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[en] In this paper, soil samples collected in the Tartarugalzinho region, State of Amapa, were analyzed by instrumental neutron activation analysis. The concentration of about 24 elements such as As, Ba, Br, Ce, Co, Cr, Cs, Fe, Hf, K, La, Lu, Na, Rb, Sb, Sc, Se, Sm, Ta, Tb, Th, U, Zr e Zn could be determined. The soil samples collected near gold mining activities, were separated into fractions smaller than 2 mm and powdered to the granulometry of 200 mesh, and homogenized. Analysis of the reference materials Buffalo River Sediment (NIST SRM 2704) and Soil 7 (IAEA) showed the accuracy and precision of the method. (author). 7 refs., 3 figs., 4 tabs
[en] Sono-chemical reactions are known since a long period of time. Undoubtedly, the chemical effects of the ultrasound are related to the acoustic cavitation. However, the origin of the processes occurred within the cavitating bubbles are still unclear. Recent discovery of the single bubble sono-luminescence and the evidences for the sono-chemical activity of the single cavitating bubble offer the opportunity to obtain more detailed information about the cavitation events. However, many researches claim the lack of correlation between the processes in the single bubble and in the multi bubble cases. The fundamental aspects of the multi bubble and single bubble sono-chemistry and sono-luminescence will be reviewed during the presentation. Also the potentials of sono-chemistry for nano-chemistry and nuclear chemistry will be discussed. (author)
[en] Chemical weathering of soils/minerals is an important process which controls the long-term neutralization of acid rain as well as the quality of surface water, ground water, and oceans. Few laboratory studies have been conducted to evaluate the response of real whole soils or soil fractions to acidification. In this research experiments were performed in a laboratory semi-continuous pH-stat reactor over the pH range 2.7 to 4.7 using Band C-horizon soil fractions from the Bear Brook Watershed, Maine, and in presence/absence of 1 to 20 mmol/L oxalate ligand in the bulk solution. Acid consumption rate and the corresponding release rates of sodium, calcium, magnesium, aluminum, iron, and silica were monitored in the laboratory reactor. Both H+-ion and oxalate promoted weathering rates were fractional order based on the concentration in bulk solution. The mixed kinetic model for the soils is: WRT = WRH + WRox = KH (H+)m + Kox [OX TD]p, where m and p are fractional orders. The hydrogen ion consumption rates were approximately equal to cation release rates on an equivalent basis for hydrogen ion promoted weathering situations where secondary precipitation was unlikely (pH < 4.7) as well as for weathering of C-horizon light fraction at pH 4.0 and oxalate concentration 1 and 5 mmol/L. The relative proportions of released species were in the neighborhood of stoichiometric ratios of bulk soil chemistry for weatherable minerals in Band C-horizon soil fractions. The experimental ratios of H/Si, Al/Si, Fe/Si, Ca/Si, Na/Si, and Mg/Si for linear weathering rates of Band C-horizon soil fractions were fairly constant in the presence and absence of oxalate ligand and strongly suggested that silica may be used as a tracer for primary mineral weathering assuming quartz is inert
[en] The conference is dedicated to the very actual problem of nuclear energy production and chemical technology, which has been in the spotlight of the world scientific community for many years - radiation and chemical safety. It is hope that the result of this Conference will be an important stage in the history of science in the area of Radiation Chemical Safety.