Solid-Phase Microextraction Measurement of Parent and Alkyl Polycyclic Aromatic Hydrocarbons in Milliliter Sediment Pore Water Samples and Determination of K_DOC Values

Abstract

The U.S. Environmental Protection Agency (EPA) narcosis model for benthic organisms in polycyclic aromatic hydrocarbon (PAH) contaminated sediments requires the measurement of 18 parent PAHs and 16 groups of alkyl PAHs ("34" PAHs) in pore water with desired detection limits as low as nanograms per liter. Solid-phase microextraction (SPME) with gas chromatographic/mass spectrometric (GC/ MS) analysis can achieve such detection limits in small water samples, which greatly reduces the quantity of sediment pore water that has to be collected, shipped, stored, and prepared for analysis. Four sediments that ranged from urban background levels (50 mg/kg total "34" PAHs) to highly contaminated (10 000 mg/kg total PAHs) were used to develop SPME methodology for the "34" PAH determinations with only 1.5 mL of pore water per analysis. Pore water was obtained by centrifuging the wet sediment, and alum flocculation was used to remove colloids. Quantitative calibration was simplified by adding 15 two- to six-ring perdeuterated PAHs as internal standards to the water calibration standards and the pore water samples. Response factors for SPME followed by GC/MS were measured for 22 alkyl PAHs compared to their parent PAHs and used to calibrate for the 18 groups of alkyl PAHs. Dissolved organic carbon (DOC) ranging from 4 to 27 mg/L had no measurable effect on the freely dissolved concentrations of two- and three-ring PAHs. In contrast, 5-80% of the total dissolved four- to six-ring PAHs were associated with the DOC rather than being freely dissolved, corresponding to DOC/water partitioning coefficients (K(DOC)) with log K(DOC) values ranging from 4.1 (for fluoranthene) to 5.6 (for benzo[ghi]perylene). However, DOC-associated versus freely dissolved PAHs had no significant effect on the total "34" PAH concentrations or the sum of the "toxic units" (calculated bythe EPA protocol), since virtually all (86-99%) of the dissolved PAH concentrations and toxic units were contributed by two- and three-ring PAHs.

Polycyclic Aromatic Hydrocarbons Degradation Techniques: A Review

“…Ter-Laak, Agbo, Barendregt, and Hermens (2006) examined the use of solid-phase extraction (SPE) in measuring freely dissolved concentrations of PAHs in soil pore water. Some researchers have suggested that solid-phase microextraction (SPME) with gas chromatographic/mass spectrometric (GC/MS) analysis can achieve detection limit as low as nanograms per litre of PAHs and alkyl PAHs in sediment pore water (Hawthorne, Grabanski, Miller, & Kreitinge, 2005). In soil samples, high resolution gas chromatography-mass spectrometry (HRGC-MS) and liquid chromatography-fluorescence detection (LC-FD) have been applied successfully in measuring the final concentrations of PAHs (Berset, Ejem, Holzer, & Lischer, 1999).…”

Demonstration and Evaluation of Solid Phase Microextraction for the Assessment of Bioavailability and Contaminant Mobility

“…These effects complicate the analysis of porewater concentrations even in carefully controlled laboratory studies such as those conducted by Lu et al (2003 2 and 2004 3 ) and make practical routine determination of porewater concentrations exceedingly difficult. Hawthorne et al (2005) 9 demonstrated an approach for the measurement of porewater concentration requiring only a small water volume under controlled laboratory conditions as long as the colloidal particles and associated contaminants could be separated from the sample. This method employs polydimethylsiloxane (PDMS) to extract and concentrate the sample (ex-situ, i.e.…”

“…in whole sediments) solid phase microextraction (SPME) technique. The use of SPME has also been employed in laboratory evaluations of porewater concentrations in whole sediments, including by Meyer et al (2000) 10 , Conder et al (2003) 11 , and Hawthorne et al (2005) 9 . The focus herein is primarily to evaluate the applicability of the approach to in-sediment (i.e.…”

Characterization of Contaminant Migration Potential Through In-Place Sediment Caps

“…Further details on the SPME method can be found in Hawthorne et al, 2005 (also in US EPA Method 8272). To verify the SPME technique used for sediment batch experiments, liquid-liquid extraction with hexane was also performed.…”