BIODEEP (EVK3-2000-00042) Second year Scientific Report
(April 1st 2002 – March 31st 2003)
Annex to WP2
Contribution of Partner 9
University of Patras – Department of Geology
Responsible Scientist: Prof. S. P. Varnavas
SUSPENDED PARTICULATE MATTER
( 2002 CRUISE )
The suspended particulate matter from the seawater column and the brines was determined
(Table 1) and analysed for Pb, Mn, Ba, Cd, Cu, Al, Li, Si and Sr.
Methodology
The .45 μm membrane filters with the particulate matter were oven dried for 12 h at 60°C
and weighed out. Then they were subjected to chemical leaching, with the addition of 20 ml of
ultrapure 2 M HCl - 1 M HNO3 mixture for 4 h at room temperature, to dissolve carbonate,
reactivate oxyhydroxide phases, more resistant (e.g. Fe3+) oxyhydroxides and metal sulfides.
The HCl/HNO3 fractions were taken individually to near-dryness in teflon beakers on a hot
plate and then redissolved in 5 ml of ultrapure 0.5 N HCl - 0.1 N HNO3 mixture. Aliquots of the
samples were then analysed by graphite furnace atomic absorption spectrometry.
Solutions for the determination of the elements were diluted with 3-distilled water to bring
the concentrations into line with the linear portion of the calibration curve in order to provide a
better sensitivity. Aliquots of the samples were then analyzed and the final concentrations
calculated by multiplying with the dilution factor. Multipoint calibrations were applied for all the
elements studied. Working standards were prepared daily by diluting with 3-distilled water the
ready to use Merck stock standards. Blank samples were taken in the same way as samples, in order
to check for any reagent effect. Blank sample signals were less than 5% of particulate metal
concentrations, while precision was checked with replicate analysis and found to be better than ±
4% for all elements studied. Instrumentation consisted of the 2001 Perkin Elmer spectrophotometer,
combined with the 700 HGA Graphite Furnace model. Pyro/platform tubes together with matrix
modification were used to increased sensitivity for Al and Mn determinations while the operational
parameters proposed by the manufacture were applied.
Results and Discussion
Geographic and Vertical Variability of Suspended Particulate Matter
Pb:
Bannock: Pb exhibits its highest concentration at the upper layers of the Bannock brine, followed by
a dramatic decrease below. Levels then fall slightly more and a small increase is then observed,
followed by a significant decrease towards the bottom. It should be noted that the lowest
concentration is found there. An increasing trend is apparent at the bottom, with final concentrations
reaching levels comparable to that at the upper layer.
Urania East: Pb presents a completely different behaviour at the Urania Basin. It is found at very
low levels in the upper layer, followed by a sharp increase below, which constitutes a peak, since a
gradual decrease is then observed with increasing depth. The bottom seems to be enriched with Pb,
since the highest concentration is found there.
Pb seems to be more abundant at the Bannock Basin, followed by the Urania basin. The mean
concentrations at both basins are very comparable, but, as the standard deviation declares, Pb values
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BIODEEP (EVK3-2000-00042) Second year Scientific Report
(April 1st 2002 – March 31st 2003)
seem to be more widespread at the Bannock Basin. The Discovery and the Atalante basins have also
comparable Pb levels. The relative abundances among the four basins are as follows:
Bannock
17
> Urania > Atalante > Discovery
3.2
2.1
1
It is apparent that Pb at the Bannock basin has a very strong correlation with Ba and Cu and a
weaker one with Ni and Si, whereas at the other basins, no correlation seems to exist between Pb
and the rest of the elements.
Pb
Pb (μg/g)
18
16
14
12
10
8
6
4
2
0
Bannock
Urania
Atalante
Discovery
Basins
Fig. 1
Cu:
Bannock: Cu manifests a similar behaviour with Pb at least at the upper layer. The upper layer is
highly enriched with Cu while concentrations fall below. A slight increase is observed with
increasing depth and a small peak is encountered in the middle depths. Towards the bottom,
concentrations decrease again and they do not present any variability. It should be mentioned that
the difference in concentrations between the upper and the bottom are enormous.
Urania: The surface layer is characterised by the highest Cu concentrations encountered, like in the
Bannock Basin, followed by a significant decrease, but not as dramatic as at the Bannock Basin.
The bottom layer seems to be also enriched with Cu, but in smaller amounts than in the upper layer.
Discovery: A decreasing trend can be clearly seen with no significant vertical variations with
increasing depth.
