Towed pumping system

Sampling the Upper 100 m of a Warm Core Ring with a Towed Pumping System... 

A towed pumping system can provide water from throughout the upper 100 m of the water column for shipboard analysis. 

Figure 1. Towed pumping system winch, framework, and cable. The system is —5.5 m long, 3 m high, and 2 m wide, and weighs —2500 kg. The winch is bolted to the deck of the ship.

Figure 2. Towed pumping system underwater vehicle.

Table I. Towed Pumping System In Situ and Associated Analytical Instrumentation...

Continuous underway sampling using a deep-towed pump and a hose-cable can examine chemical patterns in the ocean that are nearly impossible to describe by other techniques. Growing realization of the importance of mesoscale features and oceanic fronts makes use of such sampling tools an essential part of oceanography. Effective data management must be an indispensable part of any deep-towed sampling system. 

Traditional adsorption preconcentration techniques are based aroimd the passage of filtered (and sometimes acidified or otherwise pretreated) water through a column of adsorbent. After passage of the sample the compounds of interest are eluted with an appropriate solvent or solvent mixture. Such techniques can be laboratory based, in situ (pumped systems or, more rarely, in passive towed units), or, in more recent systems, can be used in online applications. 

The CS system is made up of three major components a seafloor sediment sampler, shipboard sample processor, and nondestructive elemental analysis instrumentation. It was described in detail previously (8). Design requirements for the seafloor sediment sampler are that it be in constant contact with the seafloor while being towed at speeds up to 6 knots, agitate only the upper surficial seafloor sediment and create a plume, contain a pumping means to sample the sediment slurry plume, and be capable of transporting the sediment slurry to a surface ship. These conditions were achieved by designing a towable sled that contained, within its structure, a submersible pump that was hose-connected to the surface ship. 

Our primary measurement technique was to pull seawater through a 25-mL volume chamber with a pump. The organisms emit light when stimulated by the tur-bulently flowing seawater. This light is viewed by a photomultiplier tube (PMT). Two in situ measurement systems were used on surface ships. The on-board bioluminescence detector pulls seawater from below the ship s hull for continuous realtime measurements of surface bioluminescence a bathyphotometer was used on station to depths of 100 m. An additional laboratory system was used to measure bioluminescence flashes from individual plankters isolated from plankton tows and pumped collections. 

For seawater analysis, it is possible to pump the sample directly from the sea to a shipboard analyser. The sample can then be de-gassed in-line and handled in a shipboard flow system. This possibility, and the main practical, physico-chemical and interpretative aspects, were discussed in relation to the in situ spectrophotometric determination of seawater pH [9]. The attractive features and applications of shipboard flow injection spectrophotometric determinations are discussed elsewhere [10,11]. A compact, shipboard flow analysis system incorporating a LTV photoreactor has also been reported for the determination of total phosphorus in estuarine and marine waters [12]. Another way to sample seawater is to use a towed torpedo-shaped "fish," deployed off the crane arm of a hydrographic winch at a distance of 5 m from the ship, connected to a deck mounted pump by appropriate tubing. Filtration can be incorporated in-line and the filtered sample collected or pumped directly to the flow analyser [13]. This approach (Fig. 8.1) minimises contamination and preconditions the sample, as demonstrated in the chemiluminometric determination of iron(II) in surface seawater. 

Common tethered platforms utilized from ship deck include vertical profilers, towed vehicles, and pumped flow-through systems, which can accommodate most commercially... 

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