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A method for measuring methane oxidation rates using lowlevels of 14C‐labeled methane and accelerator mass spectrometry
Author(s) -
Pack Mary A.,
Heintz Monica B.,
Reeburgh William S.,
Trumbore Susan E.,
Valentine David L.,
Xu Xiaomei,
Druffel Ellen R. M.
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.2011.9.245
Subject(s) - methane , chemistry , anaerobic oxidation of methane , environmental chemistry , mass spectrometry , environmental science , tracer , analytical chemistry (journal) , radiochemistry , nuclear physics , chromatography , physics , organic chemistry
We report a new method for methane oxidation rate measurements that uses 10 3 –10 5 times less 14 C‐CH 4 than existing measurements by taking advantage of the high sensitivity of accelerator mass spectrometry. Methane oxidation in the marine environment is a microbial process of global importance because it prevents methane released from underlying reservoirs from reaching the ocean and atmosphere. Rate measurements provide a crucial tool for assessing the efficacy of this process across a range of environments, but the current methods use high amounts of radioactive elements ( 3 H‐ or 14 C‐CH 4 ), tend to increase methane concentrations in a sample markedly over in situ levels, and are limited by strict health and safety regulations. The low‐level method presented here uses levels of 14 C‐CH 4 that are below transportation regulations, produce samples that do not require treatment as radioactive waste, and allow for tracer level rate measurements in low methane environments. Moreover, the low‐level method lays the analytical foundation for a below‐regulation rate measurement that could be used broadly and in‐situ. Parallel rate measurements with the low‐level 14 C‐CH 4 and existing 3 H‐CH 4 methods are generally consistent with a correlation coefficient of 0.77. However, the low‐level method in most cases yields slower rates than the 3 H method possibly due to temperature, priming, and detection limit effects.