Chemical techniques for assessing bioavailability of sediment-associated contaminants: SPME versus Tenax extraction

Abstract

The traditional approach for predicting the risk of hydrophobic organic contaminants (HOCs) in sediment is to relate organic carbon normalized sediment concentrations to body residues or toxic effects to organisms. However, due to the multiple variables controlling bioavailability, this method has limitations. A matrix independent method of predicting bioavailability needs to be used in order to be universally applicable. Both chemical activity (freely dissolved chemical concentrations) measured by solid-phase microextraction (SPME) and bioaccessibility (rapidly desorbing fraction) estimated by Tenax extraction have been developed to predict bioavailability of sediment-associated HOCs. The objectives of this review are to summarize a number of studies using matrix-SPME or Tenax extraction to estimate bioavailability and/or toxicity of different classes of HOCs and evaluate the strengths and weakness of these two techniques. Although the two chemical techniques assess different components of the matrix, estimates obtained from both techniques have been correlated to organism body residues. The advantages of SPME fibers are their applicability for use in situ and their potential usage for a wide array of contaminants by selection of appropriate coatings. Single time-point Tenax extraction, however, is more time-and labor-effective. Tenax extraction also has lower detection limits, making it more applicable for highly toxic contaminants. This review also calls for additional research to evaluate the role of sequestrated contaminants and ingestion of sediment particles by organisms on HOC bioavailability. The use of performance reference compounds to reduce SPME sampling time and linking chemical based bioavailability estimates to toxicological endpoints are essential to expand the applications of these methods.

Addition of contaminant bioavailability and species susceptibility to a sediment toxicity assessment: Application in an urban stream in China

“…However, it is impossible to theoretically correct the TU calculation unless a full understanding of the factors affecting bioavailability was achieved. Alternatively, bioavailability-based techniques have been proposed to provide a more accurate estimation of sediment toxicity (Reichenberg and Mayer, 2006;You et al, 2011;Cui et al, 2013), and a bioavailable TU approach was compared to the traditional TU approach for assessing toxicity to H. azteca.…”

Chronic Toxicity Thresholds for Sediment-Associated Benzo[a]pyrene in the Midge (Chironomus dilutus)

“…Instead, inclusion of bioavailability measurements into toxicity thresholds could also increase accuracy in assessing sediment risk. Tenax extraction has been shown to be an effective method for estimating the bioavailability of hydrophobic organic contaminants in sediment (You et al 2011). Therefore, additional set of chronic toxicity thresholds was also established using Tenax-extractable BaP concentrations as the dose metrics (Fig.…”

Joint toxicity of a pyrethroid insecticide, cypermethrin, and a heavy metal, lead, to the benthic invertebrate Chironomus dilutus

“…Previous studies [25,26,29,30] showed that 24-h Tenax extractable concentrations were well correlated to bioavailability and toxicity of pyrethroids in sediment. The fraction extracted by Tenax in 24 h ranged from 3.2 AE 1.2% to 34.6 AE 4.9%, with an average of 13.8 AE 8.6% for cypermethrin in sediment without Pb 2þ , whereas the fractions were slightly increased to 6.2 AE 2.5% to 51.3 AE 6.6% (mean of 27.4 AE 16.1%) in sediment with the addition of Pb 2þ .…”

“…Previous studies [25,26] showed 24-h Tenax extractable concentrations of sediment-associated hydrophobic contaminants to be an effective measure of bioavailability. Sediment samples including sediments spiked with cypermethrin alone or with a mixture of cypermethrin and Pb 2þ were collected before the sediment bioassay experiment.…”