Speciation of tetravalent plutonium in contact with humic substances and kaolinite under environmental conditions

Plutonium represents the major contribution to the radiotoxicity of spent nuclear fuel over storage times of up to several hundred thousand years. The speciation of plutonium in aquifer systems is important in order to assess the risks of high-level nuclear waste disposal and to acquire a deep knowledge of the mobilization and immobilization behavior of plutonium. In aqueous solutions, plutonium can coexist in four oxidation states and each one of them has different chemical and physical behavior. Tetravalent plutonium is the most abundant under natural conditions. Therefore, detailed speciation studies of tetravalent plutonium in contact with humic substances (HS) and kaolinite as a model clay mineral have been performed in this work. Plutonium is present in the environment at an ultratrace level. Therefore, speciation of Pu at the ultratrace level is mandatory. Capillary electrophoresis (CE) coupled to resonance ionization mass spectrometry (RIMS) was used as a new speciation method. CE-RIMS enables to improve the detection limit for plutonium species by 2 to 3 orders of magnitude compared to the previously developed CE-ICP-MS. For understanding the behavior of Pu(IV) in aqueous systems, redox reactions, complexation, and sorption behavior of plutonium were studied. The redox behavior of plutonium in contact with humic acid (HA) and fulvic acid (FA) was investigated. A relatively fast reduction of Pu(VI) in contact with HS was observed. It was mainly reduced to Pu(IV) and Pu(III) within a couple of weeks. The time dependence of the Pu(IV) complexation with Aldrich HA was investigated and a complex constant (logßLC) between 6.4 - 8.4 of Pu(IV) was determined by means of ultrafiltration taking into account the loading capacity (LC). The sorption of tetravalent plutonium onto kaolinite was investigated as a function of pH in batch experiments under aerobic and anaerobic conditions. The sorption edge was found at about pH = 1 and a maximum sorption at around pH = 8.5. In the presence of CO2 at pH > 8.5, the sorption of plutonium was decreased probably due to the formation of soluble carbonate complexes. For comparison, the sorption of Th(IV) onto kaolinite was also investigated and consistent results were found. The Pu(IV) sorption onto kaolinite was studied by XANES and EXAFS at pH 1, 4, 9 and the sorbed species on kaolinite surface was Pu(IV). Depending on the pH, only 1 - 10 % of the sorbed plutonium is desorbed from kaolinite and released into a fresh solution at the same pH value. Furthermore, the sorption of HS onto kaolinite was studied as a function of pH at varying concentrations of HS, as a prerequisite to understand the more complex ternary system. The sorption of HA onto kaolinite was found to be higher than that of FA. The investigation of the ternary systems (plutonium-kaolinite-humic substances) is performed as a function of pH, concentration of HS, and the sequences of adding the reactants. The presence of HS strongly influences the sorption of Pu(IV) onto kaolinite over the entire pH range. For comparison, the influence of HS on the sorption of Th(IV) onto kaolinite was also investigated and a good agreement with the results of Pu(IV) was obtained.

Study of the interactions of Neptunium with humic substances and the clay mineral montmorillonite by direct and non direct speciation methods

For the safety assessment of radioactive waste, the possibility of radionuclide migration has to be considered. Since Np (and also Th due to the long-lived 232-Th) will be responsible for the greatest amount of radioactivity one million years after discharge from the reactor, its (im)-mobilization in the geosphere is of great importance. Furthermore, the chemistry of Np(V) is quite similar (but not identical) to the chemistry of Pu(V). Three species of neptunium may be found in the near field of the waste disposal, but pentavalent neptunium is the most abundant species under a wide range of natural conditions. Within this work, the interaction of Np(V) with the clay mineral montmorillonite and melanodins (as model substances for humic acids) was studied. The sorption of neptunium onto gibbsite, a model clay for montmorillonite, was also investigated. The sorption of neptunium onto γ-alumina and montmorillonite was studied in a parallel doctoral work by S. Dierking. Neptunium is only found in ultra trace amounts in the environment. Therefore, sensitive and specific methods are needed for its determination. The sorption was determined by γ spectroscopy and LSC for the whole concentration range studied. In addition the combination of these techniques with ultrafiltration allowed the study of Np(V) complexation with melanoidins. Regrettably, the available speciation methods (e.g. CE-ICP-MS and EXAFS) are not capable to detect the environmentally relevant neptunium concentrations. Therefore, a combination of batch experiments and speciation analyses was performed. Further, the preparation of hybrid clay-based materials (HCM) montmorillonitemelanoidins for sorption studies was achieved. The formation of hybrid materials begins in the interlayers of the montmorillonite, and then the organic material spreads over the surface of the mineral. The sorption of Np onto HCM was studied at the environmentally relevant concentrations and the results obtained were compared with those predicted by the linear additive model by Samadfam. The sorption of neptunium onto gibbsite was studied in batch experiments and the sorption maximum determined at pH~8.5. The sorption isotherm pointed to the presence of strong and weak sorption sites in gibbsite. The Np speciation was studied by using EXAFS, which showed that the sorbed species was Np(V). The influence of M42 type melanodins on the sorption of Np(V) onto montmorillonite was also investigated at pH 7. The sorption of the melanoidins was affected by the order in which the components were added and by ionic strength. The sorption of Np was affected by ionic strength, pointing to outer sphere sorption, whereas the presence of increasing amounts of melanoidins had little influence on Np sorption.

