Soil sampling

Soil from mountainous forests is analysed for its pollutant content. The humus layer consists of organic matter and accumulates POPs both from direct deposition and from litterfall.

The mineral soil contains much less organic material and therefore typically shows only a fraction of the POP levels detected in the humus (POPs are poorly soluble in water and thus hardly leach from the humus layer).

Samples are taken from the humus layer and the uppermost 10 cm of the mineral soil beneath. This is done by collecting the entire humus layer within a 30 x 30 cm metal frame .

Since thickness and composition of the humus layer vary considerably within a forest stand, huge amounts of humus have to be collected along a rectangular grid . This yields up to 60 litres of humus per plot – an exhausting load to carry over steep and pathless terrain.

Humus is sampled within a 30 x 30 cm frame. (Image by I. Sedivy)

All humus within a 30 x 30 cm metal frame is collected for analysis.