科研之友
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摘要
RATIONALE: Quantifying the processes that control dissolved inorganic carbon (DIC) dynamics in aquatic systems is essential for progress in ecosystem carbon budgeting. The development of a methodology that allows high-resolution temporal data collection over prolonged periods is essential and is described in this study. METHODS: A novel sampling instrument that sequentially acidifies aliquots of water and utilises gas-permeable ePTFE tubing to measure the dissolved inorganic carbon (DIC) concentration and delta C-13(DIC) values at sub-hourly intervals by Cavity Ring-down spectrometry (CRDS) is described. RESULTS: The minimum sensitivity of the isotopic, continuous, automated dissolved inorganic carbon analyser (ISO-CADICA) system is 0.01 mM with an accuracy of 0.008 mM. The analytical uncertainty in delta(CDIC)-C-13 values is proportional to the concentration of DIC in the sample. Where the DIC concentration is greater than 0.3 mM the analytical uncertainty is +/- 0.1 % and below 0.2 mM stability is %26lt; +/- 0.3 %. The isotopic effects of air temperature, water temperature and CO2 concentrations were found to either be negligible or correctable. Field trials measuring diel variation in delta(CDIC)-C-13 values of coral reef associated sea water revealed significant, short-term temporal changes and illustrated the necessity of this technique. CONCLUSIONS: Currently, collecting and analysing large numbers of samples for delta(CDIC)-C-13 measurements is not trivial, but essential for accurate carbon models, particularly on small scales. The ISO-CADICA enables on-site, high-resolution determination of DIC concentration and delta(CDIC)-C-13 values with no need for sample storage and laboratory analysis. The initial tests indicate that this system can offer accuracy approaching that of traditional IRMS analysis.
- 出版日期2012-3-30
