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2007-4-25 EST最新文章和摘要
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Exposure of Engineered Nanoparticles to Human Lung Epithelial Cells: Influence of Chemical Composition and Catalytic Activity on Oxidative Stress Ludwig K. Limbach, Peter Wick, Pius Manser, Robert N. Grass, Arie Bruinink, and Wendelin J. Stark* Department of Chemistry and Applied Biosciences, Institute for Chemical and Bioengineering, ETH Zurich, CH-8093 Zurich, Switzerland, and Laboratory for Material-Biology Interactions, Empa, Swiss Federal Laboratories for Materials Testing and Research, Lerchenfeldstrasse 5, CH-9014 St. Gallen, Switzerland Received for review November 2, 2006 Revised manuscript received March 10, 2007 Accepted March 26, 2007 Abstract: The chemical and catalytic activity of nanoparticles has strongly contributed to the current tremendous interest in engineered nanomaterials and often serves as a guiding principle for the design of functional materials. Since it has most recently become evident that such active materials can enter into cells or organisms, the present study investigates the level of intracellular oxidations after exposure to iron-, cobalt-, manganese-, and titania-containing silica nanoparticles and the corresponding pure oxides in vitro. The resulting oxidative stress was quantitatively measured as the release of reactive oxygen species (ROS). The use of thoroughly characterized nanoparticles of the same morphology, comparable size, shape, and degree of agglomeration allowed separation of physical (rate of particle uptake, agglomeration, sedimentation) and chemical effects (oxidations). Three sets of control experiments elucidated the role of nanoparticles as carriers for heavy metal uptake and excluded a potential interference of the biological assay with the nanomaterial. The present results indicate that the particles could efficiently enter the cells by a Trojan-horse type mechanism which provoked an up to eight times higher oxidative stress in the case of cobalt or manganese if compared to reference cultures exposed to aqueous solutions of the same metals. A systematic investigation on iron-containing nanoparticles as used in industrial fine chemical synthesis demonstrated that the presence of catalytic activity could strongly alter the damaging action of a nanomaterial. This indicates that a proactive development of nanomaterials and their risk assessment should consider chemical and catalytic properties of nanomaterials beyond a mere focus on physical properties such as size, shape, and degree of agglomeration. -------------------------------------------------------------------------------- Global Methane Emissions from Terrestrial Plants Christopher L. Butenhoff* and M. Aslam Khan Khalil Department of Physics, Portland State University, P.O. Box 751, Portland, Oregon 97207 Received for review October 6, 2006 Revised manuscript received March 9, 2007 Accepted March 26, 2007 Abstract: Recent measurements suggest that the terrestrial plant community may be an important source of methane with global contributions between 62 and 236 Tg CH4 y-1. If true, terrestrial plants could rival wetlands as being the largest global source of methane forcing us to rethink the methane budget. While further measurements are needed to confirm the methane release rates from this source and their dependencies, in this work we use the preliminary measurements to assess the potential impact of the methane release from this source globally. Using novel techniques we extrapolate the initially reported chamber measurements to the global scale and calculate the global methane emissions from the terrestrial plant community to be in the range 20 to 69 Tg CH4 y-1. The spread in emissions is largely due to the sensitivity of the global flux to the prescribed temperature dependence of the plant emission rate, which is largely unknown. The spread of calculated emissions is in good agreement with the upper limit imposed on the source during the late pre-industrial period, which we estimate to range from 25 to 54 Tg CH4 y-1 during the years 0 to 1700 A.D. using the published atmospheric 13CH4 record. In addition, if we assume that plant emissions have been constant at the mean value of 45 Tg CH4 y-1, we find that the methane release from wildfires and biomass burning during the pre-industrial span 0-1000 A.D. must be near 12 Tg CH4 y-1, which would be in better agreement with previous estimates of the pyrogenic source during this time than a methane budget missing the plant source. We conclude that methane release from the terrestrial plant community as presently understood does not require major innovations to the global methane budget. -------------------------------------------------------------------------------- A Binary Aqueous Component Model for the Sediment-Water Partitioning of Trace Metals in Natural Waters Andrew Turner* School of Earth, Ocean and Environmental Sciences, University of Plymouth, Plymouth PL4 8AA, U.K. Received for review August 24, 2006 Revised manuscript received February 26, 2007 Accepted March 9, 2007 Abstract: A model defining the overall sediment-water partitioning of a chemical, KD, and the partitioning of its conservative components, (KD)i, is presented. With respect to many trace metals in natural waters it is proposed that, through strong and perhaps specific complexation, two independent aqueous components coexist and a binary form of the model is appropriate. For two components of a metal that exhibit unequal partitioning, an inverse relationship between KD and particle concentration is predicted. Published experimental measurements of KD for metals in river waters, derived under conditions which exclude variable concentrations of preexistent colloidal particles, displayed either an inverse dependence (Cu, Ni, and Pd) or little dependence (Cs) on particle concentration. Regarding the former, iterative fits with the binary model were better than empirical fits based on a third (colloidal) phase model, and suggested the presence of between about 10 and 75% of a particle-reactive component ((KD)1 ~ 5 × 104 to 1010 mL g-1) and 25 and 90% of a less reactive (e.g., strongly complexed) component ((KD)2 2.5 × 103 mL g-1). Regarding Cs, data indicated the presence of a single component whose KD was on the order of 103 mL g-1. These observations challenge the conventional means by which sediment-water partitioning is considered and modeled, and imply that a third phase is not always a prerequisite for the particle concentration effect frequently observed in laboratory and field studies. -------------------------------------------------------------------------------- |
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