Abstract14 C ages and δ 13 C were examined for sclerotium grains to elucidate the characteristics of these grains distributed in forest soils. The ages of the grains from surface A horizons and buried A horizons were ca 100-200 bp and ca 300-1,200 bp, respectively. In comparison with humic acid extracts, the 14 C ages were in the increasing order: humic acid fraction < humic acid Pg fraction < sclerotium grains. The δ 13 C values for sclerotium grains in surface A horizons and buried A horizons were approximately −31‰ to −28‰, and these values were approximately 2-4‰ smaller than those of humic acids and soils. The C content of the grains had a tendency to decrease with increasing 14 C ages, while the C content of humic acid was constant with age. The 14 C ages of sclerotium grains indicate the individual age of grain formation, which are more likely to assign closer ages to the beginning of soil forming than the 14 C ages of humic acid. The low δ 13 C values for sclerotium grains have presumably originated from characteristically biological organics, which may be protected from attack in soils because of their structure.
Sclerotium grains in soil contain humus-metal complexes that are probably produced from fungal metabolites. The characterization of major elements in sclerotium grains collected from volcanic ash soils in Mt Myoko was examined by X-ray photoelectron spectroscopy, FT-IR spectrometry and CHN analysis, and the concentration of trace elements was determined by PIXE (particle induced X-ray emission spectrometer) analysis. The content of major elements, C, H, N, O and Al, was approximately 47.6, 3.32, 0.78, 30.2 and 1.4% by mass, respectively. Trace elements such as Ti, Cr, Mn, Cu, Zn, Br and Pb were detected in the grains at concentrations between 10 and 100 mg g À1 . Functional carbon groups for the whole grain were characterized by the dominance of O-alkyl C associated with aromatic C. The comparison between the surface and subsurface (matrix) of the grain showed that the concentrations of O, C and N were relatively greater on the surface of sclerotium grains than in the matrix. The proportion of carbon having C-O, C¼O, and O-C¼O bonds, O and N showed a tendency to decrease from the surface towards the matrix. The proportion of C assigned as C-C and/or C-H bonds had a tendency to increase towards the matrix associated with Al.
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