Geoscience Reference
In-Depth Information
Table 3.1
von Post degree of humification.
Symbol
Description
HI
Completely undecomposed peat which, when squeezed, releases almost clear water. Plant
remains easily identifiable. No amorphous material present.
H2
Almost entirely undecomposed peat which, when squeezed, releases, clear or yellowish
water. Plant remains still easily identifiable. No amorphous material present.
H3
Very slightly decomposed peat which, when squeezed, releases muddy brown water, but from
which no peat passes between the fingers. Plant remains still identifiable, and no amorphous
material present.
H4
Slightly decomposed peat which, when squeezed, releases very muddy dark water. No peat
is passed between the fingers but the plant remains are slightly pasty and have lost some of
their identifiable features.
H5
Moderately decomposed peat, which, when squeezed, releases very 'muddy' water with a
very small amount of amorphous granular peat escaping between the fingers. The structure
of the plant remains is quite indistinct, although it is possible to recognize certain features.
The residue is very pasty.
H6
Moderately highly decomposed peat with a very indistinct plant structure.When squeezed,
about one-third of the peat escapes between the fingers.The residue is very pasty, but shows
the plant structure more distinctly than before squeezing.
H7
Highly decomposed peat. Contains a lot of amorphous material with very faintly recognizable
plant structure. When squeezed, about half of the peat escapes between the fingers. The
water, if any is released, is very dark and almost pasty.
H8
Very highly decomposed peat with a large quantity of amorphous material and very indistinct
plant structure.When squeezed, about two-thirds of the peat escapes between the fingers.
A small quantity of pasty water may be released. The plant material remaining in the hand
consists of residues such as roots and fibres that resist decomposition.
H9
Practically fully decomposed peat in which there is hardly any recognizable plant structure.
When squeezed it is fairly uniform paste.
H10
Completely decomposed peat with no discernible plant structure. When squeezed, all the
wet peat escapes between the fingers.
3.7 OXIDATION
Lowering of the groundwater table for sustained periods of time allows the organic
fraction come in contact with air, which leads to shrinkage and oxidation. Con-
sequently, the fibre structure is destroyed due to accelerated decomposition and
it becomes more amorphous-granular (Vonk, 1994). This activity may result in
significant changes in engineering properties.
Pore water
Usually peat has an acidic reaction caused by the presence of carbon dioxide and humic
acid resulting from decay. Peaty waters are practically free of salts and generally show
pH values of 4 to 7 (Lea, 1956).
