Comparison of methane concentration and stable carbon isotope data for natural samples analyzed by discrete sample introduction module - cavity ring down spectroscopy (DSIM-CRDS) and traditional methods

Online link https://cmgds.marine.usgs.gov/catalog/whcmsc/SB_data_release/DR_P99B34V1/DSIM_EnvironmentalDataMethodComparision_2021_meta.faq.html
Description A discrete sample introduction module (DSIM) was developed and interfaced to a cavity ring-down spectrometer to enable measurements of methane and CO2 concentrations and 13C values with a commercially available cavity ring-down spectrometer (CRDS). The DSIM-CRDS system permits the analysis of limited volume (5 - 100-ml) samples ranging six orders-of-magnitude from 100% analyte to the lower limit of instrument detection (2 ppm). We demonstrate system performance for methane by comparing concentrations and 13C results obtained by the DSIM and traditional methods for a variety of sample types, including low concentration (nanomolar) seawater and high concentration (> 90%) natural gas. The expansive concentration range the CRDS is able to analyze while being packaged in a field-portable analytical system greatly enhances functionality for investigating methane and CO2 dynamics, as well as other gases measured by laser absorption spectroscopy. [More]
Originators Pohlman, John W. and Casso, Michael A.

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Image showing chirp sub-bottom profiler tracklines collected by the U.S. Geological Survey on the inner-continental shelf offshore of Fire Island, NY, 2011.
Image showing chirp sub-bottom profiler tracklines collected by the U.S. Geological Survey on the inner-continental shelf offshore of Fire Island, NY, 2011.
Image of Michael Casso operating the DSIM-CRDS system on a ship during field work.
Image of Michael Casso operating the DSIM-CRDS system on a ship during field work.