Water is an essential element in ecosystems and plays an important role in various aspects of life, including ecological balance and sustainability of natural resources. To better understand the composition and characteristics of water in various environments, including seas and lakes, water sampling techniques are crucial in oceanographic research. Water sampling involves a series of methods and equipment designed to collect accurate and representative data on water conditions. One device that is often used in water sampling is the NISKIN bottle, a tool carefully designed to ensure precise sampling from various depths within the water column. The NISKIN bottle has become a top choice for researchers facing the challenge of sampling water from specific layers in the ocean or lake. Its innovative design allows high control over the sampling depth, providing optimal accuracy and representation of the water conditions at a given depth. The parameters that can be analyzed from the water samples taken are temperature, salinity, and chemical composition of the water.
Before getting into the explanation of what a nisikin bottle is, it would be nice to review a little previous material, namely the nansen bottle. The nansen bottle is a bottle invented by Fridtjof Nansen from Norway in 1894, which is in the form of a metal cylinder (originally made of brass metal) with two closing mechanisms at both ends. The bottle would be lowered to the required depth (where the water sample would be taken) and a weight called a “messenger” would be dropped onto the main line. This weight would reach the bottle and cause the top end to detach from the string, so that the bottle tipped over, triggering the valves at both ends and trapping the water sample inside.
The niskin bottle is a development of the nansen bottle. the niskin bottle was invented by Shale Niskin in 1966. Shale Niskin took the Nansen bottle and developed a bottle made of plastic elements (PVC), with no metal elements on the inside. His modification prevents some chemical reactions between the metal and the water sample taken, which could alter the content of the water sample taken. both ends of the bottle are open and each end is fitted with a spring-loaded cap or tightened with an elastic cord. Over the years, a modern variation of the Niskin bottle has emerged that uses actuated valves that can be pre-set to trip at a certain depth and be detected by a pressure switch, or remotely controlled via electrical signals sent from the surface. this variation of the Niskin bottle allows a large number of Niskin bottles to be mounted together in a circular frame called a rosette (part of a CTD device).
How Ninskin Bottle Work
Here’s how to use the niskin bottle:
- Lowering the Bottle into the Water, The NISKIN bottle is connected to a lowering device, such as a lowering wire or rope, which is usually operated from a research vessel or boat. The bottle is pulled by the lowering system into the water.
- Bottle Cap Opening, When the bottle drops into the water, both bottle caps open automatically because the water pressure outside the bottle is higher than inside. This allows water to enter the bottle freely.
- Depth Control, The operator monitors depth using a lowering rope or additional equipment, such as a pulley or winch. Depth control can be done manually.
- Bottle Cap Closure, The operator, usually with the help of a simple control system, closes both bottle caps after reaching the desired depth.
- Bottle Raising, The bottle is raised back to the water surface using the same lowering system. As the bottle rises, the bottle cap remains closed to maintain sample integrity.
- Sample Transfer, After reaching the surface, the water sample in the bottle can be transferred to a sample container or measuring device for further analysis.
Niskin Bottle Strengths and Weaknesses
Niskin Strengths:
- Precision Sampling, the NISKIN Bottle allows for depth-precise water sampling
- Pollution Avoidance, The good design of the NISKIN bottle ensures that the sample is taken without mixing with the water in the layer above it.
- Operational Flexibility, NISKIN Bottles can be operated manually or connected with automatic devices such as CTD rosettes.
Niskin Weaknesses:
- Limited Number of Samples, Each NISKIN bottle can only take one sample at a time
- Requires Additional Equipment, For optimal use, NISKIN bottles often need to be connected to additional devices such as CTDs or depth measurement instruments, which can increase operational costs and complexity.