Both the Urania and Bannock basins have similar mean Cu concentrations. However, values seem
to be more widespread in the latter. The highest Cu level is also encountered there. Concerning the
Urania – West, significant Cu amounts are recorded in the middle depths, higher than any of them
reported for Urania – East. The Atalante Basin contains also significant and comparable Cu
amounts with the other two. The Discovery Basin is the one containing the smallest Cu amounts,
like Pb. The relative abundances are as follows.
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BIODEEP (EVK3-2000-00042) Second year Scientific Report
(April 1st 2002 – March 31st 2003)
Bannock
5
μg/g
> Urania
5
> Atalante > Discovery
4
1
At the Bannock Basin, Cu is strongly correlated with Ba and Pb and less correlated with Ni and Si.
Concerning the Urania basin, there seems to be a very strong correlation with Ni and a less strong
one with Si. Finally, at the Discovery Basin, there is only a very weak correlation of Cu with Ni.
Cu
6
Cu (μg/g)
5
4
3
2
1
0
Bannock
Urania
Atalante
Discovery
Basins
Fig. 2
Bannock
Cu/Al
0
0,1
0,2
0,3
0,4
3320
3340
Depth (m)
3360
3380
3400
3420
3440
3460
Fig.3
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BIODEEP (EVK3-2000-00042) Second year Scientific Report
(April 1st 2002 – March 31st 2003)
Urania
Cu/Al
0
0,05
0,1
0,15
0,2
0,25
0,3
0,35
3540
3550
Depth (m)
3560
3570
3580
3590
3600
3610
Fig. 4
Ba:
Bannock: The vertical Ba profile seems to be quite variable. The surface layers are characterised by
high concentrations, which drop significantly below. There is a tendency for Ba to increase in the
intermediate depths, followed again by a significant drop, with the low levels at the certain depths
(3350 and 3430 m) being similar with each other. Towards the bottom, concentrations increase
gradually, with the one encountered in the deepest layers of the basin being quite comparable with
that found at the upper layer.
Urania: This profile appears to be very interesting. Ba tends to be quite stable at the surface and
upper layers. A significant drop succeeds the stability at the middle depths, followed by an increase
towards the bottom, where concentrations reach the surface levels.
Discovery: Compared with Cu, Ba shows an increasing trend with depth, gradual at the upper layers
and more dramatic as depth increases.
Both the Bannock and Urania Basins seem to be more enriched with Ba than the other two. It
should be noted that the western part of the Urania basin is even more enriched with Ba than
the eastern one and all the other basins. The Discovery Basin contains the least Ba amounts.
The relative abundances are as follows:
Bannock
4.4
> Urania
4
> Atalante > Discovery
2.5
1
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BIODEEP (EVK3-2000-00042) Second year Scientific Report
(April 1st 2002 – March 31st 2003)
Ba (μg/g)
Ba
5
4,5
4
3,5
3
2,5
2
1,5
1
0,5
0
Bannock
Urania
Atalante
Discovery
Basins
Fig.5
As has been mentioned already, Ba seems to be strongly correlated with Pb and Cu and less
strongly correlated with Ni and Si at the Bannock Basin. At the Urania and Discovery Basins, there
seems to be only a correlation with Si.
Bannock
Ba/Al
0
0,1
0,2
0,3
0,4
0,5
0,6
3320
3340
Depth (m)
3360
3380
3400
3420
3440
3460
Fig. 6
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BIODEEP (EVK3-2000-00042) Second year Scientific Report
(April 1st 2002 – March 31st 2003)
Urania
Ba /Al
0
0,05
0,1
0,15
0,2
0,25
3540
3550
depth (m)
3560
3570
3580
3590
3600
3610
Fig. 7
Ni:
Bannock: Ni exhibits its greatest concentration at the upper layers, immediately after which a
significant drop follows. An initial gradual increase is observed towards the intermediate depths,
which becomes more dramatic with increasing depth. Towards the bottom, a sharp drop is again
noted, with concentrations being at similar levels with those found at the middle depths (3350 3380 m). At the bottom, concentrations rise again towards the levels of the overlying layers of high
concentrations (3400 - 3420 m).
Urania: Like at the Bannock Basin, the highest concentrations are encountered at the upper and a
subsequent drop is also apparent in the following depths, but at a smaller extent than that observed
for the Bannock Basin. At the intermediate and lower depths, Ni seems to be quite stable, while at
the bottom, concentrations increase once more, reaching levels very similar to those at the upper
layer.
Discovery: Ni manifests an increasing trend from the upper towards the middle layers, like Ba, but a
dramatic drop is noted with increasing depth.
