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SBL443N00
-N2O-
| Observation |
| Frequency |
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Weekly |
| Method |
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GC-ECD |
| Instrument |
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Agilent 6890N |
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| Description |
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In 1997, an automated flask analysis system was developed and flask samples collected at Alert, Sable Island and Estevan Point for CO2 begun being analyzed for nitrous oxide (as well as for methane, sulphur hexafluoride, carbon monoxide and Hydrogen). A pair of air samples are collected approximately weekly in two 2L glass flasks. The flasks have dual glass barreled valves with VitonR o-ring seals. Using a pumping unit, the flasks are first flushed and then filled in parallel to 15psi with a pump. The sampling line extends to the top of nearby towers. A samples are analyzed for N2O at Environment Canada in Toronto by a gas chromatography equipped with an Electron Capture Detector.
Ambient and standard Air samples are bracket by 2 working tanks. Instrument response of the sample are compared to two standards of known N2O content. Measurements are reported in units of nanomol/mol (10^-9 mol N2O per mol of dry air (nmol/mol) or parts per billion (ppb)) relative to the WMO N2O standard scale. Further details on the flask collection/program can be found in the CO2 section. |
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| Calibration |
| Scale |
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WMO mole fraction scale |
| Description |
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All N2O measurements are referenced to a set of six 30L aluminum cylinders purchased in 2005 from Scott Marin in California and calibrated at NOAA. The mixing ratios of the 6 tanks from from 280 to 350 ppb. |
| Data Processing |
| Unit |
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ppb |
| Description |
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The automated control and sampling protocols for the GC Flask analysis system are programmed in methods and sequences within ChemStation software. An injection protocol is typically comprised of a series (~15) of alternating standard tank (High and Low) injections to ensure system stability. The start of flask sample analysis includes 2 injections from a single flask followd by single injections from the two working tanks. This in then by 2 injections from the next flask and then repeated until all flasks have been analysed. 8 to 12 flasks are attached to the system during a single run. Often, the entire sequence if repeated providing 4 individul sample analyses from each flask. Targets flasks (of known concentration) are also included in the sequence to track possible biases and system errors. |
| Average Procedure |
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