On the constancy of sediment-water partition coefficients of hydrophobic organic pollutants

Gschwend, Philip M.; Wu, Shang-Chuen

doi:10.1021/es00131a011

Cited by 555 publications

(372 citation statements)

References 7 publications

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“…This blockage of sorbent sites is contrary to the organic phase partitioning model of HOC sorption described above for equilibrium sorption. However, Wu and Gschwend (1986) Recent studies have shown that centrifugation after equilibration in typical batch sorption studies is inadequate to remove suspended solids or colloidal organic matter from the supernate (Gschwend and Wu, 1985;Voice and Weber, 1985). In this case an apparent K, (K'd) is observed:…”

Section: Sorbent Mass Dependent Partitioningmentioning

confidence: 99%

“…Therefore batch sorption experiments are expected to yield Kptrue (after Gschwend and Wu, 1985) when K oc c is small or when sorbent organic matter is sufficiently removed from the supernate. Typically, batch sorption experiments are run at total suspended solids concentrations on the order of 0l mg/L.…”

Section: Sorbent Mass Dependent Partitioningmentioning

confidence: 99%

“…Typically, batch sorption experiments are run at total suspended solids concentrations on the order of 0l mg/L. Gschwend and Wu (1985) found that the ratio of organic colloids (or non-settling particulate organic matter) was about 5% of the total organic matter concentration for their particular conditions. For a typical sediment fo, of 0.02 this would correspond to an focc of 1 mg/L.…”

Section: Sorbent Mass Dependent Partitioningmentioning

confidence: 99%

“…In two studies (Gschwend and Wu, 1985;Bowman and Sans, 1985) constant Kocs were observed when care was taken to minimize sorbing materials in the supernate, and losses to wall adsorption were considered. The explanation given for apparent sorbent mass dependent partitioning given by eqn.…”

Section: Sorbent Mass Dependent Partitioningmentioning

confidence: 99%

“…DOM has been shown to influence the biological availability of hydrocarbons and polycyclic aromatic hydrocarbons (PAH) (Boehm and Quinn, 1976;Leversee et al, 1983;, the base hydrolysis rate of the octyl ester of 2,4-D (Perdue and Wolf, 1982), and the volatilization rate of 2,2',5,5'-tetrachlorobiphenyl (Hassett and Millcic, 1985). Gschwend and Wu (1985) have modelled the partitioning of PCBs with freshwater sediments in batch sorption experiments in terms of three-phase equilibrium sorption where PCBs are sorbed to non-settling organic "colloids" in the supernatant. The effect of colloids in batch sorption experiments had also been hypothesized by Voice et al (1983) and Chiou et al (1984).…”

Section: Introductionmentioning

confidence: 99%

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The role of colloidal organic matter in the marine geochemistry of PCBs

Brownawell¹

1986

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WITHDRAWN AD -sT~i~Bñ~c i~tZ4-2-ABSTRACT Polychlorinated biphenyls (PCBs) were used as model hydrophobic organic compounds (HOC) to study physical-chemical processes which affect the speciation and fate of HOC in coastal environments. The focus of this study is on the sorption of PCBs with colloidal organic matter in seawater, and the influence of this process on the distribution of PCBs in coastal sediments. Laboratory and field experiments were used to make quantitative estimates of PCB-organic matter sorption, and to test predictions of three-phase equilibrium models.A static headspace partitioning method was developed to measure the sorption of several individual chlorobiphenyls with colloidal organic matter enriched from coastal seawater by hollow fiber ultrafiltration. This technique directly measured the dissolved phase fugacity of PCBs in experimental bottles, and avoided uncertain separation techniques often used in isolating various chemical phases. Colloidal organic carbon normalized partition coefficients (Koc) were determined from linear sorption isotherms, and increased from 1.9 x 10' (L/Kg) for 2,4'-dichlorobiphenyl to 3.5 x 10 s for 2,2',3,4,5'-pentachlorobiphenyl. Sorption tended to increase with increasing octanol-water partition coefficients (Kow) of the sorbate, and values of Koc were within a range of those reported in other experimental sorption studies with sediments and dissolved humic substances. Experimental partitioning results support the hypothesis that HOC-organic colloid sorption is similar to HOC sorption by sediment organic matter.PCBs were measured in the interstitial waters and sediments of three box cores obtained from New Bedford Harbor and Buzzards Bay, Massachusetts. The three sites studied had a wide range of sediment PCB concentrations, and reducing conditions provided environments containing high concentrations of colloidal organic matter. Dissolved organic carbon (DOC) and total sediment organic carbon (TOC) were measured in two cores to test the role of organic matter on the observed partitioning of PCBs. PCB concentrations, particularly those of less soluble chlorobiphenyls, were highly elevated in interstitial waters compared to water column concentrations at all three sites. The measured apparent distribution coefficients (K'd) of individual chlorobiphenyls did not increase with hydrophobicity (Kow) and indicate that a large fraction of PCBs in interstitial waters must be sorbed to organic colloids. A three-phase equilibrium sorption model, in which dissolved PCBs are in a dynamic equilibrium with colloidal and sediment organic matter, accounts for many aspects of the field data. There is good agreement of observed partitioning at New Bedford Station 67 and Buzzards Bay Station M with model calculations based on predictions derived from laboratory experiments of HOC sorption with sediments and organic colloids, but model calculations underpredict K'd at Station 84 in New Bedford Harbor.-3-The sediment-interstitial water results were contrasted with a study of PCB pa...

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Section: Sorbent Mass Dependent Partitioningmentioning

confidence: 99%

Section: Sorbent Mass Dependent Partitioningmentioning

confidence: 99%

Section: Sorbent Mass Dependent Partitioningmentioning

confidence: 99%

Section: Sorbent Mass Dependent Partitioningmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The role of colloidal organic matter in the marine geochemistry of PCBs

Brownawell¹

1986

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Colloid particle sizes in the Mississippi River and some of its tributaries, from Minneapolis to below New Orleans

1998

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Abstract:An on-board technique was developed that combined discharge-weighted pumping to a high-speed continuousow centrifuge for isolation of the particulate-sized material with ultra®ltration for isolation of colloid-sized material. In order to address whether these processes changed the particle sizes during isolation, samples of particles in suspension were collected at various steps in the isolation process to evaluate changes in particle size. Particle sizes were determined using laser light-scattering photon correlation spectroscopy and indicated no change in size during the colloid isolation process. Mississippi River colloid particle sizes from twelve sites from Minneapolis to below New Orleans were compared with sizes from four tributaries and three seasons, and from predominantly autochthonous sources upstream to more allochthonous sources downstream.

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