Lysimeter sampling techniques
Patent No.: 10 048 089; 10 2005 062 896; EP 07 712 322 - for mineral soils
Patent No.: 10 353 485; 10 2011 006374 - for organic soils and peatland
Soil columns can be sampled with a high degree of precision and undisturbed soil structure without the use of heavy duty equipment using the unique sampling technology for mineral soils developed and patented by UGT.
The sampling device guarantees a vertical passage of the lysimeter vessel down to the sampling depth of the soil monolith and cuts the contour of the soil monolith using a milling device which is guided concentrically around the lysimeter vessel. Due to the cutter on the face of the lysimeter vessel, the final contour of the soil monolith is formed. The lysimeter vessel accommodates the soil column to shape. Only low axial forces are required to cut the lysimeter due to reduction of the sheath friction. The soil monolith is not deformed during extraction and keeps its natural structure. For quality assurance purposes, the cutting process is monitored by a remote camera. On reaching the sampling depth, the soil column is separated from the surrounding soil area by a cutting device. After the monolith has been completely cut, it is held in place by the profile holder on the cutting device, acting as a temporary seal of the lysimeter vessel so that the monolith can be lifted safely from the sampling pit after cutting. Xray and computer tomography examinations of the soil columns extracted using this technology have shown that no cracks or structural changes occur within the monoliths using this method.
All in all the use of lightweight technology impairs the extraction point only minimally and no special requirements are placed on the properties of the ground. Furthermore, this method of extraction is very space-efficient so that the surrounding area is influenced as little as possible when extracting the soil columns. After extraction of the monoliths, the soil profile in the extraction pit is undisturbed and easily visible. This permits a good assessment of the soil profile in the lysimeter vessel and the taking of soil ring samples for laboratory investigations into soil properties. Special lysimeter vessels and patented sampling technologies have been developed for the challenges presented by organic soils particularly in bog land. Large organic soil columns can be investigated using the Moor Lysimeter. For this purpose, the lysimeter vessel is trough-shaped, 4 m long, 1 m wide and 1.5 m deep. The length of 4 m facilitates research of the lateral flow processes which are frequently to be observed in bog lands.
In order to minimise the destruction of the soil, the soil monolith is precut by means of a cutting device
on the face side of the vessel. After completion of the extraction process, the lysimeter vessel is lifted from the pit and sealed for transportation such that the soil cannot shift.
A diameter of up to 200 mm traditional column shaped monoliths can be obtained by vertical cutting
using a new extraction technology. The peatland column cutter is made of an easily adjustable basic frame, a cylindrically formed, rotating cutting tube and the tubular cartridge to accommodate the cut soil body.
Ground anchors guarantee the stability of the device also on swampy soil. The cutting element on the lower side of the cutting tube cuts through the vegetation top layer and also any organic deposits
such as roots, without shifting position. This maintains the natural structure of the soil body.
Any outflow of aqueous substrate is prevented with an adjustable vacuum in the cartridge tube above the soil column. In addition to the substrate investigation, laboratory and outdoor experiments can also be conducted on large volume undisturbed soil columns to explore substance conversion processes and microbial changes as well as tracer tests performed depending on different degrees of drainage of the peatland.
Advantages of the lysimeter extraction technology:
- Avoidance of peripheral run off between soil monolith and lysimeter vessel using special tools adapted to different soils
- No impairment of the monolithic soil structure due to congestion or compaction (no deformation) or structural changes resulting from the insertion of the vessel
- Axial guidance of the lysimeter vessel to the extraction depth, avoidance of basic breaks in the monolith
- Light-weight, mobile extraction technology for use under difficult ground conditions
- Simple relocation of the extraction technology, e.g. if impediments are encountered which impair quality such as large stones, deposits or similar at the site
- Well visible soil profile as a result of intact extraction pits providing the possibility of soil mapping after extracting the monolith
- Minimum use of area due to the small distances between the extraction points
- Low impact on site
Soil monoliths can be obtained in the following dimensions using the extraction equipment based on this technology:
|Diameter /area||Length||Type of the soil|
|110 mm||Bis 300 mm||mineral soils|
|200 mm||Bis 1000 mm||mineral soils|
|200 mm||Bis 800 mm||peatland|
|300 mm||Bis 1000 mm||mineral soils|
0.5 m² area
|Bis 2000 mm||mineral soils|
1 m² area
|Bis 3000 mm||mineral soils|
2 m² area
|Bis 2500 mm||mineral soils|
|4000 x 1000 x 1500 mm||peatland|