This paper has several special properties:

• The fabric can be produced to be equivalent to sand paper grit sizes of >120, but is considerably thinner. Thus, even constricted openings and gaps can be neatly polished.
• In a special test run, fabrics were produced that are so thin that even light shines through, allowing the treated surface to be observed during the abrasion process.
• Due to its high structural integrity and low wettability, the material maintains a floating position on water, even when subjected to strong downwards pull, and without losing its coherence.
• Undisturbed storage on the roll is ensured by torque-limiting perforation (TLP): should any forces happen to disturb the spatial attitude of the roll, the generation of any torque is effectively averted by disrupting the transmission path.
• Thanks to bulk purchase, this product is extremely cost-effective, if not to say dirt-cheap.

However, there are still some disadvantages:

• The paper is rather brittle and prone to strong wrinkling. This complicates working on rounded surfaces.
• The low adhesion capacity of the fabric surfaces impedes lifting off and retaining material abrased from organic/biologic items.

Because of cost reasons and in order to assess the human component (“user interaction”, “skin feel”, reaction to larger amounts of blood), the tests are not performed by the FMPA (materials research and testing centre), but – sadly – directly in the various university department offices.

We're not quite happy with the location of the test stand. Although it's situated in a discreet and undisturbed location, conflicts of interest must be expected:

Sculpture “Kryptos” (CIA Headquarters, Langley, VA). Foto: Jim Gillogly.

However, I see another building almost every day, where I wonder if that letter tangle contains a hidden message (e.g. “the costs for this thing boggle the mind” *gg*).

The ICMC at BTU Cottbus. Source: Wikipedia.

I think we have to wait for Herzog & de Meuron to provide a clue.

Our department (Environmental Geology) offers such practicals since 2007, but other departments have started earlier. Students of the secondary schools “Max-Steenbeck-Gymnasium” here in Cottbus and Carl-Friedrich-Gauß-Gymnasium in Frankfurt (Oder) attend practicals here as part of the “Forschungs-Bildungs-Kooperation” programme (FBK). Sorry, the schools' and FBK's websites are in German only.

Both schools have a special focus on mathematics, natural science and technology, and the students choose a practical course topic according to their elected “Leistungskurse” (intensive courses). In our case, these were either biology or chemistry. Sadly, geography intensive courses are not part of the FBK programme.

Up to now, we had three groups and topics:

• Physical properties of highly concentrated solutions of various salts (Gauß Gymnasium)
• Water quality of a small ditch flowing through a fen (Steenbeck Gymnasium)
• Release of nutrients from strongly degraded peat soils (Steenbeck Gymnasium)

Highly concentrated salt solutions

This was a project quite close to pure chemistry. The students prepared solutions of NaCl, MgCl₂, CaCl₂, MgSO₄, and a few two-salt mixtures at various, high molalities (mostly in the range of 0.5 to 5 mol/kg) and investigated how density and electrical conductivity differ between the salts and how they change a different temperatures, concentrations and mixing ratios.

They found out that some relationsships are quite linear or at least monotonic, e.g. conductivity versus temperature or density versus concentration, but are not the same (different slope, different intersect) for different salts and concentrations. But they realised that there are also non-linear dependencies, e.g. conductivity versus concentration: at very high concentrations, conductivity decreases again (obstruction of ions).

Everytime, and always too late, I realise I didn't take enough photos of our work, so you have to be satisfied with one of the resulting diagrams. For the following topics, the situation is a bit better luckily.

Example from Gauß Gymansium students' experiments: Density and electrical conductivity for MgCl₂ solutions of different molalities. “1M” = 1 mol/kg.

Quality of water flowing through a fen

My first group of students from Steenbeck Gymnasium measured discharge of a small ditch flowing through a (slightly degraded) valley fen at its beginning and end. Also, measured pH, conductivity, oxygen, temperature and alkalinity on-site, and collected water samples and analysed them for nitrogen (total, nitrate, ammonia), phosphate, dissolved organic carbon, chloride, boron (as sewage indicator).

Dressed for getting wet…

Sadly, I couldn't find a decent photo of the discharge measurements.

Vacuum filtration of sampled water in the field.

Again, I made some pictures of the sample preparation, but not of the analysis proper.

Preparation for analysis.

With these data, they could balance the fluxes entering and leaving the system. For example, denitrification within the system can be seen nicely.

Nutrient release from strongly degraded peat

This year's students took soil samples from another fen site, where the peat ist strongly degraded after long time of drainage and agricultural use. Degradation not only means a loss of soil, but also mineralisation of organic matter, i.e. nutrients like nitrogen and phosphorus which had formerly been bound in large organic molecules are now present in mobile forms like nitrate. These could then be leached out, especially when the water table rises again, and affect downstream surface water (eutrophication).

Borehole in strongly degraded peat. (Brighter material at the tip of the auger is the underlying finesand.)

In a simple laboratory setup, we try to find out what could happen after rewetting. Soil samples are extracted with water under controlled conditions (fixed temperature, fixed soil/water ratio, bottles gently rotated for 24 hours).

Overhead-shaker for the extraction of soil with water.

After that, the students measure physico-chemical parameters (pH, el. conductivity, redox) analyse the eluate for nutrient (nitrogen and phosphorus species).

Measurement of pH, electrical conductivity, temperature and redox potential.

We are still working on the project, so there are no nice results to present right now.

Blackboard by John A. Wheeler (photo by Gordon Watts)

Hat tip to Diax's Rake (Scienceblogs.de).