Targeted alpha-radionuclide therapy of functionally critically located gliomas with 213Bi-DOTA-[Thi8,Met(O2)11]-substance P: a pilot trial

Functionally critically located gliomas represent a challenging subgroup of intrinsic brain neoplasms. Standard therapeutic recommendations often cannot be applied, because radical treatment and preservation of neurological function are contrary goals. The successful targeting of gliomas with locally injected beta radiation-emitting (90)Y-DOTAGA-substance P has been shown previously. However, in critically located tumours, the mean tissue range of 5 mm of (90)Y may seriously damage adjacent brain areas. In contrast, the alpha radiation-emitting radionuclide (213)Bi with a mean tissue range of 81 microm may have a more favourable toxicity profile. Therefore, we evaluated locally injected (213)Bi-DOTA-substance P in patients with critically located gliomas as the primary therapeutic modality.

Patients with substance use and personality disorders: a comparison of patient characteristics, treatment process, and outcomes in Swiss and U.S. substance use disorder programs

Cross-cultural comparisons may increase our understanding of different models of substance use treatment and help identify consistent associations between patients' characteristics, treatment conditions, and outcomes.

Terrestrial feeding in aquatic turtles: environment-dependent feeding behavior modulation and the evolution of terrestrial feeding in Emydidae

Evolutionary transitions between aquatic and terrestrial environments are common in vertebrate evolution. These transitions require major changes in most physiological functions, including feeding. Emydid turtles are ancestrally aquatic, with most species naturally feeding only in water, but some terrestrial species can modulate their feeding behavior appropriately for both media. In addition, many aquatic species can be induced to feed terrestrially. A comparison of feeding in both aquatic and terrestrial environments presents an excellent opportunity to investigate the evolution of terrestrial feeding from aquatic feeding, as well as a system within which to develop methods for studying major evolutionary transitions between environments. Individuals from eight species of emydid turtles (six aquatic, two terrestrial) were filmed while feeding underwater and on land. Bite kinematics were analyzed to determine whether aquatic turtles modulated their feeding behavior in a consistent and appropriate manner between environments. Aquatic turtles showed consistent changes between environments, taking longer bites and using more extensive motions of the jaw and hyoid when feeding on land. However, these motions differ from those shown by species that naturally feed in both environments and mostly do not seem to be appropriate for terrestrial feeding. For example, more extensive motions of the hyoid are only effective during underwater suction feeding. Emydids evolving to feed on land probably would have needed to evolve or learn to overcome many, but not all, aspects of the intrinsic emydid response to terrestrial feeding. Studies that investigate major evolutionary transitions must determine what responses to the new environment are shown by naïve individuals in order to fully understand the evolutionary patterns and processes associated with these transitions.

Treatment outcomes of an integrated residential programme for patients with schizophrenia and substance use disorder

About half of all schizophrenic patients have a co-occurring substance use disorder, leading to poorer social and functional outcomes than obtained in non-abusing patients. To improve outcomes, integrated treatments have been designed that address the two conditions simultaneously. Results are, however, conflicting because the available effect studies are hampered by various methodological issues, among which are heterogeneous patient samples.

Moving beyond a descriptive aquatic toxicology: the value of biological process and trait information

In order to improve the ability to link chemical exposure to toxicological and ecological effects, aquatic toxicology will have to move from observing what chemical concentrations induce adverse effects to more explanatory approaches, that are concepts which build on knowledge of biological processes and pathways leading from exposure to adverse effects, as well as on knowledge on stressor vulnerability as given by the genetic, physiological and ecological (e.g., life history) traits of biota. Developing aquatic toxicology in this direction faces a number of challenges, including (i) taking into account species differences in toxicant responses on the basis of the evolutionarily developed diversity of phenotypic vulnerability to environmental stressors, (ii) utilizing diversified biological response profiles to serve as biological read across for prioritizing chemicals, categorizing them according to modes of action, and for guiding targeted toxicity evaluation; (iii) prediction of ecological consequences of toxic exposure from knowledge of how biological processes and phenotypic traits lead to effect propagation across the levels of biological hierarchy; and (iv) the search for concepts to assess the cumulative impact of multiple stressors. An underlying theme in these challenges is that, in addition to the question of what the chemical does to the biological receptor, we should give increasing emphasis to the question how the biological receptor handles the chemicals, i.e., through which pathways the initial chemical-biological interaction extends to the adverse effects, how this extension is modulated by adaptive or compensatory processes as well as by phenotypic traits of the biological receptor.

