The Van Veen grab sampler is an instrument to sample

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sa ...

in water environments. Usually it is a clamshell bucket made of stainless steel. Up to 20 cm deep samples of roughly 0.1 m² can be extracted with this instrument. It can be light-weight (roughly 5 kg) and low-tech. The smallest version even fits into hand luggage. The sampler was invented by Johan van Veen (a Dutch engineer) in 1933. A draw-back of the use of this sampler is that it tends to disturb the sediments more than a

box corer The box corer is a marine geological sampling tool for soft sediments in lakes or oceans. It is deployed from a research vessel with a wire and suitable for any water depth. It is designed for a minimum of disturbance of the sediment surface by b ...

does.

Mechanism

While letting the instrument down into the water, the two

lever A lever is a simple machine consisting of a beam or rigid rod pivoted at a fixed hinge, or '' fulcrum''. A lever is a rigid body capable of rotating on a point on itself. On the basis of the locations of fulcrum, load and effort, the lever is d ...

s with buckets at their ends are spread like an open scissor. The levers are locked in this position, and unlocked on hitting the ground. When the rope is pulled upward again, the two buckets close and grab a sample from the

sea floor The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as 'seabeds'. The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...

. File:VanVeenGrab - Locked.jpg, Van Veen grab when it is locked, ready to be lowered to the floor File:VanVeenGrab - Unlocked.jpg, It is now unlocked after hitting the floor, ready to collect sediment File:Van Veen Grab - Close.jpg, When lifting it after unlocked, the jaws will close to collect sediment inside Three small technical changes lead to variations with more mechanical parts or structure: * The Ekman grab sampler does not close the

shovels A shovel is a tool used for digging, lifting, and moving bulk materials, such as soil, coal, gravel, snow, sand, or ore. Most shovels are hand tools consisting of a broad blade fixed to a medium-length handle. Shovel blades are usually made of ...

instantly on ground contact, but a messenger weight has to be sent down in order to release springs and take the sample. * The Ponar type sampler is modified also and has additional springs which are released upon bottom contact which might be helpful for harder surfaces. * The Young modified grab sampler includes a metal frame for additional stability.

References

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External links

Instrument description at Woods Hole Oceanographic Institute

as offered by the Rickly Hydrological Company Aquatic ecology Biological oceanography Oceanography Oceanographic instrumentation

Mechanism

See also

References

External links