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In situ determination of total dissolved inorganic carbon by underwater membrane introduction mass spectrometry
Author(s) -
Bell Ryan J.,
Short R. Timothy,
Byrne Robert H.
Publication year - 2011
Publication title -
limnology and oceanography: methods
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.898
H-Index - 72
ISSN - 1541-5856
DOI - 10.4319/lom.2011.9.164
Subject(s) - seawater , chemistry , carbonate , bicarbonate , hydrostatic pressure , analytical chemistry (journal) , dissolved organic carbon , carbon dioxide , artificial seawater , salinity , fugacity , environmental chemistry , oceanography , geology , physics , organic chemistry , thermodynamics
Procedures have been developed for the determination of total dissolved inorganic carbon (DIC) in acidified seawater using an underwater mass spectrometer. Factors affecting the response of the membrane introduction mass spectrometer (MIMS) system were examined to optimize calibrations and enhance the accuracy of component ocean carbon system measurements. Laboratory studies examined the following influences on MIMS measurements of DIC: bicarbonate and carbonate contributions to the MIMS CO 2 signal intensity, linearity of MIMS response over a wide range of carbon dioxide concentrations, influence of sample salinity on membrane permeability, and capability to use acidified solutions for calibrations of both DIC and CO 2 fugacity. It was observed that (a) bicarbonate and carbonate contributions to carbon dioxide signal intensity were significant at slow flow rates, (b) MIMS response was linearly dependent on DIC within the concentration range of interest, (c) salinity has a discernable influence on membrane permeability that is, in turn, dependent on hydrostatic pressure, and (d) well calibrated MIMS measurements for both DIC and CO 2 fugacity can be obtained using acidified DIC standards. High flow rates are required during CO 2 fugacity measurements in circumneutral seawater to eliminate signal contributions from bicarbonate and carbonate.