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Long-term Fate (long-term + fate)
Selected AbstractsAccumulation of polycyclic aromatic hydrocarbons in rural soils based on mass balances at the catchment scaleENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2007Tilman Gocht Abstract Polycyclic aromatic hydrocarbons (PAHs) are hydrophobic organic pollutants that are ubiquitously distributed in the environment at relatively high concentrations. In our study we investigated the long-term fate of atmospheric PAHs in soils of rural areas, resulting from diffuse pollution based on mass balances at the catchment scale. By determining PAHs in several environmental compartments, estimates of soil storages and water fluxes were made and compared with atmospheric deposition. The results indicate that more than 90% of the incoming PAHs remain in the catchments and accumulate in the topsoils. Furthermore, revolatilization of PAHs from soils and degradation in the soils is very limited, resulting in ongoing accumulation in topsoils, in particular for low-volatile PAHs. Combustion-derived carbonaceous particles were detected in atmospheric deposition as well as in the soil samples. Since these particles are very strong adsorbents, they are suspected to play a key role in the environmental fate of the diffuse distributed PAHs. [source] Comment on "the long-term fate of polychlorinated biphenyls in San Francisco bay, (USA)"ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2005John P. Connolly No abstract is available for this article. [source] The long-term fate of polychlorinated biphenyls in San Francisco Bay (USA)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2004Jay A. Davis Abstract A simple one-box mass budget model is presented as a first step toward a quantitative understanding of the long-term fate of polychlorinated biphenyls (PCBs) in San Francisco Bay (USA). Sensitivity analysis indicated that the most influential input parameters were degradation half-life in sediment, Kow, outflow, average PCB concentration in sediment, and depth of the active sediment layer. Moderately influential parameters included organic carbon content of suspended solids, sediment burial mass transfer coefficient, and Henry's law constant. If external loading could be eliminated entirely, the mass of PCBs in the bay is predicted to drop to half of the present value in 20 years. The model predicts that sustained loading of 10 kg year,1 would prevent the total PCB mass in the bay from ever dropping below 10% of the present mass. With a sustained loading of 20 kg year,1, the model predicts that the total PCB mass would never fall below about 25% of the present mass. The half-lives in the bay for the individual PCB congeners evaluated in this report ranged from four years for PCB 18 to 30 years for PCB 194. [source] The fate of an intentional introduction of Formica lugubris to North America from EuropeJOURNAL OF APPLIED ENTOMOLOGY, Issue 4 2008A. J. Storer Abstract Red wood ants (Formica s.str.) are not prevalent in the forests of North America, but commonly occur in conifer and mixed conifer forests in northern Europe and Asia. In 1971, a European red wood ant species, Formica lugubris, was intentionally established in a 35-year-old predominantly mixed conifer plantation approximately 30 km north of QC, Canada. The purpose of its introduction was to evaluate the potential of this species as a biological control agent against conifer-defoliating Lepidoptera species. This red wood ant introduction was monitored periodically for about 5 years after establishment, but its long-term fate has not been reported. We visited this field site in 2005 and found that this species was well established, and we could locate some of the nests that resulted from the original release. We mapped and measured over 100 nests around the site of original release, which ranged from 5 cm in height to over 1 m. We estimated the population of introduced ants to have grown to over 8 million in the last 34 years. Significant clustering of nests suggests that these nests may be one supercolony. F. lugubris has become a dominant understory arthropod in this mixed forest, and is likely to have ecological impacts, including effects at the community and ecosystem level. [source] Stem cell implantation in ischemic mouse heart: a high-resolution magnetic resonance imaging investigation,NMR IN BIOMEDICINE, Issue 6 2005Ekkehard Küstermann Abstract Advances in the biology of stem cells have evoked great interest in cell replacement therapies for the regeneration of heart tissue after myocardial infarction. However, results from human trials are controversial, since the destination of the injected cells, their engraftment and their long-term fate have remained unclear. Here we investigate whether transplanted cells can be identified in the intact and lesioned murine myocardium employing high-resolution MRI. Cardiac progenitor cells, expressing the enhanced green fluorescent protein (EGFP), were labeled with ultra-small paramagnetic iron-oxide (USPIO) nanoparticles and transplanted into the intact or injured myocardium of mice. Their precise location was determined with high-resolution MRI and compared with histological tissue sections, stained with Prussian blue for iron content. These experiments showed that iron nanoparticle-loaded cells could be identified at high resolution in the mouse heart. However, ischemic myocardium (after cryoinjury or left coronary artery ligation) was characterized by a signal attenuation similar to that induced by USPIO-labeled cells in T -weighted MR images, making detection of labeled stem cells in this area by T -sensitive contrast rather difficult. In animals with myocardial injury only, the signal attenuated areas were of the same size in proton density- and T -weighted MR images. In injured animals also receiving labeled cells the lesioned area appeared larger in T - than in proton density-weighted MR images. This sequence-dependent lesion size change is due to the increased signal loss caused by the iron oxide nanoparticles, most sensitively detectable in the T -sensitive images. Thus, using the novel combination of these two parameter weightings, USPIO-labeled cells can be detected at high resolution in ischemic myocardium. Copyright © 2005 John Wiley & Sons, Ltd. [source] Re-examination of organ-cultured, cryopreserved human corneal grafts after 27 yearsACTA OPHTHALMOLOGICA, Issue 2 2009Charlotte Corydon Abstract. Purpose:, To determine the long-term fate of cryopreserved corneas. Review of 17 organ-cultered cryopreserved corneas grafted in 1978,1979. Methods:, We measured visual acuity and refraction and performed biomicroscopy, applanation tonometry and optical pachometri (CCT). Endothelial photos were taken, cells were counted and morphology was studied. Results:, Four of 16 grafted corneas were still clear after 27 years. Mean CCT was 0.52 mm, endothelial cell density was 882 cells/mm2 and visual acuity was 0.25 or better with an average of 0.6 in the four patients. Cell morphology showed irregularity in shape and size. Conclusion:, This study shows that cryopreserved endothelium can function as well as non-frozen corneas and that a regular hexagonal pattern is not essential for corneal clarity. The four grafts showed long-term durability despite the irregularity in shape and size. [source] | |||||||||||||