Native plants facilitate vegetation succession on amended and unamended mine tailings.

Facilitating the establishment of native pioneer plant species on mine tailings with inherent metal and/or acid tolerance is important to speed up natural succession at minimal cost, especially in remote areas where phytoremediation can be labor intensive. We investigated vegetation community dynamics after ∼48 years of succession along two legacy Ni-Cu mine tailings and waste rock deposits in the Sudbury Basin, Ontario, Canada with and without various site amendments (i.e. liming and fertilization) and planting. Metal/acid tolerant pioneer plants (Betula papyrifera, Populus tremuloides, Pohlia nutans) appeared to facilitate the establishment of less tolerant species. Conifers and nitrogen-fixers less tolerant to site conditions were planted at the fully amended (limed, fertilized, planted) mine tailings site in the 1970s, but conifers were not propagating at the site or facilitating understory succession. The planted nitrogen-fixing leguminous species Lotus corniculatus was, however, associated with increased diversity. These findings have implications for long-term reclamation strategies in acidic mine waste deposits utilizing native species, as primary colonizing tree species are only recently emerging as candidates for phytoremediation. Novelty statement The potential for native species to act as facilitators for vegetation colonization has rarely been investigated on tailings, despite wide use in remediation of less toxic sites. This study provides a retrospective of over 40 years of plant growth following initial treatment of toxic tailings. We observed that regardless of tailings geochemical conditions, acid/metal tolerant pioneer plants were facilitating ecological succession on acidic Ni-Cu mine tailings sites.

Removal of sewage phosphorus by adsorption and mineral precipitation, with recovery as a fertilizing soil amendment.

Clear sand adsorbs 15-35% total phosphorus (P) from septic tank effluent, but P is mobilized when low-P effluent is applied. Amorphous P compounds formed by alkali aluminate chemical addition may also be subject to leaching. Crystalline mineralization is the desired end effect that isolates P thoroughly from the water resource. Using new low-energy iron electrochemistry (EC-P process), dissolved ferrous iron reacts with sewage phosphate ions (PO4) and precipitates onto filtration medium as vivianite [Fe3(PO4)2·8H2O], as identified by scanning electron microscopy and X-ray diffraction and predicted from Eh-pH-aHPO42- phase relations. Removal rates of 90-99% in sand, soil and synthetic foam filters are obtained. The precipitation of vivianite demonstrates that P can be immobilized quickly and without intermediary adsorption phases, as with Fe-rich soils. Vitreous silicate material (VSM) or rockwool that traps and precipitates mineral P after EC-P treatment was investigated as a means of P reuse as a fertilizing soil amendment. Comparative soil leaching and growth studies using corn plants demonstrate that the VSM alone reduces P losses from soils, and that VSM which has received EC-P effluent is equivalent to or better than commercial superphosphate fertilizer.

The dynamic nature of bacterial surfaces: implications for metal-membrane interaction.

Bacterial envelopes are chemically complex, diverse structures. Chemical and physical influences from cellular microenvironments force lipids, proteins, and sugars to organize dynamically. This constant reorganization serves to maintain compartmentalization and function, but also affects the influence of charged functional groups that drive electrochemical interactions with metal ions. The interactions of metal species with cell walls are of particular interest because (i) metals must be taken up or excluded to maintain cell function, and (ii) electrochemical interactions between charged metals and anionic ligands are inevitable. In this review we explore the associations of metals with metal-reactive ligands found within bacterial envelopes, and outward to include those within biofilm matrics. The mechanisms that underpin metal binding to these ligands have not been well considered with respect to the dynamic organization of the biological structures themselves. Bacteria respond sensitively and rapidly to growth environment with de novo syntheses of chemical constituents, which can impact metal interactions. We discuss causes of membrane chemical variability as observed in laboratory experiments, and offer consequences for this adaptability in natural settings. The structural impacts of metal ion associations with bacterial envelopes are often overlooked. This review explores how dynamic bacterial surface chemistry influences metal binding and, in turn, how metal ions impact membrane organization in laboratory and natural conditions.

Speciation of vanadium in oilsand coke and bacterial culture by high performance liquid chromatography inductively coupled plasma mass spectrometry.

A simple and sensitive method for the speciation of vanadium(III), (IV), and (V) was developed by using high performance liquid chromatography and inductively coupled plasma mass spectrometry (HPLC-ICPMS). The EDTA-complexed vanadium species were separated on a strong anion exchange column with an eluent containing 2 mM EDTA, 3% acetonitrile, and 80 mM ammonium bicarbonate at pH 6. Each analysis was complete in 5 min. The detection limits were 0.6, 0.7 and 1.0 microg L(-1) for V(III), V(IV), and V(V), respectively. The method was applied to coke pore water samples from an oilsand processing/upgrading site in Fort McMurray, Alberta, Canada and to Shewanella putrefaciens CN32 bacterial cultures incubated with V(V). In the coke pore water samples, V(IV) and V(V) were found to be the major species. For the first time, V(III) was detected in the bacterial cultures incubated with V(V).

Intracellular manganese granules formed by a subsurface bacterium.

The demonstrated ability of prokaryotes to form internal metal oxide particles during active metabolism has been restricted to Fe. Mineral-bound Mn(IV) is a known electron acceptor during dissimilatory metal reduction by Shewanella putrefaciens, yet no internal deposits of Mn have been reported to form during anaerobic respiration. We observed distinct nanometre-sized Mn-rich granules in the cytoplasm when either birnessite or pyrolusite (beta-MnO(2)) served as the electron acceptor during growth. During rapid Mn reduction, additional precipitates of Mn were also observed in the periplasm together with the cytoplasmic granules. The bacteria did not accumulate detectable Mn in the outer membrane during formation of the internal precipitates. This is the first report of an intracellular Mn solid produced by bacteria and coupled anaerobically to DR.

Intracellular iron minerals in a dissimilatory iron-reducing bacterium.

Among prokaryotes, there are few examples of controlled mineral formation; the formation of crystalline iron oxides and sulfides [magnetite (Fe3O4) or greigite (Fe3S4)] by magnetotactic bacteria is an exception. Shewanella putrefaciens CN32, a Gram-negative, facultative anaerobic bacterium that is capable of dissimilatory iron reduction, produced microscopic intracellular grains of iron oxide minerals during growth on two-line ferrihydrite in a hydrogen-argon atmosphere. The minerals, formed at iron concentrations found in the soil and sedimentary environments where these bacteria are active, could represent an unexplored pathway for the cycling of iron by bacteria.