Dirt level in sugar cane consignments delivered to the factory is dependent on soil type, in association with harvesting system and weather conditions. Efforts for reducing soil in harvested cane have been made by sugar cane millers, especially improving the washing system installed before crushing. Instrumental neutron activation analysis has shown its potential for assessing dirt reductions in the washed material. Knowledge of elemental concentrations in the different soil fractions highlights the reliability of such measurements especially when taking into account the soil characteristics.
Neutron activation analysis was used to develop a method of measuring the soil content in a sugar cane consignment. When sugar cane is cut and taken to the sugar and alcohol industries, different quantities of soil are loaded with the stalks, depending on harvesting mechanization and weather conditions. Despite the washing process before crushing, significant amounts of soil have been found in cane delivered to mills. Different soils were sampled at several mills in the State of São Paulo, as well as sugar cane stalks of the SP70-1143 variety grown on such soils. Elements present in soil but not in sugar cane have been studied to act as tracers of unwanted impurities. Sc has proved to be an efficient tracer of the soil entering these industries with the sugar cane.
This work shortly describes the main steps involved in the design and development of the software package Quantu, created to conduct k0-standardized NAA. The package comprises a database as well as two individual programs. Quantu-MCA is dedicated to (g-ray spectrum analysis and Quantu-INAA is the interface for the database administration, also dealing with k0-method calculations.
Soil is usually carried to the mills, as an impurity in sugar cane, leading to economic drawbacks for the industry. The quantification
of this dirt is important to identify its causes and for routine quality control. Several methods have been used for this
purpose, however, no single one has been pointed out as an industrial standard. The use of a γ-ray emitting radionuclide of
natural occurence was investigated and, after several soil and cane radioactivity analyses,212Pb was chosen as the best tracer. Calibration curves developed with the addition of soil in clean cane, from 0 to 10% (dry
mass), demonstrated the linearity of the method. Analyses of eleven samples taken from consignments showed that the procedure
was consistent and reliable when compared to the traditional ash method.
The elemental composition of pine trees as a function of age was achieved by the tree-ring method. By using instrumental neutron activation analysis, trace elements were determined in individual rings ofPinus elliottii var.elliottii of 32, 14 and 9 years, from an implanted forest ofPinus sp., Buri, São Paulo, far away from industrial pollution. Different components of the system such as needles, pith, bark, soil and litter were also analyzed for 18 elements (As, Br, Ce, Co, Cs, Eu, Fe, Hf, K, La, Mn, Na, Rb, Sc, Sm, Yb, Zn, and Zr). Al, B, Ba, Ca, Fe, K, Mg, and P concentrations were determined by atomic absorption and/or emission spectrometry (AAS; ICP-AES). Some elements have showed similar radial distribution of the concentration for the three ages. Abrupt concentration changes in the pith and ring-bark boundary corresponding to the first and last growth rings were observed.
Neutron activation analysis was performed on aluvial soil samples from several sites on the floodplains of the Amazon River and its major tributaries for trace elements determination. The spatial and temporal variations of chemical composition of floodland sediments in the Amazon basin are discussed. No significant difference was found in trace elemental distribution in the floodland soils along the Amazon main channel, even after the source material has been progressively diluted with that from lowland draining tributaires. It was also seen that the average chemical composition of floodplain soils compares well with that of the suspended sediments.
The experimental work involved the efficiency determination of three coaxial hyperpure Ge detectors, using point-like sources placed at various distances from the top cover of the detectors. Curves were fitted to the experimental data and a microcomputer routine was developed to calculate the efficiencies of cylindrical sources, including self-attenuation correction. Tested at various source and distance conditions, the procedure showed results sufficiently consistent for routine k0-INAA.
Selenium detection limits of INAA are normally above its concentration in most biological materials. Gamma-gamma coincidence
methodology can be used to improve the detection limits and uncertainties in the determination of selenium. Here, some edible
parts of plants were measured using a HPGe detector equipped with a NaI(Tl) active shielding, producing spectra both in normal
and coincidence modes. The results presented the reduction of the detection limits of selenium by a factor of 2 to 3 times
and improvement in the uncertainty of up to 2 times.
Authors:N. Nepomuceno, E. Fernandes, and M. Bacchi
Brazil has become the largest producer of biomass ethanol derived from sugar cane. The industrial production is based on the fermentation of sugar cane juice by yeast, inside of large volume vats, in a fed-batch process that recycles yeast cells. To study the dynamics of chemical elements in each operating cycle, five stages of the fementation process were considered: must, yeast suspension, wine, non-yeast wine and yeast cream. For this, a mass balance of the terrigenous elements, Ce, Co, Cs, Eu, Fe, Hf, La, Na, Sc, Sm, and Th, and the sugar cane plant elements, Br, K, Rb, and Zn, were established in fementation vats of an industrial scale unit, with sampling undertaken during different climatic conditions (dry and rainy periods). A similar distribution of the sugar cane characteristics elements was found for the stages analysed, while for the terrigenous elements a trend of accumulation in the yeast cream was observed. Preferential absorption of Br, K, Rb, and Zn by yeast cells was indicated by the smaller concentrations observed in yeast suspension than in yeast cream.
Uranium mining activities at Poços de Caldas plateau, Brazil, generated huge amounts of sulfidic waste rocks which were dumped into piles around the mine pit, requiring control measures to minimize the environmental impact. In this work, the sampling and the homogenization of these waste rocks are studied and their elemental analysis by instrumental neutron activation analysis (INAA) using normal (about 200 mg) and large (about 2 kg) samples. The results obtained allowed us to conclude that the waste rocks are extremely heterogeneous requiring even larger quantities of sample for its characterization.