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Table 5 Relative intensities of the CP/MAS 13 C NMR spectra in different particle-size fractions isolated from the O/A horizon (0–10 cm) in 3 topographic positions

From: Characterization of soil organic matter in perhumid natural cypress forest: comparison of humification in different particle-size fractions

Topographic Particle-size C functional groups (%) A/ O-A ratioa Aromaticityb
position (μm) alkyl O- alkyl di- O-alkyl aromatic carboxyl   
Summit Coarse (>250) 28.4 42.9 9.9 13.7 5.1 0.54 0.14
  Medium (250 ~ 53) 31.2 42.4 9.3 11.8 5.3 0.60 0.12
  Fine (53 ~ 2) 36.9 41.8 8.2 8.3 4.7 0.74 0.09
  Very fine (<2) 41.2 41.7 7.1 5.3 4.6 0.84 0.06
Footslope Coarse (>250) 29.5 41.5 9.5 13.5 6.0 0.58 0.14
  Medium (250 ~ 53) 31.8 42.2 8.9 11.5 5.5 0.62 0.12
  Fine (53 ~ 2) 34.9 39.4 8.5 11.4 5.8 0.73 0.12
  Very fine (<2) 41.5 35.7 6.8 9.3 6.7 0.98 0.10
Lakeshore Coarse (>250) 28.8 45.3 10.2 11.1 4.6 0.52 0.12
  Medium (250 ~ 53) 28.4 44.4 10.6 11.8 4.9 0.52 0.12
  Fine (53 ~ 2) 34.7 41.8 8.7 9.2 5.6 0.69 0.10
  Very fine (<2) 38.3 42.1 7.8 6.9 4.9 0.77 0.07
  1. a alkyl-C peak area (0–50 ppm)/( (O-alkyl-C + di-O-alkyl C) peak area (50–110 ppm) ).
  2. b aromatic C peak area (110–165 ppm)/ ((alkyl-C + O-alkyl-C + di-O-alkyl C + aromatic C) peak area (0–165 ppm)).