Dissolved Gases in the Water Column

*DATASET-NAME : Inorganic chemistry: dissolved gases in the water column, in Southern Adriatic, Otranto Strait Sea and Ionian Sea.

*TIME-PERIOD : 1997 to present

*GEOGRAPHIC COVERAGE : Southern Adriatic Sea, Northern Ionian Sea

*PROJECT : MASTIII/MTPII/MATER, MAss Transfer and Ecosystem Response

*PARAMETERS : Tritium, Helium, Neon and delta3He measurements with quality flag in water column at standard or selected depths.

CODE

NAME

UNIT

ACCURACY

Minimum value

Maximum value

tritium

tritium

TU

 

 

 

helium

helium

nanomol/kg

0.75%

1.0

2.0

delta-3he

delta3 He

%

0.36%

-2

30

neon

neon

nanomol/kg

0.67%

4.0

8.0

qual

quality flag (4 digit number): digit 1 for tritium, digit 2 for helium, 3 for delta3 He and 4 for neon

 

 

111

999

*INSTRUMENTS : Noble gas mass spectrometer.

*DESCRIPTION, OBJECTIVES, METHODOLOGY :
40 ml water samples are filled into cupper tubes at sea which are pinched off. In the laboratory the gas amount is vacuum extracted from the sample and transferred in a specially designed helium/ neon isotope mass spectrometer. Two helium isotopes 3He, 4He and two Neon iostopes 20Ne, 22Ne are measured. Air aliquots provide the instrument calibration and monitor sensitivity changes. Intercalibration between individual air measurements is achieved by a large reservoir of air which has been kept since the beginning of our measurements.
Small air bubbles are sometimes enclosed in the copper tubes during the sampling procedure leading to contamination of the samples. Since neon has no internal sources in the ocean air contamination of the samples can be corrected for using the neon excess in the sample. Samples have been assigned quality flags to identify these corrections. The quality flag is a three digit number, the meaning of the flags is as following: 1 sample taken but not measured; 2 good measurement; 3 questionable measurement, 4 bad measurement (too low); 5 bad measurement (too high); 6 mean of replicate samples; 7 air contamination corrected; 8 helium contamination; 9 sample not drawn.
The helium and neon concentrations represent both the sum of the two isotopes. For helium they are nearly identical to 4He which is 106 times more abundant than 3He, for neon the isotope 22Ne makes up 10% of the sum. delta3He is the deviation of the isotopic ratio R=3He/4He in the water sample compared to that in air Ra=1.384 10-6 . delta3He=((R/Ra)-1)*100 [%].
In contrast to neon internal sources of helium in the ocean exist. This is either tritiugenic helium productio or terrigenic release of helium from the ocean floor. These internal additions of helium in the ocean can be used to identify and trace water masses and the combination of helium and tritium measurements allows a dating procedure.

*VOLUME/NUMBER OF PROFILES : 103 values/9 profiles and 94 values/7 profiles

*REFERENCE :

*LABORATORY in charge of helium and tritium measurements :
University of Bremen, IUP, Fb1
Dept. of Traceroeacongraphy
P.O. Box 330 440
28334 Bremen, Germany

*STORAGE-MEDIUM : Hard disk.

*AVAILABILITY : Data availability is submitted to the originator permission.
OSSERVATORIO GEOFISICO SPERIMENTALE
Department of Oceanology
PO BOX 2011
IT-34016 TRIESTE
Italy
tel : +39 40 21401

*COMPLETED-BY : Dr. Birgit Klein, UNIVERSITY OF BREMEN-GERMANY

*ENTRY-DATE : 1999-02-17

Available Data Set(s) Processing Level
MAI2 AUG 97 - Dissolved Gases in the Water Column IN VALIDATION
MAI7 FEB 99 - Dissolved Gases in the Water Column IN VALIDATION


Last update 12/01/2001

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