Methods to assess bioavailability of hydrophobic organic contaminants: Principles, operations, and limitations

Abstract

Many important environmental contaminants are hydrophobic organic contaminants (HOCs), which include PCBs, PAHs, PBDEs, DDT and other chlorinated insecticides, among others. Owing to their strong hydrophobicity, HOCs have their final destination in soil or sediment, where their ecotoxicological effects are closely regulated by sorption and thus bioavailability. The last two decades has seen a dramatic increase in research efforts in developing and applying partitioning based methods and biomimetic extractions for measuring HOC bioavailability. However, the many variations of both analytical methods and associated measurement endpoints are often a source of confusion for users. In this review, we distinguish the most commonly used analytical approaches based on their measurement objectives, and illustrate their practical operational steps, strengths and limitations using simple flowcharts. This review may serve as guidance for new users on the selection and use of established methods, and a reference for experienced investigators to identify potential topics for further research.

Influences of artificial root exudate components on the behaviors of BDE-28 and BDE-47 in soils: desorption, availability, and biodegradation

“…For example, the S w values of BDE-28 and BDE-47 in 60 g/L oxalic acid solution were 2.5 and 1.9 times higher than the corresponding S w values in water. n-Butanol has been used as an appropriate extraction solvent to determine the availability of organic contaminants in soils (Cui et al 2013;Liste and Alexander 2002;Kelsey et al 1997). Enhanced availability of some organic contaminants including PAHs and PCBs in soils by root exudates have been reported (White et al 2003(White et al , 2006Luo et al 2006), which were consistent with the observations of this study.…”

“…Sorption and desorption of organic contaminants are fundamental processes controlling their transportation in soils (Tolls 2001). The uptake of organic contaminants was determined by their bioavailability and biotransformation in soils, which have been addressed as the key processes affecting their toxicity to and accumulation in biota (Cui et al 2013;Semple et al 2003). These diverse processes coexist for organic contaminants in soils and influence each other; therefore, a thorough investigation of these processes is necessary in order to comprehensively understand the unique behaviors of organic contaminants in soils.…”

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

“…As a desorption-based measurement, a single point 24-h Tenax extraction has been conducted to estimate bioavailability of sediment-associated CUPs (Cornelissen et al, 1997;Cui et al, 2013). About 3 g (dry weight, dw) of sediment, 3 mg of NaN 3 used to prevent microbial degradation, 40 ml of reconstituted water, several copper sheets used to remove sulfur and 1 g of Tenax beads were added into a screw-capped glass tube.…”

“…As an activity-based measurement, matrix-SPME measured the freely-dissolved CUP concentrations (Mayer et al, 2000;Cui et al, 2013). Ten cm of disposable SPME fibers coated with 10 mm polydimethylsiloxane were protected in a stainless envelope with 110 mm openings.…”

“…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.…”