Bestimmung von Atrazin,Terbutylazin und ihrer Desethyl- sowie Hydroxymetaboliten in Boden mittels SFE und HPLC/UV-DAD

Determination of Atrazine, Terbutylazine and their Deethyl- and Hydroxymetabolites in Soil by SFE and HPLC/UV-DAD The supercritical fluid extraction (SFE) (CO₂ and CH₃OH as modifier) of the herbicides atrazine and terbutylazine as well as their deethyl- and hydroxymetabolites from soil was investigated. The analytes were determined after extraction by HPLC/UV-DAD using a C18 column. The limits of detection of the chromatographic step were between 0.01 μg/mL and 0.07 μg/mL, the relative standard deviations between 0.8% and 1.4%. With the aid of a control chart, the stability of the chromatographic system was evaluated. For extraction, soil was spiked with 5 μg/g for each component. For SFE, CO₂ and methanol as modifier were used, and a pressure program was applied. Beside SFE, Soxhlet extraction with methanol and a solid-liquid extraction with acetone/water by shaking were carried out. For chlorine-containing triazines, the recovery rates were comparable for all extraction methods. The following recovery rates for SFE were obtained: deethylterbutylazine 77.4%, terbutylazine 80.2%, deethylatrazine 87.4%, atrazine 92.6%. However, the recovery rates for the hydroxymetabolites (4.1% for hydroxyatrazine, 21% for hydroxyterbutylazine) were not satisfying compared with the “classical” methods of extraction (above 50%). The limits of detection for the total process (SFE and HPLC/UV-DAD) estimated by the signal to noise ratio amounted 0.08 μg/g soil for chlorine-containing derivates, for hydroxyatrazine 2…3 μg/g, and for hydroxyterbutylazine 0.8 μ/g.     

The violent past of Cygnus X-2

Cygnus X-2 appears to be the descendant of an intermediate-mass X-ray binary (IMXB). Using Mazzitelli's stellar code we compute detailed evolutionary sequences for the system and find that its prehistory is sensitive to stellar input parameters, in particular the amount of core overshooting during the main-sequence phase. With standard assumptions for convective overshooting a case B mass transfer starting with a 3.5-M_⊙ donor star is the most likely evolutionary solution for Cygnus X-2. This makes the currently observed state rather short-lived, of order 3 Myr, and requires a formation rate > 10⁻⁷–10⁻⁶ yr⁻¹ of such systems in the Galaxy. Our calculations show that neutron star IMXBs with initially more massive donors (≳4 M_⊙) encounter a delayed dynamical instability; they are unlikely to survive this rapid mass transfer phase. We determine limits for the age and initial parameters of Cygnus X-2 and calculate possible dynamical orbits of the system in a realistic Galactic potential, given its observed radial velocity. We find trajectories which are consistent with a progenitor binary on a circular orbit in the Galactic plane inside the solar circle that received a kick velocity ≤200 km s⁻¹ at the birth of the neutron star. The simulations suggest that about 7 per cent of IMXBs receiving an arbitrary kick velocity from a standard kick velocity spectrum would end up in an orbit similar to Cygnus X-2, while about 10 per cent of them reach yet larger Galactocentric distances.     

The compensating effect of glaciers: Characterizing the relation between interannual streamflow variability and glacier cover

