Release rates of polynuclear aromatic hydrocarbons from natural sediments and their relationship to solubility and octanol-water partitioning

Abstract

Abstract. Sediment effiux rates of six polynuclear aromatic hydrocarbons (PAHs) were determined employing a novel boundary-layer flux chamber which concentrates trace organics using solid phase extraction techniques. Sediment cores were collected from the Elizabeth River, Virginia and were monitored over a 48 h period for PAH fluxes into uncontaminated seawater. The observed flux rates were related to solubility and octanol-water partition coefficients (Kow) of the PAHs. Flux rates for the six PAHs varied from 0.028 to 0.646 p.g/L/d on a concentration basis and 43.0 to 1,000 p~g/m2/d on an areal basis. The resulting flux rate coefficients (k2) were determined to be well correlated to solubility (R 2 = 0.82) and inversely related to Kow (R 2 = 0.75). The empirically determined sediment flux dynamics fit well with theoretical relationships that have been previously established for bioconcentration kinetics and octanol/water partitioning systems. Thus, it appears possible to predict flux rates of other hydrophobic organic chemicals from ambient sediment and water concentrations, Kow information, and the proposed empirical models.

Field study on desorption rates of polynuclear aromatic hydrocarbons from contaminated marine sediment

“…In addition, the surface area of sediment particles involved in sediment‐water partitioning was much greater in gas‐stripping desorption than in laboratory and field desorption conditions, where partitioning was limited to the bulk sediment‐water interface. Compared with the present field desorption kinetic data, the slower desorption kinetics revealed by Helmstetter and Alden [6] were probably caused by the lack of good water exchange and flushing in the flux chamber. The present field data suggest that desorption rates of nonionic hydrophobic organic pollutants from contaminated sediment upon their disposal in the field are about 10‐ to 100‐fold faster than those estimated by flux chamber desorption but 10‐ to 100‐fold slower than those estimated by gas‐stripping experiments.…”

“…These data were obtained by extracting the desorbed PAHs directly from the aqueous phase with solid sorbent. Helmstetter and Alden [6] have reported even slower desorption rates of PAHs in their enclosed flux chamber designed to mimic field desorption. The k 2 values of naphthalene, phenanthrene, pyrene, fluoranthene, and benzo[ b ]fluoranthene were 2.6 × 10 −4 , 2.1 × 10 −5 , 4.5 × 10 −6 , 4.3 × 10 −6 , and 1.8 × 10 −7 /d, respectively.…”

“…Understanding the environmental fate of the various pollutants in disposed sediment is thus of practical value from an environmental management point of view. Indeed, the transport and environmental fate of hydrophobic organic pollutants in contaminated coastal sediments has attracted much attention in the last decade [3–6].…”

Desorption kinetics of hydrophobic organic chemicals from sediment to water: A review of data and models

“…The lack of any discernible trend between aqueous solubility and desorption rate constants was surprising considering that a study of fluxes from sediment beds contaminated with polycyclic aromatic hydrocarbons (PAHs) showed a strong correlation ( r 2 = 0.82) between release rates and solubility [49]. However, it is clear that flux from bed sediments at ambient conditions (i.e., no stirring) is not the same as desorption from resuspended particles.…”

Towards a complete mass balance and model for PCBs and PAHs in a small rural lake, Cumbria U.K.

“…The major inputs to the water column of lakes are riverine inputs, direct atmospheric deposition (both wet and dry), and sediment resuspension (Neff 1979;Swackhamer and Eisenreich 1991). The fate of PCBs and PAHs in the aquatic system has been a subject of extensive study for a number of years (McVeety and Hites 1988;Swackhamer et al 1988;Baker and Eisenreich 1990;Achman et al 1993;Helmstetter and Alden 1994). Upon entry into the aquatic environment they rapidly associate with suspended particulate material and sediments.…”