CATCHMENT SCALE MONITORING AND MODELLING OF PHOSPHORUS USING FLOW INJECTION ANALYSIS AND AN EXPORT COEFFICIENT MODEL

Acquiring high quality in situ analytical data with good temporal resolution is required for developing models of phosphorus transport and biogeochemical behaviour. Chapter One describes the behaviour of phosphorus in the aquatic environment, its sources, its role in the eutrophication process and legislation to control its release into aquatic systems. It also summarises analytical techniques for the determination of phosphorus in natural waters. An examination of the hypothesis that the export coefficient modelling approach can be used to predict phosphorus loading in the River Frome catchment, Dorset on an armual and seasonal (monthly) basis is presented in Chapter Two. The model predicted an annual (1998) phosphorus load of 25,605 kg yr'\ compared with an observed (measured) value of 23,400 kg yr'V Monthly loads agreed well with monthly observed values except during months of variable discharge. Chapter Three describes a study on the comparison of sample storage protocols for the determination of total oxidised nitrogen (TON) and filterable reactive phosphorus (FRP) in the River Frome and Tamar Estuary. The results showed that optimum storage conditions were highly matrix dependent, with significant differences in measured FRP concentration over time between the River Frome and Tamar Estuary (due to different calcium concentrations) and between samples of different salinities (due to different bacterial populations). Chapter Four describes the development and deployment of a portable flow injection (FI) monitor for phosphorus determination in the River Frome. The automated monitor, incorporating solenoid micropumps and switching valves, a miniature CCD spectrometer, a graphical programming environment and a tangential flow filtration unit, achieved a detection limit of 0.67 pM and was able to monitor at high temporal resolution (every 30 min). Chapter Five examines historical water quality indicators and data fi-om recent shortterm, high temporal monitoring campaigns using the FI monitor in order to identify the key factors affecting phosphorus concentrations in the River Frome. Results showed the importance of catchment geology (chalk-based) and hydrological conditions in relation to other physico-chemical parameters in controlling phosphorus behaviour.Centre for Ecology & Hydrology, Dorset, U

Modeling the Oxidative Metabolic Breakdown of Ethanol and Its Effects on the Cardiovascular System

Chronic ethanol consumption contributes to the global prevalence’s of cardiovascular disease by mechanisms involving an inflammatory response and consequent lipid peroxidation. Cytochrome p450 is a part of the microsomal ethanol oxidizing system (MEOS) and can utilize iron complexes and the reductant NADPH to catalyze the breakdown of acute/chronic ethanol consumption. However, efficacy of MEOS to prevent cardiovascular burden induced by ethanol consumption is not clear. PURPOSE: To demonstrate the response of the cardiovascular system in response to the oxidative metabolic breakdown of ethanol via MEOS. METHODS: An extensive literature search provided data to develop a mechanistic model of the metabolism of chronic and low volume ethanol consumption. Artificial neural networks were utilized to construct a colormap of correlation coefficients between ethanol consumption and markers of inflammation and lipid peroxidation. RESULTS: The model showed that 3.5 standard drinks (50g of alcohol) were sufficient to increased levels of malondialdehyde and C-Reactive Protein. CONCLUSION: These data indicate that ethanol consumption to a level equal to or above 3.5 standard drinks is sufficient to induce cardiovascular stress through increased reactive oxygen species and consequent inflammation, lipid peroxidation, and oxidative stress. The results also provide the foundation for targeted preventative or therapeutic interventions to enhance MEOS that may reduce the cardiovascular burden of alcohol consumption

Design and fabrication of chemically robust three-dimensional microfluidic valves

A current problem in microfluidics is that poly(dimethylsiloxane) (PDMS), used to fabricate many microfluidic devices, is not compatible with most organic solvents. Fluorinated compounds are more chemically robust than PDMS but, historically, it has been nearly impossible to construct valves out of them by multilayer soft lithography (MSL) due to the difficulty of bonding layers made of non-stick fluoropolymers necessary to create traditional microfluidic valves. With our new three-dimensional (3D) valve design we can fabricate microfluidic devices from fluorinated compounds in a single monolithic layer that is resistant to most organic solvents with minimal swelling. This paper describes the design and development of 3D microfluidic valves by molding of a perfluoropolyether, termed Sifel, onto printed wax molds. The fabrication of Sifel-based microfluidic devices using this technique has great potential in chemical synthesis and analysis

High temporal resolution field monitoring of phosphate in the River Frome using flow injection with diode array detection

Abstract The design and deployment of an in situ flow injection (FI) monitor for high temporal resolution monitoring of phosphate in the River Frome, Dorset, UK, is described. The monitor incorporates solenoid, self-priming micropumps for propulsion, solenoid-operated switching valves for controlling the fluidics and a miniature CCD spectrometer for full spectrum (200-1000 nm) acquisition and operates in a graphical programming environment. A tangential filtration unit is attached to the sample inlet line to remove suspended particulate matter and prevent blockage of the micropumps and valves. Detection (at 710 nm) is based on molybdenum blue chemistry with tin(II) chloride reduction. The detection limit is 0.67 M PO 4 and the linear range can be adjusted by using different wavelengths for detection. Pump noise is eliminated by subtraction of the signal at a non-absorbing wavelength (447 nm). Data from an intensive (sample every 30 min) field trial on the River Frome performed in October 2000 are presented, and the implications of the data for refining an export coefficient model for phosphorus from the catchment are discussed

