CICEET Progress Report for the period 9/16/05 Through 3/15/06

Project Title: An in situ sediment porewater sampler for organic micropollutants based on solid phase microextraction (SPME) technology
Principal Investigator(s): Keith A. Maruya, Eddy Y. Zeng and Steven M. Bay
Project Start Date: 9/1/05 (anticipated); 11/14/05 (actual)

Figures

Figure 1

Figure 2

Figure 3

Figure 4

Tables

Table 1

Tasks to meet objectives
(1) A theoretical (mathematical) model of SPME porewater sampler performance was generated using mass balance and partitioning theory for hydrophobic organic compounds (HOCs)

(2) A 28 d bioassay was carried out to determine toxic effects, if any, to live benthic invertebrates exposed to prototype samplers in field-collected sediments.

(3) Static bench-scale experiments were performed to compare the equilibrium distribution and kinetics of sorption of model HOCs using different SPME coating thicknesses.

Progress on Tasks
Tasks 1, 2 and 3 were completed and results presented herein.

Difficulties
An agreement for funding (dated November 14, 2005) was received in mid-November of 2005, roughly 75 days after the anticipated project start date (9/1/05). This resulted in delays in procuring necessary project supplies to initiate radiolabled experiments; securing documents to sponsor a visiting (foreign) student from co-PI Zeng’s home institution (in China); and initiating key Year 1 experiments and tasks.

Project Objectives for Next Reporting Period

Objectives
(4) Create a uniformly aged test sediment spiked with project target analytes for sampler calibration and optimization experiments
(5) Validate theoretical model with SPME-sediment microcosm experiments
(6) Select optimum coating thickness(es) and perform calibration experiments for target analytes for these thicknesses

Tasks to Meet Objectives
(4) Procure native and radiolabled HOCs, obtain and process field-collected sediments, spike with target analytes, and equilibrate for a minimum of 60 d
(5) Design and perform spiked sediment column experiments to begin validation of theoretical model generated in Task (1)
(6) Analyze and synthesize data from Task (3) and prepare manuscript; design and perform experiments to calibrate SPME fibers for remainder of target analytes

Work Plan for Next Reporting Period
4) Draft and submit manuscript. Design and initiate static calibration experiments for remainder of target analytes
(5) Procure chemicals, obtain reference field sediments, prepare stock spiking solutions (native and radiolabled analytes), spike and age sediments for > 60 d.
(6) Design and initiate experiments with spiked sediment to determine (a) relationship between C_sed and C_pw,m as determined by the sampler and (b) V_s,min and t_eq using fiber-sediment only systems

Anticipated Success in Meeting Project Objectives
(4) First draft of manuscript completed (2/06). Submission expected 4/06. Initiation of calibration experiments expected 3/06
(5) All chemicals procured (1/06). Sediments spiked (3/06), aging to be completed by 5/06
(6) (a) Initial design completed (1/06). Final design and experiment initiation expected 6/06. (b) Design completion expected 7/06. Experiment initiation expected 9/06

Overall Project Timeline Update
See Table 1

Preliminary Data
Theoretical model of sampler performance (V_s,min and C_pw,m). A theoretical (mathematical) mass balance and HOC partitioning model was generated to evaluate a priori the performance of our SPME porewater sampler. We derived the governing equations to predict the minimum sediment volume (V_s^min) required to achieve non-depletive conditions, and dissolved phase HOC porewater concentrations (C_pw) as functions of HOC- and sediment specific characteristics in a conceptual three compartment system. The resulting model predicted that V_s^min was independent of HOC concentrations both in sediment and porewater, but did vary with hydrophobicity (~ log K_ow), the fraction of sediment porewater (f_pw), and the SPME sorbent volume (V_f) (Figure 1). Moreover, the effects of these parameters were minimized as log K_ow approached 4­5. Model predictions of C_pw, a proxy for SPME-based detection limits in porewater, were inversely proportional to log K_ow (Figure 2), and decreased with increasing sediment volume (V_s) at low V_s values. The model suggested that sediment HOC concentrations required for SPME are also independent of K_ow. The implications of our modeling results are that parts per trillion (ng/L) or lower detection limits are possible, and that relatively small sediment volumes (~ 1 mL) participate in exchange equilibria among sediment, porewater and the SPME fiber. Hence, large sediment HOC reservoirs are not needed to improve the detection sensitivity of SPME-based porewater samplers in situ.

