Selenium status in some Egyptian soils.

Author(s): H.H.A.Sabrynal, N.S.M.Yahiya, E.A.M.Abdel-Rahman, S.A.Radwan

Fifteen surface soil samples (0 -30 cm) representative of some the Egyptian soils types were collected fromareas along ElsalamCanal, Sinai, Sewa Oasis and El- Nubaria. The samples were five samples from both Sewa Oasis and along ELSalamcanal at west desert and the north coastal, respectively. Four samples fromSinai and one sample fromNubaria. The study areas are irrigating with different irrigation water qualities and have morphological variations. The collected soil samples were chemically analyzed for some chemical and physical properties, total Se, Se fractions and Se species. To assess the behavior of various geological Se, the collected Soil samples were partitioning to investigate the significance of different Se fractions in assessing solid – phase speciation and geochemical transformation. The Se fractions extracted by the partitioning technique were aqueous (0.25 M KCl) exchangeable (1MKH2PO4), acid extractable (4MHCl), sulfide and humic bound (KClO3 + 12M HCl) and siliceous (HNO3+H2SO4+HCLO4). Selenite and Selenate in each sample were measured by hydride generation atomic adsorption spectrometer.The chemical fractionation of soil Se, ranged between, 0.011to 0.293,0.02 to 0.280, 0.03 to 0.360, 0.033 to 1.211 and 0.061 to 0.710 ppm, for aqueous, exchangeable, acid extractable, sulfide and humic bound and siliceous, respectively. The amount of fraction-Se in soils did not correlated significantly with most of the studied soil properties with exception of the siliceous fraction that related significantlywith pH (0.638*). Total Se was found to vary from 0.17 to 1.95 ppm. These levels are positively correlated significantly with exchangeable, acid extractable and sulfide extractable and siliceous fractions. The coefficient correlations were, 0.507*, 0.582*, 0.882**and 0.512*, respectively.Also, the species (Se+4) of aqueous and exchangeable fractions are positively correlated significantly with the total Se. The coefficient correlations were, 0.811** and 0.527*, respectively.

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