Evolving neural network optimization of cholesteryl ester separation by reversed-phase HPLC

Cholesteryl esters have antimicrobial activity and likely contribute to the innate immunity system. Improved separation techniques are needed to characterize these compounds. In this study, optimization of the reversed-phase high-performance liquid chromatography separation of six analyte standards (four cholesteryl esters plus cholesterol and tri-palmitin) was accomplished by modeling with an artificial neural network–genetic algorithm (ANN-GA) approach. A fractional factorial design was employed to examine the significance of four experimental factors: organic component in the mobile phase (ethanol and methanol), column temperature, and flow rate. Three separation parameters were then merged into geometric means using Derringer’s desirability function and used as input sources for model training and testing. The use of genetic operators proved valuable for the determination of an effective neural network structure. Implementation of the optimized method resulted in complete separation of all six analytes, including the resolution of two previously co-eluting peaks. Model validation was performed with experimental responses in good agreement with model-predicted responses. Improved separation was also realized in a complex biological fluid, human milk. Thus, the first known use of ANN-GA modeling for improving the chromatographic separation of cholesteryl esters in biological fluids is presented and will likely prove valuable for future investigators involved in studying complex biological samples

Evaluation of phosphorus concentrations in relation to annual and seasonal physico-chemical water quality parameters in a UK chalk stream

The aim of this paper was to examine historical physico-chemical water quality parameters (1990�1997) in the River Frome, East Stoke (NGR SY867868), in order to show both annual and seasonal (monthly) trends. EpCO2 (defined as the partial pressure of CO2 in natural water divided by the equilibrium partial pressure of CO2) levels ranged from mean values of 6.32±0.41 in spring/summer to 7.86±1.17 in autumn/winter. A decreasing trend in mean annual EpCO2 was also observed, with a high of 9.61 in 1990 and a low of 5.22 in 1996. The variations were attributed to changes in pH, which showed an inverse relationship with river discharge (r2=0.47). Both pH and EpCO2 levels were strongly linked to biological activity with increases caused by primary productivity. Filterable reactive phosphorus (FRP) and total phosphorus (TP) concentrations correlated with river discharge. The results showed that the majority of the phosphorus load was transported during storm events, which agrees with results from an export coefficient model predicting phosphorus loading in the Frome catchment. Recent River Frome monitoring campaigns using an in situ flow-injection (FI)-based monitor were in agreement with phosphorus concentration and related physico-chemical trends observed during historical sampling and laboratory analysis.<br/

Phosphorus loading in the Frome catchment, UK

This paper describes the results of an export coefficient modeling approach to predict total phosphorus (TP) loading in the Frome catchment, Dorset, UK from point and diffuse sources on a seasonal (monthly) basis in 1998 and on an annual basis for 1990�1998. The model predicted an annual TP load of 25605 kg yr-1, compared with an observed (measured) value of 23400 kg yr-1. Monthly loads calculated using the export coefficient model agreed well with monthly observed values except in months of variable discharge, when observed values were low, probably due to infrequent, and therefore unrepresentative, sampling. Comparison between filterable reactive phosphorus (FRP) and TP concentrations observed in the period 1990�1997 showed that trends in FRP could be estimated from trends in TP. A sensitivity analysis (varying individual export coefficients by ±10%) showed that sewage treatment works (STWs) (3.5%), tilled land (2.7%), meadow�verge�seminatural (1.0%), and mown and grazed turf (0.6%) had the most significant effect (percent difference from base contribution) on model prediction. The model was also used to estimate the effect of phosphorus stripping at STWs in order to comply with a pending change in the European Union wastewater directive. Theoretical reduction of TP from the largest STW in the catchment gave a predicted reduction in TP loading of 2174 kg yr-1. This illustrates the value of this seasonal export coefficient model as a practical management tool. <br/

Biologically driven neural platform invoking parallel electrophoretic separation and urinary metabolite screening

This work reveals a computational framework for parallel electrophoretic separation of complex biological macromolecules and model urinary metabolites. More specifically, the implementation of a particle swarm optimization (PSO) algorithm on a neural network platform for multiparameter optimization of multiplexed 24-capillary electrophoresis technology with UV detection is highlighted. Two experimental systems were examined: (1) separation of purified rabbit metallothioneins and (2) separation of model toluene urinary metabolites and selected organic acids. Results proved superior to the use of neural networks employing standard back propagation when examining training error, fitting response, and predictive abilities. Simulation runs were obtained as a result of metaheuristic examination of the global search space with experimental responses in good agreement with predicted values. Full separation of selected analytes was realized after employing optimal model conditions. This framework provides guidance for the application of metaheuristic computational tools to aid in future studies involving parallel chemical separation and screening. Adaptable pseudo-code is provided to enable users of varied software packages and modeling framework to implement the PSO algorithm for their desired use