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Three‐phase modeling of polycyclic aromatic hydrocarbon association with pore‐water‐dissolved organic carbon
Author(s) -
Mitra Siddhartha,
Dickhut Rebecca M.
Publication year - 1999
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.5620180611
Subject(s) - dissolved organic carbon , partition coefficient , pore water pressure , chemistry , total organic carbon , environmental chemistry , sediment , hydrocarbon , polycyclic aromatic hydrocarbon , carbon fibers , organic matter , phase (matter) , aqueous two phase system , geology , chromatography , organic chemistry , materials science , paleontology , geotechnical engineering , composite number , composite material
Log–log plots of measured organic carbon‐normalized sediment pore‐water distribution coefficients ( K ′ OC S) for several polycyclic aromatic hydrocarbons (PAHs) versus their octanol‐water partition coefficients ( K ′ ow S) at two sites in the Elizabeth River, Virginia, show large deviations from linearity. Organic‐carbon normalized distribution coefficients for these PAHs between sediments and pore waters decreased by more than two orders of magnitude with depth as well. To determine to what extent pore water dissolved and colloidal organic carbon (DOC) was responsible for the observed nonlinearity and decrease in K ′ OC , a three‐phase model was used to estimate pore‐water PAH‐DOC binding coefficients ( K DOC ). Partitioning of PAHs to pore‐water DOC (i.e., K DOC ) enhances the observed “dissolved” phase PAH concentration, especially for high‐ K ow compounds, contributing to the nonlinearity in K ′ OC ‐ K ow plots. However, our application of the three‐phase partitioning model to these data indicate that, at most, pore‐water PAH‐DOC binding accounts for one order of magnitude of the observed decrease in K ′ OC with depth in the sediment bed. The results of this study are consistent with three‐phase partitioning theory for hydrophobic organic compounds between sediment organic matter, pore‐water DOC, and freely dissolved aqueous phases in natural systems.