*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 |