6 research outputs found
The release and migration of activation products from corrosion-resistant metal specimens in marine sediments
Sulfur isotope measurement of sulfate and sulfide by high-resolution MC-ICP-MS
Author Posting. © Elsevier B.V. , 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Chemical Geology 253 (2008): 102-113, doi:10.1016/j.chemgeo.2008.04.017.We have developed a technique for the accurate and precise determination of 34S/32S isotope
ratios (δ34S) in sulfur-bearing minerals using solution and laser ablation multiple-collector
inductively coupled plasma mass spectrometry (MC-ICP-MS). We have examined and
determined rigorous corrections for analytical difficulties such as instrumental mass bias,
unresolved isobaric interferences, blanks, and laser ablation- and matrix-induced isotopic
fractionation. Use of high resolution sector-field mass spectrometry removes major isobaric
interferences from O2+. Standard–sample bracketing is used to correct for the instrumental mass
bias of unknown samples. Blanks on sulfur masses arising from memory effects and residual
oxygen-tailing are typically minor (< 0.2‰, within analytical error), and are mathematically
removed by on-peak zero subtraction and by bracketing of samples with standards determined at
the same signal intensity (within 20%). Matrix effects are significant (up to 0.7‰) for matrix
compositions relevant to many natural sulfur-bearing minerals. For solution analysis, sulfur
isotope compositions are best determined using purified (matrix-clean) sulfur standards and
sample solutions using the chemical purification protocol we present. For in situ analysis, where
the complex matrix cannot be removed prior to analysis, appropriately matrix-matching
standards and samples removes matrix artifacts and yields sulfur isotope ratios consistent with
conventional techniques using matrix-clean analytes. Our method enables solid samples to be
calibrated against aqueous standards; a consideration that is important when certified,
isotopically-homogeneous and appropriately matrix-matched solid standards do not exist.
Further, bulk and in situ analyses can be performed interchangeably in a single analytical session
because the instrumental setup is identical for both. We validated the robustness of our analytical
method through multiple isotope analyses of a range of reference materials and have compared
these with isotope ratios determined using independent techniques. Long-term reproducibility of
S isotope compositions is typically 0.20‰ and 0.45‰ (2σ) for solution and laser analysis,
respectively. Our method affords the opportunity to make accurate and relatively precise S
isotope measurement for a wide range of sulfur-bearing materials, and is particularly appropriate
for geologic samples with complex matrix and for which high-resolution in situ analysis is
critical.Support was provided by National Science Foundations grants OCE-0327448 to P.R.C. and
W.B. and OCE-0622982 to O.J.R. Support for L.A.B. was provided by the Woods Hole
Oceanographic Institution Plasma Facility Development Grant (NSF-EAR/IF-0318137)
The release and migration of activation products from corrosion-resistant metal specimens in marine sediments
An investigation of the release of Ni-63, Co-60, and Fe-55 from Inconel
600 and 347SS stainless steel specimens implanted in marine sediment for one
year is described. Radiochemical analysis of the sediment from overcores of
the metal specimens permits estimation of integrated activities, release rates,
and diffusion coefficients of the three radionuclides. Disturbance of the
sediment upon recovery limits the values to order of magnitude estimates. The
redox chemistry of the sediments is characterized by measurement of several
naturally occurring oxidizing agents and is correlated with the behavior of
the radionuclides. Details of the deployment, sampling and analytical procedures
are also given
The HITRAN 2008 molecular spectroscopic database
This paper describes the status of the 2008 edition of the HITRAN molecular spectroscopic database. The new edition is the first official public release since the 2004 edition, although a number of crucial updates had been made available online since 2004. The HITRAN compilation consists of several components that serve as input for radiative-transfer calculation codes: individual line parameters for the microwave through visible spectra of molecules in the gas phase; absorption cross-sections for molecules having dense spectral features, i.e. spectra in which the individual lines are not resolved; individual line parameters and absorption cross-sections for bands in the ultraviolet; refractive indices of aerosols, tables and files of general properties associated with the database; and database management software. The line-by-line portion of the database contains spectroscopic parameters for 42 molecules including many of their isotopologues. © 2009 Elsevier Ltd.SCOPUS: ar.jinfo:eu-repo/semantics/publishe