INVESTIGATION OF HEAVY METALS IN SEA WATER, NEUSTON AND MULTI-NET CATCHES

Surface water samples and neuston organisms were collected continuously and partly investigated On board for heavy rnetals, and partly prepared for analysis in the AWI. The horizontal heavy metal distribution is to be correlated with hydrographical, chemical and biological parameters. Various surface currents were encountered on this leg: Benguela Current, South Equatorial Current, Guinea Current, Equatorial Counter Current, North Equa- torial Current, Atlantic Recirculation, Canary Current and the Portugal Current. A particular aim was to investigate the correlation of metal concentration in water with the metal content of organisrns.

Individually selected neuston organisms are to be investigated for their rnetal inventory and the variation of these data with location.

Investigations into the biogeochemical cycle of heavy metals are to be started with this, in particular into the role of plankton in heavy metal binding, in chemical transformation and in transportation into the deep sea.

In addition, a newly constructed "clean room" container was used and tested for the first time. The 20' container consists of an outer room containing the air circulation, air filtration, air conditioning in- stallations and a refrigerator and deep freezer and a work room (class 10,000 particleslm3). This room contains in addition a clean bench (class 100 particles/m3), a vent with separate in and out ports, a Milli-Q-pure water apparatus and a work bench.

An aluminium neuston sledge was used for neuston catches, on min before sunrise, the second 20 min after sunset.

After the catch, single individuals were isolated under binocular microscopes, grouped under various systematic taxa and deep frozen in pre-cleaned 2 ml Eppendorf vials, PP vials or 50 ml Kautex flasks. After freeze drying and acid digestion, an analysis of lead, cadmium, copper and possibly nicke1 and zinc will take place in the laboratory with the aid of flameless Zeemann-AAS.

A snorkel System 3 m under the ship's bottom with a direct pipe to the "clean room" container was originally planned for continuous water sampling. The snorkel could not unfortunately be used with the available, unlockable lid in the hydrographical moon pool due to high vibration.

A fully Teflon 500 ml-water sampler with titanium fittings (Mercos- sampler, HYDROBIOS) was used for water sampling from the bow boom. The Mercos-samplers were used

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with the ship stationary

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from the bow boom 8 m in front of the ship's bow, 14 m above the water surface, using a high grade steel winch, a 5 mm Kevlar line and a counterweight covered with synthetic material, and operated in about 1

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2 m of water depth. For comparison water samples were taken by hand from a rubber dinghy at two stations at a distance of 1

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2 km from the ship.

For vertical zooplankton sampling, a multinet

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5 nets with 200 pm mesh size and a mouth opening of 50 X 50 cm

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was used. The heave speed was 1 mlsec. In order to prevent metal contamination from the ship and the wire, 10 liter GO-FLO samplers were used for deep water sampling and driven on a Hostalen covered wire.

Both equipments were operated down to 1200 m. In this way two central bodies of water could be sampled in the Angola Basin, the Guinea Basin and the Sierra Leone Basin. In the first place, the South Atlantic Central Water with its warm surface layer and secondly, the water immediately below that, the Antarctic Intermediate Water. For both northerly deep water stations

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the Cape Verde and Canary Basins

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infiows from the Eastern North

Atlantic Central Water and that under it. the Mediterranean Water, will appear during analysis.

The biomass in the multi-net catches was very small. Copepods, chaetognaths, decapods, euphausiids, fish larvae and hyperiid arnphipods were preserved for metal analysis. It was, however, remarkable that especially at depths of 800

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1200rn, large individual copepods and chaetognaths were found.

Anodic stripping voltammetry on a rotating mercury film electrode made it possible to analyse the concentration of cadrnium, lead and copper on board the ship in spite of their very low content in the Atlantic water.

The polargraph and cell stand equipment used were types 384B and Rotel 2 from the EG&G PAR company. The cell stand was operated in the clean bench where the sarnples were also bottled and acidified (40

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50 ml sea water plus 1 pl HCI suprapurelml sea water).

Because of their low concentrations, the metals were enriched for 50 minutes on ex-situ-modus generated mercury film. During the following "stripping", the voltage range from -0.85 V to -0.1 V was run at a rate of 6.7 mV/s. The oxidation potential lay atabout -0.76 V for Cd, -0.55 V for Pb and -0.40 V for Cu. After the first and second spiking with a rnetal standard, the enrichment time was reduced by a half and then by a third.

The remaining samples are to be worked on in the AWI.

Furthermore, all samples are to undergo UV photolysis and once again measured. This achieves better resolution of the peaks and suppresses disturbances from DOM.

At 43 stations 450 neuston samples were gathered and assigned to various systematic categories, which are compiled in Table 17.

Table 17. COMPILATION OF NEUSTON ORGANISMS

CNIDARIA

Siphonophora Velella Physalia Porpita other Cnidaria

PLATHELMINTHA Planaria ANNELIDA

Polychaeta

CHAETOGNATHA 4

Tab. 17 cont'ed

no of sarnoles MOLLUSCA

Heteropoda

Pterotrachea 8

Atlanta 1 7

Pteropoda, thecosomat 3 1

Pteropoda, gymflOSOmat 3

Glaucus 3

Janthina 14

Nudibranchia 2

Cephalopoda 11

INSECTA

Halobates micans 17

CRUSTACEA

Isopoda 8

Copepoda 2 6

Pontellidea 9

Sapphirinidae 2

Cirripedia

Lepas 1

Ostracoda 1

Amphipoda Hyperiidea

Oxycephalidae Phronima Hyperiidea, "lilac"

Mysidacea Euphausiacea Decapoda

Natantia Luzifer Reptantia Phyllosorna-Larvae TUNICATA

Thaliacea Pyrosoma VERTEBRATA

Pisces

Myctophida juv.

Exocoetidae juv.

Scornberesox saurus juv.

Coryphaena equiselis juv.

Mola rnola juv.

other fish larvae

Heavy rnetal analyses carried out on board with the aid of stripping voltamrnetry are shown in table 18.

Table 18. CONCENTRATIONS OF CADMIUM, LEAD AND COPPER IN SOUTH AND NORTH ATLANTIC WATERS

Station Lat. Long. Long Cadmium Lead Copper Degr. Min Degr. Min ng/I ng/l ngll

¥M/- +€/

1.2.6 INVESTIGATION OF INORGANIC AND ORGANIC TRAGE

Im Dokument 3) nd VIIl5 of 'Polarstern" in (Seite 184-189)