A Passive Sampler Based on Solid Phase Microextraction for Quantifying Hydrophobic Organic Contaminants in Sediment Porewater.

Environmental Toxicology and Chemistry (Impact Factor: 3.23). 12/2008; DOI: 10.1897/08-322.1
Source: PubMed


Sediment quality assessment is often hindered by the lack of agreement between chemical and biological lines of evidence. One limitation is that the bulk sediment toxicant concentration, the most widely used chemical parameter, does not always represent the bioavailable concentration, particularly for hydrophobic organic compounds (HOCs) in highly contaminated sediments. In the present study, we developed and tested a porewater sampler that utilizes solid phase microextraction (SPME) to measure freely dissolved ("bioavailable") HOC concentrations. A single polydimethylsiloxane (PDMS) coated SPME fiber is secured in a compact protective housing that allows aqueous exchange with whole sediment while eliminating direct contact with sediment particles. Fibers with three PDMS coating thicknesses were first calibrated for 12 model PAH, PCBs, DDTs and chlordanes, representing HOCs of current regulatory concern. Pre-calibrated samplers were exposed to spiked estuarine sediment in lab microcosms to determine the time to equilibrium and equilibrium concentrations across a range of sediment contamination. Time to equilibrium ranged from 14 to 110 days with 30 days being sufficient for more than half of the target HOCs. Equilibrium SPME measurements, ranging from 0.009 to 2400 ng/L, were highly correlated with but in general lower than HOC porewater concentrations determined independently by liquid-liquid extraction. This concept shows promise for directly measuring the freely dissolved concentration of HOCs in sediment porewater, a previously difficult to measure parameter that will improve our ability to assess the impacts of contaminated sediments.

8 Reads
  • [Show abstract] [Hide abstract]
    ABSTRACT: Solid-phase microextraction (SPME) has shown potential as an in situ passive-sampling technique in aquatic environments. The reliability of this method depends upon accurate determination of the partition coefficient between the fiber coating and water (K(f)). For some hydrophobic organic compounds (HOCs), K(f) values spanning 4 orders of magnitude have been reported for polydimethylsiloxane (PDMS) and water. However, 24% of the published data examined in this review did not pass the criterion for negligible depletion, resulting in questionable K(f) values. The range in reported K(f) is reduced to just over 2 orders of magnitude for some polychlorinated biphenyls (PCBs) when these questionable values are removed. Other factors that could account for the range in reported K(f), such as fiber-coating thickness and fiber manufacturer, were evaluated and found to be insignificant. In addition to accurate measurement of K(f), an understanding of the impact of environmental variables, such as temperature and ionic strength, on partitioning is essential for application of laboratory-measured K(f) values to field samples. To date, few studies have measured K(f) for HOCs at conditions other than at 20° or 25 °C in distilled water. The available data indicate measurable variations in K(f) at different temperatures and different ionic strengths. Therefore, if the appropriate environmental variables are not taken into account, significant error will be introduced into calculated aqueous concentrations using this passive sampling technique. A multiparameter linear solvation energy relationship (LSER) was developed to estimate log K(f) in distilled water at 25 °C based on published physicochemical parameters. This method provided a good correlation (R(2) = 0.94) between measured and predicted log K(f) values for several compound classes. Thus, an LSER approach may offer a reliable means of predicting log K(f) for HOCs whose experimental log K(f) values are presently unavailable. Future research should focus on understanding the impact of environmental variables on K(f). Obtaining the data needed for an LSER approach to estimate K(f) for all environmentally relevant HOCs would be beneficial to the application of SPME as a passive-sampling technique.
    Environmental Science & Technology 09/2010; 44(18):6917-25. DOI:10.1021/es101103x · 5.33 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: This literature review covers the risk assessment process and addresses both ecological and human receptors. The review covers the risk assessment literature including methodology, analysis, interpretation, management, uncertainty, policy, and regulatory guidance. The review is divided into ecological and human health sections. The focus of the review is on the risk assessment process as it is applied to ecological systems and human health, site investigation and remediation, and natural resources. The objective is to provide an overview of the scope of the literature published in 2010.
    Water Environment Research 12/2010; 83(10):1876-1905. DOI:10.2175/106143011X13075599870252 · 0.87 Impact Factor
  • Source
Show more


8 Reads
Available from