Sediment porewater partitioning of polycyclic aromatic hydrocarbons in three cores from Boston Harbor, Massachusetts
No abstract available.
Massachusetts↗
Geology topics
S.E. Mcgroddy
Publications and source records attributed to S.E. Mcgroddy.
Partition characteristics of polycyclic aromatic hydrocarbons on soils and sediments
The partition behavior was determined for three polycyclic aromatic hydrocarbons (PAHs), i.e., naphthalene, phenanthrene, and pyrene, from water to a range of soil and sediment samples. The measured partition coefficients of the individual PAHs between soil/sediment organic matter (SOM) and water (i.e., K(oc) values) are relatively invariant either for the 'clean' (uncontaminated) soils or for the clean sediments; however, the mean K(oc) values on the sediments are about twice the values on the soils. This disparity is similar to the earlier observation for other nonpolar solutes and reflects the compositional differences between soil and sediment organic matters. No significant differences in K(oc) are observed between a clean coastal marine sediment and freshwater sediments. The coastal sediments that are significantly impacted by organic contaminants exhibit higher K(oc) values. At given K(ow) values (octanol-water), the PAHs exhibit much higher K(oc) values than other relatively nonpolar solutes (e.g., chlorinated hydrocarbons). This effect is shown to result from the enhanced partition of PAHs to SOM rather than from lower K(ow) values of PAHs at given supercooled liquid solute solubilities in water. The enhanced partition of PAHs over other nonpolar solutes in SOM provides an account of the markedly different correlations between log K(oc) and log K(ow) for PAHs and for other nonpolar solutes. The improved partition of PAHs in SOM stems apparently from the enhanced compatibility of their cohesive energy densities with those of the aromatic components in SOM. The approximate aromatic fraction in soil/sediment organic matter has been assessed by solid-state 13C-NMR spectroscopy.The partition behavior was determined for three polycyclic aromatic hydrocarbons (PAHs), i.e., naphthalene, phenanthrene, and pyrene, from water to a range of soil and sediment samples. The measured partition coefficients of the individual PAHs between soil/sediment organic matter (SOM) and water (i.e., Koc values) are relatively invariant either for the `clean' (uncontaminated) soils or for the clean sediments; however, the mean Koc values on the sediments are about twice the values on the soils. This disparity is similar to the earlier observation for other nonpolar solutes and reflects the compositional differences between soil and sediment organic matters. No significant differences in Koc are observed between a clean coastal marine sediment and freshwater sediments. The coastal sediments that are significantly impacted by organic contaminants exhibit higher Koc values. At given Kow values (octanol-water), the PAHs exhibit much higher Koc values than other relatively nonpolar solutes (e.g., chlorinated hydrocarbons). This effect is shown to result from the enhanced partition of PAHs to SOM rather than from lower Kow values of PAHs at given supercooled liquid solute solubilities in water. The enhanced partition of PAHs over other nonpolar solutes in SOM provides an account of the markedly different correlations between log Koc and log Kow for PAHs and for other nonpolar solutes. The improved partition of PAHs in SOM stems apparently from the enhanced compatibility of their cohesive energy densities with those of the aromatic components in SOM. The approximate aromatic fraction in soil/sediment organic matter has been assessed by solid-state 13C-NMR spectroscopy.
Environmental Science & Technology↗
Comparison of the in situ and desorption sediment-water partitioning of polycyclic aromatic hydrocarbons and polychlorinated biphenyls
In situ sediment−porewater partitioning of polycyclic aromatic hydrocarbons (PAHs) measured in three cores from Boston Harbor, MA, has led us to suggest that only a fraction of the total measured sediment PAH concentration is a vailable for e quilibrium p artitioning (AEP fraction). To test this, aqueous PAH concentrations were measured in laboratory desorption experiments using subsamples of the same Boston Harbor sediments. The observed concentrations were consistent with what we predicted from the field-derived AEP values: C aqueous = ( C sediment × AEP)/( f oc × K oc ) where f oc is the fraction organic carbon in the sediment and K oc is the organic carbon normalized sediment−water partition coefficient. Equilibrium partitioning models based on the total measured sediment PAH concentrations overestimated the measured aqueous PAH concentrations by as much as 100 times in some cases. Only a small fraction of the sediment phenanthrene and pyrene concentrations (1−40%) appeared to be available for equilibrium partitioning. Both in situ and laboratory desorption aqueous polychlorinated biphenyl (PCB) concentrations were consistent with equilibrium partitioning models and the assumption that 100% of these compounds was available for equilibrium partitioning. These results are particularly important to efforts to predict the environmental mobility and bioavailability of the PAHs.
Massachusetts↗