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Stable carbon isotope analysis of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) in natural waters – Results from a worldwide proficiency test
Author(s) -
Geldern Robert,
Verma Mahendra P.,
Carvalho Matheus C.,
Grassa Fausto,
DelgadoHuertas Antonio,
Monvoisin Gael,
Barth Johannes A. C.
Publication year - 2013
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.6665
Subject(s) - seawater , dissolved organic carbon , environmental chemistry , isotopes of carbon , chemistry , total inorganic carbon , carbon fibers , stable isotope ratio , mineralogy , total organic carbon , oceanography , carbon dioxide , geology , materials science , physics , organic chemistry , quantum mechanics , composite number , composite material
RATIONALE Stable carbon isotope ratios of dissolved inorganic (DIC) and organic carbon (DOC) are of particular interest in aquatic geochemistry. The precision for this type of analysis is typically reported in the range of 0.1‰ to 0.5‰. However, there is no published attempt that compares δ 13 C measurements of DIC and DOC among different laboratories for natural water samples. METHODS Five natural water samples (lake water, seawater, two geothermal waters, and petroleum well water) were analyzed for δ 13 C DIC and δ 13 C DOC values by five laboratories with isotope ratio mass spectrometry (IRMS) in an international proficiency test. RESULTS The reported δ 13 C DIC values for lake water and seawater showed fairly good agreement within a range of about 1‰, whereas geothermal and petroleum waters were characterized by much larger differences (up to 6.6‰ between laboratories). δ 13 C DOC values were only comparable for seawater and showed differences of 10 to 21‰ for other samples. CONCLUSIONS This study indicates that scatter in δ 13 C DIC isotope data can be in the range of several per mil for samples from extreme environments (geothermal waters) and may not yield reliable information with respect to dissolved carbon (petroleum wells). The analyses of lake water and seawater also revealed a larger than expected difference and researchers from various disciplines should be aware of this. Evaluation of analytical procedures of the participating laboratories indicated that the differences cannot be explained by analytical errors or different data normalization procedures and must be related to specific sample characteristics or secondary effects during sample storage and handling. Our results reveal the need for further research on sources of error and on method standardization. Copyright © 2013 John Wiley & Sons, Ltd.