CHEMICAL CHARACTERIZATION OF SOIL ORGANIC mTrER
BY CURIE-POINT PYROLYSIS-GAs CHROMATOGRAPHY
Kisaburo SAMUKAWA
Department of Agricultural Chemistry.
University of Osaka Prefecture
1-1 Gakuen-cho. Saka1. Osaka 593
A rapid and reproducible chemical characterization ofwhole soils was carried out by Curie-point pyrolysis
gas-chromatography (Py-GC).

Samples can be analyzed

directly after drying and grinding without further
pretreatment. cluster analysis correctly classified
the resulting pyrograms into each soil type.
Humic substances, the major organic constituents of soils andfacent sediments. are widely distributed over the earth's surface.
The classification of humic substances is based upon solubility
differences in aqueous solutions at different pHs. There have been
many reports on the methods of extraction and analysis of soil organic matters[1].
Pyrolysls-gas chromatography (Py-GC) has been shown to be Very
useful as an analytical technique. Pyrograms of biomaterials arc
very complex[2]. The patterns of variation are not easily discernible by visual 1nspcctlon. Multivariate analysis is needed todetermine cluster patterns as a way or elucidating the chemicalfeatures that discriminate between clusters. Analysis or who]e
soils by pyrolysls-gas chromatography is limited in use[3l. Themajor objective of this study was to cvaluate Py-GC pattern recognition as a method for the chemical characterization of wholesoil.
Soil (approximately 10 mg/sample) was applied to a ferromagnetic foil and brought to a Curic temperature of 590℃ by a Curicpoint

pyrolyzer (Japan Analytical Industry Co.. LTD.. JIIP-3).

The temperature rise time was approximately 0.2 s and the foil washeld at the end temperature for 3 s. The pyrolyzer head was maintained at a constant temperature or 250℃. The resulting

pyrolyzate components were solved on a DB-wax fused sillica
capillary column (0.25 mm i.d. x 30 m long. film thickness 0.25um). The capillary gas Chromatograph (Hitachi Manufacture L.td.. G3000) was equipped with a flame ionization detector and helium wasthe carrier gas.

Peak areas were obtained using automatic in-tegrator (Hitachi Manufacture Ltd., D 2500).
The samples analyzed in this study were all obtained from theOsaka Prefecture (A.B.C and D) except the soil E sample(IbarakiPrefecture). Each soil was analyzed three times by Py-GC.
Data summarizing the properties and sources of the soil samples
analyzed in this study are shown in Table 1. Pyrolysls of wholesoil at a Curie temperature of590℃ yields

complex chro-matograms(Fig. 1). The pyrograms of the whole soil samples
could not be

distinguishedfrom one another by visual
1nspectlorl.

Therefore. only

the most prominent 50 peaks
wereselectedcharacterizein ordertothe difference

among these soils.

The identification of the pyrogram peaks was carried out by
capillary GC-MS (Hitachi Manufacture Ltd.. M 2000). The peaks wereidentified as acetaldehyde(Peak No.4). aceton(Peak No.7).
acetonitrile (Peak No.18). toluene(Peak No.20). pyridine(PeakNo.28), 3-methyl furan(Peak No.36). acetic acid(Peak No.40).
furfura1(Peak No.41), 5-methylfuran(Peak No.46),

pheno1 (PeakNo.55), and cresol(Peak No.57).
Pyrograms of the whole soil samples are very complex and overall patterns of variation are not easily discernible by visual inspection. Ohya and Komai[4] reported that cluster analysis offatty acid composition was useful for the identification ofrelationships among isolated bacteria. and consequently, washelpful in the study of the qualitative effects of heavy metals onbacteria communities. Hence, we applied the cluster analysis tothese pyrogram
Figure 2 shows adendrogram obtainedusing multivariateanalysis. The result
straightforwardly
gives relationships
among the fivesoils. The soils ofA and B are ident1cal except that soil
B was treated withlime to amend thesoil pH. These twosoils and soil C are
clearly distinguished from the othersoils. The similarity of soil D shows alitt1e low value incomparison with this group(soils A.B and C).
Furthermore. the results in the dendrogram indicate that soil
E. volcanic ash soil. is very different from the other soils. Thedendrogram also indicates the similarity and dissimilarity between
the groups of whole soil pyrograms. The soils A and C are themost similar each other. and the soils A and E the most dissimilar.

It might reflect the chemical structure or soil organic

matters. For example. the presence of furfural and methyl furan
is consistent with a result of thermal decomposition

orpolysaccharide[5].
In this study the Py-GC profiles obtained from five kinds ofsoil were compared by cluster analysis.

The cluster analysis

classified the pyrograms into each soil group.