Carlos Tadeu Carvalho do Nascimento

Gamaespectrometria aplicada em solo agrícola no noroeste do Estado do Rio de Janeiro

The present work presents the use of gamma-ray spectrometry applied to precision agriculture in a sub-tropical area. Our dataset comprises measurements both in rock and residual soil. The soil dataset shows a reduction of 20% on U and Th and 10% on K, when compared to rock samples. This difference could be related to K supplementation associated to chemical fertilization.

Radiação gama e resistividade elétrica em solo com aplicação de carbonatito e fertilizantes agrícolas no Distrito Federal

EMBRAPA (Empresa Brasileira de Pesquisa Agropecuaria) and Brasilia University developed a research project about the viability of carbonatite rock as agricultural fertilizer. As an initial experiment, several mixtures of carbonatite, limestone, phosphorous and potassium compounds were added as fertilizers in an oxisol area (red-latosol, according with Brazilian System of Soil Classification), in Distrito Federal, central Brazil. The experiment area was divided in 56 plots (4 × 7m) and each plot received a fertilizer mixture. The purpose of this work was to verify if the addition of fertilizer mixture to the soil modified its radiometric and resistivity properties and if it is possible to identify this change. Gamma-ray and electrical resistivity measurements were obtained in an experimental area and in a natural savannah type vegetation area. The results showed that the fertilizer addition modified soil natural properties causing a small increase in K, U, Th levels and decreasing ten times electrical resistivity. A low contrast of radiation was observed between plots, and then it was not possible to differentiate the several treatments in base of gamma-ray measurements. Electrical resistivity was efficient to identify three groups of plots related to mixtures characteristics, respectively with phosphorous, potassium and limestone / carbonatite predominance.

Processamento e interpretação de dados aerogamaespectrométricos da bacia hidrográfica do rio São Domingos, noroeste do estado do Rio de Janeiro

In the present work we show the results of an airborne gamma-ray data processing and interpretation in the Northwestern portion of Rio de Janeiro State. The studied area is characterized by small private lands with a low-level technological agriculture soil handling techniques. Our results show that weathering processes may control the isotopes distribution in the region.

Estudo da compactação do solo por meio de ensaios geotécnicos e de métodos geofísicos

The main objective of this work is to investigate the effect of sand-gravel compaction piles on the behavior of loose sand deposits. Reduced model tests were carried out on an artificial sand deposit filling a trench 1.5 m wide, 3.0 m long and 2.5 m deep, excavated in a clay rich soil. In situ geotechnical tests and DC electrical resistivity measurements were carried out before and after the construction of compaction piles, in order to characterize the changes in the sand deposit. Conductivity anomalies were observed in the position of the compaction piles with better performance. These anomalies are caused by the