MTP II - MATER





ADRIATIC/IONIAN BASIN

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.

*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 R_a=1.384 10^-6 . delta³He=((R/R_a)-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

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