Spatial heterogeneity of methane ebullition in a large tropical reservoir

Tropical reservoirs have been identified as important methane (CH(4)) sources to the atmosphere, primarily through turbine and downstream degassing. However, the importance of ebullition (gas bubbling) remains unclear. We hypothesized that ebullition is a disproportionately large CH(4) source from reservoirs with dendritic littoral zones because of ebullition hot spots occurring where rivers supply allochthonous organic material. We explored this hypothesis in Lake Kariba (Zambia/Zimbabwe; surface area >5000 km(2)) by surveying ebullition in bays with and without river inputs using an echosounder and traditional surface chambers. The two techniques yielded similar results, and revealed substantially higher fluxes in river deltas (～10(3) mg CH(4) m(-2) d(-1)) compared to nonriver bays (<100 mg CH(4) m(-2) d(-1)). Hydroacoustic measurements resolved at 5 m intervals showed that flux events varied over several orders of magnitude (up to 10(5) mg CH(4) m(-2) d(-1)), and also identified strong differences in ebullition frequency. Both factors contributed to emission differences between all sites. A CH(4) mass balance for the deepest basin of Lake Kariba indicated that hot spot ebullition was the largest atmospheric emission pathway, suggesting that future greenhouse gas budgets for tropical reservoirs should include a spatially well-resolved analysis of ebullition hot spots.     

Sorption of uranium(VI) onto ferric oxides in sulfate-rich acid waters

The mechanisms of the uranium(VI) sorption on schwertmannite and goethite in acid sulfate-rich solutions were studied by Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. The samples were prepared under N2 atmosphere and initial uranium(VI) concentrations of 1 x 10(-5) (pH 6.5) to 5 x 10(-5) M (pH 4.2). The ionic strength was adjusted using 0.01 M Na2SO4 or 0.01 M NaClO4, respectively. The EXAFS structural parameters for uranium(VI) sorbed on goethite in sulfate-rich, acid and near-neutral solutions indicate that uranium(VI) forms an inner-sphere, mononuclear, bidentate surface complex. This complex is characterized by a uranium-ferric-iron distance of approximately 3.45 A. Uranium(VI) sorbed onto schwertmannite in acid and sulfate-rich solution is coordinated to one or two sulfate molecules with a uranium-sulfur distance of 3.67 A. The EXAFS results indicate formation of binuclear, bidentate surface complexes and partly of mononuclear, monodentate surface complexes coordinated to the structural sulfate of schwertmannite. The formation of ternary uranium(VI)-sulfate surface complexes could not be excluded because of the uncertainty in assigning the sulfate either to the bulk structure or to adsorption reactions. The uranium(VI) adsorption onto schwertmannite in perchlorate solution occurs predominantly as a mononuclear, bidentate complexation with ferric iron due to the release of sulfate from the substrate.     

用于文化纸的同一平台概念

Voith Paper过去一直在制造大型、高速、高产的纸机。机中由于采用靴式压榨,Braviken PM53(1996年一系列纸机中的一台)成为世界上第一台车速超过1800m/min的纸机。机中1997年设计的Gratkorn 11(三星),年产量47万吨,仍为世界上产量最高的高级纸纸机。机中1998年交货的中国大港1、2号纸机,是世界上最宽的纸机,网宽达10.5m。机中这三项全球范围的业绩反映了Voith Paper1996～1998年的最尖端技术。可以清楚地看出是如何逐步采用新开发的成果。机中在世界许多地区,二次纤维的使用量在不断增长,而另一方面可以清楚地看到:用于回用的回收纸的质…     

Time-resolved laser fluorescence spectroscopy study on the interaction of curium(III) with Desulfovibrio äspöensis DSM 10631T

The influence of microorganisms on migration processes of actinides has to be taken into account for the risk assessment of potential high-level nuclear waste disposal sites. Therefore it is necessary to characterize the actinide-bacteria species formed and to elucidate the reaction mechanisms involved. This work is focused on the sulfate-reducing bacterial (SRB) strain Desulfovibrio ?sp?ensis (D. ?sp?ensis) DSM 10631T which frequently occurs in the deep granitic rock aquifers at the Asp? Hard Rock Laboratory (Asp? HRL), Sweden. We chose Cm(III) due to its high fluorescence spectroscopic sensitivity as a model system for exploring the interactions of trivalent actinides with D. ?sp?ensis in the trace concentration range of 3 x 10(-7) mol/L. A time-resolved laser fluorescence spectroscopy (TRLFS) study has been carried out in the pH range from 3.00 to 7.55 in 0.154 mol/L NaCl. We interpret the pH dependence of the emission spectra with a biosorption forming an inner-sphere surface complex of Cm(III) onto the D. ?sp?ensis cell envelope. This Cm(III)-D. ?sp?ensis-surface complex is characterized by its emission spectrum (peak maximum at 600.1 nm) and its fluorescence lifetime (162 +/- 5 micros). No evidence was found for incorporation of Cm(III) into the bacterial cells under the chosen experimental conditions.     

