Enhanced Accessibility of Polycyclic Aromatic Hydrocarbons (PAHs) and Heterocyclic PAHs in Industrially Contaminated Soil after Passive Dosing of a Competitive Sorbate

To assess the exposure to polycyclic aromatic hydrocarbons (PAHs) it is important to understand the binding mechanisms between specific soil constituents and the organic pollutant. In this study, sorptive bioaccessibility extraction (SBE) was applied to quantify the accessible PAH fraction in industrially contaminated soil with and without passive dosing of a competitive sorbate. SBE experiments revealed an accessible PAH fraction of 41 ± 1% (∑16 US EPA PAHs + 5 further PAHs). The passive dosing of toluene below its saturation level revealed competitive binding and resulted in an average increase of the accessible fraction to 49 ± 2%, whereby primarily the accessibility of higher molecular weight PAHs (log <i>K</i>_ow > 6) was affected. Competitive binding was verified using the same soil with only desorption-resistant PAHs present. In this experiment, passive dosing of toluene resulted in desorption of 13 ± 0.4% PAH. We explain increased PAH desorption after addition of toluene by competitive adsorption to high-affinity sorption sites while acknowledging that toluene could additionally have increased PAH mobility within the soil matrix. Findings suggest that the presence of copollutants at contaminated sites deserves specific considerations as these may increase accessibility and thereby exposure and mobility of PAHs

Equilibrium Sampling of Hydrophobic Organic Contaminants in Sediments

Passive samplers are useful novel tools for assessing contaminant exposure and evaluating its potential for adverse environmental effects. Passive equilibrium samplers enable the quantification of freely dissolved concentrations (Cfree) of organic contaminants in sediments. Cfree allows a direct assessment of (1) contaminant exchange and equilibrium status between sediment and overlying water, (2) benthic bioaccumulation, and (3) potential toxicity to benthic organisms. Thus, the use of equilibrium samplers improves the mechanistic understanding of fate and transport processes in sediments. Equilibrium samplers can be applied for hazard and risk assessment and management of contaminated sediments of aquatic environments. The objective of this chapter is to provide introductory guidance on the use of passive equilibrium samplers for sediments contaminated with hydrophobic organic contaminants, whereby three different approaches are recommended: (1) silicone-coated glass jars, (2) SPME fibers that can be used ex situ with sediments that had been sampled in the field, and (3) SPME fibers that can be exposed directly in the field (in situ) when they are installed in a protective housing that is buried in the sediment. After reading this chapter, users will have a fundamental understanding of equilibrium passive samplers and their potential applications to sediments