ESTUDO DA EVOLUÇÃO DA MATÉRIA ORGÂNICA DO SOLO UTILIZANDO O CARBONO-14 PRODUZIDO NOS ENSAIOS TERMONUCLEARES ATMOSFÉRICOS

J. M. FLEXOR, P. F. S. LÔBO, J. L. RAPAIRE

Resumo


The specific activities (14C/12C) of the free fulvic acids (FFA), humic acids (HA) and humine (H) of the 0-5 cm layer of ferralitic florestal soil of Bahia exhibited: δ14C(FFA) = = (15 ± 1)%; δ14C(HA) = (25 ± 1)% and δ14C(H) = (36 ± 1)%. Laws of conservation regarding the evolution of the specific activity of atmospheric CO2(for 13°S latitude), applied to a simple model of fractionation of organic matter, allowed to the estimation of the formation rates for the three fractions (0-5 cm) qFFA = 0.005 kg/m2; qHA = 0.037 kg/m2 and qH = 0.180 kg/m2. Simplified hypotheses lead to mean residence times, for the (0-5 cm) layer, of TFFAR = 7 years, TAHR = 15 years, and THR = 34 years. The obtained sequence for the above residence times agrees with the generally admitted hypotheses.

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