|
| 
Hohenpeissenberg
-NOy-
| Observation |
| Category |
: |
Air sampling observation |
| Situation |
: |
ongoing |
| Time zone |
: |
Local time +1 |
| Sampling |
| Sampling height |
: |
18 |
| Description |
: |
continuous |
| Sampling and analysis frequency |
: |
Continuous. Depending on LDL, the integration time varies from 30 seconds to 10 minutes. |
| Sampling environment |
: |
Hohenpeissenberg is an isolated mountain at 985 m a.s.l., 40 km north of Zugspitze (Alps) in a hilly area. The mountain rises 300m above the surrounding area, which is populated to an extent typical for central Europe and partly covered with meadows (~ 70%) and forests (~ 30%). The Meteorological Observatory situated on top of Hohenpeissenberg mountain has a long history of meteorological and climatological observations (since 1781) and is well-known for its long ozone record.
Main source for nitrogen oxides in central Europe is traffic exhaust. After several hours (noon, summer) to a couple of days (Winter) nitrogen oxides are converted to higher oxides (HNO3) and removed by deposition processes.
NOy is the sum of all nitrogen oxides with
oxidation number larger than 2:
NOy =(NO+NO2+NO3+2*N2O4+2*N2O5+HNO2+HNO3+PAN+Alkylnitrates+....) |
| Description for sampling analysis |
: |
In situ NO-O3 chemoluminescence analyser (LDL: 50 ppt)with self build gold converter.
PFA inlet line, heated to 3°C above ambient air temperature to avoid condensation.
The analyser switches every 3 minutes between NO and NOy mode (self-built gold converter).
|
| Instrument and Analysis |
| Measurement method |
: |
Chemiluminescence |
| Current status and history of instrument |
: |
since Oct.1998: ECO Physics CLD 770 AL ppt #77301 with self built Au converter
Manufacturer: ECO Physics GmbH, Switzerland |
| Description of instrument |
: |
Time resolution is about 4 minutes with a LDL of 50 ppt. The instrument is linear over a wide range from LDL up to at least 100 ppb.
For specific measurement without interferences the „prechamber mode is used. Pure O2 for generating ozone and a special reaction chamber design is used for enhancement of counting rates.
The Analyzer switches every 3 minutes between NO mode and NOy mode with Au converter. For reduction of NOy to NO pure CO gas is used.
|
| Calibration |
| Current scale employed in the measurement |
: |
Certified NO in N2 in cylinders, gas phase titration (GPT) with ozone and dynamic dilution with synthetic air is used for calibration.
Station standard by NPL, different working standards by "Air Liquide".
|
| Measurement calibration |
: |
Calibration and zero check is carried out every second day.
Certified NO in N2 in cylinders, gas phase titration with O3 and dynamic dilution with synthetic air is used for calibration. For zero measurement synthetic air is applied.
Twice per year multi point calibration with at least 5 calibration points ranging from 0 to 100 ppb.
Additionally a HNO3 permeation source is used to check conversion efficiency and inlet line losses. |
| Scale and calibration(treasability) |
: |
standard gases:
NO(2.5), 10.36ppm, Air Liquide, #9153160001 , #7597B
NO(2.5), 102 ppm, Air Liquide, #05600200366 , #1056
NO2 , 10.9 ppm, Linde , # 257609020001 , #2517604
Intercomparison with other instruments:
1)NO-O3 chemoluminescence of Juelich Research Centre (FZJ)in May 1998 with excellent agreement.The NO analyser of FZJ is regularly compared to a NIST standard. Because NO2 is measured as NO the results of NO comparison are also valid for NO2.
2)NO-O3 chemoluminescence of National Aerospace Center (DLR) in December 1999 with excellent agreement (also for NO).
3)NO-O3 chemoluminescence of National Aerospace Center (DLR) in August 2002 with excellent agreement (also for NO and NOy).
4)Several months in 2002, 2003 and 2004 with NaI-method of the Federal Envionmental Agency with good agreement.
5)NO-O3 chemoluminescence of Max Planck Institute for chemistry Mainz in August 2005 with excellent agreement (deviation < 1%).
|
| Data Processing |
| Measurement unit |
: |
ppb |
| Data processing |
: |
The data acquisition system provides one minute mean raw data. Zero/calibration factors and data protocols are used to convert raw data into calibrated data. Invalid data caused by local impact, malfunction or other effects were recognized by comparison/correlation with other trace substances and meteorological data or with information from the station logbook and were rejected.
10 min mean values are generated by calculating the arithmetic mean of the remaining data with number of data being more than 6. |
| Processing for averaging |
: |
Processing for Hourly Data:
Hourly data take the arithmetic mean of respective one minute mean validated data with the number of data more than 40.
Processing for Daily Data:
Daily data take the arithmetic mean of respective hourly data with the number of hourly data more than 16.
Processing for Monthly Data:
Monthly data take the arithmetic mean of respective hourly data with the number of daily data more than 20 (for February more than 19, respectively). |
| Data flag |
: |
Only validated, representative data are sent to th WDCGG. |
| Data remarks |
: |
|
| Other Information |
| Scientific aim |
: |
Understanding of nitrogen cycle, tracer for anthropogenic impact, interpretation with respect to ozone formation. |
| Reference |
: |
Stefan Gilge, Measurement of reactive Trace Gases at Hohenpeissenberg as Part of GAW, in „The German Contribution to the WMO/GAW Program: Upon the 225th anniversary of GAW Hohenpeissenberg Observatory, ed. W.Fricke, GAW Report 169, 2006
http://www.dwd.de/gaw
|
|
| submitted by Meteorological Observatory Hohenpeissenberg, German Meteorological Service |
|
|
