Nansen bottle
The Nansen bottle or tilting thermometer is a hydrographic device for taking water samples from certain depths. Moreover, it has receptacles for special mercury - thermometer with which the temperature of the sea heat and the hydrostatic pressure can be measured at the desired depth. It was constructed in 1910 by the oceanographer Fridtjof Nansen .
The "bottle" is a slim cylinder made of metal or plastic. The two tapered ends of this cylinder can each be closed with a cover. It is attached to a line at the top and bottom and lowered into the sea. When the desired depth is reached, a drop weight, called a “messenger”, is slid down the rope. When it hits an unlocking mechanism, it unhooks the cylinder at the top and it then rotates 180 °, its upper end tilting downwards. During this rotation, the two valves , which are located at the axial ends of the cylinder, are tightly closed. In this way the water sample is enclosed and can be brought to the surface undisturbed. The water can then be withdrawn through a small tap.
With the help of a mercury tilt thermometer, the water temperature is measured during the tilting process. When the nansen bottle is tilted, the mercury thread is torn by gravity at a narrowing of the capillary and the mercury is divided into 2 parts (in the column or reservoir). This fixes the length of the column and the in-situ temperature can be read off after it has been retrieved. Since the water pressure would influence the temperature measurement by compressing the reservoir, the thermometer is protected by a pressure-resistant housing. At the same time, an unprotected thermometer is carried along and tilted; the following comparison of the two measurements makes it possible to determine not only the temperature but also the pressure.
Often another messenger weight is triggered by the tilting mechanism, which slides further down the line and hits another nansen bottle attached at a greater depth and triggers its mechanism. By arranging a number of bottles and weights on a line on top of each other and letting them down, a number of samples and temperature and pressure measurements can be obtained within a whole column of water in a very short time.
Successor Niskin bottle
Nansen bottles occasionally attached to different points on a long rope require time-consuming handling both when lowering and lifting them up. In 1966 Shale Niskin patented the slim Niskin bottle . A plurality of such bottles, each standing upright around a probe for measurement of electrical conductivity (salt concentration), temperature and pressure (depth) ( C onductivity, T emperature, D epth) mounted form a CTD rosette , the Nansen bottles in practice have largely replaced. The rosette is the only part attached to the end of the rope that is left in the depth and can also come up at the bottom. The 3 - or more - data measured in parallel can be transmitted live via a cable upwards and logged. At the desired places in the depth, a Niskin bottle - flushed lengthways - is closed by cable remote control and thus the water sample is fixed, which usually only happens when it is pulled up in order to change the sample temperature as little as possible during transport. The Alfred Wegener Institute's CTD rosette carries around 12 Niskin bottles with a volume of 12 liters each.
In order to sample seawater close to the seabed, i.e. in the sediment / water flow boundary layer, a three-legged bottom water scoop is stably placed on the bottom. With a radially protruding, stiff flow vane, its prismatic outer frame is aligned with the current water flow. Several Niskin bottles are mounted horizontally on a frame at different distances from the floor, at the desired sampling heights. In order to achieve a safe flow through the bottles, this bottle-bearing frame rotates sufficiently with its own smaller flow vane with changing flow direction within a 120 ° wide sector.
Footnotes
- ↑ Pierre Tardent: Marine Biology: An Introduction. Thieme, Stuttgart 2005, p. 162, Fig. 74.
- ↑ http://medienportal.univie.ac.at/uniview/detail/artikel/neues-vom-forschungsschiff/ ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. Gerhard J. Herndl, News from the research ship, October 18, 2010, water samples using a CTD rosette from a depth of up to 6000 m, ship Pelagia, accessed on December 20, 2014
- ↑ http://www.kum.homepage.t-online.de/dt/BWSGestell.pdf Bodenwasserschöpfer K / MT 420, website of the manufacturer, kum-kiel.de, accessed on December 20, 2014