Meltwater from glaciers is not only a stable source of water but also affects downstream streamflow dynamics. One of these dynamics is the interannual variability of streamflow. Glaciers can moderate streamflow variability because the runoff in the glacierized part, driven by temperature, correlates negatively with the runoff in the non-glacierized part of a catchment, driven by precipitation, thereby counterbalancing each other. This is also called the glacier compensation effect (GCE), and the effect is assumed to depend on relative glacier cover. Previous studies found a convex relationship between streamflow variability and glacier cover of different glacierized catchments, with lowest streamflow variability at a certain optimum glacier cover. In this study, we aim to revisit these previously found curves to find out if a universal relationship between interannual streamflow variability and glacier cover exists, which could potentially be used in a space-for-time substitution analysis. Moreover, we test the hypothesis that the dominant climate drivers (here precipitation and temperature) switch around the suggested optimum of the curve. First, a set of virtual nested catchments, with the same absolute glacier area but varying non-glacierized area, were modelled to isolate the effect of glacier cover on streamflow variability. The modelled relationship was then compared with a multicatchment data set of gauged glacierized catchments in the European Alps. In the third step, changes of the GCE curve over time were analysed. Model results showed a convex relationship and the optimum in the simulated curve aligned with a switch in the dominant climate driver. However, the multicatchment data and the time change analyses did not suggest the existence of a universal convex relationship. Overall, we conclude that GCE is complex due to entangled controls and changes over time in glacierized catchments. Therefore, care should be taken to use a GCE curve for estimating and/or predicting interannual streamflow variability in glacierized catchments.     

Structural control of low-sulfidation epithermal gold mineralization in the Rosario–Bunawan district, East Mindanao Ridge, Philippines

The Rosario–Bunawan district is situated about 200 km north of Davao City, the capital of the Mindanao Island, Southern Philippines. Gold is produced from the Co-O mine, containing about 2,034,000 t of ore at 10.9 g/t Au, and in numerous small-scale operations by local miners. Epithermal gold mineralization in the Rosario–Bunawan district and the Co-O mine is confined to narrow (0.2–4 m) low-sulfidation quartz–chalcedony–calcite veins in volcanic and volcaniclastic wall rocks. Three major vein orientations are distinguished: (1) the NNW–SSE-trending set with a sinistral strike-slip sense of deformation (Philippine Fault trend); (2) the ENE–WSW-trending dextral strike-slip set (Palawan trend) and associated veins in the Riedel geometry; and (3) the WNW–ESE-trending conjugate set (Co-O trend). Three structural stages are defined: (1) extensional shear or shear veins formed in the Co-O, the Philippine Fault, and Palawan trends during regional NW–SE compression and near vertical vein opening (D₁); (2) reactivation of veins in the Philippine Fault, veins associated with the Palawan, and, to a lesser extent, the Co-O trends during E–W compression and near horizontal N–S-oriented vein opening (D₂). New D₂ extensional shear or shear veins formed in the Philippine Fault, and structures associated with the Palawan and associated Riedel trends; (3) the D₃-stage block faulting subsequently displaced all of the auriferous veins. The auriferous Rosario–Bunawan district is situated between two splays of the Philippine Fault, which acted as a lateral ramp system during the oblique convergence of the Philippine Sea plate and the Eurasian plate. The oblique convergence resulted in a change from a compressional (D₁) to a transpressional (D₂) regime, which was a prerequisite for the two-stage vein opening and hydrothermal mineralization, leading to an economic gold enrichment. D₁ compressional tectonics may have caused an elevated geothermal gradient in shallow crustal levels, forming the heat source for the fluid plumbing system, which is at variance to typical epithermal deposits formed in extensional zones. D₂ thrusting of a limestone nappe together with syn-tectonic diorite intrusions may have further increased the geothermal gradient, maintaining the fluid plumbing system. The limestone nappe may, at the same time, have represented an aquitard forcing the hydrothermal fluids into the volcanic and volcaniclastic wall rocks, which is regarded as critical for the two-stage gold mineralization in the Rosario–Bunawan district.     

