NGR lake sediment

Keyword Definition

NGR lake sediment

An ideal sample is taken from a lake less than 5 km2 and >3m deep, with a single central basin from which the sample is obtained. Sampling is carried out using float-equipped helicopters with a 2 man crew plus the pilot. To collect the lake sediment material, a hollow-pipe, bottom –valved sampler is attached to an external winch and rope system. The sampler can also be hand-lined. When the helicopter has landed and is stationary, the sampling apparatus is released and allowed to sink unimpeded to the lake bottom. Generally, the full length of the sampler will penetrate the bottom sediment. The sample obtained, extending from the butterfly valves to several centimetres below the triangular port, represents a 30-35 cm section of lake sediment from several tens of centimetres below the water-sediment interface. The material is retrieved from the sampler by inserting a plastic scoop into the barrel through the triangular port, inverting he sampler and then ‘thumping’ the sampler on a wood plank screwed onto a plywood platform attached to the helicopter float. The sediment samples are then placed in high wet-strength paper bags, approximately 10x15x15 cm with a double fold top, and put into a partitioned aluminium tray. It is important to collect a full bag of sample material. One to two kg of wet lake sediment will shrink to a hard, dark brown to black lustreless ‘brick’ about the size of a golf ball weighing 50 to 100 grams depending on the LOI content of the sample.

Hierarchical classification

Sample >> Lithosphere >> Unconsolidated >> Terrestrial >> Fluvial >> Lake sediments >> Centre basin >> Grab sample >> NGR lake sediment



Category: Analysed material

The different kinds of sample material collected in the field have been classified hierarchically. Examples: “till”, “soil”, “vegetation”. Taken from the “Sample_Types_SHARED” database table.

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