Reactive transport modelling of biogeochemical processes and carbon isotope geochemistry inside a landfill leachate plume
article
The biogeochemical processes governing leachate attenuation inside a landfill leachate plume (Banisveld, the Netherlands) were revealed and quantified using the 1D reactive transport model PHREEQC-2. Biodegradation of dissolved organic carbon (DOC) was simulated assuming first-order oxidation of two DOC fractions with different reactivity, and was coupled to reductive dissolution of iron oxide. The following secondary geochemical processes were required in the model to match observations: kinetic precipitation of calcite and siderite, cation exchange, proton buffering and degassing. Rate constants for DOC oxidation and carbonate mineral precipitation were determined, and other model parameters were optimized using the nonlinear optimization program PEST by means of matching hydrochemical observations closely (pH, DIC, DOC, Na, K, Ca, Mg, NH4, Fe(II), SO4, Cl, CH4, saturation index of calcite and siderite). The modelling demonstrated the relevance and impact of various secondary geochemical processes on leachate plume evolution. Concomitant precipitation of siderite masked the act of iron reduction. Cation exchange resulted in release of Fe(II) from the pristine anaerobic aquifer to the leachate. Degassing, triggered by elevated CO2 pressures caused by carbonate precipitation and proton buffering at the front of the plume, explained the observed downstream decrease in methane concentration. Simulation of the carbon isotope geochemistry independently supported the proposed reaction network. © 2003 Elsevier B.V. All rights reserved. Chemicals / CAS: calcium carbonate, 13397-26-7, 13701-58-1, 14791-73-2, 471-34-1; calcium, 7440-70-2; carbon, 7440-44-0; carbonic acid, 3812-32-6, 463-79-6; chlorine, 13981-72-1, 7782-50-5; iron oxide, 1332-37-2; iron, 14093-02-8, 53858-86-9, 7439-89-6; magnesium, 7439-95-4; methane, 74-82-8; potassium, 7440-09-7; proton, 12408-02-5, 12586-59-3; sodium, 7440-23-5; Carbon Isotopes; Cations; Water Pollutants, Chemical
Topics
13CBiogeochemistryLandfillModellingNatural attenuationReactive transportAttenuationBiodegradationCalciteCarbonComputer simulationDegassingDissolutionGeochemistryIsotopesMethaneOrganic compoundsPrecipitation (chemical)ProtonsThermal plumesBiogeochemical processesDissolved organic carbon (DOC)Landfill leachate plumesReactive transportLeachate treatmentcalciumcalcium carbonatecarboncarbonic acidchlorineironiron oxidemagnesiummethaneorganic carbonpotassiumprotonsodiumbiogeochemistrycarbon isotopelandfillleachatenatural attenuationpollutant transportreactive transportaquiferarticlebiodegradationbiogeochemistrygeochemistryion exchangelandfillleachingmodeloxidationplumeprecipitationpriority journalreductionCarbon IsotopesCationsComputer SimulationModels, TheoreticalNetherlandsOxidation-ReductionPrecipitationRefuse DisposalWater MovementsWater Pollutants, ChemicalBeneluxEurasiaEuropeNetherlandsWestern Europe
TNO Identifier
237804
ISSN
01697722
Source
Journal of Contaminant Hydrology, 70(3-4), pp. 249-269.
Pages
249-269
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