Geochemical characterization of the potential trace metal mobility in cohesive sediments

The Acid-Producing Potential (APP) and the Acid-Consuming Capacity (ACC) are introduced as basic parameters for long-term pollution assessment of mud disposal. They can be obtained by a four-step sequential leaching technique. The concentration of Ca extracted by the first Na-acetate step permits calculating the ACC. Both the Fe- and S-fractions deliberated by subsequent leaching steps are used to calculate the APP. When the APP of a sample is substacted from its ACC, a negative value indicates a potential increase of the bioavailability of the toxic metal load upon disposal of this mud in oxic environments.     

Crystal field spectra and jahn teller effect of Mn3+ in clinopyroxene and clinoamphiboles from India

Blanfordite (I), winchite (II), and juddite (III), all showing vivid colors and pleochroism, from highly oxidized parageneses of Indian gondites were studied by microprobe, Mössbauer, and microscope-spectrophotometric techniques and by X-ray structure refinements. The compositions of the Mn-bearing minerals were close to diopsideacmite (I) and magnesio-arfvedsonite to magnesio-riebeckite (II and III). Transition metal ions are located inM(1)-octahedra (I) or predominantlyM(2)-octahedra (II, III). Mössbauer spectra of⁵⁷Fe(IS, ΔE _Q) are typical of octahedral Fe³⁺ only. Polarized absorption spectra in the UV/VIS/NIR ranges explain color and pleochroism of the minerals. The position of the UV-“edge” is correlated with Fe³⁺-contents of the minerals, except for judditeE ∥Z, where the edge shows an unusual low energy position. This is most likely due to Mie-scattering of submicroscopic inclusions of braunite with nearly uniform dimensions. In the VIS range, the spectra are dominated by a complex band system between 15,000 and 20,000 cm^?1. Energies and ?-values of component bands are compatible with those of Mn³⁺ d-d transitions in other Mn³⁺-bearing silicates. The polarization behavior of component bands can best be explained by aC ₂(C2″) symmetry of the crystal field. The Jahn-Teller splitting (<9,000 cm^?1) of the⁵ E _g ground state of Mn³⁺ inO _h crystal fields is appreciably smaller than in other Mn³⁺-silicates. Crystal field parameters 10Dq, (I) 13,650, (II) ca. 11,640, and (III) 11,925 cm^?1, are near to that in piemontite. The crystal field stabilization energy of Mn³⁺, (I) 146, (II) ca. 140, (III) 142 \({{{\text{kJ}}} \mathord{\left/ {\vphantom {{{\text{kJ}}} {\text{g}}}} \right. \kern-0em} {\text{g}}}{\text{ - atom}}_{{\text{Mn}}^{{\text{3 + }}} } \) , is appreciably smaller than that found in other Mn³⁺-silicates (piemontites and manganian andalusites, viridines and kanonaite).     

Motion Analysis in SAR Images of Unfocused Objects Using Time–Frequency Methods

Synthetic aperture radar (SAR) image formation processing assumes that the scene is stationary, and to focus an object, one coherently sums a large number of independent returns. Any target motion introduces phases that distort and/or translate the target's image. Target motion produces a smear primarily in the azimuth direction of the SAR image. Time-frequency (TF) modeling is used to analyze and correct the residual phase distortions. An interactive focusing algorithm based on TF modeling demonstrates how to correct the phase and to rapidly focus the mover. This is demonstrated on two watercraft observed in a SAR image. Then, two time-frequency representations (TFRs) are applied to estimate the motion parameters of the movers or refocus them or both. The first is the short-time Fourier transform, from which a velocity profile is constructed based on the length of the smear. The second TFR is the time-frequency distribution series, which is a robust derivative of the Wigner-Ville distribution that works well in this SAR environment. The smear is a modulated chirp, from which a velocity profile is plotted and the phase corrections are integrated to focus the movers. The relationship between these two methods is discussed. Both methods show good agreement on the example.     

