While particulate matter (PM) in the atmosphere can lead to a wide array of negative health effects, the cause of toxicity is largely unknown. One aspect of PM that likely affects health is the chemical composition, in particular the transition metals within the particles. Chromium is one transition metal of interest due to its two major oxidation states, with Cr(III) being much less toxic compared to Cr(VI). Using microfocused X-ray absorption near edge structure (micro-XANES), we analyzed the Cr speciation in fine particles (diameters < or = 2.5 microm) collected at three sites in the Sacramento Valley of northern California. The microfocused X-ray beam enables us to look at very small areas on the filter with a resolution of typically 5-7 micrometers. With XANES we are able to not only distinguish between Cr(VI) and Cr(III), but also to identify different types of Cr(III) and more reduced Cr species. At all of our sampling sites the main Cr species were Cr(III), with Cr(OH)3 or a Cr-Fe, chromite-like, phase being the dominant species. Cr(VI)-containing particles were found only in the most urban site. All three sites contained some reduced Cr species, either Cr(0) or Cr3C2, although these were minor components. This work demonstrates that micro-XANES can be used as a minimally invasive analytical tool to investigate the composition of ambient PM.
While atmospheric particles can have adverse health effects, the reasons for this toxicity are largely unclear. One possible reason is that the particles can contain toxic metals such as chromium. Chromium exists in the environment in two major oxidation states: III, which is an essential nutrient, and VI, which is highly toxic and carcinogenic. Currently little is known about the speciation of chromium in airborne particles or how this speciation is altered by atmospheric reactions. To investigate the potential impacts of atmospheric aging on the speciation and toxicity of chromiumcontaining particles, we collected chromium and chromium-iron combustion ultrafine particles on Teflon filters and exposed the particles to a combination of light, ozone, water vapor, and, in We thank Dr. Matthew Newville of the GSECARS at the Advanced Photon Source (APS), Argonne National Laboratory, for his assistance. The majority to the X-ray data presented above were collected at GeoSoilEnviroCARS (Sector 13), which is supported by the National Science Foundation-Earth Sciences (EAR-0217473), Department of Energy-Geosciences (DE-FG02-94ER14466) and the State of Illinois. Use of the APS was supported by the U.S. Department of Energy under Contract No. W-31-109-Eng-38. We would also like to thank Dr. Matthew Marcus of beamline 10.3.2 of the Advanced Light Source (Lawrence Berkeley National Laboratory), which is supported by the US Department of Energy (DE-AC02-05CH11231). Portions of this research were also carried out at the Stanford Synchrotron Radiation Laboratory, operated by Stanford University on behalf of the U.S. Department of Energy. Finally, we thank David Paige (Paige Instruments) for constructing the ozone generator, John Newberg and Mike JimenezCruz for building the ozone dilution and delivery system, and Michelle Gras of the UC Davis Interdisciplinary Center for Plasma Mass Spectrometry for conducting the ICP-MS analyses. This work was supported by grant number 5 P42 ES04699 from the National Institute of Environmental Health Sciences (NIEHS) of the NIH, and by a fellowship from the UC Davis NEAT-IGERT program to Michelle Werner (NSF IGERT Grant # 9972741). Partial support was also provided by the U.S. Department of Energy under contract number DE-AC02-05CH11231. The contents of this paper are solely the responsibility of the authors and do not necessarily represent the official views of the NIEHS, NIH.Address correspondence to Cort Anastasio, One Shields Avenue, Department of Land, Air & Water Resources, University of California, Davis, CA 95616. E-mail: canastasio@ucdavis.edu some cases, basic or acidic conditions. After the aging process, the aged and not-aged samples were analyzed for Cr oxidation state using X-ray Absorption Near Edge Spectroscopy (XANES). We found that the aging process reduced Cr(VI) by as much as 20% in chromium particles that had high initial Cr(VI)/Cr(total) ratios. This reduction of Cr(VI) to Cr(III) appears to be due to reactions primarily with light and hydroperoxyl radical (HO 2 ) in the...
Vanadium phthalocyanine and porphyrin complexes, in conjunction with methylaluminoxane (MAO) or EtAlCl2 cocatalyst, have been found to catalyze the homopolymerization of ethene. In addition, the copolymerization of ethene with propene and 1-decene was achieved with the vanadium phthalocyanine complex and MAO. Nickel phthalocyanine complex was also found to catalyze the polymerization of ethene in the presence of MAO. However, only dimerization was observed when EtAlCl2 was used as the cocatalyst.Key words: phthalocyanine, porphyrin, polymerization, copolymerization, ethene, propene, 1-decene.
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