共查询到20条相似文献，搜索用时 93 毫秒
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Robert Riding 《Geological Journal》2005,40(2):246-247
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Ernst Lffler 《Quaternary Research》1979,11(3):388-389
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V. Neck 《Geochimica et cosmochimica acta》2006,70(17):4551-4555
In a recent study [Rao, L., Srinivasan, T.G., Garnov, A.Yu., Zanonato, P., Di Bernardo, P., Bismondo, A., 2004. Hydrolysis of neptunium(V) at variable temperatures (10-85 °C). Geochim. Cosmochim. Acta68, 4821-4830.] the hydrolysis of Np(V) was investigated at 10-85 °C by absorption spectroscopy, potentiometry, and microcalorimetry along the titration of Np(V) solutions with tetramethylammonium hydroxide up to pH 10. However, there is strong evidence that the precautions to avoid competing reactions with carbonate were not sufficient and that the measured effects are not caused by the formation of Np(V) hydroxide complexes but primarily by the formation of Np(V) carbonate complexes. The reported equilibrium constants, enthalpies, entropies, and heat capacities for the complexes NpO2OH(aq) and are severely in error and must not be used for the geochemical modeling of neptunium. If the hydrolysis constants reported by Rao et al. [Rao, L., Srinivasan, T.G., Garnov, A.Yu., Zanonato, P., Di Bernardo, P., Bismondo, A., 2004. Hydrolysis of neptunium(V) at variable temperatures (10-85 °C). Geochim. Cosmochim. Acta68, 4821-4830] are used to calculate neptunium solubilities in alkaline solutions relevant for nuclear waste repositories, the Np(V) concentrations are overestimated by orders of magnitude. 相似文献
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Peter W. Scott 《Geological Journal》2016,51(1):161-162
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Pagani et al. [Pagani M., Lemarchand D., Spivack A., and Gaillardet J. (2005). A critical evaluation of the boron isotope-pH proxy: the accuracy of ancient ocean pH estimates. Geochim. Cosmochim. Acta69(4), 953-961] use data from previous boron isotope studies to suggest that the fractionation between boric acid and borate in seawater as well as the history of δ11B in seawater are poorly understood, thus limiting our ability to capture realistic ocean pH with this proxy. Although we agree with the authors that the long recognized uncertainty in the secular variation of δ11Bseawater imposes a temporal limit on paleo-pH reconstructions, their evaluation of the δ11B/pH relationship in carbonates is flawed. Potential complications from vital, temperature and dissolution effects reported in that paper are based on studies that are experimentally and/or analytically poorly constrained. Using published validation studies we will demonstrate that many of the problems outlined by Pagani et al. have already been addressed, or are based on misinterpretations of previous work. Most importantly, statistical evaluation suggests empirical data are best described by a fractionation of ∼20‰. Recent paleoreconstructions confirm that the boron isotope proxy can be used with confidence, if sample selection and analyses are done carefully. 相似文献
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Louis G. Zachos 《Geological Journal》2014,49(3):329-329
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