Fulvic acids (FAs) from topsoil and ground water solutions were investigate
d to discover effects of land use and peat degradation on their molecular c
hemical composition and thermal proper-ties. The FAs were extracted from th
ree Gleysols under arable land, intensive and extensive grassland, and from
three Histosols under alder forest, extensive grassland, and a natural suc
cession in a long-term (> 200 years) cultivated fen area. Functional groups
and molecular subunits of the FAs were investigated by C-13 Nuclear Magnet
ic Resonance (C-13 NMR) spectroscopy. Thermal properties and structural mol
ecular subunits were investigated by off-line pyrolysis, and Pyrolysis-Fiel
d Ionization Mass Spectrometry (Py-FIMS). The C-13 NMR spectra showed that
the FAs from topsoil solutions had smaller proportions of alkyl C (mean: -8
%) and more aromatic C (mean: + 6 %) than FAs from ground water. This clea
r differentiation of dissolved FAs in the soil profiles is consistent with
Py-FIMS data which have shown enrichments of lipids in ground water FAs. Fu
rthermore, Py-FIMS revealed that the FAs from topsoils were richer in pheno
ls + lignin monomers, carbohydrates, as well as mostly aromatic NI-containi
ng compounds. These molecular subunits of FAs, relatively enriched in topso
il, were also the main indicators of land use and peat degradation. For top
soil solutions, the proportions of phenols + lignin monomers and carbohydra
tes increased stepwise with peat degradation in Gleysols and Histosols. Cor
respondingly, the thermal properties indicated the incorporation of these c
ompounds into FAs by chemical bonds of larger thermal stability. Statistica
l evaluation by principal component analysis of Py-FIMS clearly supported t
he differentiation of FAs according to the origin from topsoils and ground
water, different soil types, and land use and peat degradation. Hence, it i
s concluded that water soluble FAs can be utilized as objective ecological
indicators for soil effects on adjacent ground and surface waters.