The effects of copper and zinc on Spirulina platensis (Nordst.) Geitl. growth and the capability of this cyanobacterium for accumulation of these heavy metals (HMs) were studied. S. platensis tolerance to HMs was shown to depend on the culture growth phase. When copper was added during the lag phase, its lethal concentration was 5 mg/l, whereas 4 mg/l were lethal during the linear growth phase. Zinc concentration of 8.8 mg/l was lethal during the linear but not lag phase of growth. HM-treated S. platensis cells were capable for accumulation of tenfold more copper and zinc than control cells. Independently of Cu 2+ content in the medium and of the growth phase, cell cultures accumulated the highest amount of this metal as soon as after 1 h, which may be partially determined by its primary sorption by cell-wall polysaccharides. A subsequent substantial decrease in the intracellular copper content occurred due to it secretion, which was evident from the increased metal concentration in the culturing medium. When zinc was added during the linear growth phase, similar pattern of its accumulation was observed: the highest content after 1 h and its subsequent decrease to the initial level. When the initial density of the culture was low and the cells had much time to adapt to HM, zinc accumulated during the entire linear growth phase, and thereafter the metal was secreted to the medium. The mechanisms of S. platensis tolerance to HM related to both their sorption by the cell walls and secretion of metal excess into the culturing medium and its conversion into the form inaccessible for the cells are discussed.
Florencite (Sm), a new mineral species of the florencite subgroup, was found in association with xenotime (Y) in quartz veins of the Maldynyrd Range of the Subpolar Urals as thin zones within rhombohe dral crystals of florencite (Ce) with faceting by {01 1} and {10 2}. The thickness of particular florencite (Sm) zones is 0.01-0.1 mm, and the total thickness of a series of such zones is 1-3 mm. Florencite (Sm) is colorless and pale pink or pale yellow with white streaks; its Mohs hardness is 5.5-6.0. Its measured and cal culated densities are 3.70 and 3.743 g/cm 3 , respectively. The mineral is transparent, nonpleochroic, and uniaxial (positive), and ω = 1.704(2) and ε = 1.713(2). The electron beam's fluorescence spectrum was 592 nm (intense green luminescence of Sm 3+ ) and 558 nm (yellow luminescence of Nd 3+ ). The chemical composi tion was as follows (microprobe, average of 2 WDS, wt %):
The previous and new data on minerals and mineral assemblages of the Sugur copper deposit in Sugur Mountains of South Urals are summarized. The ores of the deposit host abundant calcite, andradite, diopside, magnetite, chromite and serpentine together with pyrite, chalcopyrite, chalcocite, pyrrhotite, millerite, and rare baddeleyite. The genesis of the deposit was previously considered both contact-metasomatic and hydrothermal. The new data allow us to attribute copper mineralization to a skarn-carbonatite system, which is locally recognized in the Karabash ultramafc massif.
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