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Project Specific Aims :

Impact of groundwater-surface water dynamics on in situ remediation efficacy and bioavailability of NAPL contaminants PIs: Michael Unger, Aaron Beck Virginia Institute of Marine Science, College of William & Mary, Gloucester Point, VA

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Project Specific Aims :

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  1. Impact of groundwater-surface water dynamics on in situ remediation efficacy and bioavailability of NAPL contaminants PIs: Michael Unger, Aaron Beck Virginia Institute of Marine Science, College of William & Mary, Gloucester Point, VA Collaborator/RTC: Josef Rieger, The Elizabeth River Project, Portsmouth, VA • Project SpecificAims: • Quantify non-equilibrium dissolution and sorption effects on PAH flux and concentration due to porewater advection dynamics • Determine the impact of seawater intrusion on DNAPL mobility at contaminated coastal sites • Develop a noveltracermethodformeasuringgroundwateradvectionandcontaminantflux • Validate mechanisms determined in laboratory experiments at two contaminated field sites undergoing in situ remediation in the Elizabeth River, VA

  2. Experimental design: Coupledlaboratory and fieldapproach • Laboratory experiments: • Bench-scale column studies to evaluate mechanisms controlling sorption and dissolution mediated PAH flux (flow rate and oscillating flow, PAH compound properties, sediment properties) • Column studies to examine salinity-enhanced NAPL mobility during seawater intrusion in coastal aquifers • Batch reactor experiments to demonstrate advection-driven radionuclide disequilibrium and develop field methods for PAH flux measurement • In situ experiments at two remediation sites: • Measurement of PAH flux and apparent bioavailability (direct and tracer-estimated) • Evaluation of temporal and geochemical controls on NAPL and PAH mobility at site remediated by in situ capping • Evaluation of natural attenuation of PAH contamination along groundwater flowpath in shallow coastal aquifer

  3. Study Sites: Contaminated with PAH and DNAPL from Historical Creosote Facilities in the Southern Branch of the Elizabeth River, VA N Elizabeth River Chesapeake Bay Atlantic Wood Industries Superfund Site Contact: Randy Sturgeon, EPA Money Point ERP Sediment Remediation Site Contact: Joe Rieger, ERP • Sites contain a wide range of PAH contamination and various stages of ongoing sediment remediation • Some areas contain DNAPL on surface post-remediation (dredging & capping) • Methods are needed to better understand and predict DNAPL and PAH transport at sediment remediation sites to assure long-term success

  4. Background: In situ remediation – In-situ Capping • Armoringagainstresuspension • Physicalisolationofcontaminatedsediments • Resistance totransportprocesses EPA, 2005 • Cap materialsareusuallycoarseandpermeable —methodonlyused at siteswithlowgroundwaterflow • In situ remediation at projectstudysitesincludesdredgingofthemostcontaminatedsediments, coupledwith in situ cappingwithcoarsesandsandgravel

  5. Background: Porewateradvection at subaqueouscontaminatedsites Old paradigm: Groundwaterflowcontrolledbyterrestrialhydraulichead (Darcy flow) New paradigm: Groundwateradvectioncontrolledby a suiteofphysicalforcingmechanisms groundwater • Non-Darcy groundwateradvectionusually 10-100 foldgreaterthancanonicalgroundwaterflowestimates • Flow comprisesbothmeteoricgroundwaterandrecirculatedsurfacewater • Unconventionalgroundwateradvectionisubiquitous in permeable sediments, andusuallydominateschemicaltransportfromsedimentstosurfacewaters • ► Doesthisaffect in situ remediationsuccess? after Ataie-Ashtiani et al., 2001 after Santos et al., 2012

  6. Methods: Antibody Biosensor Technology for PAH Analysis • KinExA Inline Sensor - Fluorescence detection, rapid (minutes), small sample volume (1mL) • PAH selective antibody (Spier et al., 2009, Anal. Biochem.,Spier et al., 2011, Environ. Chem. Tox.) • Sensitive (sub-ppb) • and precise • Antibodies can be selected for various • targets (i.e., 3-5 rings) • A new PAH antibody, 2G8, developed as part of our previous NIEHS-SRP funded work will allow sensitive measurement of a wide range of PAH compounds in environmental pore water samples (Li et al., in preparation). 1 3G10 IC50 values came from analysis of cell culture supernatant, estimated values because of PAH solubility limitations. 210C10 and 4D5 are commercially PAH antibodies, IC50 values used here came from analysis in our lab.

  7. Methods: Pore water sampling and analysis • Real-time analysis can be used to map [PAH] in sediment pore water in the field • Dissolved phase (0.47 μm) pore water samples are collected and analyzed on board and up to 30 samples can be surveyed in 1 day • Small volume samples analyzed on board by biosensor and larger volume samples can be brought back to the lab for GC-MS • Good correlation between biosensor & GC-MS in complex environmental samples

  8. Methods: Naturally-occurringradionuclidetracers of porewateradvection • Uraniumandthoriumradionuclideserieshaveparent-daughterpairswith different solubilitypropertiesthatcanimpart environmental signaturesreflectinggroundwatertransport • Multiple isotopes forsingleelementsprovidetracersaffectedby different time scalemechanisms • Focus forthisprojectis on thorium-radium pairs (4 isotopes) and radium-radon pairs (2 isotopes) Th Ra Ra decay, recoil sand grain Ra advection • Ra andThmeasuredbydelayedcoincidencecounting (RaDeCC) • Radon measuredbyalphadecay (RAD7) sorption decay Ra Th Ra Th < 1 >>> 1

  9. Preliminaryresultsandprogress • Laboratory experimentstovalidateradionuclidetracermodel • Field applicationconsistentwithexpectedeffectofvariation in sedimentpermeability (Beck and Cochran, in prep.) • In situ remediation design based on hydrologicestimatesofgroundwaterflow: • Medium Flow = 0.3 cm/y (usedforsite design) High Flow = 3300 cm/y • Preliminary total advectionestimatebyradionuclidetracer = 4400 – 15000 cm/y • PAH flux via advection-facilitatedtransportis 104-fold greaterthanpredictedby Darcy flow, andexposure/bioavailabilitytotheoverlyingecosystemequallyenhanced Pore water concentrations alone do not predict bioavailability, chemical flux measurements are needed to predict exposure in the water column (Unger et al., in preparation)

  10. Research TranslationCoordinating our NIEHS-SRP research with study site remediation goals Project design aligned with ongoing remediation work at two sites in Elizabeth River, VA Money Point – Site managers Joe Rieger (ERP-RTC) and Dave Koubsky (ERP). Meeting to discuss remediation goals and timing at Money Point (01/2015, Portsmouth, VA). VIMS to present NIEHS-SRP research plan at remediation plan review meeting (February 16-18) to coordinate sampling with remediation data needs. Atlantic Wood Industries - Randy Sturgeon (EPA Site manager), Marc Gutterman (USACE), Andrea Henry (USACE) and Rob Pruhs (USACE). VIMS NIEHS-SRP research sampling coordinated with Superfund site remediation monitoring. • The specific aims of this project are designed to help us understand: • How porewater–surface water dynamics and seawater intrusion control PAH mobility, bioavailability, and risk for human exposure • How unconventional groundwater advection processes at subaqueous contaminated sites affect in situ remediation success, and ways to optimize in future situ cap design and performance monitoring • Outcomes of this project for remediation planning and site management include: • Development of new tools to measure surface water/ground water exchange and effect on pollutant (PAH) flux at contaminated sediment sites • Guidance for using site-specific flow characteristics to help design successful long-term remediation strategies

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