C‐18‐coated silica particles as a surrogate for benthic uptake of hydrophobic compounds from bedded sediment
ABSTRACT To simulate the bioaccumulation of neutral organic contaminants by infaunal benthos, the partitioning of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) between a contaminated estuarine sediment and admixed C-18-coated silica particles was measured. The concentrations of lower chlorinated PCB congeners (less than five chlorine atoms per molecule) on the C-18-coated silica particles reached apparent steady state within 300 h while congeners with greater numbers of chlorine atoms required much greater time periods (greater than 1 year) to reach apparent steady state. Polycyclic aromatic hydrocarbons showed less partitioning from sediment to the C-18 particles than PCB congeners, although the log Kow ranges of the compounds in these comparisons were similar. The biota sediment accumulation factors, defined as the lipid-normalized contaminant concentration in an exposed organism divided by the organic carbon-normalized contaminant concentration of the sediment, were calculated for these exposures using the C-18 of the particles as the lipid. The results from these exposures agreed closely with those measured in studies where living benthic organisms were exposed to contaminated sediment.
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ABSTRACT: Polydimethylsiloxane (PDMS) materials were used to quantify levels of the photosynthesis inhibitor sorgoleone in the undisturbed rhizosphere of sorghum plants. The materials used included stir bars coated with PDMS (stir bar sorptive extraction), technical grade optical fiber coated with a thin film of PDMS (matrix-solid phase microextraction), and PDMS tubing. PDMS tubing retained the most sorgoleone. As analyzed by high performance liquid chromatography, amounts of sorgoleone retained on the PDMS materials increased with time. Other materials tested (polyurethane foam plugs, C18 and Tenax disks, and resin capsules) proved less suitable, as they were subject to sometimes extensive penetration by fine root hairs. These results demonstrate the potential for PDMS-based materials to monitor the release of allelochemicals in the undisturbed rhizosphere of allelopathic plants. Unlike extraction procedures that recover all available compounds present in the soil, PDMS functions in a manner more analogous to plant roots in sorbing compounds from soil solution or root exudates. Information on chemical dynamics in the rhizosphere is crucial for evaluating specific hypotheses of allelopathic effects, understanding allelopathic mechanisms, and assessing the importance of allelopathic processes in plant communities.Journal of Chemical Ecology 03/2005; 31(2):221-36. DOI:10.1007/s10886-005-1337-x · 2.24 Impact Factor
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ABSTRACT: ACKNOWLEDGMENTS 'y t I would like to thank my major advisor, Dr. Todd Anderson, for help, advice, and encouragement throughout my graduate research program. Todd served as an academic,mentor both inside and outside of the lab and helped me acquire valuable knowledge,and lab experience as an environmental scientist. I also thank my committee members. Dr. George Cobb and Dr. Scott McMurry, for their time, advice, and suggestions on my thesis. Thank you goes to many other people in the Institute, especially to Ed Scollon and Debbie Shupack, who provided me tremendous help and advice as senior students. While not directly involved in this research, many other students, professors, and staff in the Institute also made the working place