Physical Properties Laboratory |
| Staff Liaison: Peter Blum |
All physical property data models have been upgraded and converted to a relational data model for the JANUS database.
A report was presented to the Shipboard Measurements Panel (SMP) on the performance of the electrical conductivity apparatus obtained by ODP/TAMU from Dr. Volkhardt Spiess of Bremen University. Though data obtained by Spiess's group on cores in the LDEO Repository were shown to be of good quality, the apparatus obtained by ODP/TAMU exhibited precision problems. Hence, SMP has recommended not to deploy the apparatus on the JOIDES Resolution.
This system will replace the old shipboard device built by Woods Hole Oceanographic Institute (WHOI), which has been in service for many years. The Teka system was tested thoroughly and is ready for deployment on Leg 168. With the high interest in heat flow during Legs 168 and 169, this instrument will play an especially vital role. One of the main drawbacks of the Teka system, when compared with the old WHOI system, is the fact that only one probe is used at any time. This will cause, especially on high-recovery legs, a low depth resolution (1 to 2 measurements per core). It is, therefore, recommended that further development is necessary (toward a multiprobe system). Such a development may require an RFP.
Tests conducted during Leg 156 indicate that, in principle, useful information on the concentrations of K (±14%), U (±24%), and Th (±16%) can be obtained. It was also shown that acquiring 2048-channel data had no real advantage over only 256 or fewer channels.
At present, density calibration is carried out with two aluminum rods of different diameters to yield 2.7 and 1.0 g/cm3, respectively. Because the thinner rod is used to simulate the bulk density of water, but has the attenuation property of aluminum, initial estimates of the bulk density must be fluid corrected. It was suggested that instead of the smaller aluminum rod, a water core be used for calibration. SMP agrees that this is, in principle, an excellent approach and deserves to be tested.
Three methods are presently available for volume determination to be used to calculate density and related properties:
SMP has recommended that the bulk volume sampling method for density measurement be eliminated from the shipboard measurement program, and that salt corrections should use a standard correction of 0.035 (salinity = 35) with the corresponding density of standard seawater.