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Baltic Sea
-VOCs-
| Observation |
| Category |
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Air sampling observation |
| Situation |
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ongoing |
| Time zone |
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UTC |
| Sampling |
| Sampling height |
: |
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| Description |
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flask |
| Sampling and analysis frequency |
: |
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| Sampling environment |
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| Description for sampling analysis |
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| Instrument and Analysis |
| Measurement method |
: |
Gas Chromatography (FID) |
| Current status and history of instrument |
: |
|
| Description of instrument |
: |
The GC analysis involves drying of approximately 600 cc (STP)
of sample gas, then preconcentration of analytes on an adsorbent bed,
followed by thermal desorption onto a short capillary guard column
and main capillary column (HP-Plot AL2O3/KCl 0.53 mm x 60 m) for separation,
and finally detection by a Flame Ionization Detector (FID).
The gas chromatograph used is a HP-5890 series II.
Drying is accomplished by running the sample gas through a tube cooled
to -25ｰC. The custom-built preconcentration system is cooled to -35ｰC
and uses Carboxen 1000 and Carboxen 1016 as adsorbents.
Desorption is controlled at 310ｰC. The flask analysis system is
completely automated, allowing analysis of up to 12 flasks in one sequence. |
| Calibration |
| Current scale employed in the measurement |
: |
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| Measurement calibration |
: |
Analysis of air samples are compared to analysis of synthetic
and compressed air standards. One compressed air standard is run
twice a day to check on the stability of the FID response, the other
standards are ran at least twice a month to determine the response of
the FID. Blanks are prepared by running compressed air through a heated
bed of PtO. Blank samples are analyzed twice daily.
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| Scale and calibration(treasability) |
: |
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| Data Processing |
| Measurement unit |
: |
pmol/mol |
| Data processing |
: |
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| Processing for averaging |
: |
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| Data flag |
: |
NOAA ESRL uses a 3-column quality control flag where each column
is defined as follows:
column 1 REJECTION flag. An alphanumeric other
than a period (.) in the FIRST column indicates
a sample with obvious problems during collection
or analysis. This measurement should not be interpreted.
column 2 SELECTION flag. An alphanumeric other than a
period (.) in the SECOND column indicates a sample
that is likely valid but does not meet selection
criteria determined by the goals of a particular
investigation.
column 3 COMMENT flag. An alphanumeric other than a period (.)
in the THIRD column provides additional information
about the collection or analysis of the sample.
WARNING: A "P" in the 3rd column of the QC flag indicates
the measurement result is preliminary and has not yet been
carefully examined by the PI. The "P" flag is removed once
the quality of the measurement has been determined.
If both the first and second column contain a period (e.g., "..." and "..I"),
the sample is RETAINED.
FLAGS DESCRIPTION:
'...' is a good sample
1st column flags:
'P..' flag: poor flask pair agreement
Since samples are collected in pairs, the pair difference is calculated.
If the mixing ratio x falls between the below margins,
and the difference exceeds abs(dx) the flag is applied.
x <= 10 and dx > |5|
11 > x <= 25 and dx > |10|
26 > x <= 63 and dx > |20|
64 > x <= 156 and dx > |40|
157 > x <= 391 and dx > |80|
392 > x <= 977 and dx > |160|
978 > x <= 2441 and dx > |320|
2442 > x <= 6104 and dx > |640|
6105 > x <= 15259 and dx > |1280|
'A..' flag: no data obtained
This flag is applied when there was an instrument failure or if the amount of air left
in the flask was too low for an analysis
'*..' flag:
This flag is applied when an unstable baseline made the peak integration impossible
'D..' flag:
This flag is applied when this particular compound was below the detection limit
of our measurement
'C..' flag:
This flag is applied when a contamination was found
3rd column flags:
'..C' flag:
This flag is applied when the amount of air left in the flask was too low for the
instrument to draw the standard volume for analysis. In that case an analysis
was performed with a reduced sampling volume.
We feel that this data set best represents hydrocarbons distribution in the remote,
well-mixed global troposphere. It is possible, and even likely, that some values
represent poorly mixed air parcels influenced by local anthropogenic sources.
Users of these data should be aware that further data screening is necessary.
We will provide advice in selecting the data that will best fit the goals
of user's particular investigation.
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| Data remarks |
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| Other Information |
| Scientific aim |
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| Reference |
: |
Helmig, D., Bottenheim J., Galbally I. E., Lewis A., Milton M. J. T.,
Penkett S., Plass-Duelmer C., Reimann S., Tans P., Theil S. (2009)
Volatile Organic Compounds in the Global Atmosphere. Eos Trans. AGU, 90(52),
Feature.
Pollmann J., Helmig D., Hueber J., Plass-Duelmer C., and Tans P. (2008)
Sampling, storage, and analysis of C2-C7 non-methane hydrocarbons
from the US National Oceanic and Atmospheric Administration Cooperative
Air Sampling Network glass flasks. J. Chromatogr., 1188, 75-87.
Helmig D., Hueber J., Tans P. (2014) Non-Methane Hydrocarbons from the NOAA ESRL Surface Network, 2004-2013.
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| submitted by Earth System Research Laboratory, NOAA |
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