Probe beam deflection combined with cyclic voltammetry studies of C-60-modified electrode film

C-60 films, prepared by solution casting, were studied by means of in situ probe beam deflection (PBD) combined with cyclic voltammetry (CV). PBD is a powerful technique for investigation of phenomena at the electrode/electrolyte interface in acetonitrile with quaternary ammonium and alkali metal salts as supporting electrolytes. In tetra-n-butylammonium (TBA(+)) salt solution, a stable CV can be obtained during the first two reduction/reoxidation waves. On reduction, injection of cations to maintain charge balance and dissolution of small amount of C-60(-) (TEA(+)) and/or C-60(2-) (TBA(+))(2) are detected. During the reoxidation process ejection of cations and injection of anions occur simultaneously, especially for the second reoxidation wave. In the case where TBABr is the supporting electrolyte, the accompanied behavior is more complicated than in TBABF(4), TBAClO(4), and TBAPF(6) solutions. A small pair of prewaves in CV are proposed due to oxidation/reduction of C-60 domains but not dissolution/redeposition of C-60 film. Extending the potential scan range to the third reduction wave, no apparent corresponding reoxidation wave is related to the third reduction wave, the electroactivity of the film disappears rapidly and dissolution of C-60 film is observed. In tetraethylammonium (TEA(+)) and NAClO(4) solutions, the electrochemistry of the C-60 films is unstable, and potential scans lead to dissolution of flaking of the film.

GAS-PHASE ION-MOLECULE REACTIONS OF BUCKMINSTERFULLERENE C-60 WITH SOME SMALL ORGANIC-COMPOUNDS IN MASS-SPECTROMETER

In chemical ionization mass spectrometry (CIMS) gas phase C-60(+) or C-60 can react with fragment ions from three chloromethane and four multichloroethane molecular ions via ion-molecule reactions. A dozen of gas-phase adduct ions of C-60 are observed, and most of them contain chlorine atoms. The results of the comparison and analysis show that the relative intensities of adductions are not directly proportional to the corresponding fragment ions in the MS of reagents,which implies that some fragment ions containing radicals are more reactive with C-60(+) or C-60. This indicates that the alkene-like C-60(+) or C-60 can act as a radical sponge in addition reactions.

Ocean urea fertilization for carbon credits poses high ecological risks

The proposed plan for enrichment of the Sulu Sea, Philippines, a region of rich marine biodiversity, with thousands of tonnes of urea in order to stimulate algal blooms and sequester carbon is flawed for multiple reasons. Urea is preferentially used as a nitrogen source by some cyanobacteria and dinoflagellates, many of which are neutrally or positively buoyant. Biological pumps to the deep sea are classically leaky, and the inefficient burial of new biomass makes the estimation of a net loss of carbon from the atmosphere questionable at best. The potential for growth of toxic dinoflagellates is also high, as many grow well on urea and some even increase their toxicity when grown on urea. Many toxic dinoflagellates form cysts which can settle to the sediment and germinate in subsequent years, forming new blooms even without further fertilization. If large-scale blooms do occur, it is likely that they will contribute to hypoxia in the bottom waters upon decomposition. Lastly, urea production requires fossil fuel usage, further limiting the potential for net carbon sequestration. The environmental and economic impacts are potentially great and need to be rigorously assessed. (C) 2008 Elsevier Ltd. All rights reserved.

黄土高原中部60万年来黄土—古土壤序列有机碳同位素研究

Vegetation is very sensitive to climate change. Carbon isotopes in paleosol have been widely used to contruct the propotion of plants using C3 and C4 photosynthetic pathways. δ13C of Loess organic matter were analyzed on the loess- paleosols samples from Jingchuan sections and Luochuan S4—S5 sequence. This paper presents a long carbon isotope time series, covering the last 600kyr. δ13C record of Loess organic matter in Jingchuan is correlated with marine oxygen isotope records. Basing on former research work, this paper discusses temperature, rainfall and P CO2 effect on δ13Corg value. In the interglacial periods, carbon isotope is more sensitive than other proxies and indicates several climate fluctuations. The main conclusions are as follows: 1. Obtained δ13C composition from paleosols and loess sediments in Jingchuan range of -20.0‰ to -24.6‰, the maximum biomass of C4 is 35%, indicating a C3 and C4 mixed steppe with C3 dominated. C4 plant is not always expansion during paleosols periods. The minimum values of Jingchuan section appeared in S4 soil, and the vegetation was almost pure C3 plant at that time. δ13Corg value in S5-2 is also lower than loess in S5, reaching the minimum valus of S5 soil. 2. PCO2 variation has little impact on δ13Corg value in interglacial periods for the last 600kyr. The correlation between δ13Corg value curve and magnetic susceptibility curve as proxy of summer monsoon in general, means summer monsoon drive C4 plant expansion during glacial and interglacial. 3. The lowerδ13Corg values in S4 and S5-2 appear at Jingchuan and Luochuan, suggest origin from woodland or C3 grassland. Whatever vegetation it is, indicate strengthened East Asian summer monsoon and increase of precipitation. C4 plant percentage is lower in S5-1 and S1 which have stronger summer monsoon, than S0 and S2. And it also indicates increase of precipitation.δ13Corg values has not always non-linearity correlation with summer monsoon. 4. The maximum entroy spectral analysis of δ13C values of the last 600kyr indicates there is 21 kyr cycles in Loess sequence. It means that summer monsoon in the Chinese Loess Plateau also has the precession cycles like its origin low latitude.