Multi-element contamination in soils from major mining areas in Northeastern of Brazil.

Mining has become one of the main factors in the global biogeochemical cycle of potentially toxic elements. Therefore, it is considered one of the anthropogenic activities with the greatest negative impact on the environment. These impacts are maximized in semiarid regions, where mining activities can lead to soil degradation and decrease in land productivity. This study aimed to assess the level of contamination in natural, urban, and agricultural soils of three important mining areas, where approximately 80,000 people live, and pollution levels have never been determined before. For this purpose, soil samples were collected around iron, uranium, and vanadium mines, as well as in the main human settlements of the region. The concentrations of 34 elements were determined by instrumental neutron analysis activation (INAA) and inductively coupled plasma optical emission spectrometry (ICP OES) techniques. Pollution indices (CF, EF, mCd, PLI, and REEP) revealed that there is a moderate to heavy level of pollution for 89% of the analyzed elements. Additionally, an extreme contamination level was observed in 78% of the samples, for at least one element. Statistical analyses were performed to identify patterns in the distribution and common sources of pollution. The results suggest that the concentrations for Al, Ba, Hf, Na, Pb, Rb, REE, Ta, Th, U, Zn, and Zr are associated with geogenic causes. However, the influence of anthropogenic sources such as agriculture and mining on the accumulation of these elements in soils should not be disregarded. In contrast, the contents of As, Br, Cd, Co, Cr, Cs, Cu, Fe, K, Mn, Ni, Sc, Ti, and V reflect the direct impact of anthropogenic sources.

Long-term performance assessment of HPGE detectors used in the neutron activation analysis laboratory of IPEN-CNEN/SP (Brazil).

In this work, verification data for 11 HPGe detectors from two different manufacturers and three different intrinsic configurations were analyzed in respect to the stability of both the efficiency and resolution for the 122keV peak from 57Co and the 1332keV peak from 60Co. The results allow a discussion about the stability of these parameters over time (in some cases, almost 15 years), their sensitivity to imminent detector failures and their performance after a failure has been corrected; moreover, the results show a clear correlation between the manufacturer or configuration and the long-term performance of the detector.

Measurements of k0 and Q0 values for 64Zn(n,γ)65Zn and 68Zn(n,γ)69mZn reactions with covariance analysis.

The values of k(0) and Q(0) for (64)Zn(n,γ)(65)Zn and (68)Zn(n,γ)(69m)Zn reactions were determined experimentally. The irradiations were performed near the core of the IEA-R1 3.5MW nuclear research reactor of the Nuclear and Energy Research Institute - IPEN-CNEN/SP, in São Paulo, Brazil. The results for the neutron field parameters f and α were 49.7(19) and -1.1(31)×10(-3), respectively. The resulting values of k(0) and Q(0) for (64)Zn(n,γ)(65)Zn reaction were 5.63(8)×10(-3) and 1.69(6), respectively, and the corresponding values for (68)Zn(n,γ)(69m)Zn reaction were 4.00(6)×10(-4) and 2.34(4), respectively. These results were compared with the literature.

Excited levels in 149Pm from the decay of 149Nd.

The level structure of 149Pm has been investigated by studying the gamma rays emitted following the beta(-) decay of 149Nd (T(1/2)=1.7h). The singles and the gammagamma coincidence spectra were taken using HPGe detectors with high energy resolution. The energy and relative intensities of 198 gamma rays have been determined, 45 for the first time and several multiplets were resolved using bidimensional data analysis. A decay scheme with 51 levels has been proposed. This includes 6 new levels, at 1407, 1368, 1364, 1329, 1293 and 1181keV. The present results permitted assignments of spin and parity for a number of these levels.

Energy levels in 139La from the decay of 139Ba.

The gamma-ray spectrum of 139La following the beta- decay of 139Ba has been studied using both singles and gammagamma coincidence spectroscopy techniques. The energies and intensities of 30 gamma-transitions have been determined, which include three new transitions placed in the level scheme. Two new levels at 1524.6 and 1900.3 keV excitation energies are proposed and a number of gamma-transitions have been confirmed. On the basis of these results a precise decay scheme is proposed.