Geology topics

R.G. Luthy

Publications and source records attributed to R.G. Luthy.

4 recordsLinked to original sources

USGS2011

Assessment of field-related influences on polychlorinated biphenyl exposures and sorbent amendment using polychaete bioassays and passive sampler measurements

Field-related influences on polychlorinated biphenyl (PCB) exposure were evaluated by employing caged deposit-feeders, Neanthes arenaceodentata, along with polyoxymethylene (POM) samplers using parallel in situ and ex situ bioassays with homogenized untreated or activated carbon (AC) amended sediment. The AC amendment achieved a remedial efficiency in reducing bioaccumulation by 90% in the laboratory and by 44% in the field transplants. In situ measurements showed that PCB uptake by POM samplers was greater for POM placed in the surface sediment compared with the underlying AC amendment, suggesting that tidal exchange of surrounding material with similar PCB availability as untreated sediment was redeposited in the cages. Polychlorinated biphenyls bioaccumulation with caged polychaetes from untreated sediment was half as large under field conditions compared with laboratory conditions. A biodynamic model was used to confirm and quantify the different processes that could have influenced these results. Three factors appeared most influential in the bioassays: AC amendment significantly reduces bioavailability under laboratory and field conditions; sediment deposition within test cages in the field partially masks the remedial benefit of underlying AC-amended sediment; and deposit-feeders exhibit less PCB uptake from untreated sediment when feeding is reduced. Ex situ and in situ experiments inevitably show some differences that are associated with measurement methods and effects of the environment. Parallel ex situ and in situ bioassays, passive sampler measurements, and quantifying important processes with a model can tease apart these field influences.

Environmental Toxicology and Chemistry↗

USGS2009

Measurement and modeling of polychlorinated biphenyl bioaccumulation from sediment for the marine polychaete neanthes arenaceodentata and response to sorbent amendment

Bioaccumulation rates of polychlorinated biphenyls (PCBs) for the marine polychaete Neanthes arenaceodentata were characterized, including PCB uptake rates from water and sediment, and the effect of sorbent amendment to the sediment on PCB bioavailability, organism growth, and lipid content. Physiological parameters were incorporated into a biodynamic model to predict contaminant uptake. The results indicate rapid PCB uptake from contaminated sediment and significant organism growth dilution during time-series exposure studies. PCB uptake from the aqueous phase accounted for less than 3% of the total uptake for this deposit-feeder. Proportional increase of gut residence time and assimilation efficiency as a consequence of the organism's growth was assessed by PCB uptake and a reactor theory model of gut architecture. Pulse-chase feeding and multilabeled stable isotope tracing techniques proved high sediment ingestion rates (i.e., 6?10 times of dry body weight per day) indicating that such deposit-feeders are promising biological indicators for sediment risk assessment. Activated carbon amendment reduced PCB uptake by 95% in laboratory experiments with no observed adverse growth effects on the marine polychaete. Biodynamic modeling explained the observed PCB body burdens for N. arenaceodentata, with and without sorbent amendment.

Environmental Science & Technology↗

USGS2007

Biodynamic modeling of PCB uptake by Macoma balthica and Corbicula fluminea from sediment amended with activated carbon

Activated carbon amendment was assessed in the laboratory as a remediation strategy for freshwater sediment contaminated with polychlorinated biphenyls (PCBs) from the Grasse River (near Massena, NY). Three end points were evaluated: aqueous equilibrium PCB concentration, uptake into semipermeable membrane devices (SPMDs), and 28-day bioaccumulation in the clam Corbicula fluminea. PCB uptake by water, SPMDs, and clams followed similar trends, with reductions increasing as a function of carbon dose. Average percent reductions in clam tissue PCBs were 67, 86, and 95% for activated carbon doses of 0.7, 1.3, and 2.5% dry wt, respectively. A biodynamic model that incorporates sediment geochemistry and dietary and aqueous uptake routes was found to agree well with observed uptake by C. fluminea in our laboratory test systems. Results from this study were compared to 28-day bioaccumulation experiments involving PCB-contaminated sediment from Hunters Point Naval Shipyard (San Francisco Bay, CA) and the clam Macoma balthica. Due to differences in feeding strategy, M. balthica deposit-feeds whereas C. fluminea filter-feeds, the relative importance of the aqueous uptake route is predicted to be much higher for C. fluminea than for M. balthica. Whereas M. balthica takes up approximately 90% of its body burden through sediment ingestion, C. fluminea only accumulates approximately 45% via this route. In both cases, results strongly suggest that it is the mass transfer of PCBs from native sediment to added carbon particles, not merely reductions in aqueous PCB concentrations, that effectively reduces PCB bioavailability and uptake by sediment-dwelling organisms. ?? 2008 American Chemical Society.

Environmental Science & Technology↗

USGS2007

Biological uptake of polychlorinated biphenyls by Macoma balthica from sediment amended with activated carbon

This work characterizes the efficacy of activated carbon amendment in reducing polychlorinated biphenyl (PCB) bioavailability to clams ( Macoma balthica ) from field-contaminated sediment (Hunters Point Naval Shipyard, San Francisco Bay, CA, USA). Test methods were developed for the use of clams to investigate the effects of sediment amendment on biological uptake. Sediment was mixed with activated carbon for one month. Bioaccumulation tests (28 d) were employed to assess the relationships between carbon dose and carbon particle size on observed reductions in clam biological uptake of PCBs. Extraction and cleanup protocols were developed for the clam tissue. Efficacy of activated carbon treatment was found to increase with both increasing carbon dose and decreasing carbon particle size. Average reductions in bioaccumulation of 22, 64, and 84% relative to untreated Hunters Point sediment were observed for carbon amendments of 0.34, 1.7, and 3.4%, respectively. Average bioaccumulation reductions of 41, 73, and 89% were observed for amendments (dose = 1.7% dry wt) with carbon particles of 180 to 250, 75 to 180, and 25 to 75 μm, respectively, in diameter, indicating kinetic phenomena in these tests. Additionally, a biodynamic model quantifying clam PCB uptake from water and sediment as well as loss through elimination provided a good fit of experimental data. Model predictions suggest that the sediment ingestion route contributed 80 to 95% of the PCB burdens in the clams.

Environmental Toxicology and Chemistry↗