Unlike for all the other elements, Ni seems to be more abundant at the Atalante basin. The Bannock
and Urania Basins contain similar Ni concentrations. It should be noted that like for the rest of the
elements, the western Urania Basin, is more enriched with Ni than the eastern part. The Discovery
Basin is once more the one with the smaller Ni amounts. The relative order in abundances is
changed in this case and is as follows:
Atalante > Urania
1.6
1.3
> Bannock > Discovery
1.2
1
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BIODEEP (EVK3-2000-00042) Second year Scientific Report
(April 1st 2002 – March 31st 2003)
Ni
Ni (μg/g)
1,8
1,6
1,4
1,2
1
0,8
0,6
0,4
0,2
0
Bannock
Urania
Atalante
Discovery
Basins
Fig. 8
It can be clearly seen that the differences in abundance are not striking among the four basins,
opposite to those observed for all the other elements.
Ni does not seem to have any strong correlation with any of the rest of the elements at the Bannock
Basin. It is more correlated with Ba and less with Cu, Pb, and Si. Regarding the Urania Basin, Ni is
very strongly correlated with Cu and much less correlated with Si, while at the Discovery Basin,
there is only a very weak correlation with Cu.
Bannock
N i/Al
0
0,02
0,04
0,06
0,08
0,1
0,12
3320
3340
Depth (m)
3360
3380
3400
3420
3440
3460
Fig. 9
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BIODEEP (EVK3-2000-00042) Second year Scientific Report
(April 1st 2002 – March 31st 2003)
Urania
Ni/Al
0
0,01
0,02
0,03
0,04
0,05
0,06
0,07
3540
3550
Depth (m)
3560
3570
3580
3590
3600
3610
Fig. 10
Si:
Bannock: Si presents an interesting vertical profile. The surface concentrations are of the highest
encountered, but as depth increases they drop sharply to below detection limit, followed by a
sudden rise again in the middle depths and at very high levels. Towards the bottom, Si levels drop
to below detection limit once more and the deepest waters are characterised by very small Si
amounts.
Urania: Si is found at its highest levels at the surface, followed by a sharp concentration decrease
towards the intermediate waters. In the middle depths and towards the bottom, there is a tendency
for Si to be stable.
Discovery: Like Ni, Si also shows an increasing trend from the surface and towards the middle
layers, followed by stability.
All four basins appear to contain similar Si amounts, with no striking differences among them
observed. The Bannock and Urania Basins are the ones most enriched with Si. Like for the rest of
the elements, the western part of the Urania basin at the depth from which the sample was taken, is
more abundant than the corresponding one at the eastern part. In this case however, the amount
reported is found to be quite comparable to the high levels encountered at different depths from the
eastern part (surface and towards the bottom). The relative order in abundances is slightly changed
in this case as well, as the Atalante Basin is the one with the smallest Si amounts:
Bannock
2.1
> Urania
2.1
> Discovery > Atalante
1.3
1
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BIODEEP (EVK3-2000-00042) Second year Scientific Report
(April 1st 2002 – March 31st 2003)
Si
2,5
Si (μg/g)
2
1,5
1
0,5
0
Bannock
Urania
Atalante
Discovery
Basins
Fig. 11
Like Ni, Si is correlated with all the other elements at the Bannock Basin, but the correlation is not
strong. The same situation applies to the Urania Basin apart from the fact that there is no correlation
between Si and Pb, whereas there seems to be only a correlation between Si and Ba at the
Discovery Basin.
Bannock
Si/Al
0
0,02
0,04
0,06
0,08
0,1
0,12
0,14
3320
3340
Depth (m)
3360
3380
3400
3420
3440
3460
Fig. 12
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BIODEEP (EVK3-2000-00042) Second year Scientific Report
(April 1st 2002 – March 31st 2003)
Urania
Si /Al
0
0,02
0,04
0,06
0,08
3540
3550
Depth (m)
3560
3570
3580
3590
3600
3610
Fig. 13
Mn:
Bannock: The vertical profile of Mn presents significant variability. There seems to be a decreasing
trend from the surface towards the intermediate depths, which is followed by a sharp increase at
3400m, where the highest amount is reported. Concentrations then fall suddenly to extremely low
levels. Towards the bottom, an increasing trend reaching surface values is observed but at the
bottom, Mn concentrations are very low.
Urania: Mn is characterised by stability through the water column at the eastern part of the Urania
Basin. The diagram however, includes the depth from which the sample from the western part was
taken, which accounts for the peak of high concentration towards the bottom. The bottom part is
described by low Mn amounts.
Discovery: An increasing trend is clearly apparent with increasing depth.