Spectroscopic characterization of the uranium carbonate andersonite Na2Ca[UO2(CO3)3] x 6H2O

The uranium carbonate andersonite Na2Ca[UO2(CO3)3] x 6H2O was synthesized and identified with classical analytical and spectroscopic methods. The classical methods applied were powder X-ray diffraction (XRD), nitric acid digestion, and scanning electron microcopy combined with energy-dispersive spectroscopy (SEM/EDS). To characterize andersonite spectroscopically, time-resolved laser-induced fluorescence spectroscopy (TRLFS), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FT-IR) were used. Natural and synthetic andersonite samples were characterized with the nondestructive TRLFS by six fluorescence emission bands at 470.6, 486.1, 505.4, 526.7, 549.6, and 573.9 nm. In addition, andersonite was characterized by FT-IR measurements by the appearance of the asymmetric stretching vibration of the uranyl cation [v3(UO2(2+))] at 902 cm(-1) with a shoulder at 913 cm(-1). XPS measurements verified the composition of the synthetic andersonite sample. The measured intensity ratios of the XPS lines agree with the stoichiometry of Na2Ca[UO2(CO3)3] x 6H2O. The XPS features of the inner valence molecular orbitals are characteristic of the [UO2(CO3)3]4- structural moiety. These spectroscopic methods can be used to identify in a fingerprinting procedure secondary U(VI) phases in mixtures with other phases or as thin coatings on mineral and rock surfaces.     

U(VI)-kaolinite surface complexation in absence and presence of humic acid studied by TRLFS

Time-resolved laser-induced fluorescence spectroscopy (TRLFS) was applied to study the U(VI) surface complexes on kaolinite in the presence and absence of humic acid (HA). Two uranyl surface species with fluorescence lifetimes of 5.9 +/- 1.4 and 42.5 +/- 3.4 micros and 4.4 +/- 1.2 and 30.9 +/- 7.2 micros were identified in the binary (U(VI)-kaolinite) and ternary system (U(VI)-HA-kaolinite), respectively. The fluorescence spectra of adsorbed uranyl surface species are described with six and five fluorescence emission bands in the binary and ternary system, respectively. The positions of peak maxima are shifted significantly to higher wavelengths compared to the free uranyl ion in perchlorate medium. HA has no influence on positions of the fluorescence emission bands. In the binary system, both surface species can be attributed to adsorbed bidentate mononuclear surface complexes, which differ in the number of water molecules in their coordination environment. In the ternary system, U(VI) prefers direct binding on kaolinite rather than via HA, but it is sorbed as a uranyl-humate complex. Consequently, the hydration shell of the U(VI) surface complexes is displaced with complexed HA, which is simultaneously distributed between kaolinite particles. Aluminol binding sites are assumed to control the sorption of U(VI) onto kaolinite.     

Exposure of an adult population to perfluorinated substances using duplicate diet portions and biomonitoring data

Because dietary intake is supposed to be an important route of human exposure we quantified the dietary intake of perfluorooctane sulfonate (PFOS), perfluorooctanoate (PFOA), perfluorohexane sulfonate (PFHxS), perfluorohexanoate (PFHxA), and perfluorooctane sulfonamide (PFOSA) using 214 duplicate diet samples. The study was carried out with a study population of 15 female and 16 male healthy subjects aged 16-45 years. The participants collected daily duplicate diet samples over seven consecutive days in 2005. Duplicate samples were homogenized and their ultrasonic extracts were cleaned up by SPE and subjected to HPLC-ESI-MS/MS. In addition, individual intakes were estimated based on blood levels of PFOS and PFOA using a pharmacokinetic model. Blood samples were collected once during the sampling period. The median (90th percentile) daily dietary intake of PFOS and PFOA was 1.4 ng/kg b.w. (3.8 ng/kg b.w.) and 2.9 ng/kg b.w. (8.4 ng/kg b.w.), respectively. PFHxS and PFHxA could be detected only in some samples above detection limit with median (maximum) daily intakes of 2.0 ng/kg b.w. (4.0 ng/kg b.w.) and 4.3 ng/kg b.w. (9.2 ng/kg b.w.), respectively. Because PFOSA could not be detected above the limit of detection of 0.2 ng/g f.w. this indirect route of exposure seems to be of less significance. Overall, the results of this study demonstrate that the German population is exposed to PFOS and PFOA, but the median dietary intake did not reach the recommended tolerable daily intake by far. Biomonitoring data predict an exposure in a comparable range. We suppose that, normally, food intake is the main source of exposure of the general population to PFOS and PFOA.     

