Guarapuava, Paraná, Brazil
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- SourceAvailable from: Edivaldo Lopes Thomaz[Show abstract] [Hide abstract]
ABSTRACT: Fire has been recognized as an important environmental process that affects soil systems. Here, we have reported the effects of temperature on soil aggregate properties of aggregate stability, mean weight diameter, water repellency, water retention, and soil carbon depletion due to soil heating. The study was performed under laboratory conditions by using a muffle furnace. However, realistic temperature gradients from 25 to 650 °C were obtained previously through measurements in the field. The soil tested here is a subtropical Humic Cambisol with 500 g kg− 1 clay content. Most of our results were different from those reported in the literature. Following the temperature gradient, we found a sharp threshold at ~ 550 °C. The threshold indicated two different mechanisms that affect soil aggregate properties. The first mechanism, which affects the physical characteristics of the aggregates, was associated with organic matter and water repellency reduction (≤ 550 °C). The second mechanism was due to the thermal fusion of particles and recrystallization of mineral clays at 650 °C. The reduction in soil organic carbon had a linear effect on aggregate stability, mean weight diameter, and water retention following a temperature gradient. We noted that the longer exposure time at moderate to high temperatures could not compensate for the effect of a very high peak temperature lasting for a short time on soil aggregates. For the tested soil, we found a mixed response pattern explaining the effect of soil heating on aggregate stability.
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ABSTRACT: Slurry sampling electrothermal atomic absorption spectrometry was used for direct determination of Cr, Pb and Cd in honey without sample pretreatment. The honey slurries were prepared in aqueous solution containing hydrogen peroxide and nitric acid. The slurries were directly introduced in the pyrolytic graphite tubes. Pd-Mg was used as a chemical modifier only for Cd determination. Analytical curves were performed with aqueous standards for Pb and Cr and with addition of fructose for Cd. The quantification limits for Cd, Pb and Cr were 2.0, 5.4 and 9.4ngg(-1), respectively. Acceptable precision of the methodology was obtained through repeatability and intermediate precision. In the accuracy study, recoveries were satisfactory (94-101%) for the three elements. The methodology was applied in honey from Paraná (Brazil). The concentrations of Pb, Cd and Cr ranged from 141 to 228ngg(-1), <2.0 to 8ngg(-1) and 83 to 94ngg(-1), respectively.
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ABSTRACT: The sweet potato (Ipomoea batatas L.) is a crop of great importance in developing countries, as a food staple, for animal feed, and potentially for biofuel. Development of cultivars adapted to specific regions within these countries would be useful. To start a breeding program, the first step is the establishment of a germplasm bank. We initiated a sweet potato germplasm bank with accessions collected from the highlands of Paraná State, Brazil. To establish this germplasm bank, we carried out numerous sweet potato-collecting expeditions in regions with an altitude above 700 meters in this region; 116 genotypes currently comprise this collection. The genetic diversity of this germplasm bank was estimated using inter simple sequence repeat (ISSR) markers. Polymorphic information content (PIC), marker index (MI), and resolving power (RP) were calculated to determine the viability of ISSR markers for use in sweet potato genetic studies. The correlation between PIC and MI (r(2) = 0.81) and between MI and RP (r(2) = 0.97) were positive and significant, indicating that ISSR markers are robust for sweet potato identification. Two ISSR primers, 807 and 808, gave the best results for all attributes, and thus could be used as representative ISSR primers for the genetic analysis of sweet potato. Cluster analysis and principal component analysis indicated high genetic variability (0.51 of similarity among all genotypes); genotypes collected from different counties grouped together.
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