The Urania, Bannock and Discovery basins appear to contain comparable amounts of Mn, with the
Urania being the most enriched. The values reported at the Bannock Basin are the most widespread
nevertheless, declaring greater variability. The relative abundances among the four basins is as
follows:
Urania
7
> Bannock
5.6
> Discovery > Atalante
5
1
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BIODEEP (EVK3-2000-00042) Second year Scientific Report
(April 1st 2002 – March 31st 2003)
Mn
8
7
Mn (μg/g)
6
5
4
3
2
1
0
Bannock
Urania
Atalante
Discovery
Basins
Fig. 14
At the Urania Basin, the highest concentrations at 3587 and 3602m correspond to the highest ratio
values, whereas for the remaining depths, the trend is not so clear. The same situation applies to the
Bannock Basin, where high ratio values result from very low concentrations and vice versa. Finally,
the highest ratio values are encountered at the Discovery Basin compared with the other two.
Bannock
Mn/Al
0
0,05
0,1
0,15
0,2
0,25
0,3
3320
3340
Depth (m)
3360
3380
3400
3420
3440
3460
Fig. 15
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BIODEEP (EVK3-2000-00042) Second year Scientific Report
(April 1st 2002 – March 31st 2003)
Urania
Mn/Al
0
0,05
0,1
0,15
0,2
3540
3550
Depth (m)
3560
3570
3580
3590
3600
3610
Fig. 16
Fe:
Iron in Bannock Basin exhibits its highest value in the upper layer. Also a distinct peak is observed
at 3400 m. At Urania Basin a very distinct Fe peak is encountered at 3590 m.
For better evaluation the metal/Al ratios were calculated ( Table 2) and their profiles for each Basin
were drawn.
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BIODEEP (EVK3-2000-00042) Second year Scientific Report
(April 1st 2002 – March 31st 2003)
Fe
300
Fe (μg/g)
250
200
150
100
50
0
Bannock
Urania
Atalante
Discovery
Basins
Fig. 17
Bannock
Fe /Al
0,00
0,50
1,00
1,50
2,00
2,50
3,00
3,50
4,00
3320
3340
Depth (m)
3360
3380
3400
3420
3440
3460
Fig. 18
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BIODEEP (EVK3-2000-00042) Second year Scientific Report
(April 1st 2002 – March 31st 2003)
Urania
Fe/Al
0,00
0,50
1,00
1,50
2,00
2,50
3,00
3,50
3540
3550
Depth (m)
3560
3570
3580
3590
3600
3610
Fig. 19
Conclusions
1) On average the concentrations of Pb and Ba in SPM in the Basins studied decrease in the
following order:
Bannock > Urania > Atalante > Discovery
2) The average concentrations of Cu in SPM decrease in the following order in the four basins:
Bannock = Urania > Atalante > Discovery
3) The average concentrations of Si in SPM in the four basins decrease in the following order:
Bannock > Urania > Discovery > Atalante
4) The average concentrations of Ni in SPM in the four basins decrease in the following order:
Atalante > Urania > Bannock > Discovery
5) Very characteristic peaks in most of the elements studied were observed in Urania Basin at 3590
m, in Bannock Basin at 3360 m and in Discovery Basin at 3690 m.
6) The average concentrations of Al in SPM in the four Basins decrease in the following order:
Urania > Bannock > Discovery > Atalante
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BIODEEP (EVK3-2000-00042) Second year Scientific Report
(April 1st 2002 – March 31st 2003)
7) The average concentrations of Fe in SPM in the four Basins decrease in the following order:
Urania > Bannock > Discovery > Atalante
8) In Bannock Basin much greater Ba/Al ratios were observed relative to the other basins.
9) On the basis of the correlation coefficients calculated among the element concentrations in
Urania Basin the following element grouping can be recognized:
-
Ni – Cu – Si – Sr – Al. This group does not show any dependence on the quantity of
SPM. It should represent the lithogenous fraction.
Ni – Cu – Pb – Cd. This group shows strong positive correlation with SPM quantity. It
may represent the sulphide fraction.
Ba – Cr – Si – Li. It shows no correlation with SPM content. It shows strong negative
correlation with Mn. This group should represent the biogenic fraction. The role of Li in
the geochemical processes should be investigated further. It is noted that Li does not
correlate with Al.
All groups are negatively correlated with Mn.
10) In Bannock Basin the following group of elements are recognized:
-
Ba – Ni – Cu – Pb –Cr – Fe – Cd – Al
Si – Mn
Li is negatively correlated with all elements.
11) In Discovery Basin the Fe/Al ratios and Mn/Al ratios are markedly higher compared with all
other Basins.
15