Formatted Title:

Biomimetic Extraction with Polydimethylsiloxane as an Indicator of Toxicity of Petroleum Mixtures before and after Sediment Remediation

Background/Objectives:

Assessment of total petroleum hydrocarbons from contaminated sites demands routine and reliable measurements at low levels. This includes post-remedy, which are often challenged by limited detection due to high efficiency of amendments used. Further, typical analyses often focus on single constituents. Biomimetic extraction (BE) with polydimethylsiloxane (PDMS) passive sampling has been demonstrated as a fast and sensitive method for determining toxicity of unresolved hydrocarbon mixtures in aquatic systems^(1,2). The method measures a pooled response of the bioavailable fraction of petroleum hydrocarbons (total area), which is translated to molar concentration on the PDMS sampler. The molar concentration is then related to toxic thresholds in target lipid of aquatic organisms. The primary objective of this study was to evaluate the effect of activated carbon (AC) on reducing bioavailability of unresolved hydrocarbons in different sediments. The experimental setup was designed to establish parameters that would allow prediction of BE changes in environmental settings following remedial efforts.

Approach/Activities:

Three sediments with a variety of petroleum hydrocarbon compositions were evaluated with a non-depletive BE approach using standard 30 µm PDMS fibers. The assessment was conducted for sediments with and without AC addition. Sediments were also evaluated with a depletive BE approach for determination of total extractable BE using PDMS coated sheets. Solvent extracts were analyzed using large volume injection GC-FID. The effectiveness of AC was then assessed by calculating percent reductions and was further used for calculating apparent sorption coefficients for AC (K_AC).

Results/Lessons Learned:

The highest total BE was determined for IHC sediment (225 µmol/g), whereas the lowest for LDW (7.8 µmol/g) with 6 µm PDMS sheets. The non-depletive and depletive BE data were used to estimate BE partition coefficients K_BE, L/kg. The AC yielded BE reductions ranging from 25 to 92% depending on the sediment and AC dosage used, corresponding to K_AC of 48800 to 396000 L/kg. The effectiveness of AC was inversely correlated with the amount of organic matter and the presence of NAPL in the sediments. The collected data were used to build an estimate of the long-term toxicity of sediments under natural recovery, in situ capping with AC amendment and in situ treatment with AC. The CapSIM model was used to predict BE in the surficial sediments over time in each scenario. Results and parameter values provide a basis for predicting BE as a toxicity indicator over time for in situ treatment and capping in addition to routine screening of sediments at contaminated sites to support design of treatment remedies.

Letinski et al., 2014 Marine Pollution Bull 86:247-282.
Redman et al., 2018 Chemosphere 199: 585-594.

Thomas Parkerton

Affiliation

Refine Results

(Group 2, Poster Board #38) Biomimetic Extraction with Polydimethylsiloxane as an Indicator of Toxicity of Petroleum Mixtures before and after Sediment Remediation