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, sand an ...

in water environments. Usually it is a

clamshell bucket A bucket (also called a scoop to qualify shallower designs of tools) is a specialized container attached to a machine, as compared to a bucket adapted for manual use by a human being. It is a bulk material handling component. The bucket has an ...

made of

stainless steel Stainless steel is an alloy of iron that is resistant to rusting and corrosion. It contains at least 11% chromium and may contain elements such as carbon, other nonmetals and metals to obtain other desired properties. Stainless steel's corros ...

. 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 Low technology (low tech; adjective forms: low-technology, low-tech, lo-tech) is simple technology, as opposed to '' high technology''. History Historical origin Primitive technologies such as bushcraft, tools that use wood, stone, whoo ...

. The smallest version even fits into

hand luggage The term hand luggage or cabin baggage (normally called carry-on in North America) refers to the type of luggage that passengers are allowed to carry along in the passenger compartment of a vehicle instead of a separate cargo compartment. Passen ...

. The sampler was invented by

Johan van Veen Johan van Veen (Uithuizermeeden, 21 December 1893 – The Hague, 9 December 1959) was a Dutch hydraulic engineering, hydraulic engineer. He is considered the father of the Delta Works. Education Johan van Veen was the fifth child of seven in a ...

(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 div ...

s with

buckets A bucket is typically a watertight, vertical cylinder or truncated cone or square, with an open top and a flat bottom, attached to a semicircular carrying handle called the ''bail''. A bucket is usually an open-top container. In contrast, a ...

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. 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 o ...

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