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Bromine in peat and related humic acids from ombrotrophic bog and implications in the reconstruction of its fate
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Bromine in peat and related humic acids from ombrotrophic bog and implications in the reconstruction of its fate
No full textInfluence of extractant on quality and trace elements content of peat humic acids
No full textAmong several extractants used to isolate humic acids (HA) from terrestrial environments, sodium hydroxide (NaOH) and sodium pyrophosphate (Na4P2O7) are the most utilized. In order to evaluate the influence of these different extractant solutions on the HA quality and on their trace elements content, HA were isolated from five Sphagnum-peat samples using three different solutions: (a) 0.5 M NaOH; (b) 0.1 M Na4P2O7; (c) 0.5 M NaOH + 0.1 M Na4P2O7. The obtained HA have been analyzed with respect to ash content, elemental composition, main atomic ratios and characterized by FT-IR and total luminescence (TL) spectroscopies. In addition, both raw peat and HA have been analyzed using X-ray fluorescence in order to determine the Br, Cu, Fe, Ni, Pb and Zn contents. Results showed that HA extracted with NaOH and NaOH + Na4P2O7 are quite similar with respect to ash, elemental contents and spectroscopic characteristics, while Na4P2O7 solution, which in general reduces the extraction yield, seems to affect the nature of HA, featuring a more complex and aromatic character. With respect to the contents in the corresponding raw peat samples, the HA fractions were richer in Br, Cu and Ni, regardless of the extractant used, and poorer in Fe, Pb and Zn. Further, Br, Cu, Ni and Zn were more concentrated in HA extracted with Na4P2O7 than in those extracted with NaOH and NaOH + Na4P2O7, probably because of the greater affinity of these elements for these more aromatic humic molecules
Il comportamento del bromo tra torba ed acidi umici estratti da due profili ombrotrofici (peat bogs)
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Bromine in peat and related humic acids from ombrotrophic bog and implications in the reconstruction of its fate
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Enrichment and depletion of major and trace elements, and radionuclides in ombrotrophic raw peat and corresponding humic acids
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