Airborne near-real-time monitoring of assembly and parking areas in case of large-scale public events and natural disasters

A critical requirement for an effective and coordinated response by public entities tasked with management, security, and relief during large-scale public events or natural disasters is the availability of current situational information. However, today there is a lack of comprehensive operational systems allowing a near-real-time (NRT) collection, visualization, and provision of situational information for larger areas. In this study a methodological framework is proposed, which allows an NRT extraction and visualization of situational information based on aerial image acquisition. The framework combines digital image analysis using a generic supervised information extraction approach based on statistical modeling with a downstream web-based visualization component realized through an automatic update of web services. Even though being applicable for different scenarios, the workflow will be demonstrated for the specific use-case of a NRT monitoring of open spaces including assembly and parking areas. Compared to other approaches, image analysis results indicate a high robustness and a low demand for computational power sources (7 seconds per image). Due to a high degree of automation, the proposed workflow contributes to a NRT ‘end-to-end’ monitoring system, which was developed within the VABENE (German acronym for ‘traffic management under large-scale public events and disaster conditions’) project covering all parts from the acquisition of raw aerial imagery to the dissemination of information products to end-users.     

LINET—An international lightning detection network in Europe

During the past years a VLF/LF lightning detection network (LINET) was developed at the University of Munich, which provides continuous data for both research and operational purposes. In particular, the network introduces five new features: a) total lightning capability: both cloud-to-ground strokes (CG) and cloud lightning (IC) are measured; b) low-amplitude reporting: weak lightning events from discharge channel with currents well below 5 kA are detected within the central part of the network, whereby IC events dominate; c) new 3D-discrimination: a time-of-arrival method is utilized to separate CG from IC with good reliability, provided that the sensor baseline does not exceed ~ 250 km; d) IC emission height: for each cloud event a height is determined which is thought to reflect the central region of the involved channel; and e) optimised location accuracy: due to precision and combined action of all influential network components, complemented by site-error corrections, the position accuracy of strokes reaches an average value as small as ~ 150 m, whereby false locations (‘outliers’) rarely occur. During international co-operations LINET has been deployed in four continents: Europe (initially Germany), South America (area of Bauru, Brazil), Australia (around Darwin), and Central Africa (Benin). Since the features quoted above could be verified in the tests, a 65-sensor network was established in Europe and started on May 1, 2006, in co-operation with the service company nowcast. LINET covers a wide area approximately from longitude − 10° to 25° to latitude 35° to 66°; it is available for scientific projects and officially utilized by the German Weather Service for operational purposes. Meanwhile, the network was extended by deployment of additional sites so that it comprises about 90 sensors in 17 countries.     

Early diagenetic processes during Mn-carbonate formation: evidence from the isotopic composition of authigenic Ca-rhodochrosites of the Baltic Sea

The formation of authigenic Ca-rich rhodochrosite (ACR) in sapropelic sediments of the Gotland Basin, Baltic Sea, is governed by deepwater renewal processes whereby saline water from the North Atlantic flushes the brackish anoxic Baltic Deeps. The carbon and oxygen isotopic compositions of these Mn-carbonates suggest that ACR formation takes place just below the sediment surface and that dissolved compounds from the deepwater column, such as water and bicarbonate molecules, were incorporated in ACR during authigenesis. Porewaters near the sediment surface display δ¹⁸O values of −5.4‰ (VSMOW) and are generally depleted in ¹⁸O, compared to the oxygen isotopic composition of water in equilibrium with Mn-carbonate solid solutions (ACR δ¹⁸O values are −4.6‰). This suggests that early burial diagenetic processes significantly modify the initial isotopic composition of water during Mn-carbonate formation. The reduction of sulfate having δ¹⁸O values of +8.4‰ accounts for a permanent enrichment of porewater ¹⁸O and observed δ¹⁸O values at depth equal to −4.6‰. However, this process does not explain the observed disequilibrium in the oxygen isotopic composition between water and ACR close to the sediment surface where Mn-carbonate formation takes place. Based on isotopic mass balance calculations, we suggest that MnO₂ with δ¹⁸O values of +8.9‰ released oxygen enriched in ¹⁸O into the anoxic porewaters close below the sediment surface. This process should occur after oxygenation events during deepwater renewal when MnO₂ accumulates at the surface of anoxic sediments. Manganese carbonates formed in these waters display δ¹⁸O values of ∼1.0‰ heavier than values expected solely from the initial deepwater composition. This quantitatively explains the discrepancy between paleosalinities calculated from ACR δ¹⁸O based on Mn-carbonate/water isotopic equilibrium fractionation and direct observations for the same period. Our results emphasize the important role of microbial MnO₂ reduction during rhodochrosite authigenesis and suggest that Mn(II) activity, rather than alkalinity, is the limiting component for sedimentary Mn-carbonate formation.     

