Verbleib und Ökotoxizität von SiO2 und CeO2-Nanomaterialien im System Boden - Pflanze

Aufgrund des breiten Anwendungsspektrums von nSiO2 und nCeO2 sind Einträge dieser Nanomaterialien (NM) in den Boden über verschiedene Expositionspfade umweltrelevant hinsichtlich Verbleib und Ökotoxizität im System Boden - Pflanze. Im Rahmen des Projekts DENANA (Designkriterien für Nachhaltige Nanomaterialien, BMBF-FKZ: 03X0152) wurden diesbezüglich verschiedene, u.a. dotierte und funktionalisierte, NM nebst ionischen Referenzen und Bulkmaterialien getestet. Ergebnisse aus Kurz- und Langzeitversuchen mit höheren Pflanzen deuten darauf hin, dass nSiO2- bürtiges Silicium (Si) maßgeblich in gelöster Form von Pflanzen aufgenommen wird. Im Fall von Winterweizen (Triticum aestivum L.) wurde Si oberirdisch in Form sekundärer Neubildungen akkumuliert. Eine partikuläre Aufnahme konnte bislang weder für nSiO2 noch für nCeO2 nachgewiesen werden. Auch zeigten die getesteten Sorten keine erhöhte Akkumulation von Si oder Cerium (Ce) im Weizenkorn, sodass eine Gefährdung der Lebensmittelsicherheit durch Weizenmehlprodukte als gering einzustufen ist. Unterdessen deutete eine Steigerung des Phosphor (P)-Ernährungszustands der Pflanzen infolge Applikation von nSiO2 zum Substrat auf eine Verdrängung von P durch Si von Bindungsplätzen im Boden, mit potentiellen Implikationen für die Pflanzendüngung. Ökotoxikologische Wirkungen durch nSiO2 wurden in umweltrelevanten Konzentrationen weder auf höhere Pflanzen noch auf Ammonium oxidierende Bodenmikroorganismen beobachtet. Hinsichtlich nCeO2 wurde jedoch in einem Fall (NM-212 aus dem OECD Sponsorship Programm) nach Alterung in Böden eine reproduzierbare, signifikante Hemmung der Reproduktion des Kompostwurms Eisenia andrei sowie Fluchtverhalten induziert. Weiterhin konnte, trotz ausbleibender Hemmung der Biomasseproduktion, bei Weizenpflanzen mithilfe von in vivo Messungen zum Zustand des Photosystem II konzentrationsabhängig eine Stressreaktion auf nCeO2 festgestellt werden

The regional and global significance of nitrogen removal in lakes and reservoirs

Author Posting. © The Author(s), 2008. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Biogeochemistry 93 (2009): 143-157, doi:10.1007/s10533-008-9272-x.Human activities have greatly increased the transport of biologically available N through watersheds to potentially sensitive coastal ecosystems. Lentic water bodies (lakes and reservoirs) have the potential to act as important sinks for this reactive N as it is transported across the landscape because they offer ideal conditions for N burial in sediments or permanent loss via denitrification. However, the patterns and controls on lentic N removal have not been explored in great detail at large regional to global scales. In this paper we describe, evaluate, and apply a new, spatially explicit, annual-scale, global model of lentic N removal called NiRReLa (Nitrogen Retention in Reservoirs and Lakes). The NiRReLa model incorporates small lakes and reservoirs than have been included in previous global analyses, and also allows for separate treatment and analysis of reservoirs and natural lakes. Model runs for the mid-1990s indicate that lentic systems are indeed important sinks for N and are conservatively estimated to remove 19.7 Tg N yr-1 from watersheds globally. Small lakes (< 50 km2) were critical in the analysis, retaining almost half (9.3 Tg N yr-1) of the global total. In model runs, capacity of lakes and reservoirs to remove watershed N varied substantially (0-100%) both as a function of climate and the density of lentic systems. Although reservoirs occupy just 6% of the global lentic surface area, we estimate they retain approximately 33% of the total N removed by lentic systems, due to a combination of higher drainage ratios (catchment surface area : lake or reservoir surface area), higher apparent settling velocities for N, and greater N loading rates in reservoirs than in lakes. Finally, a sensitivity analysis of NiRReLa suggests that, on-average, N removal within lentic systems will respond more strongly to changes in land use and N loading than to changes in climate at the global scale.The NSF26 Research Coordination Network on denitrification for support for collaboration (award number DEB0443439 to S.P. Seitzinger and E.A. Davidson). This project was also supported by grants to J.A. Harrison from California Sea Grant (award number RSF8) and from the U.S. Geological Survey 104b program and R. Maranger (FQRNT Strategic Professor)

The Length of Working Life in Spain : Levels, Recent Trends, and the Impact of the Financial Crisis

While there has been considerable debate about extending the length of working life, relatively little is known about this issue. We use data from the Spanish Continuous Working Life Sample for 2004--2013 to calculate period working life tables, which in turn allows us to assess the impact of the financial crisis on working life expectancy in Spain. Before the recession hit, working life expectancy in Spain was around 38 years for males and 33 years for females. The recession had a tremendous impact on the Spanish labor market, but the effects differed considerably by gender and occupational category. Men working in skilled non-manual jobs were less affected, while men working in unskilled manual jobs lost close to 14 years of working life expectancy. Women were less affected than men. With working life expectancy decreasing, the average proportion of lifetime spent in unemployment and outside the labor market increased markedly, whereas the average number of years spent in retirement changed only a little. When we decompose losses in working life expectancy by age group, we find that economic fluctuations affect both older and younger workers. This result suggests that policies that focus on retirement ages only are incomplete. We also compare our findings to the results obtained by Sullivans method, which is based on prevalence rates rather than the incidence-based working life table approach. We find that the use of Sullivans approach does not accurately reflect the levels of and the trends in working life expectancy.Peer reviewe

A molecular scheme for the reaction between acetylcholine and nicotinic channels.

In outside-out patches of mouse-muscle membrane, embryonic-like channels were activated by pulses of acetylcholine (ACh). On increasing the ACh concentration, the rate of desensitization, 1/tau d, increased linearly with the peak open probability, indicating desensitization from the open state. Desensitization had only one time constant tau d at each ACh concentration. Recovery from desensitization was only approximately 10 times slower than desensitization, whereas the probability of steady-state channel opening, declined to < 0.01 with > 10(-6) M ACh. The peak probability of opening in > 10(-4) M ACh pulse was close to 1. A linear reaction scheme was not compatible with these results. The scheme had to be expanded resulting in a circular scheme with two additional ACh binding steps to desensitized channel states. The approximate rate constants of all reaction steps in the circular scheme could be determined using computer simulations. The model predicted that clusters of channel opening had the average duration tau d at the respective ACh concentration. In cell-attached patches on intact muscle fibers, similar average cluster durations were observed at the respective ACh concentration. This indicates that tau d in the intact muscle fibers has similar values as in outside-out patches