Cupric Oxide Oxidation Products of Tropical Peat Soils

Abstract

Cupric oxide oxidation was used in order to examine the composition of lignin-derived phenolic compounds and to estimate the degree of lignin alteration of tropical peat soils. Kaila's pyrophosphate index (PPI) was used to assess the degree of decomposition of peat soils. Tropical peat soil samples were collected from soil profiles in three areas of Indonesia including of 11 sites, located in reclaimed / cultivated areas and under forest stands. Oxidation of these samples produced vanillyl and syringyl phenols as major components while cinnamyl phenol as a minor component. Phenolic aldehydes almost always predominated, followed by phenolic acids. High correlations between the yield of the oxidation products and PPI suggested that lignin-derived oxidation products could be used to describe the alteration of lignin in tropical peat soils. Based on the samples studied, two groups of lignin alteration with depth were recognized, which could be best described by acid to aldehyde ratios. The first group was observed in inland peat soils associated with a relatively more anaerobic history of alteration in the lower layers and the second group in marginal peat soils. The pattern of lignin alteration with depth also revealed that reclamation / cultivation mostly affected the surface layers to a depth of about 40 cm. Key Words: CuO oxidation, decomposition, lignin alteration, phenolic compounds, tropical peat soils.