Ba and Ni speciation in a nodule of binary Mn oxide phase composition from Lake Baikal

The partitioning and incorporation mechanism of Ni and Ba in a ferromanganese nodule from Lake Baikal were characterized by X-ray microfluorescence, microdiffraction, and absorption spectroscopy. Fe is speciated as goethite, and Mn as romanechite (psilomelane) and 10 Å-vernadite (turbostratic buserite) with minor 7 Å-vernadite (turbostratic birnessite). Barium is associated with romanechite and Ni with vernadite in distinct and irregularly distributed layers, and each type of Mn oxide is separated from the other type by goethite. The binary Mn oxide banding pattern is interpreted by a two-mode accretionary model, in which the variation in Ba flux induced by hydrothermal water pulses determines whether a tectomanganate (romanechite) or phyllomanganate (vernadite) is formed during the ferromanganese nodule accretion. Consistent with the dependence of Ni sorption on pH and the circumneutral pH of the lake water, nickel is mainly substituted isomorphically for Mn in the manganese layer, and is not sorbed at vacant Mn layer sites in the interlayer.     

Application of Gibbs Energy Minimization to ModelEarly-Diagenetic Solid-Solution Aqueous-Solution EquilibriaInvolving Authigenic Rhodochrosites in Anoxic BalticSea Sediments

The natural early-diagenetic environment ``anoxicporewater – authigenic mineral phases' has beencharacterized in sediment of the Gotland Deep,Baltic Sea, by a closed-system model. Occurrence ofcarbonate precipitates as thin almost pure whitelaminae was considered as a natural experiment forlong-term equilibration between these phases andporewater. Plots of distribution coefficientsindicate that metastable equilibrium exists betweenporewater and the authigenic Ca-rich rhodochrositephases below 7 cm depth. A thermodynamic model ofporewater geochemistry at in situ P = 25 barand T = 5 °C was developed using the Gibbsenergy minimization (GEM) approach. The values of isobaric-isothermal potentials of Mn, Ca, Fe, Mg,Sr, Ba, C, and O, calculated from the porewatercomposition, were used in a new ``dual thermodynamic'calculation approach to estimate solid activitycoefficients of the end-members in the non-idealsolid solution (Mn, Ca, Mg, Sr, Ba, Fe)CO₃,i.e., at full major and minor multi-componentcomplexity. The regular Margules interactionparameters for the composing binaries estimated bythis model were _Mn-Ca = 1.9 ± 0.5,_Mn-Mg = 0.6,_Ca-Mg = 3.7,_Mn-Fe = 0.2,_Ca-Fe = 2.8,_Mn-Sr = 9.7,_Ca-Sr = 2.15,_Mn-Ba = 4.0,_Ca-Ba = 1.4,validating the theoretical predictions given byLippmann in his pioneering 1980's paper. Thestrictly thermodynamic equilibrium model is not onlyable to match both the measured porewater andcarbonate solid-solution composition, but also topredict that the porewater pH, pe, alkalinity, anddissolved Mn, Fe, and S concentrations arecontrolled by the authigenic mineral bufferingassemblage mackinawite-greigite-rhodochrosite. Ourmodel is only compatible with the idea of ACRformation with typical composition (X_Mnbetween 70–75%) in the topmost sediment layerwhich, however, needs a major source ofMn_aq ^II. This is provided by reduction ofparticulate Mn oxides precipitated in significantamounts in the water column upon major inflow eventsin the Baltic Sea. The model enables also to set upscenarios of changing environmental conditions, e.g.,to predict the non-linear response of the carbonatesolid-solution composition to changes in Mn loading,alkalinity and salinity of the sediment-watersystem. The results suggest that the major andespecially minor element contents (Sr, Mg, Ba) inauthigenic carbonates can be applied as anenvironmental paleoproxy.