Sampling rosette samplers

Up to 1974, hydrographic data were collected with reversing water bottles and thermometers, and titration of chlorinity for salinity, using certified standard seawater as the reference. From 1974, temperature and salinity profiles were measured with CTD, but up to 1988, nutrient samples were still collected with reversing water bottles. From 1988, CTD-Rosette samplers have been used. An overview of the NERI devices, methods, and uncertainties is given in Table 11.8. 

With the introduction of the rosette sampler and the echo sounder, choosing the depth at which a sample is to be taken is a simple exercise in chart reading. Samples can be taken at any specified depth or in any specified water mass. Using much less sophisticated equipment on a cruise in the South Pacific [167], we were able to take water samples in the Antarctic Intermediate Water from 63 °S almost to the Equator, in order to demonstrate a horizontal continuity and vertical discontinuity in organic particulate content associated with a particular water mass. 

To avoid the potential problems of filtration, centrifugation immediately after sampling might be advantageous. Kerouel and Aminot (1987), for example, proposed a device whereby the subsample for nutrient analyses from the rosette sampler is collected in a polypropylene bottle and, without further handling, is centrifuged and injected directly into the... 

Station salinity samples for analysis with a salinometer are taken from water samplers that are closed at desired depths or pressures. In many cases, a rosette sampler is used that carries Niskin or comparable water sampling bottles (see Chapter 1). Ihe bottles are mounted in one or more rings on a frame. Closing the bottles at desired pressure levels is triggered from the deck unit in the ship s laboratory. New s tems allow selection of bottles individually and not just in the order of their position on the frame. Most frequently, and necessary for WOCE standards, the rosette sampler is operated together with a CTD that is mounted on the rosette s frame. The CTD s on-line pressure information is then used for controlled closing of the water samplers. 

Radionuclides are usually extracted from filtrates of discrete samples (from the Rosette sampler, Gerard bottles or from the ship s seawater supply) by coprecipitation as Fe(OH)3, Mg(OH)2, Mn02, BaS04, PbS04 or Co-APDC. If quantitative recovery cannot be guaranteed, yield tracers are used. The sample volume has to be known accurately. Large volumes can be metered with a water meter (approximately 1 % error). Samples of approximately 25 L can conveniently be weighed on board with a balance (precision approximately 50 g). 

Syiplinq, Discrete water column samples were obtained with 5-L Niskin bottles attached to a General Oceanics Rosette fitted with Plessey Environmental Systems model 9040 CTD. A 1-L aliquot of seawater was transferred from the Niskin samplers into glass-stoppered bottles in such a way that air bubbles were not trapped. The bottles were then stored in the dark at... 

Deadweight in air (kg) in parantheses limited suitability intelligent rosette multi-bottle water sampling system small volume sampler FSl SURE-FIRE submersible array Niskin non-metallic convertible surface water sampling bottles. 

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