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

Rapid Communications in Mass Spectrometry

By:
, , and
https://doi.org/10.1002/rcm.3832

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Abstract

BaSO4 precipitated from mixed salt solutions by common techniques for SOmath image isotopic analysis may contain quantities of H2O and NOmath image that 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 SOmath image and NOmath image and the δ18O values of the H2O, NOmath image, and SOmath image. Typical δ18O errors are of the order of 0.5 to 1‰ in many sample types, and can be larger in samples containing atmospheric NOmath image, which can cause similar errors in δ17O and Δ17O. These errors can be reduced by (1) ion chromatographic separation of SOmath image from NOmath image, (2) increasing the salinity of the solutions before precipitating BaSO4 to minimize incorporation of H2O, (3) heating BaSO4under 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 NOmath image. These procedures are demonstrated for SOmath image 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 SOmath image sources 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 water samples
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
Description:
12 p.
First page:
4109
Last page:
4120
Country:
United States