Chemical fractionation of heavy metals in soils around oil installations, Assam
摘要:
The chemical fractionation of lead, cobalt, chromium, nickel, zinc, cadmium and copper in soils around Lakwa oil field, Assam, India was studied using a sequential extraction method. It is evident from the study that the residual fraction is the most important phase for the seven heavy metals under study. Among non-residual fractions metals are mostly associated with the Fe-Mn oxides fraction. The association of heavy metals with organic matter was observed in the following order: copper> cadmium> zinc> lead. The concentration of Pb in the carbonate fraction for both the seasons is higher compared with other metals, which may pose environmental problems due to its highly toxic nature. The comparatively low concentration of metals in the exchangeable fraction indicates low bioavailability. Correlations between physicochemical parameters and metal fractions of soil do not show consistent behaviour. The local mean values of metals when compared with the accepted values of normal abundance and geochemical background, indicates two to four fold increases in this area. However, the values are within the range of normal abundance. As well as from natural soil geochemical behaviour, anthropogenic influence might have a close bearing on the association of metals with the soil system in the studied area.
A Convenient Synthesis of Phosphorodithioates and Novel Conversion of Epoxides to Thiiranes
作者:Babak Kaboudin、Hamid Norouzi
DOI:10.1055/s-2004-829176
日期:——
Alumina-supported ammonium acetate under microwave irradiation was found to be an efficient reagent for the preparation of phosphorodithioates from phosphorus pentasulfide undersolvent-freecondition. A simple, efficient, and new method has been developed for the synthesis of thiiranes from epoxides through a one-pot reaction of epoxides with the mixture of phosphorus pentasulfide in the presence of ammonium acetate