Sulfide oxidation and acid mine drainage formation within two active tailings impoundments in the Golden Quadrangle of the Apuseni Mountains, Romania

Sulfidic mine tailings have to be classified as one of the major source of hazardous materials leading to water contamination. This study highlights the processes leading to sulfide oxidation and acid mine drainage (AMD) formation in the active stage of two tailings impoundments located in the southern part of the Apuseni Mountains, in Romania, a well-known region for its long-term gold-silver and metal mining activity. Sampling was undertaken when both impoundments were still in operation in order to assess their actual stage of oxidation and long-term behavior in terms of the potential for acid mine drainage generation. Both tailings have high potential for AMD formation (2.5 and 3.7 wt.% of pyrite equivalent, respectively) with lesser amount of carbonates (5.6 and 3.6 wt.% of calcite equivalent) as neutralization potential (ABA=-55.6 and -85.1 tCaCO(3)/1000 t ) and showed clear signs of sulfide oxidation yet during operation. Sequential extraction results indicate a stronger enrichment and mobility of elements in the oxidized tailings: Fe as Fe(III) oxy-hydroxides and oxides (transformation from sulfide minerals, leaching in oxidation zone), Ca mainly in water soluble and exchangeable form where gypsum and calcite are dissolved and higher mobility of Cu for Ribita and Pb for Mialu. Two processes leading to the formation of mine drainage at this stage could be highlighted (1) a neutral Fe(II) plume forming in the impoundment with ferrihydrite precipitation at its outcrop and (2) acid mine drainage seeping in the unsaturated zone of the active dam, leading to the formation of schwertmannite at its outcrop.     

Differentiation between proteolytic activation and autocatalytic conversion of human prothrombin. Activation of recombinant human prothrombin and recombinant D419N-prothrombin by snake venoms from Echis carinatus and Oxyuranus scutellatus

Recombinant human prothrombin (r-prothrombin) and recombinantmutant prothrombin with active site Asp419 substituted by Asn(D419N-prothrombin) were expressed in recombinant CHO cells,isolated and purified from the fermentation supernatant. Ther-Prothrombin and D419N-prothrombm were digested by both Echiscarinatus venom and Oxyuranus scutellatus venom. Prior to, duringand after activation, generation of thrombin activity and theproteolytic degradation of the prothrombin polypeptide chainwere analysed. Owing to the recombinant preparation and inactivityof D419N-prothrombin and its activation products, the proteolyticaction of E.carinatus and O.scutellatus venoms could be studiedwithout addition of thrombin inhibitor, without interferencefrom autocatalytic digestion of prothrombin and in the absenceof any other blood coagulation protease. The comparison betweenthe activation of r-prothrombin and D419N-prothrombin by snakevenoms permitted differentiation between proteolytic activationand autocatalytic conversion of prothrombin. Incubation of D419N-prothrombinwith E.carinatus venom resulted in the generation of stableD419N-meizothrombin by hydrolysis of the peptide bond Arg320-Ile321.By contrast, O.scutellatus venom exhibited activity towardspeptide bonds Arg320-Ile321 and Arg271-Thr272 and lower activitytowards peptide bond Arg155-Ser156, thus converting D419-prothrombininto D419N-thrombin and also liberating Fragment-1, Fragment-2and Fragment-1/2 activation peptide. Activation of r-prothrombinby E.carintitus and O.scutellatus venoms demonstrated the autocatalyticpotential of prothrombin-derived molecules and indicated thatmeizothrombin hydrolysed the cleavage between Fragment-2 andthrombin A-chain in the meizothrombin molecule, but not in prothrombin,preferentially at position Arg284-Thr285. By contrast, bothmeizothrombin and thrombin exhibited no detectable activitytowards peptide bond Arg320-Ile321 between thrombin A- and B-chain,although this site exhibits the optimum sequence for thrombincleavage.     

Expanding an Efficient,Electrically Driven and CNT‐Tagged P450 System into the Third Dimension: A Nanowired CNT‐Containing and Enzyme‐Stabilising 3 D Sol–Gel Electrode

Although electrochemically catalysed P450 reactions have been described, their efficiency and applicability remained limited. This is mostly due to low enzyme activity, laborious protein immobilisation and the small electrode surface. We established a novel protein immobilisation method for a determined orientation and electrical wiring of the enzyme without post‐expression modification. By genetic introduction of an anchor‐peptide our method is applicable for screening medium to large mutant libraries and detection by an electrode system. The system was expanded by using wired carbon nanotubes within a sol‐gel matrix to create a three dimensional electrode.