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 Specific Aims: 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 novel tracer method for measuring groundwater advection and contaminant flux Validate mechanisms determined in laboratory experiments at two contaminated field sites undergoing in situ remediation in the Elizabeth River, VA

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 Experimental design: Coupled laboratory and field approach

Chesapeake Bay Atlantic Wood Industries Superfund Site Contact: Randy Sturgeon, EPA Money Point ERP Sediment Remediation Site Contact: Joe Rieger, ERP Study Sites: Contaminated with PAH and DNAPL from Historical Creosote Facilities in the Southern Branch of the Elizabeth River, VA 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 Elizabeth River

Background: In situ remediation – In-situ Capping 1.Armoring against resuspension 2.Physical isolation of contaminated sediments 3.Resistance to transport processes EPA, 2005 Cap materials are usually coarse and permeable — method only used at sites with low groundwater flow In situ remediation at project study sites includes dredging of the most contaminated sediments, coupled with in situ capping with coarse sands and gravel

groundwater after Ataie-Ashtiani et al., 2001 Background: Porewater advection at subaqueous contaminated sites New paradigm: Groundwater advection controlled by a suite of physical forcing mechanisms after Santos et al., 2012 Old paradigm: Groundwater flow controlled by terrestrial hydraulic head (Darcy flow) Non-Darcy groundwater advection usually fold greater than canonical groundwater flow estimates Flow comprises both meteoric groundwater and recirculated surface water Unconventional groundwater advection is ubiquitous in permeable sediments, and usually dominates chemical transport from sediments to surface waters ► Does this affect in situ remediation success?

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.) Methods: Antibody Biosensor Technology for PAH Analysis Sensitive (sub-ppb) and precise Antibodies can be selected for various targets (i.e., 3-5 rings) Inhibitor 2G83G C10 2 4D5 2 IC 50 nMIC 50 µg/LIC 50 nMIC 50 µg/LIC 50 nMIC 50 µg/LIC 50 nMIC 50 µg/L Benzo(a)pyrene >30000> Chrysene >30000 > Pyrene Phenanthrene Anthracene >30000> C10 and 4D5 are commercially PAH antibodies, IC 50 values used here came from analysis in our lab. 1 3G10 IC 50 values came from analysis of cell culture supernatant, estimated values because of PAH solubility limitations. 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).

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

Methods: Naturally-occurring radionuclide tracers of porewater advection sand grain Th Ra decay, recoil advection sorption Ra Th < 1 Ra Th >>> 1 decay Uranium and thorium radionuclide series have parent-daughter pairs with different solubility properties that can impart environmental signatures reflecting groundwater transport Multiple isotopes for single elements provide tracers affected by different time scale mechanisms Focus for this project is on thorium-radium pairs (4 isotopes) and radium-radon pairs (2 isotopes) Ra and Th measured by delayed coincidence counting (RaDeCC) Radon measured by alpha decay (RAD7)

Preliminary results and progress In situ remediation design based on hydrologic estimates of groundwater flow: Medium Flow = 0.3 cm/y (used for site design) High Flow = 3300 cm/y Preliminary total advection estimate by radionuclide tracer = 4400 – cm/y PAH flux via advection-facilitated transport is fold greater than predicted by Darcy flow, and exposure/bioavailability to the overlying ecosystem equally enhanced Laboratory experiments to validate radionuclide tracer model Field application consistent with expected effect of variation in sediment permeability 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) (Beck and Cochran, in prep.)

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 Research Translation Coordinating 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.