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- The most commonly used water-sampling bottle at present is the Niskin bottle,
with spring-loaded end-caps with rubber washers. These are plastic
(polyvinylchloride) bottles with stoppers at each end. The stoppers are held
together by a rubber cord or spring that pulls them together from inside the
bottle. The water-tight closures at both top and bottom, equipped with
subsampling spigot and air vent, can be remotely triggered at pre-determined
depths in the water column to collect seawater samples for discrete chemical
and biological measurements. To cock these bottles, lanyards are used to pull
the stoppers away from the bottle, leaving the bottle wide open for water to
flow through. The bottle is tripped by activating a firing mechanism that
releases the lanyard, allowing the stoppers to close on the bottle thereby
trapping the seawater sample.
Niskin bottles can capture a much larger volume of seawater than the older
Nansen bottles. Reversing thermometers on Niskin bottles are mounted in a
spring-loaded frame that rotates the thermometers at the same time that the
Niskin bottle stoppers are closed. These are used with most rosette samplers,
the most common arrangement for water bottles, where a single frame carries up
to 36 water bottles. Water bottles are mounted in a single frame that is
attached to the end of the oceanographic wire. This has an electrical
conductor incorporated; the bottles can be closed when desired on electrical
command from the deck.
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