Protection and Active Decontamination of Dairy Cattle Heifers against Lipophilic Toxins (PCBs) from Diet.

We studied the effects of a hydrophobized reversed-phase feed adsorbent in the form of a polyoctylated polysilicate hydrogel (POPSH) on productivity indicators, metabolic adaptation, and on the level of polychlorinated biphenyls (PCBs) in the blood of growing Holsteinized black-and-white heifers during the transition period. Two groups of two-month-old heifers of 20 head each were used. The experimental group received POPSH in addition to the main diet. The use of the adsorbent led to an increase in daily weight gain by 19.9% and to a decrease in the total concentration of PCB congeners found in whole blood by 40%. The greatest decrease in concentration (35-52%) was observed for tetra-, penta- and hexachlorobiphenyls. These results demonstrate the possibilities of effective protection of calves from lipophilic toxins of feed and their active decontamination.

The use of coarse, separable, condensed-phase organic carbon particles to characterize desorption resistance of polycyclic aromatic hydrocarbons in contaminated sediments.

Physical separations were employed to characterize the source of desorption-resistant behavior for polycyclic aromatic hydrocarbons (PAHs) in laboratory- and field-contaminated sediments. Size and density separation of laboratory-contaminated sediments did not effectively separate the amorphous-phase (volatile) and condensed-phase (nonvolatile) organic carbon as measured by thermal oxidation at 375 degrees C. These separations also did not result in sediment fractions with significantly different desorption characteristics as measured by apparent partition coefficients. Coarse particles from a field-contaminated sediment from Utica Harbor (UH; Utica, NY, USA), however, could be directly separated into sandy fractions and organic fractions that were composed of woody organic matter, charcoal or charred vegetative matter, and coal-like and coal-cinder particles. Chemical analysis showed that coal-like (glassy, nonporous) and coal-cinder (porous, sintered) particles exhibited very high PAH concentrations and high apparent partition coefficients. These particles also exhibited significantly higher condensed-phase (nonvolatile) organic carbon contents as defined by thermal oxidation at 375 degrees C. The apparent partition coefficients of PAHs in the coal-cinder particles were a good indication of the apparent partition coefficients in the desorption-resistant fraction of UH sediment, indicating that the coarse particles provided a reasonable characterization of the desorption-resistance phenomena in these sediments even though the coarse fractions represented less than 25% of the organic carbon in the whole sediment.

Desorption resistance of polycyclic aromatic hydrocarbons and duration of exposure.

The desorption-resistant fraction of laboratory-spiked phenanthrene in two Louisiana (USA) sediments was not observed to be significantly different, but the two sediments exhibited different condensed-phase organic carbon contents, as defined operationally by the organic carbon remaining after combustion of the sediment at 375 degrees C. Only 3% of the original saturated phenanthrene in the sediments was not readily removed by exposure to a nonpolar polymeric resin and sorbent XAD-2. Allowing the laboratory-spiked contaminants to age for periods of up to three years yielded little difference in the desorption-resistant characteristics of the sediments. Field-contaminated sediments from Utica Harbor (Utica, NY, U.S.A.) and Rouge River (Detroit, MI, USA) that had a lengthy (decades to a century) period of contamination, however, exhibited significantly different desorption-resistant contaminant fractions, consistent with the fractions of condensed-phase organic carbon in the sediments. Measurements of the fraction that could be rapidly desorbed using the XAD-2 sorbent also accounted for essentially all desorption to pore water and, thus, provided a good prediction of effective bulk partition coefficients. It was concluded that the condensed-phase organic carbon was a good indicator of the potential for desorption resistance in field-contaminated sediments and that the rapidly desorbing fraction provided a quantitative indicator of its significance.

Modeling biphasic sorption and desorption of hydrophobic organic contaminants in sediments.

A model was developed to predict biphasic sorption and desorption of hydrophobic organic compounds in contaminated sediments. The model was based on relatively rapid porous diffusion in amorphous organic carbon and slow solid-phase diffusion in condensed-phase organic carbon. The model was used to simulate measured solid-fluid phase desorption (rates and pore-water concentrations) for four polycyclic aromatic hydrocarbons exhibiting a range of hydrophobicities (phenanthrene, anthracene, pyrene, and benzo[a]pyrene) in two field-contaminated sediments from Utica Harbor (Utica, NY, USA) and Rouge River (Detroit, MI, USA). Pore-water concentrations have been related to bioavailability, indicating the potential usefulness of the model to predict bioavailability. Key model parameters included the fraction of condensed-phase carbon (estimated by combustion at 375 degrees C), partition coefficient to the condensed-phase carbon (estimated by desorption measurements on coal-like particles physically separated from Utica Harbor sediments), and diffusivity and ratio of volume to surface area of the condensed-phase organic matter (fitted to measured desorption data on both sediments and for the measured polycyclic aromatic hydrocarbons). Best fit for the diffusion coefficient in the condensed-phase organic matter was 8.5 x 10(-20) m2/s, and ratio of volume to surface area was 2 microm. These parameters estimated measured pore-water concentrations of all polycyclic aromatic hydrocarbons in both sediments with an average error of 46% and a correlation coefficient of 0.76 and the fast-desorbing fractions (as measured by the fraction removed with a nonpolar polymeric sorbent XAD-2) with an average error of approximately 30% and a correlation coefficient of 0.54 (14% and 0.76, respectively, for all but benzo[a]pyrene). Modeling results were relatively insensitive to the two fitted parameters, with changes of an order of magnitude or more being required to affect the correlation between the model and observations significantly.