Fate-and-Transport-of-Ethanol-in-the-Environment：在环境中的命运和运输的乙醇ppt课件.ppt

Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,*,*,Fate and Transport of Ethanol in the Environment,Presented to the Environmental Protection Agency Blue Ribbon Panel,Presented by,Michael C.Kavanaugh,Ph.D.,P.E.,Andrew Stocking,May 24,1999,Outline,Properties,Fate and Transport,Biological Field/Lab Studies,Impact on BTEX Plume Lengths,Remediation and Treatment,Conclusions,Research Needs,Objectives,The fate and transport of ethanol in the environment is well understood;however,the interactions between ethanol and other gasoline constituents and their resulting fate and transport is not well understood.,Our objectives are to assess the likely fate and transport of ethanol in the soil and water within a range of geochemical conditions.,Production and History of Use,94%of Ethanol produced from corn fermentation,Ethanol must be denatured prior to use,addition of 2%to 5%of approved denaturant,In 1998,15%of all oxygenated gasoline contained ethanol,5.4%by volume ethanol corresponds to 2%by weight oxygen,Ethanol commonly added up to 10%by volume,Oil companies in Brazil use 24%ethanol by volume,Key Questions,What is the fate of constituents of concern in gasoline following an ethanol release to the subsurface?,What is the fate of ethanol following release to surface water?,What is the impact of gasoline releases with ethanol on existing plumes-BTEX or MTBE?,Comparative Properties of Ethanoland Other Gasoline Additives,Significance of Properties,Properties,Aqueous Solubility,Vapor Pressure,Henrys Constant,Octanol/Water Partition Coefficient,Biodegradability,Reactivity,Structure,Examples of Significance,Rate of migration;bioavailability,Volatilization from LNAPL;Soil vapor extraction,Volatilization from water;Air stripping,Rate of migration;Adsorption Potential,Plume size;in-situ biodegradation,Oxidation potential,Biodegradability;oxidation potential,Aqueous Solubility,Raoults Law(holds for low contaminant concentrations),C,gw,=Sol,theoretical,X,gasoline,C,MTBE,gw,(48,000 ppm)(11%)=5,280 ppm,C,benzene,gw,(1,750 ppm)(1%)=17.5 ppm,Does not hold for miscible contaminants(e.g.ethanol,TBA,methanol),Actual source area ethanol concentrations higher than MTBE.i.e.,10,000 mg/L),Fast dissolution,Lower sorption,Potential cosolvency effect,Theoretical Solubility mg/L,Vapor Pressure(mm Hg),As pure ethanol-low vapor pressure,In hydrocarbon plume-non-ideal behavior-highly polar,Much higher effective vapor pressure,Reid vapor pressure(18 psi)greater than MTBE(8 psi)or benzene(2 psi),greater tendency to volatilize,Vapor Pressure mm Hg at 25,o,C,Henrys Law Constant(H),H(atm-m,3,)/(mole)/RT =H-,R=0.08206(atm-m,3,)/(mole-K);T=,o,K=,o,C+273,Ethanol Henrys Constant=0.000252,Henrys Constant 10,000 ppm will increase BTEX solubility,Ethanol 10%in gasoline with 5-fold dilution factor results in groundwater concentrations of 20,000 ppm,Conceptual Model of BTEX Plume Elongation,Vadose Zone,Biodegradation of Ethanol,Limited field studies to date,Expected to rapidly biodegrade in groundwater and surface water,Toxic at high concentrations(100,000 ppm),One known methanol field study,Borden Field Site:half-life=40 days,Numerous microcosm laboratory studies of ethanol,Corseuil shows 80-100 mg/L degrading rapidly,Aerobically-5 days,Anaerobically-12 to 25 days,Summary of Literature Biodegradation Rates,1)Estimated from Corseuil et.al.,1997;2)Aronson et.al.,1997;3)USGS,1998;4)Barker et.al.,1998;,*Determined in a laboratory;,*Estimated from first principles.,Ethanol Effect on BTEX Degradation,Corseuil et al.,1998,Ethanol retarded BTEX aerobic biodegradation in laboratory;rapidly reduced oxygen concentrations,No benzene degradation observed under anaerobic conditions,Ethanol slowed toluene anaerobic degradation,Hunt et al.,1997,Degradation of toluene completely inhibited until all the ethanol was degraded(aquifer microcosm),Barker et al.,1990,Methanol inhibits degradation of BTEX due to initial toxic levels;later due to depletion of electron acceptors,Conceptual Model of BTEX Plume Elongation,Conceptual Model,Modeling Assumptions,Modeled the degradation of benzene with and without ethanol present,Alkane interactions and degradation were not considered,Source area ethanol concentrations were assumed to be 4000 ppm(assumes 20-fold dilution),Modeling Assumptions(cont.),2-D Domenico Analytical Model includes:,first order decay rate,advection,retardation,dispersion,Sensitivity Analysis of subsurface variables,groundwater velocity:0.004-0.4 feet/day,organic carbon content:0.01-0.005,Results,Typical BTEX plumes in California and Texas travel no further than 300 ft from source,Addition of ethanol to gasoline may extend BTEX plumes by 25%to 40%,Higher source area ethanol concentrations would suggest a larger effect,Historical Benzene Plume Lengths,Source:TX-Mace and Choi,1998,CA-LLNL,1995;LLNL,1998,Plume Length(ft),Cumulative Percentile,?,?,Technical Options for Remediation and Treatment of Ethano。