CO2 Radiocarbon Analysis to Quantify Organic Contaminant Degradation MNA and Engineered Remediation Approaches
Technical Report,01 Oct 2015,30 Sep 2019
NAVAL RESEARCH LAB WASHINGTON DC WASHINGTON United States
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This report summarizes SERDP ER2338 efforts at the Naval Air Station North Island NASNI IR-5 Unit 2 and OU-1920 study sites with preliminary information on recent deployments at Indian Head Naval Surface Warfare Center IR-17 and IR-57. This report includes equipment and sampler designs, deployment and long-term monitoring activities at field sites to determine in situ chlorinated volatile organic compound cVOC degradation. Samples from one-year collections at IR-5U2 and OU-1920 were analyzed for overall respirationCO2 production, CO2 radiocarbon content, and ancillary measurements cations, contaminant concentrations, well casing methane. CO2 collection rate measurements were used to create and refine zone of influence ZOI simulations. A two end-member isotope mixing model was used to determine the respiration attributable to fossil contaminant sources during each one-month CO2 trap deployment. A background well no contamination was used at each site to represent contemporary CO2 age from natural root and soil respiration. All data were converted to rates per unit volume and interpolated over the site for each 1-month trap deployment. These data were then compiled to determine an overall cVOC degradation over the site over the one-year period. CO2 traps were deployed at two sites Indian Head NSWC in February 2017, IR-17 and IR-57. Both sites have TCE contamination. Over one year of1-2 month samplings have been collected and analyzed for respiration rate. ZOI simulations have been performed to provide a volumetric basis. Radiocarbon analysis has been delayed. An ad hoc effort has been initiated to assemble a CO2 cryogenic distillation line to purify CO2 for gas-source inlet AMS at Woods Hole Oceanographic Institutions NOSAMS lab. This would reduce analytical costs almost 10-fold and allow greater spatial and temporal resolution for the radiocarbon method.
- Environmental Health and Safety