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Hohenpeissenberg
-H2O2-
| Observation |
| Category |
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Air sampling observation |
| Situation |
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June, 2006 |
| Time zone |
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Local time +1 |
| Sampling |
| Sampling height |
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18 |
| Description |
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continuous |
| Sampling and analysis frequency |
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The analyzer provides continuous data. The data acquisition system provides one minute mean data. |
| Sampling environment |
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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.
H2O2 and ROOH are secondary trace gases which are formed by reaction of peroxiradicals with each other. They are important trace gases for understanding the oxidation capacity of the atmosphere and the radical cycles. Most important sink is heterogenic deposition.
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| Description for sampling analysis |
: |
Teflon PFA inlet line, heated to 3°C above ambient air temperature to avoid condensation.
Hydrogen peroxide and soluble organic hydroperoxides (H2O2 and ROOH) are detected by means of ECF (enzyme-catalyzed fluorescence). At first, the substances are transferred from gas phase into liquid phase. Afterwards a monomeric dye is added. Only H2O2 and ROOH form from this monomer with the help of special enzymes a dimeric dye capable of fluorescence.
The excitation of this dimer occurs in the UV range, irradiated by a cadmium lamp, the detection by a photomultiplier. The instrument is a dual channel system. Channel 1 detects all hydroperoxides, channel 2 only the organic hydroperoxides (by use of catalase). Hydrogen peroxide is achieved by difference of the two channels. This device was improved at MOHp, now working with enhanced detection limit (LDL: = 0.05 ppb).
All solutions are stored in a refrigerator. |
| Instrument and Analysis |
| Measurement method |
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ECF : enzyme catalyzed fluorescence
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| Current status and history of instrument |
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Jan 1997 - Oct 2005 currently interrupted
AL 2002 ; Aero Laser GmbH, Germany |
| Description of instrument |
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| Calibration |
| Current scale employed in the measurement |
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| Measurement calibration |
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3-point-calibration is carried out twice a week, zero and span check once a day.
Liquid H2O2 standards which are titrated against a KMnO4 standard solution are used for calibration. For zero measurement synthetic air and/or H2O2 free ambient air (by use of an ozone scrubber)is used.
Additionally a H2O2 permeation source is used to check the whole system inclusive inlet line.
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| Scale and calibration(treasability) |
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Liquid H2O2 standards which are titrated against a KMnO4 standard solution. |
| Data Processing |
| Measurement unit |
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ppb |
| Data processing |
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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. |
| Processing for averaging |
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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 |
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| Data remarks |
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!! IMPORTANT !! :
In the time interval July 2004 up to September 2004 the second Channel of the H2O2 analyser was out of order. In this time intervall the "H2O2" data represents the sum of H2O2 and organic hydroperoxides. |
| Other Information |
| Scientific aim |
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Oxidation capacity of the atmosphere, interpretation with respect to ozone formation. |
| Reference |
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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.Frick, GAW Report 169, 2006
http://www.dwd.de/gaw |
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| submitted by Meteorological Observatory Hohenpeissenberg, German Meteorological Service |
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