Compatibility of prototype sampler to benthic invertebrates. Live specimens of the annelid Nereis virens and the bivalve Macoma nasuta were exposed in four 5 gal glass aquaria each containing a 5 cm layer of sieved, marine sediments and conditioned, flow-through seawater. Two aquaria each contained sediment and organisms, and sediment/organisms/SPME sampler, with a fifth aquarium serving as a water quality (no organisms or sampler) control. Flow through conditions and water quality was maintained/monitored as prescribed in ASTM/EPA 28 d bioaccumulation assay guidance manuals. Water quality parameters (pH, salinity, DO, temperature and total NH₃) measured on days 1, 5, 12, 19, 22 and 26 remained within acceptable ranges. Survival of M. nasuta after 28 d was high (10 of 10; 100%) for both tanks with SPME samplers; the recovery of N. virens was highly variable among all tanks, however, survival was greatest in the two tanks with SPME samplers. Thus, it was concluded that the present sampler design is compatible with benthic invertebrates, and should not affect their viability in Year 2 lab bioassay experiments, or during Year 3 field deployments.

Effect of coating thickness on PDMS-water partitioning. A static SPME procedure combined with liquid-liquid extraction (LLE) was used to determine the poly(dimethyl)siloxane (PDMS)-water partition coefficients (K_f) for selected polychlorinated biphenyl congeners (PCBs), including PCB 1, 15, 28, 47, 101, 153, 180, 202, 206, and 209. SPME measurement accuracy was validated against the recovery of ¹³C-labeled PCB surrogates. The effects of coating thickness (7, 30, and 100 mm) and sample volume (130 mL and 2 L) on the K_f values were examined experimentally and confirmed with paired t tests. Whereas a dependence of K_f values on coating thickness was found for a few heavily chlorinated congeners (Figure 3), no significant differences in log K_f were found between the two reservoir sample volumes for either the 7-µm and 100-µm coatings. The lone exception to these observations was for PCB 206. Overall, K_f values obtained with 2-L sample containers were consistently higher than those reported in the literature, which is attributable to the selection of appropriate equilibrium times (t_eq) and direct measurements of aqueous analyte concentrations using LLE. Appropriate t_eq values for the target PCBs as a function of coating thickness were also surmised from time series experiments carried out to 30 d (Figure 4).

Dissemination
Publications:
(1) Yang ZY, Zeng EY, Xia H, Wang JZ, Mai BX, Maruya KA. Application of a static solid-phase microextraction procedure combined with liquid-liquid extraction to determine poly(dimethyl)siloxane-water partition coefficients for selected polychlorinated biphenyls. submitted to J Chromatogr A.

Workshops: None

Conferences:
(1) Maruya KA, Zeng EY, Noblet JA, Peng J, Schiff KC. Passive in situ measurement of organic pollutants for the coastal environment using solid phase microextraction (SPME) technology. 40th Western Regional Meeting American Chemical Society, Jan. 22-25, 2006, Anaheim/Orange, CA.

Manuals, Protocols: None

Outreach Activities:
(1) Invited seminar “Solid phase microextraction (SPME): a multipurpose in situ sampling technology for organic pollutants in coastal systems”, Department of Civil and Environmental Engineering, University of Southern California, Los Angeles, CA, February 17, 2006. (~15 participants)

Contact with End Users:
This project is incorporated into the 2006-07 SCCWRP Draft Research Plan, and was formally presented to SCCWRP’s Technical Advisory Group on 2/16/06. Group members represent large POTWs, regulatory agencies and other primary stakeholders involved with the regulation and management of organic pollutants in contaminated sediments. (~25 participants)

Patent, Copyright, Invention Disclosure Activity: None

Expenditures
A total of $16,464.85 was encumbered by SCCWRP for the period 9/1/05 to 12/31/05. A total of $24,536 of the $45,000 subcontract to co-PI Dr. Eddy Zeng at the Guangzhou Institute of Geochemistry has been encumbered to date. Because SCCWRP projects are invoiced quarterly, expenditures for the period 1/1/06 to 3/15/06 were not available at time of press. Because of the delay in the actual contract start date, the expenditures to date are in the range anticipated for the work accomplished in this reporting period.

End User Advisor Feedback
Name: Chris Beegan
Organization: State Water Resources Control Board, California
Location: Sacramento, CA
Phone number: 916 341 5577
E-mail: cbeegan@waterboards.ca.gov
1) At this stage, what are the potential applications for this research? Please discuss how you and others could potentially use the technology. SPME porewater sampling technology would provide a direct measure of bioavailability of sediment-associated organic pollutants. This measure could be incorporated into guidelines for sediment quality objectives currently under development for the State of California. Results of these preliminary analyses are promising, and suggest that SPME porewater sampling technology could become a valuable tool applicable to sediment quality assessment and stressor identification.

2) What, if anything, has changed about this project's potential applicability since the last reporting period (not applicable to the first Progress Report)? N/A

3) Do you see any key challenges that the researchers may want to address or keep in mind? Sampler sensitivity, practicality (cost) and response time in situ.

4) Does this report offer you enough information to adequately address the above questions? Yes

5) Other feedback? None