|
| 
Estevan Point
-CO-
| Observation |
| Category |
: |
Air sampling observation |
| Situation |
: |
ongoing |
| Time zone |
: |
UTC |
| Sampling |
| Sampling height |
: |
40 |
| Description |
: |
continuous |
| Sampling and analysis frequency |
: |
Hourly |
| Sampling environment |
: |
Coastal Site |
| Description for sampling analysis |
: |
The continuous measurement of CH4 and CO at Estevan is made using an Agilent gas chromatograph (Model 6890N) employing flame ionization detection. The system is fully automated via HP Chemstation software.
Ambient air is delivered to the GC at approximately 5 L min-1 by a vacuum pump via a dedicated 0.95 cm o.d. sample line that extends to the top of the. The air passes through a membrane filter, then through a pressure relief valve set at ~1 atmosphere to release excess pressure and is then dried to a dew point of around -60 degress C by passing the air through a glass trap submerged in an -80 degree C methanol bath. All standard gases are supplied to the GC from pressurized gas cylinders equipped with high-purity, two-stage gas regulators.
CO and CH4 are first passed on to a 4'x1/8" pre-column (Molesieve 5a) and then passed on to 4'x1/8" analytical column (Unibeads 1s). The pre-column is back flushed allowing late eluting components and contamination to be passed back to the room. All columns are contained in the same oven and maintained at 80¡C. An electronic pressure controller is used to control the nitrogen carrier gas flow rate (~60 ml/min). CH4 elutes at ~2 minutes and CO at ~4 minutes after injection. After the CH4 elutes, a 1/16¡É 6-port two-position valve is switched, allowing the CO to pass through a heated Nickel catalyst. The catalyst converts the CO to CH4, permitting the analysis of CO to be done on the FID. The shunting configuration also avoids having the oxygen to pass through the catalyst, thus eliminating potential contamination as well as a large air peak that can cause baseline irregularities to occur near the CH4 peak.
Measurement cycles consist of repeated series of standard gas and ambient air injections. The peak height for the standard injection is used to calculate the CH4 mole fraction of the ambient injections.
The CO and measurements are reported relative to the WMO assigned measurement scales.. Analytical precision based on replicate injections for standard tank gas is approximately 1.5 ppb for CH4 and 2 ppb for CO. |
| Instrument and Analysis |
| Measurement method |
: |
Gas Chromatography (FID) |
| Current status and history of instrument |
: |
GC-FID |
| Description of instrument |
: |
Agilent 6890N |
| Calibration |
| Current scale employed in the measurement |
: |
WMO mole fraction scale |
| Measurement calibration |
: |
|
| Scale and calibration(treasability) |
: |
|
| Data Processing |
| Measurement unit |
: |
ppb |
| Data processing |
: |
|
| Processing for averaging |
: |
Processing for Daily Data:
Daily and monthly data is averaged only afternoon data. To do this we convert the date/time field to local standard time and then average the data from 1600-1900 inclusive.
Processing for Monthly Data:
Daily and monthly data is averaged only afternoon data. To do this we convert the date/time field to local standard time and then average the data from 1600-1900 inclusive. |
| Data flag |
: |
|
| Data remarks |
: |
|
| Other Information |
| Scientific aim |
: |
Environment Canada's Greenhouse Gas Measurement Program operates a network of stations to accurately measure atmospheric concentrations of greenhouse gases from coastal, interior and arctic regions in Canada. The data are used to:
• Identify trends; seasonal variability and spatial distribution of greenhouse gases in Canada.
• Provide a coherent and consistent picture of the present and past states of greenhouse gases in the atmosphere, as a result of changing atmospheric transport patterns, emissions from natural sources, such as from wetlands and forests and emissions to the atmosphere due to human activities, including the burning of fossil fuels.
• Provide the scientific and policy-making communities with high quality baseline and trend information that contributes to the development and evaluation of mitigation plans and tracks the effectiveness of Canadian and international policies and regulations. |
| Reference |
: |
|
|
| submitted by Environment Canada |
|
|
