thumbnail

Effects of nitrate and water on the oxygen isotopic analysis of barium sulfate precipitated from solution

Rapid Communications in Mass Spectrometry

By:
, ,
DOI: 10.1002/rcm.3832

Links

Abstract

BaSO4 precipitated from mixed salt solutions by common techniques for SO isotopic analysis may contain quantities of H2O and NOthat introduce errors in O isotope measurements. Experiments with synthetic solutions indicate that δ18O values of CO produced by decomposition of precipitated BaSO4 in a carbon reactor may be either too low or too high, depending on the relative concentrations of SO and NO and the δ18O values of the H2O, NO, and SO. Typical δ18O errors are of the order of 0.5 to 1‰ in many sample types, and can be larger in samples containing atmospheric NO, which can cause similar errors in δ17O and Δ17O. These errors can be reduced by (1) ion chromatographic separation of SO from NO, (2) increasing the salinity of the solutions before precipitating BaSO4 to minimize incorporation of H2O, (3) heating BaSO4 under vacuum to remove H2O, (4) preparing isotopic reference materials as aqueous samples to mimic the conditions of the samples, and (5) adjusting measured δ18O values based on amounts and isotopic compositions of coexisting H2O and NO. These procedures are demonstrated for SO isotopic reference materials, synthetic solutions with isotopically known reagents, atmospheric deposition from Shenandoah National Park, Virginia, USA, and sulfate salt deposits from the Atacama Desert, Chile, and Mojave Desert, California, USA. These results have implications for the calibration and use of O isotope data in studies of SOsources and reaction mechanisms.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Effects of nitrate and water on the oxygen isotopic analysis of barium sulfate precipitated from solution
Series title:
Rapid Communications in Mass Spectrometry
DOI:
10.1002/rcm.3832
Volume
22
Issue:
24
Year Published:
2008
Language:
English
Publisher:
Wiley
Contributing office(s):
Branch of Regional Research-Eastern Region
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Rapid Communications in Mass Spectrometry
First page:
4109
Last page:
4120
Country:
United States