Occurrence and rates of terminal electron-accepting processes and recharge processes in petroleum hydrocarbon-contaminated subsurface

The occurrence and rates of terminal electron acceptor processes, and recharge processes in the unsaturated zone of a boreal site contaminated with petroleum hydrocarbons in the range C(10) to C(40) were examined. Soil microcosms were used to determine the rates of denitrification, iron (Fe) reduction, sulfate (SO(4)) reduction, and methanogenesis in two vertical soil profiles contaminated with oil, and in a noncontaminated reference sample. Furthermore, the abundances of the 16S rRNA genes belonging to Geobacteracaea in the samples were determined by real-time quantitative polymerase chain reaction (PCR). Analyses of ground water chemistry and soil gas composition were also performed together with continuous in situ monitoring of soil water and ground water chemistry. Several lines of evidence were obtained to demonstrate that both Fe reduction and methanogenesis played significant roles in the vertical profiles: Fe reduction rates up to 3.7 nmol h(-1) g(-1) were recorded and they correlated with the abundances of the Geobacteracaea 16S rRNA genes (range: 2.3 x 10(5) to 4.9 x 10(7) copies g(-1)). In the ground water, ferrous iron (Fe(2+)) concentration up to 55 mg L(-1) was measured. Methane production rates up to 2.5 nmol h(-1) g(-1) were obtained together with methane content up to 15% (vol/vol) in the soil gas. The continuous monitoring of soil water and ground water chemistry, microcosm experiments, and soil gas monitoring together demonstrated that the high microbial activity in the unsaturated zone resulted in rapid removal of oxygen from the infiltrating recharge thus leaving the anaerobic microbial processes dominant below 1.5 m depth both in the unsaturated and the saturated zones of the subsurface.     

Threat-sensitive feeding strategy of immature sticklebacks (Gasterosteus aculeatus) in response to recent experimental infection with the cestode Schistocephalus solidus

Threat-sensitive decision-making might be changed in response to a parasitic infection that impairs future reproduction. Infected animals should take more risk to gain energy to speed up their growth to achieve early reproduction and/or to strengthen their immune response. To avoid correlational evidence, we experimentally infected and sham-infected randomly selected immature three-spined sticklebacks with the cestode Schistocephalus solidus. For 7 weeks we determined the threat-sensitive foraging decisions and growth of individual sticklebacks in the presence of a live pike (Esox lucius). The experimenters were blind with respect to the infection status of the fish. In contrast to previous studies, our recently infected fish should have been almost unconstrained by the parasite and thus have been able to adopt an appropriate life history strategy. We found a strong predator effect for both infected and uninfected fish: the sticklebacks’ risk-sensitive foraging strategy resulted in significantly reduced growth under predation risk. Infected fish did not grow significantly faster under predation risk than uninfected fish. Since infected fish consumed much less prey in the presence of the predator than did infected fish in its absence, they obviously did not use the opportunity to maximize their growth rate to reach reproduction before the parasite impairs it. Received: 21 June 1999 / Revised: 27 November 1999 / Accepted: 5 September 2000     

The use of (micro)-X-ray absorption spectroscopy in cement research

Long-term predictions on the mobility and the fate of radionuclides and contaminants in cementitious waste repositories require a molecular-level understanding of the geochemical immobilization processes involved. In this study, the use of X-ray absorption spectroscopy (XAS) for chemical speciation of trace elements in cementitious materials will be outlined presenting two examples relevant for nuclear waste management. The first example addresses the use of XAS on powdered cementitious materials to determine the local coordination environment of Sn(IV) bound to calcium silicate hydrates (C-S-H). Sn K-edge XAS data of Sn(IV) doped C-S-H can be rationalized by corner sharing binding of Sn octahedra to Si tetrahedra of the C-S-H structure. XAS was further applied to determine the binding mechanism of Sn(IV) in the complex cement matrix. The second example illustrates the potential of emerging synchrotron-based X-ray micro-probe techniques for elucidating the spatial distribution and the speciation of contaminants in highly heterogeneous cementitious materials at the micro-scale. Micro X-ray fluorescence (XRF) and micro-XAS investigations were carried out on Co(II) doped hardened cement paste. These preliminary investigations reveal a highly heterogeneous spatial Co distribution. The presence of a Co(II)-hydroxide-like phase Co(OH)2 and/or Co-Al layered double hydroxide (Co-Al LDH) or Co-phyllosilicate was observed. Surprisingly, some of the initial Co(II) was partially oxidized and incorporated into a Co(III)O(OH)-like phase or a Co-phyllomanganate.     

Chemical Engineering of Enzymes: Altered Catalytic Activity, Predictable Selectivity and Exceptional Stability of the Semisynthetic Peroxidase Seleno-Subtilisin

2  H). As a consequence, the former proteolytic enzyme gained peroxidase activity and catalyzed the selective reduction of hydroperoxides. Due to the identical binding sites of the semisynthetic peroxidase and the protease, the substrate selectivity of seleno-subtilisin was predictable in view of the well-known selectivity of subtilisin.