Reduction of iodate in seawater during Arabian Sea shipboard incubations and in laboratory cultures of the marine bacterium Shewanella putrefaciens strain MR-4     

Anna M. Farrenkopf  Michael E. Dollhopf  Sinad Ní Chadhain  George W. Luther  III  Kenneth H. Nealson 《Marine Chemistry》1997,57(3-4)

Shipboard incubations from the US JGOFS cruise to the Arabian Sea (TN045) March, 1995 showed evidence of iodate reduction in 0.45 μ (Gelman Supor membrane) filtered seawater samples collected from intermediate depths (200–600 m) within the oxygen minimum zone (OMZ). Inorganic chemical reduction of iodate in these samples was ruled out as no free sulfide was measurable and concentrations of ammonia and nitrite were found to be less than 5 μM. To examine whether the reduction of iodate observed at sea could have been the result of bacterial metabolism, reduction of iodate (IO₃⁻) to iodide (I⁻) by Shewanella putrefaciens strain MR-4 was studied in artificial seawater using electrochemical methods. MR-4 is a ubiquitous marine bacterium which may be of considerable importance when considering redox zonation in the water column because it is a facultative anaerobe and may switch amongst a suite of electron acceptors to support metabolism. In all experiments MR-4 reduced all iodate to iodide. The rate of formation of [I⁻]in the culture followed pseudo-first order kinetics. This is the first report of the marine bacterial reduction of iodate where the concentrations of iodide and iodate were measured directly. Our results may help to explain the depth distribution of iodine speciation reported in productive waters like the Arabian Sea and for the first time couple iodine speciation with bacterial productivity in the ocean.  相似文献   

What controls dissolved iron concentrations in the world ocean? — a comment     

George W. Luther  III  Jingfeng Wu 《Marine Chemistry》1997,57(3-4)

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Ultraviolet observations in Puppis with the space telescope ‘Glazar’     

H. M. Tovmassian  R. KH. Hovhannessian  R. A. Epremian  D. Huguenin  Yu. M. Khodjayants  M. N. Krmoyan  A. L. Kashin  A. P. Alexandrov  Yu. V. Romanenko 《Astrophysics and Space Science》1992,188(2):217-231

The results of observations of 159 stars at 1640 Å in Puppis made with the space telescope Glazar are presented. It is shown that the observed stars are members of different groups of stars situated at distances of about 120, 370, 700, 1250, 2400, and 4000 pc. The last two groups belong to the Pup OB1 and the Pup OB2 stellar associations.There is relatively little absorption in the observed region. The absorbing matter is mainly concentrated in small clouds.It is suggested that three stars — CP –27°4197, HD 60479, and HD 61672-are embedded in a dust envelope and that the star HD 60057 has a hot subdwarf companion.Forty-four of the observed stars are new OB or early A-type stars, spectral types of which were not known.  相似文献   

Electrochemical Evidence for Pentasulfide Complexes with Mn2+, Fe2+, Co2+, Ni2+, Cu2+ and Zn2+     

Steven J. Chadwell  David Rickard  George W. Luther III 《Aquatic Geochemistry》1999,5(1):29-57

A series of stable pentasulfide complexes of the common base metals, Mn, Fe, Co, Ni, Cu and Zn exist in aqueous solutions at ambient temperatures. Pure sodium pentasulfide was prepared and reacted with the divalent cations of Mn, Fe, Co, Ni, Cu and Zn in aqueous solution at ambient temperature. The S52- complexes were found to exist as determined by voltammetric methods.Pentasulfide complexes with compositions assigned as [M(1-S5)] and [M2(- S5)]2+ occur for Mn, Fe, Co and Ni where only one terminal S atom in the S52- binds to one metal (1 = mono-dentate ligand or M-S-S-S-S-S, = ligand bridging two metal centers or M-S-S-S-S-S-M). Conditional stability constants are similar for all four metals with log 1 between 5.3 and 5.7 and log 2 between 11.0 and 11.6. The constants for these pentasulfide complexes are similar to the tetrasulfide complexes and are approximately 0.4–0.8 log units higher than for comparable bisulfide complexes [M(SH)]+ as expected based on the higher nucleophilicity of S52- compared to HS-. Voltammetric results indicate that these are labile complexes.As with the bisulfide and tetrasulfide complexes, Zn(II) and Cu(II) are chemically distinct from the other metals. Zn(II) reacts with pentasulfide to form a stable monomeric pentasulfide chelate, [Zn(1-S5)] with log = 8.7. Cu(II) reacts with pentasulfide to form a complex with the probable stoichiometry [Cu(S5)]2 with log estimated to be 20.2. As with the other four metals, these complexes are comparable with the tetrasulfide complexes. Discrete voltammetric peaks are observed for these complexes and indicate they are electrochemically inert to dissociation. Reactions of Zn(II) and Cu(II) also lead to significant breakup of the polysulfide.The relative strength of the complexes is Cu > Zn > Mn, Fe, Co, Ni. Cu displaces Zn from [Zn(1- S5)] and both Cu and Zn displace Mn, Fe, Co and Ni from their pentasulfide complexes.  相似文献   

