggests that this hybrid bioreactor could achieve longer runs between medium cleanings and higher VOC removal efficiencies than a single RDB bioreactor without an ASP portion at the same organic loading rate.     

Adaptation reveals multiple levels of representation in auditory stream segregation.

When presented with alternating low and high tones, listeners are more likely to perceive 2 separate streams of tones (“streaming”) than a single coherent stream when the frequency separation (Δ?) between tones is greater and the number of tone presentations is greater (“buildup”). However, the same large-Δ? sequence reduces streaming for subsequent patterns presented after a gap of up to several seconds. Buildup occurs at a level of neural representation with sharp frequency tuning. The authors used adaptation to demonstrate that the contextual effect of prior Δ? arose from a representation with broad frequency tuning, unlike buildup. Separate adaptation did not occur in a representation of Δ? independent of frequency range, suggesting that any frequency-shift detectors undergoing adaptation are also frequency specific. A separate effect of prior perception was observed, dissociating stimulus-related (i.e., Δ?) and perception-related (i.e., 1 stream vs. 2 streams) adaptation. Viewing a visual analogue to auditory streaming had no effect on subsequent perception of streaming, suggesting adaptation in auditory-specific brain circuits. These results, along with previous findings on buildup, suggest that processing in at least 3 levels of auditory neural representation underlies segregation and formation of auditory streams. (PsycINFO Database Record (c) 2010 APA, all rights reserved)