A diatom‐based reconstruction of summer sea‐surface salinity in the Southern Okinawa Trough,East China Sea,over the last millennium

A high‐resolution diatom record from site MD05‐2908 in the Southern Okinawa Trough, East China Sea, reveals pronounced multidecadal‐ to centennial‐scale palaeoceanographic changes throughout the last millennium. Summer sea‐surface salinity (SSS) was reconstructed using a weighted averaging partial least squares diatom‐based training set. The reconstructed SSS shows slightly decreasing values during the period AD 905–1930 with considerable fluctuations superimposed on this general trend. Relatively high‐salinity conditions during the interval AD 905–1450 probably suggest a low flood frequency in north‐eastern Taiwan. Furthermore, the high SSS values are associated with a strong and stable influence of the Kuroshio Current on the Southern Okinawa Trough during the Medieval Climate Anomaly. The period AD 1450–1930 is characterized by three low‐salinity intervals (AD 1450–1500, AD 1625–1725 and AD 1770–1880) separated by periods of relatively high salinity. The low SSS intervals indicate increased freshwater discharge into the Southern Okinawa Trough during the Little Ice Age, probably as a result of higher flood frequencies in north‐eastern Taiwan. Spectral and wavelet analyses suggest that this pattern was linked to multidecadal variations in summer SSS, presumably associated with the Pacific Decadal Oscillation. Copyright © 2012 John Wiley & Sons, Ltd.     

Exotic pollen as an indicator of variable atmospheric circulation over the Labrador Sea region during the mid to late Holocene

Variability in the abundance of exotic (non‐native) pollen in sediment cores has long been considered as a potential proxy for changing atmospheric circulation, but the difficulty of gaining sufficient total exotic pollen and the incomplete understanding of atmospheric pollen transport patterns has hindered its application. In light of recent advances in the study of pollen transport, we present an exotic pollen record from two fjord sediment cores taken from the west (Placentia Bay, Newfoundland) and east (Narsaq Sund, Greenland) Labrador Sea as a basis for studying variations in regional atmospheric circulation. The two cores cover the last ca. 5500 years and indicate a shift in dominant spring/summer air masses at ca. 2000 (southern Greenland) and 3000 cal a BP (Newfoundland) transporting reduced concentrations of pollen from southerly and south‐westerly vegetation zones. This may suggest a shift away from more dominantly zonal atmospheric circulation (a feature of positive North Atlantic Oscillation years) to more frequent meridional circulation. These results support sea ice/sea‐surface temperature proxy reconstructions from Newfoundland, investigated as part of the same project, which also suggest increased winter atmospheric circulation during the early part of the time period studied. In this region, more positive North Atlantic Oscillation years, and therefore more zonal atmospheric circulation, are associated with increased atmospheric circulation in both the winter and the summer seasons. Copyright © 2011 John Wiley & Sons, Ltd.     

Sediment‐budget modelling of multi‐sourced basin fills: application to recent deposits of the western Adriatic mud wedge (Italy)

We analysed modern mass‐accumulation patterns on the western Adriatic mud wedge (Italy), an elongated belt of shelf mud formed by coalesced prodeltas of the Adige, Po, and Apennine rivers, as part of an integrated strategy aimed at producing a quantitative sediment budget model for muddy continental shelves sourced by multiple compositionally distinct fluvial systems. Sediment provenance and source‐specific accumulation rates of surface sediments were quantified by combining results of grain‐size analysis and geochemical analysis of specific size fractions with bulk mass accumulation rates. Statistical classification algorithms adapted to compositional data were used to partition the total (geochemical) variation of sediment properties into size‐related and provenance‐specific factors. We identified geochemically distinct fluvial end‐member sediment types in two different grain‐size fractions, which were grouped into sediments derived from the Apennine rivers, and sediments derived from the Po and Adige rivers. Compositional fingerprints (end‐member compositions) of each source area were estimated by taking into account relative rates of fluvial sediment supply from rivers as predicted by numerical modelling. The end members allow us to explain geochemical compositional variation of mud‐wedge surface sediments in terms of provenance and size‐selective dispersal, and map mass accumulation rates of sediments from individual source areas (grain size<63 μm), as well as bulk sand accumulation rates (grain size>63 μm) across the western Adriatic mud wedge. The source‐specific rates of fine‐grained sediment supply derived from geostatistical estimates of mass‐accumulation rates were used to calibrate the numerical model of sediment supply to present‐day conditions.