Geochemical Associations of Sellafield-Derived Radionuclides in Saltmarsh Deposits of the Solway Firth

This paper describes a study of the geochemical associations of Sellafield waste radionuclides in saltmarsh sediments from south-west s]Scotland. The contaminant radionuclides are transported to this environment in association with particulate material and ¹³⁷Cs was found to be predominantly (80-98%) non-extractable. In the case of ^239+240Pu there was a redistribution from the oxalate extractable oxide fraction to the pyrophosphate extractable organic fraction as a consequence of on-shore transfer of contaminated sediment. The relatively aggressive nature of the chemical extractants required to remove the radionuclides from the sediments suggests that they were in a form which was unlikely to result in their being released into the aquatic environment or taken up by plants. Plutonium had a greater potential mobility or bioavailability than Cs. Values of K^D for the desorption of ¹³⁷Cs from the sediment by freshwater, groundwater and seawater were all approximately 10⁵ L kg^-1, confirming its immobility in this environment. The desorption K_D values for stable ¹³³Cs were all approximately 10⁶ L kg^-1, so the stable Cs did not have a significant influence on the radiocaesium in this sediment.     

Remediation and future land use: Incorporating reuse considerations into Superfund activities

The U.S. Environmental Protection Agency (US EPA) is placing increased emphasis on the selection and implementation of remedies that accommodate the reasonably anticipated future use of contaminated land. These remedies result in the long‐term protection of human health and the environment. Postconstruction reuse of the land can significantly benefit communities in other ways as well. The launching of the Superfund Redevelopment Initiative in 1999 and the Return to Use Initiative in 2004 reflects an evolution in the US EPA's understanding of what actions can be taken to support the reuse of Superfund sites from discovery through long‐term stewardship. Through these initiatives, the US EPA has increased its understanding of site reuse and continues to explore and implement reuse assessment, reuse planning, and other tools effective in integrating reuse considerations with response activities throughout the remedial process. © 2005 Wiley Periodicals, Inc.     

Effect of photosensitizer riboflavin on the fate of 2,4,6-trinitrotoluene in a freshwater environment

The effect of riboflavin (1 microM) on the fate of TNT (20 mg/l) in a natural water environment was studied. The relative contribution of photolysis, microbial assemblages and freshwater matrix to TNT degradation was examined. The rates, extent and products of TNT and riboflavin transformation were compared under different experimental conditions. It was found that riboflavin significantly enhanced the degradation of TNT in natural water environment. Thus it is a potentially useful photosensitizing agent for the treatment of TNT-contaminated surface water. Furthermore, in the presence of riboflavin, two new intermediates with max. absorption wavelength of 230 nm were found, demonstrating that transformation of TNT in the presence of riboflavin undergoes different pathways.     

Reduction of Ag(I), Au(III), Cu(II), and Hg(II) by Fe(II)/Fe(III) hydroxysulfate green rust

Green rusts are mixed Fe(II)/Fe(III) hydroxides that are found in many suboxic environments where they are believed to play a central role in the biogeochemical cycling of iron. X-ray absorption fine structure analysis of hydroxysulfate green rust suspensions spiked with aqueous solutions of AgCH(3)COO, AuCl(n)(OH)(4-n), CuCl(2), or HgCl(2) showed that Ag(I), Au(III), Cu(II), and Hg(II) were readily reduced to Ag(0), Au(0), Cu(0), and Hg(0). Imaging of the resulting solids from the Ag(I)-, Au(III)-, and Cu(II)-amended green rust suspensions by transmission electron microscopy indicated the formation of submicron-sized particles of Ag(0), Au(0), and Cu(0). The facile reduction of Ag(I), Au(III), Cu(II), and Hg(II) to Ag(0), Au(0), Cu(0), and Hg(0), respectively, by green rust suggests that the presence of green rusts in suboxic soils and sediments can have a significant impact on the biogeochemistry of silver, gold, copper, and mercury, particularly with respect to their mobility.     

Sensory cues associated with host detection in a marine parasitic isopod

Parasite population dynamics and the evolution of life history characteristics are strongly associated with the process of host infection. Parasites with free-living life stages have a narrow window to infect a host and have evolved a number of mechanisms to detect and locate a host. Cymothoa excisa is a parasitic isopod that is commonly found on the Atlantic croaker, Micropogonias undulatus, in the Gulf of Mexico. Here, we determined the infection window that constrains host-searching behavior in C. excisa and tested the behavioral response of the free-swimming larvae (mancae) to visual and chemical cues. Mancae were found to have an infection window of 7 days. Mancae were responsive to both visual and chemical cues. Our findings are the first to show that cymothoid isopods use visual and chemical cues to locate a host and that individuals display a host-locating strategy that maximizes host encounter rate, while reducing energy expenditure.     

Geochemical associations of plutonium and γ-emitting radionuclides in caithness soils and marine particulates

Geochemical associations of plutonium and artificial γ-emitting radionuclides have been investigated in soils and marine particulate material from the immediate vicinity of the Dounreay Nuclear Power Development Establishment (DNPDE) Caithness. The artificial radionuclides present in these materials arise from a variety of sources: world-wide nuclear weapons test fallout, direct deposition from atmospheric discharges at DNPD, and the return to land of activity previously discharged to sea (containing contributions from Dounreay and Sellafield). The levels, although sufficient to permit satisfactorily low counting errors, are of negligible radiological significance, the plutonium being more than 1000 times less than the NRPB Generalised Derived Limit (GDL) for well-mixed soil. Sequential leaching using selective extractants was performed to quantify the percentages of each nuclide in the following notional fractions: (a) readily available, (b) exchangeable and bound at specific adsorption sites, (c) chelated as insoluble organic complexes, (d) associated with sesquioxides, and (e) residual. Plutonium was found to be associated mainly with phases (c) and (d), while the γ-emitters present in the marine particulate material showed quite varied distributions. The degree of chemical fixation in the particulates follows the sequence ⁴⁰K¹³⁷Cs¹⁰⁶Ru¹²⁵Sb^239,240Pu¹⁴⁴Ce⁶⁰Co^154,155Eu.     

Criteria and air-toxic emissions from in-use automobiles in the National Low-Emission Vehicle program

The U.S. Environmental Protection Agency (EPA) implemented a program to identify tailpipe emissions of criteria and air-toxic contaminants from in-use, light-duty low-emission vehicles (LEVs). EPA recruited 25 LEVs in 2002 and measured emissions on a chassis dynamometer using the cold-start urban dynamometer driving schedule of the Federal Test Procedure. The emissions measured included regulated pollutants, particulate matter, speciated hydrocarbon compounds, and carbonyl compounds. The results provided a comparison of emissions from real-world LEVs with emission standards for criteria and air-toxic compounds. Emission measurements indicated that a portion of the in-use fleet tested exceeded standards for the criteria gases. Real-time regulated and speciated hydrocarbon measurements demonstrated that the majority of emissions occurred during the initial phases of the cold-start portion of the urban dynamometer driving schedule. Overall, the study provided updated emission factor data for real-world, in-use operation of LEVs for improved emissions modeling and mobile source inventory development.