A novel approach to the characterization of an Andosol humic acid

J.A. GONZÁLEZ-PÉREZ; M. AVENA; M. BRIGANTE; G. ZANINI; R. GONZÁLEZ-VÁZQUEZ; T. VERDEJO; F.J. GONZÁLEZ-VILA

Tallin

Congreso; 12th Nordic-Baltic IHSS Symposium on Natural Organic Matter in Environment and Technology; 2009

International Humic Substances Society (IHSS)-Nordic Baltic Chapter

Andosols are soils usually formed from a volcanic substrate, with thick dark A horizons (melanic epipedon) that stores large amounts of organic carbon (5-20% weight) mainly in the form of stable humic fractions. The unusual properties of these soils are strongly affected by poorly crystalline materials like allophanes, imogolite and other Fe and Al oxyhydroxides that induce aggregation with organic compounds generating structures with a high degree of stability and soils with much more organic matter (OM) than other soils under similar conditions. The HA studied was originally extracted and purified from a soil with andic characteristics according to the procedures recommended by the IHSS (elemental composition: N 4.86%, C 52.57%, H 5.06%, O 37.18%, S 0.33%). In this work, Double-Shot Py-GC/MS was used to investigate the molecular features of HA that enters in solution in aqueous media (pH 8.5) at different extraction times. Total desorption (280º C) and pyrolysis (500º C) products were analysed in the original HA and in six fractions obtained after re-precipitation of the dissolved HA (pH 1.5).