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Table 2 Relative distribution (%) of signal area over the chemical shift regions (ppm) and indexes of aromaticity (Ar) and hydrophobicity (HB), as assessed from 13C-CPMAS–NMR spectra of different humic extracts

From: Molecular characteristics of humic substances from different origins and their effects on growth and metabolism of Pinus laricio callus

Extractsa

Carboxyl-C

(190–160)

O-Aryl-C

(160–145)

Aromatic-C

(145–110)

O-Alkyl-C

(110–60)

CH3O/C–N

(60–45)

Alkyl-C

(45–0)

Ar

HB

HA-C

5.3

5.5

35.7

14.7

7.8

31.0

41.2

3.2

HA-D

9.7

3.2

15.7

26.0

13.0

32.4

18.9

1.4

HA-E

11.5

4.1

14.8

22.8

11.5

35.2

18.9

1.5

HA-F

5.6

4.8

64.5

6.6

2.3

16.3

69.3

6.5

HA-G

11.3

4.0

14.2

28.5

11.0

31.0

18.1

1.2

HA-H

7.7

8.6

53.1

8.8

6.1

15.8

61.7

4.1

HA-I

6.7

3.8

15.8

26.1

11.8

35.8

19.6

1.6

HA-L

9.6

5.6

20.6

16.9

10.0

37.3

26.2

2.2

HA-M

10.3

4.8

15.8

23.7

13.5

31.9

20.6

1.5

HA-N

6.7

6.1

39.9

9.2

2.3

35.7

46.1

4.9

FA-O

10.8

4.4

15.7

42.4

10.2

16.4

20.2

0.7

FA-P

15.2

3.8

7.8

32.4

13.5

27.4

11.6

0.8

FA-Q

13.0

3.7

15.0

40.2

11.3

16.8

18.7

0.7

  1. aHA-C from Leonardite; HA-D from oak forest soil; HA-E from compost after 150 d maturation; HA-F from treated Lignite; HA-G from compost after 30 d maturation; HA-H from an oxidized coal; HA-I from fir and beech forest soil; HA-L from peat; HA-M from vermicompost; HA-N from a Lignite; FA-O from a loamy agricultural soil; FA-P a sandy loam agricultural soil; FA-Q from a volcanic forest soil