Abstract

MOSQUERA, Carmen S.; MARTINEZ; GUERRERO, Jairo A.  and  HANSEN, Eddy W.. STRUCTURAL CHARACTERIZATION OF ORGANIC MATTER OF THREE SOILS FROM AQUITANIA-BOYACÁ, COLOMBIA. Rev.Colomb.Quim. [online]. 2010, vol.39, n.1, pp.47-60. ISSN 0120-2804.

Generally, soil organic matters may differ in structure, composition and conformation according to their origin and age. In the present work structural composition of three soil organic matters, as determined by IR and solid-state CPMAS ¹³C-NMR spectroscopy of two Inceptisol soils (I01 and I02) and one Histosol soil (H03) from the Aquitania-Boyacâ town in Colombia are presented (in these soils farmers have grown large onion crops). Measurements were performed at two different depths 0 - 10 and 40 - 50 cm, respectively. According to the IR spectra the presence of OH-groups (from phenols, carboxylic acids and alcohols), aromatic and aliphatic groups were identified. The ¹³C NMR spectra revealed a decreasing amount of organic matter with increasing depth in the following relative order: H03-0 = 100 and H03-40 = 88, I02-0 = 23 and I02-40 = 0, and finally I01-0 = 17 and I01-40 = 12. The carbon peaks resonating in the ô = 108-50 ppm region of the spectra (N- and O-alkyls and acetals) dominated in almost all the extracted soils, with aromatic carbon peaks (δ = 168-108 ppm) showing the second most intense peaks for the samples I01-0 and H03-40. The aliphatic carbon (δ = 0-50 ppm) revealed the second most intense peaks in samples I01-40, I02-0 and H03-0. Finally, carbonyl carbon (δ = 220-162 ppm) contributed the smallest signal intensity in all the three soil samples.

Keywords : soil organic matter; infrared spectroscopy; nuclear magnetic resonance; inceptisol and histosol.