quantifying ecosystem services provided by hyporheic exchange

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Stanley B. Grant and Morvarid Azizian Civil and Environmental Engineering, University of California Irvine & Infrastructure Engineering, University of Melbourne. Objectives. Present an analytical model of benthic exchange and reaction Pumping of solute across bedforms - PowerPoint PPT Presentation

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Accessing the Efficiency of Constructed Wetlands by Analyzing Water Quality Parameters

QUANTIFYING ECOSYSTEM SERVICES PROVIDED BY HYPORHEIC EXCHANGE

Stanley B. Grant and Morvarid AzizianCivil and Environmental Engineering, University of California Irvine & Infrastructure Engineering, University of Melbourne

ObjectivesPresent an analytical model of benthic exchange and reactionPumping of solute across bedformsAdvection-dominated mass transportFirst-order reaction in sedimentEvaluate modelCompare to numerical solutionDerive solution for solute flux into the sedimentApplicationCorrelations for mass transfer coefficientTrade-off between volume of water processed in the sediment and extent of reaction

streamline geometry

pressure headvelocity fieldElliot and Brooks Velocity Model

normalize by wave number

variable definitions

predicted concentration field

predicted concentration field (analytical)Solution approach (neglect dispersion & diffusion)Numerical simulation results

variable definitions

flux into sediment bedmass-transfer-limited flux

Numerical approach (governing equations)

variable definitions

advection/dispersion equationdispersion tensorpredicted concentration field (numerical)Numerical and analytical solutions near-identicalNumerical simulation carried out with COMSOLMechanical dispersion & molecular diff. negligibleDirichlet b.c. at surface causes gradient artifactApplicationsAnalytical model supports use of mass transfer coefficient

Flux ~ conc. diff. in upwelling & downwelling zonesMass transfer coefficient = downwelling velocityEcosystem servicesFlux into sediment = mass removal in sedimentMass removal in sediment = ecosystem service (N, P, C processing; CEC removal)Model identifies trade-off between volume of water processed by hyporheic zone and extent of reaction in sediment (hard to optimize both)AcknowledgementsFunding by the National Science Foundation Partnerships for International Research and Education (PIRE) Award No. OISE-1243543. A huge THANK YOU to Keith Stolzenbach (UCLA), Megan Rippy (UCI), Mike Stewardson (UoM), and Perran Cook (Monash Univ).

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