Abstract
BackgroundIn soils contaminated by hydrophobic organic compounds, the concentrations are less indicative of potential exposure and distribution than are the associated chemical activities, fugacities and freely dissolved concentrations. The latter can be measured by diffusive sampling into thin layers of polymer, as in, for example, solid phase micro-extraction. Such measurements require equilibrium partitioning of analytes into the polymer while ensuring that the sample is not depleted. We introduce the validation of these requirements based on parallel sampling into polymer layers of different thicknesses.ResultsEquilibrium sampling devices were made by coating glass vials internally with 3–12 μm thick layers of polydimethylsiloxane (PDMS). These were filled with slurries of a polluted soil and gently agitated for 5 days. The concentrations of 7 polycyclic aromatic hydrocarbons (PAHs) in the PDMS were measured. Validation confirmed fulfilment of the equilibrium sampling requirements and high measurement precision. Finally, chemical activities of the PAHs in the soil were determined from their concentrations and activity coefficients in the PDMS.ConclusionPAHs' thermodynamic activities in a soil test material were determined via a method of uptake into PDMS. This can be used to assess chemical exposure and predict diffusion and partitioning processes.
Highlights
In soils contaminated by hydrophobic organic compounds, the concentrations are less indicative of potential exposure and distribution than are the associated chemical activities, fugacities and freely dissolved concentrations
polycyclic aromatic hydrocarbons (PAHs)' thermodynamic activities in a soil test material were determined via a method of uptake into PDMS
Determining equilibrium partitioning concentrations in PDMS coatings After sampling the soil in PDMS coated vials, the quantities of PAHs in the PDMS were extracted to methanol, measured by HPLC, and plotted against the PDMS volumes (Figure 3)
Summary
In soils contaminated by hydrophobic organic compounds, the concentrations are less indicative of potential exposure and distribution than are the associated chemical activities, fugacities and freely dissolved concentrations. The latter can be measured by diffusive sampling into thin layers of polymer, as in, for example, solid phase micro-extraction. That the chemical activity of a hydrophobic organic soil pollutant is important for its bioavailability has recently been proposed [6]. One reason for this is that partitioning occurs spontaneously down gradients in chemical activity. Equilibrium partitioning is defined by equal chemical activities, forming the basis for equilibrium partitioning theory [7] and (page number not for citation purposes)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