Bio-volatilization of polonium: Results from laboratory analyses     

N. Hussain  T. G. Ferdelman  T. M. Church  George W. Luther III 《Aquatic Geochemistry》1995,1(2):175-188

Polonium, like other elements in the Group VI Oxygen series (S, Se, Te), has the potential to form volatile alkyl derivatives. This may be evident in its pervasive radioactive excesses in the atmosphere and coastal waters, and its deficiency in surface open ocean waters. We present evidence for the formation of volatile polonium species. The first evidence comes from duplicating experiments that proved the existence of volatile tellurium, its Group VI congener. Cultures of bread mold at room temperature spiked with polonium tracers showed a significant and reproducible loss of about 0.5% per day of volatile polonium species. In another set of experiments, between 30–50% loss of²¹⁰Po was observed from Floridan groundwater when nitrogen was bubbled through it over durations of 5–30 minutes. Polonium volatility is highly relevant for biogeochemical studies because it may provide a natural radiochemical tracer for recycling of similar volatile sulfur and other Group VI metal species between the geosphere, atmosphere, and hydrosphere.  相似文献   

Lagrangian particle tracking of a toxic dinoflagellate bloom within the Tampa Bay estuary   总被引：1，自引：0，他引：1  

Heather Havens  Mark E. Luther  Steven D. Meyers  Cynthia A. Heil 《Marine pollution bulletin》2010,60(12):2233-2241

A coastal risk assessment system simulates the basic physical mechanisms underlying contaminant transport in Tampa Bay. This risk assessment system, comprised of a three-dimensional numerical circulation model coupled to a Lagrangian particle tracking model, simulates the transport and dispersion of a toxic dinoflagellate bloom. Instantaneous velocity output from the circulation model drives the movement of particles, each representing a fraction of a K. brevis bloom, within the model grid cells. Hindcast simulations of the spatial distribution of the K. brevis bloom are presented and compared with water sample concentrations collected during the peak of the bloom. Probability calculations, herein called transport quotients, allow for rapid analysis of bay-wide K. brevis transport showing locations most likely to be impacted by the contaminant. Maps constructed from the transport quotients provide managers with a bay-wide snapshot of areas in Tampa Bay most at risk during a hazardous bloom event.  相似文献   

DISCUSSION OF the Editorial, "U.S. International Outreach in Ground-Water Hydrology: Moving in the Wrong Direction," by Jay H. Lehr     

Luther W. Hyde 《Ground water》1986,24(6):808-808

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Studies of the Hydrodynamic Properties in Biological Clarification Plants Using Radiotracers     

H.-G. Koennecke  D. Luther  K. Koepping  J. Schoen  H. Ulrich 《洁净——土壤、空气、水》1984,12(4):431-434

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Heavy metal distribution in Newark Bay sediments     

A. Lee Meyerson  George W. Luther  James Krajewski  Richard I. Hires 《Marine pollution bulletin》1981,12(7):244-250

Bottom sediments have been analysed from Newark Bay, New Jersey, for zinc, lead, cadmium, and mercury. The bottom sediment analyses show that the bay sediments are enriched over background levels up to 65 times for zinc, 128 times for lead, 180 times for cadmium, and 155 times for mercury. Analyses of the metal distribution and of available tidal hydraulic data indicate the metal concentrations are due to a combination of source and tidal hydraulics. Dye tracer experiments gathering Lagrangiantype data appear to yield the best result in the investigation of metal trasport phenomena.  相似文献   

南京地区梅山、凤凰山铁矿尾矿利用探讨     

陈小华 《江苏地质》2000,24(3):181-183

介绍梅山铁矿、凤凰山铁矿的尾矿特征,探讨利用澳大利亚新型重选设备进行铁矿尾矿再选的可能途径。对于降低铁矿山尾矿库存量,保护环境,合理利用资源,具有一定的意义。  相似文献