1999 Volume 70 Issue 6 Pages 769-774
We compared the spectroscopic and physicochemical properties of the humic acids isolated from charred grassland plants after HNO_3 treatment (C-HA) and from the A horizon of Kuro- bokudo (S-HA). 1) The shapes of the absorption curves in the UV and visible regions of the C-HA and S-HA were featureless, and their humic acids belonged to the A-type. 2) The carbon and hydrogen contents of C-HA were almost the same as those of S-HA, while the nitrogen content of C-HA was much higher than that of S-HA and the oxygen content of C-HA was lower than that of S-HA. The atomic [O]/[C] and [O]/[H] ratios of C-HA were lower than those of S-HA. These analytical data of C-HA, except for the nitrogen content, fell within the ranges of those of A-type soil humic acids reported previously. 3) The ^<13>C-NMR spectra of C-HA and S-HA were similar to each other, and the values of their carbon species were in the order of aromatic-C ≫ carbonyl- C > carbohydrate-C≒aliphatic-C. The values of the aromatic-C and carbonyl-C were lower in C-HA than in S-HA. The reverse was true for carbohydrate-C and aliphatic-C. 4) The FT-IR spectrum of C-HA resembled that of S-HA. 5) The XRD patterns of C-HA and S-HA indicated that these humic acids had graphite-like structures.
