Table 1.
Elemental composition, carboxylic and phenolic acidity and carbon distribution in 13C NMR spectra (ppm) of total humic extracts (THE) and its size-fractions (high molecular size, HMS and low molecular size, LMS) separated during acetic acid treatment and dialysis.
| Element | Acidity | 13C NMR | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| HS | C | H | N | O | S | COOH | Phenolic-OH | 0-48 | 48-105 | 105-145 | 145-165 | 165-190 | HI/HBb | ADc |
| % | meq g−1 | % Carbon distribution | ||||||||||||
| THE1a | 58.1b* | 4.2a | 3.6c | 36.1a | 0.31a | 5.2b | 5.0b | 27.3a | 42.5a | 15.6c | 7.2a | 7.4d | 0.99 | 45.5 |
| HMS1 | 56.2c | 4.1a | 2.8d | 35.5a | 0.15b | 4.5b | 5.5b | 18.8b | 44.1a | 18.7b | 7.4a | 11.0c | 1.22 | 58.1 |
| LMS1 | 54.5d | 4.5a | 5.5b | 32.2a | 0.13b | 6.2ab | 5.5b | 18.1b | 20.2b | 32.1a | 5.2b | 24.4b | 0.80 | 67.3 |
| THE2 | 59.3a | 4.0a | 3.8c | 38.4a | 0.28a | 5.5b | 6.0b | 21.2b | 42.4a | 19.4b | 7.0a | 10.0c | 1.10 | 55.4 |
| HMS2 | 55.5d | 3.9a | 2.9d | 34.6a | 0.20ab | 5.0b | 5.8b | 20.9b | 43.2a | 18.7b | 6.8a | 10.4c | 1.15 | 54.9 |
| LMS2 | 52.4e | 4.2a | 7.8a | 33.1a | 0.15b | 7.5a | 8.8a | 14.8c | 15.2c | 33.7a | 6.5a | 29.8a | 0.82 | 73.1 |
a(1) soil with Pinus mugo cover and (2) soil with Pinus sylvestris cover.
bHI/HB = hydrophobic index = [(48–105) + (165–190)]/[(0–48) + (105–165)].
cAD = aromaticity degree = (105–165)/(105–0)* Values within column followed by the same label are not statistically different at p = 0.05 by Student-Newman-Keuls (Sokal and Rohlf, 1969).