Predictors of substance use reduction in an epidemiological first-episode psychosis cohort

Aim To assess the predictors of a significant decrease or cessation of substance use (SU) in a treated epidemiological cohort of first-episode psychosis (FEP) patients. Method Participants were FEP patients of the Early Psychosis Prevention and Intervention Centre in Australia. Patients' medical files were reviewed using a standardized file audit. Data on 432 patients with FEP and baseline co-morbid substance use disorder (SUD) were available for analysis. Predictors of reduction/cessation of SU at follow up were examined using logistic regression analyses. Results In univariate analyses, a reduction/cessation of SU was predicted by baseline measures reflecting higher education, employment, accommodation with others, cannabis use disorder (CUD) only (rather than poly-SUDs), better global functioning and better premorbid social and occupational functioning, later age at onset of psychosis, and a diagnosis of non-affective psychosis. In multivariate analysis, CUD alone and better premorbid social and occupational functioning remained significant predictors. Conclusions Addressing SUDs and social and occupational goals in people with FEP may offer opportunities to prevent SUDs becoming more severe or entrenched. Further longitudinal research on recovery from SU and FEP is needed to disentangle directions of influence and identify key targets for intervention.

Local targeting of malignant gliomas by the diffusible peptidic vector 1,4,7,10-tetraazacyclododecane-1-glutaric acid-4,7,10-triacetic acid-substance p

PURPOSE: Malignant glial brain tumors consistently overexpress neurokinin type 1 receptors. In classic seed-based brachytherapy, one to several rigid (125)I seeds are inserted, mainly for the treatment of small low-grade gliomas. The complex geometry of rapidly proliferating high-grade gliomas requires a diffusible system targeting tumor-associated surface structures to saturate the tumor, including its margins. EXPERIMENTAL DESIGN: We developed a new targeting vector by conjugating the chelator 1,4,7,10-tetraazacyclododecane-1-glutaric acid-4,7,10-triacetic acid to Arg(1) of substance P, generating a radiopharmaceutical with a molecular weight of 1,806 Da and an IC(50) of 0.88 +/- 0.34 nmol/L. Cell biological studies were done with glioblastoma cell lines. neurokinin type-1 receptor (NK1R) autoradiography was done with 58 tumor biopsies. For labeling, (90)Y was mostly used. To reduce the "cross-fire effect" in critically located tumors, (177)Lut and (213)Bi were used instead. In a pilot study, we assessed feasibility, biodistribution, and early and long-term toxicity following i.t. injection of radiolabeled 1,4,7,10-tetraazacyclododecane-1-glutaric acid-4,7,10-triacetic acid substance P in 14 glioblastoma and six glioma patients of WHO grades 2 to 3. RESULTS: Autoradiography disclosed overexpression of NK1R in 55 of 58 gliomas of WHO grades 2 to 4. Internalization of the peptidic vector was found to be specific. Clinically, the radiopharmeutical was distributed according to tumor geometry. Only transient toxicity was seen as symptomatic radiogenic edema in one patient (observation period, 7-66 months). Disease stabilization and/or improved neurologic status was observed in 13 of 20 patients. Secondary resection disclosed widespread radiation necrosis with improved demarcation. CONCLUSIONS: Targeted radiotherapy using diffusible peptidic vectors represents an innovative strategy for local control of malignant gliomas, which will be further assessed as a neoadjuvant approach.

Substance use disorder treatment programs in Switzerland and the USA: Program characteristics and 1-year outcomes

AIM: This study compared matched samples of substance use disorder (SUD) patients in Swiss and United States (US) residential treatment programs and examined the relationship of program characteristics to patients' substance use and psychosocial functioning at a 1-year follow-up. DESIGN AND SETTING: The study used a prospective, naturalistic design and a sample of 10 public programs in the German-speaking part of Switzerland and 15 US public treatment programs. PARTICIPANTS: A total of 358 male patients in Swiss programs were matched on age, marital status and education with 358 male patients in US programs. A total of 160 Swiss and 329 US patient care staff members also participated. MEASUREMENT: Patients completed comparable inventories at admission, discharge and 1-year follow-up to assess their substance use and psychological functioning and receipt of continuing care. Staff members reported on program characteristics and their beliefs about substance use. FINDINGS: Compared to Swiss patients, US patients had more severe substance use and psychological problems at intake and although they did not differ on abstinence and remission at follow-up, had somewhat poorer outcomes in other areas of functioning. Swiss programs were longer and included more individual treatment sessions; US programs included more group sessions and were more oriented toward a disease model of treatment. Overall, length of program, treatment intensity and 12-step orientation were associated with better 1-year outcomes for patients in both Swiss and US programs. CONCLUSIONS: The sample of Swiss and US programs studied here differed in patient and treatment characteristics; however, in general, there were comparable associations between program characteristics and patients' 1-year outcomes. These findings suggest that associations between treatment processes and patients' outcomes may generalize from one cultural context to another.