Danny Reible – University of Texas Heidi Blischke - GSI 1 Polydimethyl siloxane 2 Solid Phase Microextraction

 Determine whether exceedances of performance standards from the record of decision and/or comparison criteria of more recent water quality criteria from EPA have occurred at any of the locations sampled. For this objective to be successful, low level detection limits for carcinogenic PAHs are necessary.  Assess concentration gradients between near surface and at depth. For this objective to be successful, samples from discrete intervals within the vertical sediment cap profile are required.  Define trends in interstitial water concentrations that may provide early warning signs of potentially significant contaminant migration through a cap (i.e. migration that may lead to exceedances of performance standards in the near future). For this objective to be successful, detection limits must be sufficiently low to detect PAHs to identify trends.

PAH< surface threshold PAH> deep threshold PAH>thresholds PAH< surface threshold PAH<deep threshold PAH> surface threshold PAH<deep threshold  No Evidence of Cap breakthrough    AWQS noncompliant. No Evidence of Bottom- Up breakthrough Currently Compliant with AWQS AWQS noncompliant. Evidence of Bottom-Up breakthrough

 Average deviation <5%  Average deviation ~12%

 Pros:  Lower detection limits for CPAHs – well below NRWQC  Early warning of increasing concentrations  Cons:  Naphthalenes have higher detection limits  Detection limit function of hydrophobicity Detection Limits in smaller fiber (not used at M&B)

 24 SPME passive samplers were installed:  2 surface water (background) locations  22 sediment cap monitoring locations  After 7 days of exposure, 23 samplers were retrieved:  One sampler was lost (Location 4)

 Target sample depths:  6” below the top of the armoring layer  6” into the sand cap  12” into the sand cap The actual sample depths varied slightly from the target depths.

 Pre deployment  Fiber and sampler cleaning (solvent rinse)  Fiber placement in sampler  Deployment  Via divers except at shore  Difficulty in achieving target depths in armored area  Retrieval after 1 week  Sectioned on site and placed into pre-filled autosampling vial  Shipped back to UT and analyzed directly

 Static Lab Expts  Anacostia River  Slow Equilibrium?  Low cap sorption capacity  Speed Equilibrium?  Tides  Groundwater flow

 Estimation  Performance Reference Compounds  Time Series  Two different size fibers  Puget Sound data shown  7 days  Tidal system but no shoreline  Nonsorbing cap

 PDMS  Fiber-water partition coefficient (error ~ 10%))  Equilibrium  PRC or two size fibers (failed in first application to site)  Experience suggests near equilibrium for low MW PAH but high MW PAH may be underestimated  Maximum underestimation ~factor of 2-3  Site specific kinetic evaluation is recommended or use of thin fibers  Conventional pore water sampling (Henry’s probe)  Poor detection limits (often near criteria)  Poor depth control  Potential for solids resuspension and sampling artifacts  Includes both dissolved and colloidally/particulate bound contaminants

 35% of possible compound detects measured  LPAHs were detected more frequently than other PAHs  Acenapthene and phenanthrene were detected in all samples  Only LPAHs were detected in the two background samples  The three most hydrophobic compounds were not detected in any samples (likely due to low mobility)  Dibenz(a,h)anthracene  Benzo(g,h,i)perylene  Indeno(1,2,3-cd)pyrene

 Near shore vertical concentration profiles are fairly uniform.  Concentrations either stay the same or increase slightly with depth.  Possibly due to mixing caused by tidal fluctuations.

 Off shore vertical concentration profiles display greater gradients than near shore profiles.  Concentrations increase with depth.

 Individual PAH concentrations were compared for Locations 5, 9, 12, and 16.  All concentrations increased at Location 5.  Locations 9 and 16 showed some concentrations increasing and some decreasing  Most concentrations decreased at Location 12.

NRWQC

 Only one exceedance: chrysene at location 5  about 12 inches into the sand portion of the cap  inches below sediment water interface.  µg/L (duplicate µg/L)  Two other detections approached NRWQC at the deepest sample intervals:  Benz(a)anthracene was 80% of the criterion at Location 5  Benz(a)anthracene was 60% of the criterion at Location 16  All other compound concentrations at all other locations and depths were well below the NRWQC.

Site 5 ~100 times higher than adjacent site (local contamination)

 35% of possible compound detections  compared to less than 10% in conventional approaches  50%+ in preceding years suggesting general downward trend  LPAHs detected more frequently than LPAHs  No comparison criteria exceeded in inter-armoring or 6 inches into sand cap  One cPAH (chrysene) exceeded at 12 inches into sand cap at Location 5  Few increases noted at 12 inches into sand cap in 2010 samples relative to 2009 – will get trend data in 5-year sampling events for early warning Sediment cap is protective of surface water and functioning as designed

 SPME  Detection limits << criteria  More detections from which to draw conclusions  Higher spatial resolution (no dilution by withdrawing excessing water volume)  Eliminates particulate and colloidal artifacts  Minimal sample processing  1 day placement, 1 day retrieval vs 1 week conventional sampling requirement  More biologically relevant indicator