137Cs profiles in erosion plots with different soil cultivation

Summary Cesium-137 methodology has been successfully used to assess soil erosion. Seven erosion plots were sampled to determine the ¹³⁷Cs profile and to assess the erosion rates. Cesium-137 profile for native pasture plot showed an exponential decline below 5 cm depth, with little ¹³⁷Cs activity in the superficial layer (0-5 cm). Cesium-137 profile for wheat-soybean rotation plot in conventional tillage showed a uniform distribution with depth. For this plot, the soil loss occurs more in middle than upper and lower level. Cesium-137 profile for wheat-soybean rotation and wheat-maize rotation plots in no-tillage showed a similar result to the native pasture, with a minimum soil loss in the superficial layer. Cesium-137 profile for bare soil and cultivated pasture plots are similar, with a soil erosion rate of 229 t ha^-1 year ^-1 . In the plots with a conventional tillage a greater soil loss occur in middle than upper and lower level. In no-tillage cultivation plots occurs soil loss in lower level, but no sign of soil loss neither gain in the upper level is observed. Cesium-137 methodology is a good tool to assess soil erosion and the ¹³⁷Cs profile gives possibility to understand the soil erosion behavior in erosion plots.     

Copper pyrovanadate electrodes prepared by combustion synthesis: evaluation of photoelectroactivity

Journal of Solid State Electrochemistry - Photoelectrodegradation of dyes using semiconductors under visible light is currently a major research topic. In this work, copper pyrovanadate (Cu2V2O7)...     

Applicability of an X-ray and gamma-ray portable spectrometer for activity measurement of environmental soil samples

This paper presents a study on the applicability of a commercial X-ray and gamma-ray portable spectrometer (Rover) for in situ gamma-ray spectrometry. This portable spectrometer consists of a 3 × 3 × 1 mm (CdTe) Cadmium Telluride detector and a 30 × 30 mm [NaI (Tl)] Sodium Iodide detector. The radioactive sources used were ²⁴¹Am, ¹³³Ba, ¹⁵²Eu and ¹³⁷Cs tablet type, sealed with aluminum and polyethylene, as well as soil samples contaminated with ¹³⁷Cs. With the aid of these radioactive sources, this study determined the efficiency curve for both detectors. In addition, measurements were carried out to identify the minimum detectable activity (MDA) for both detectors, using time acquisition change ranging from 900 s to 138 h, depending on which detector was utilized and the sample distance. The results for the tablet-type sources were as follows: The MDA for the CdTe detector, while positioned 4.15 cm from the ¹³⁷Cs source, was 15 kBq and 6 kBq for energy lines 32 keV and 661.65 keV, respectively. However, when the distance between the source and detector was 100 cm, the 661.65 keV line presented a MDA of 68 kBq. Results for the soil samples were as follows: Using the CdTe detector, positioned 4.15 cm from the source, the MDA was 73 Bq for the ¹³⁷Cs 32 keV line. In relation to the ⁷Be soil samples, the MDA was 301 Bq when the detector was 4.15 cm from the source. Using the NaI (Tl) detector to analyze the ¹³⁷Cs 661.65 keV line, the MDA was 8 kBq when the detector was 100 cm from the tablet-type source. For the soil sample containing ¹³⁷Cs, the MDA was 7.4 Bq when the source was 2.8 cm from the NaI (Tl) detector. For those samples containing ⁷Be, and measured at the same distance (2.8 cm), the MDA was of 9.6 Bq. Based on the minimum detected activities obtained for both detectors, it is concluded that the in situ gamma-ray spectrometric system used to quantify soil sample activities with ¹³⁷Cs and ⁷Be is only appropriate when those activities are around one or more orders of magnitude larger than the usual radioactivity levels found in the environment. Even though it is a commercialized machine, the Rover system’s manufacturer does not provide the information cited in this abstract.     

Analysis of saliva and gingival crevice fluid by total reflection X‐ray fluorescence (TXRF)

The study of liquid biological samples with the use of various techniques has become a routine task nowadays. Saliva has been a study object for the correlation of chemical elements with a disorder in human body. Saliva is an aqueous hypotonic fluid and transparent and produced by various secretory glands (parotid, submandibular, sublingual, and smaller glands). This paper uses the technique of total reflection X‐ray fluorescence (TXRF) to analyze saliva samples collected in duct of the parotid gland and the gingival crevice between first (tooth 46) and second (tooth 47) grinding teeth of seven individuals. Using the TXRF technique, the main objective of this work was to assess the results obtained quali‐quantitatively. The chemical elements identified in saliva samples of the parotid gland and the gingival crevice were P, S, Cl, K, Ca, Ti, Mn, Fe, Cu, Zn, Se, Br, Rb, and Pb. Although different elements have been identified in the analyzed samples, the identified chemical elements have varied from one individual to another. Comparing the results obtained from the saliva samples of parotid gland and the gingival crevice, it could be observed in the gingival crevice other elements not found in the parotid gland. Therefore, the sampling strategy and the TXRF technique was able to differentiate chemical elements in the samples of the parotid gland and the gingival crevice. Copyright © 2016 John Wiley & Sons, Ltd.